Stepped gasket for thermal interface and method of making and using same

Abstract

Described herein are thermal interfaces or joints that include a gasket material, such as a stepped gasket, and / or further include a shim therein, and methods for making the same. The thermal interfaces or joints described above can form part of a device and can be useful in low contact pressure and / or low pressure applications. At least a second layer of the stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates that exhibit deformation, warping, or bending of the plates, as compared to a non-stepped single layer gasket.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Patent Application No. 17 / 492,349, filed October 1, 2021, which is incorporated by reference in its entirety.

[0002] FIELD OF THEINVENTION The present invention is in the field of thermal interface and gasket materials, and methods for making and using them. [Background technology]

[0003] 2. Background of the Invention It is known that thermal interfaces or joints are formed with at least two plates fastened together, such as by bolts, and a compressible material, such as a gasket, between the plates. At least one of the plates is subject to undesirable plate deformation or curvature. The inclusion of a gasket material between two bolted plates can lead to even greater deformation or curvature, and a thinner gasket can limit but not eliminate the degree of plate deformation or curvature. Plate deformation or curvature can cause the formation of a gap(s), reducing and / or restricting the contact area between the plate and the gasket, adversely affecting the ability of the thermal interface to efficiently transfer heat. While the contact area can be increased by uniformly increasing the thickness of the gasket, a thicker gasket can result in greater plate deformation or curvature. Since plate deformation or curvature increases with maximum bowing (near the fastening (bolt) location), increasing the gasket thickness increases the curvature, thereby making it difficult to achieve consistent central contact without resorting to an extremely thick gasket.

[0004] A significant challenge therefore is to address the shortcomings of known thermal interfaces or joints due to limitations caused by plate deformation.

[0005] Thus, there is a need to address the formation of gap(s) caused by plate deformation in fastened thermal interfaces or joints.

[0006] It is therefore an object of the present invention to provide a thermal interface or joint with an increased contact region / area that at least minimizes the negative effects caused by plate deformation.

[0007] It is also an object of the present invention to provide means for making and using such a thermal interface or joint. Summary of the Invention [Means for solving the problem]

[0008] Summary of the Invention Described herein are thermal interfaces or joints, and methods for making the same. Such thermal interfaces or joints include: First and second plates; a stepped gasket between the first and second plates; and One or more fasteners joining the first and second plates. Can include; at least one of the first and / or second plates exhibits plate deformation, warping, or curvature; The stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area less than the surface area of ​​the first base layer;

[0009] At least a second layer of the stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates that exhibit deformation, warping, or curvature of the plates compared to a non-stepped single layer gasket.

[0010] A thermal interface or joint includes two plates, a base plate (bottom plate) and a top plate, which typically exhibit deformation, warping, or curvature when the two plates are fastened (e.g., bolted) or during the manufacture of the plates. The top and bottom plates can be made of any suitable material with any suitable shape and dimensions, and thickness to be used as a thermal interface. The two plates are usually made of the same material and have the same shape and dimensions, and optionally the same thickness.

[0011] The top and bottom plates of the thermal interface or joint are fastened by one or more fasteners, which join the first and second plates through one or more holes present in the top and bottom plates. There may be any number of one or more fastener holes in both plates at the same location on each plate as may be required to join the two plates with fasteners. One or more fasteners may be used to fasten the first (base or bottom) plate and the second (top) plate through each of the fastener holes that may be present. The one or more fasteners may be selected from threaded fasteners, clamps, clips, push pins, rivets, air presses, hydraulic presses, or combinations thereof.

[0012] In some examples, for the described thermal interfaces and joints, at least one or more additional contact areas provided by the use of a stepped gasket results in increased temperature uniformity of the first and / or second plates that exhibit plate deformation, warping, or bowing, thereby providing an average thermal conductivity across the thermal interface that is at least 25%, 30%, 40%, or 50% higher than that of the same thermal interface having a single layer gasket that is not internally stepped. Thermal conductivity is defined as the time rate of steady-state heat flow through a unit area of ​​the thermal interface or joint induced by a unit temperature difference between the thermal interface surfaces.

[0013] In certain examples, for the described thermal interfaces and joints, at least one or more additional contact areas provided by the use of a stepped gasket result in an increased contact area between the stepped gasket and at least one of the first and / or second plates exhibiting plate deformation, warping, or bowing, thereby providing an average thermal conductivity across the thermal interface that is at least 25%, 30%, 40%, or 50% higher than that of the same thermal interface having a single layer gasket that is not internally stepped. Thermal conductivity is defined as the time rate of steady state heat flow through a unit area of ​​the thermal interface or joint induced by a unit temperature difference between the thermal interface surfaces.

[0014] The use of a stepped gasket introduces one or more contact regions or areas between the stepped gasket and a plate that exhibit deformation or curvature compared to the use of a single layer gasket. The stepped gasket can be designed to match or modify (improve) the thermal profile of the plate. The stepped gasket can distribute contact loads more evenly due to better overall uniformity. The number of layers of the stepped gasket and the relative locations of the layers present in the stepped gasket can be positioned based on interface curvature modeling to properly position or create a desired number of contact points or areas that improve the thermal performance of the thermal interface or joint.

[0015] The use of a stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates exhibiting plate deformation, warping, or curvature, compared to the use of a non-stepped single layer gasket. For a given stepped gasket, each included layer may provide at least 1, 2, 3, or 4 independent contact areas with at least one of the first and / or second plates exhibiting plate deformation, warping, or curvature, compared to a gasket without that layer. In some examples, the one or more contact areas resulting from the use of a stepped gasket can be said to contact at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the surface of at least one of the first and / or second plates exhibiting plate deformation, warping, or curvature. In some examples, the contact area or areas resulting from the use of a stepped gasket can be said to contact at least about 5%-25%, about 5%-50%, about 5%-75%, or about 5%-90%, and subareas within ranges, of at least one surface of the first and / or second plate that exhibits deformation, warping, or bowing of the plate. The formation of the contact area or areas and the resulting increased contact area between the gasket and the plate results in an increased overall thermal conductivity of the thermal interface or joint.

[0016] In some examples, each of the multiple layers of the stepped gasket is independently made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomers, rubber, and acrylic.

[0017] In some examples, the stepped gasket can be made of a multi-layer or multi-tiered structure comprising carbon nanotube arrays or sheets. For example, the stepped gasket can be a multi-layer or multi-tiered structure. Such stepped gaskets are described in more detail below.

[0018] The thermal interfaces and joints described above may also include one or more shims thereon. The one or more shims may be placed or positioned around, near, and / or behind one or more fasteners or fastener holes present in the plate(s). In some examples, when the one or more fasteners are potted inserts, the one or more shims may reduce stress on the potted insert by at least about 10, 20, 30, 40, 50, 60, 70, 80, or 90% compared to a comparable thermal interface without the one or more shims present. In some examples, the one or more shims have a height selected to be equal to the height of the first layer of the stepped gasket. In some examples, the one or more shims are positioned as far back as possible from the fastener holes and fasteners, such as at the very edge of the plate. In some examples, the shims are made of metal foil, preferably aluminum foil or copper foil. In some other examples, the shims are made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic. In yet another example, the shim is made of a multi-layer or multi-tiered structure.

[0019] Thermal interfaces or joints with an internal stepped gasket: (1) providing a first and a second plate; (2) preparing a stepped gasket; (3) placing a stepped gasket between the first and second plates; (4) joining the first and second plates with one or more fasteners; A method comprising: at least one of the first and / or second plates exhibits deformation, warping, or bowing of the plate when joined by the one or more fasteners; The stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area less than the surface area of ​​the first base layer; at least a second layer of the stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates that exhibit plate deformation, warping, or curvature as compared to a non-stepped single layer gasket; It can be prepared according to the method.

[0020] In some other examples, the effects of plate deformation, warping, or bending can be countered by including one or more shims at the thermal interface or joint with a single layer gasket therein. For example, the thermal interface or joint may include: First and second plates; a single layer gasket between the first and second plates; and One or more fasteners joining the first and second plates. may include at least one of the first and / or second plates exhibits plate deformation, warping, or curvature; The one or more shims are present around, near, and / or behind the one or more fasteners to reduce and / or mitigate deformation, warping, or bowing of the first and / or second plates.

[0021] Such thermal interfaces or joints having a shim with a single layer gasket inside are: (1) providing a first and a second plate; (2) providing a single layer gasket; (3) disposing a single layer gasket between the first and second plates; (4) disposing one or more shims between the first and second plates; (5) A method comprising joining first and second plates with one or more fasteners, at least one of the first and / or second plates exhibits deformation, warping, or bowing of the plate when joined by the one or more fasteners; one or more shims are present around, near, and / or behind one or more fasteners to reduce and / or mitigate deformation, warping, or curvature of the first and / or second plates; It can be prepared according to the method.

[0022] The thermal interfaces or joints described above may form part of devices including, but not limited to, personal computers, server computers, memory modules, graphics chips, radar and radio frequency (RF) devices, disk drives, displays including light emitting diode (LED) displays, lighting systems, automotive control units, power electronics, solar cells, batteries, communications equipment such as mobile phones, thermoelectric generators, and imaging equipment including MRI.

[0023] In certain instances, the thermal interfaces or joints described throughout this specification are useful in low contact pressure and / or low pressure applications. Low pressure may refer to pressures below ambient pressure or 1 atm, such as in the range of about 0.01 to less than about 1 atm. In some instances, low pressure may refer to vacuum, such as in aerospace applications, where such thermal interfaces or joints may be used in satellites or spacecraft / systems. Under vacuum conditions, the thermal interfaces or joints are particularly useful because the additional contact points enabled by the stepped gasket can substantially increase the area involved in heat transfer across the joint, unlike applications at atmospheric pressure, where air in the separation gap between the plates may contribute to heat transfer. Furthermore, the use of thick gaskets to make contacts in space applications can be problematic, as deformation of the plates following the thick gasket can result in stresses in the potted inserts, which can lead to the insertion being pulled out during the life of the spacecraft. In certain instances, the thermal interfaces or joints described are useful at temperatures below ambient, below freezing, or at cryogenic temperatures (such as those experienced in space). [Brief description of the drawings]

[0024] [Figure 1A] FIG. 1A is a non-limiting cross-sectional representation of a thermal interface 100 having two plates 110 (with the top plate showing deformation, warping, or bending of the plate), two fasteners 120 (i.e., bolts), and a thin single layer gasket 130 between the plates.

[0025] [Figure 1B] FIG. 1B is a non-limiting cross-sectional representation of a thermal interface 200 having two plates 210 (with the top plate showing deformation, warping, or bending of the plate), two fasteners 220 (i.e., bolts), and a thick single layer gasket 230 between the plates.

[0026] [Diagram 2] FIG. 2 is a non-limiting cross-sectional representation of a thermal interface 300 having two plates 310 (wherein the top plate exhibits plate deformation, warping, or curvature), two fasteners 320 (i.e., bolts), and a stepped gasket 330 (having three steps) between the plates providing multiple contact areas 340 between the top plate and the stepped gasket exhibiting plate deformation, warping, or curvature.

[0027] [Figure 3A] FIG. 3A is a non-limiting cross-sectional representation of a stepped gasket having a first base layer 410 and a second layer 420 on the first base layer.

[0028] [Figure 3B] FIG. 3B is a non-limiting cross-sectional representation of a stepped gasket having a first base layer 510, a second layer 520 on the first base layer, and a third layer 530 on the second layer.

[0029] [Figure 4] FIG. 4 is a non-limiting top view of a plate and gasket 600 having a bottom plate 610 with multiple fastener holes 620, and a stepped gasket having a first base layer 630, a second layer 640 on the first base layer, and a third layer 650 on the second layer.

[0030] [Figure 5A] FIG. 5A is a non-limiting cross-sectional representation of a thermal interface 700 having two plates 710 (with the top plate showing deformation, warping, or bending of the plate), two fasteners 720 (i.e., bolts), and a single layer gasket 730 having two shims 740 thereon.

[0031] [Figure 5B]FIG. 5B is a non-limiting cross-sectional representation of a thermal interface 800 having two plates 810 (with the top plate showing deformation, warping, or curvature of the plate), two fasteners 820 (i.e., bolts), a single layer gasket 830, and two shims 840 disposed on the edges of the bottom plate.

[0032] [Figure 6A] FIG. 6A is a non-limiting top view of a plate and shims 900 having a bottom plate 910 with multiple fastener holes 940 and ¼ half-ring shims 920 and ½ half-ring shims 930 around, near, and / or behind the fastener holes.

[0033] [Figure 6B] FIG. 6B is a non-limiting top view of a plate and shim 1000 having a bottom plate 1010 with multiple fastener holes 1030 and two rectangular shims 1020 behind the fastener holes.

[0034] [Figure 7] 7 is a graph of experimental heat transfer data as a function of applied contact pressure for gaskets with various numbers of layers (1, 2, 3, and 4). A best fit power law function was superimposed on each data set.

[0035] [Figure 8] FIG. 8 is a non-limiting representation of a 50 cm by 36 cm, 18 mm thick plate demonstrating the 22 bolt hole configuration.

[0036] [Figure 9A] FIG. 9A shows a non-limiting top view of a stepped gasket having a base layer (gray) with a second layer (black) on top.

[0037] [Figure 9B] FIG. 9B shows a non-limiting top view of a stepped gasket having a base layer (gray) with a second layer (black) on top.

[0038] [Figure 9C] FIG. 9C shows a non-limiting top view of a stepped gas get having a base layer (gray) and a second layer (black) thereon that forms a strip shape.

[0039] [Figure 10] FIG. 10 is a bar graph of the temperature difference at the center of the plate for Samples 1-4 tested in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Detailed Description of the Invention I. Definition "Compliant" or "Compliance" as used herein refers to the ability of a material to conform when in contact with one or more surfaces such that efficient conformance to the irregularities of the adjacent surfaces provides a sufficient or high contact area at the interface between the surfaces and the material.

[0041] As used herein, "Interdigitation" or "Interdigitating" refers to the ability and or degree to which one or more individual nanostructured elements of an array or sheet penetrate or penetrate adjacent nanostructured elements of another array or sheet when two different arrays or sheets are contacted or stacked.

[0042] As used herein, a "carbon nanotube array" or "CNT array" or "CNT forest" refers to a plurality of carbon nanotubes aligned perpendicular to a surface of a material. Carbon nanotubes are said to be "vertically aligned" when they are substantially perpendicular to the surface on which they are supported or attached. Nanotubes are said to be substantially vertical when they are oriented, on average, within 30, 25, 20, 15, 10, or 5 degrees from the surface normal.

[0043] As used herein, "carbon nanotube sheet" or "CNT sheet" refers to a plurality of carbon nanotubes aligned in a plane to create a free-standing sheet. The carbon nanotubes are said to be "aligned in a plane" when they are substantially parallel to the surface of the sheet they form. The nanotubes are said to be substantially parallel when they are oriented, on average, at more than 40, 50, 60, 70, 80, or 85 degrees from the surface normal of the sheet.

[0044] "Coating material," as used herein, generally refers to polymers and / or molecules that can bind to CNTs through van der Waals bonding, π-π stacking, mechanical wrapping, and / or covalent bonds, and to metal, metal oxide, or semiconductor material surfaces through van der Waals bonding, π-π stacking, and / or covalent bonds.

[0045] As used herein, "elastic recovery" refers to the ability of a material to return to its original shape after being compressed, expanded, stretched, or other deformation.

[0046] "Compression set," as used herein, refers to the permanent deformation of a material that is left when a force, such as compression, is applied to the material and the force is subsequently removed.

[0047] "Plate deformation, warping, or curvature" as used herein refers to any deformation, warping, or curvature of a plate compared to its planar state that results from a reactionary "normal" force when two plates are fastened (i.e., bolted) causing upward bending around the force of the fasteners, and compressible materials such as the base plate and gasket of a thermal interface or joint provide a lever effect on the top plate. In some cases, plate deformation, warping, or curvature may also result during fabrication of the plate(s) from processes such as milling, casting, rolling, or bonding.

[0048] "Fastener spacing" or "bolt spacing" as used herein refers to the distance between fasteners, such as bolts, which can include fasteners that are immediately next to each other or directly opposite each other (opposing edges of a plate).

[0049] "Shim" as used herein refers to a small piece of material that can be placed, for example, around, near (i.e., at the edge) and / or behind multiple fastener holes on a plate to create a height or thickness mismatch between the shim and the surrounding area of ​​the interface. When fastened (i.e., bolted), the shim can create a reaction force behind the fastener (i.e., bolt) that counteracts the reaction force of the gasket and plate that causes the initial deformation. The shim can increase the contact area, pushing it further into the plate and away from the fastener location.

[0050] Numerical ranges disclosed in this application include, but are not limited to, temperature ranges, pressure ranges, integer ranges, conductivity and resistance ranges, time ranges, and thickness ranges. Any type of disclosed range individually discloses each possible numerical value that such range may reasonably encompass, as well as any subranges and combinations of subranges encompassed therein. For example, the disclosure of a pressure range is intended to individually disclose all possible temperature values ​​that such range may encompass that are not inconsistent with the disclosure herein. II. Thermal Interface or Joint with Stepped Gasket

[0051] A thermal interface or joint formed of at least two plates fastened by, for example, nuts and bolts, and a compressible material, such as a gasket between the plates, where at least one of the plates is known to undergo undesirable plate deformation, warping, or bending.

[0052] The inclusion of gasket material between two bolted plates may result in even greater plate deformation, warping, or curvature in some instances. A thinner gasket may limit but not eliminate the extent of plate deformation, warping, or curvature. As an example, FIG. 1A shows a cross-sectional representation of a thermal interface 100 having two plates 110, two fasteners 120 (i.e., bolts), and a thin, single-layer gasket 130 between the plates, with the top plate exhibiting plate deformation, warping, or curvature. However, plate deformation, warping, or curvature reduces and / or adversely affects the contact-dependent heat transfer capability of the thermal interface, as it separates the plates from the gasket. Thus, to offset the negative thermal penalty of plate deformation, warping, or curvature, the thickness of the gasket may be uniformly increased to better accommodate the plate deformation, warping, or curvature, thereby resulting in an increased contact area. However, a thicker gasket may result in greater plate deformation, warping, or curvature. For example, FIG. 1B shows a cross-sectional view of a thermal interface 200 having two plates 210, two fasteners 220 (i.e., bolts), and a thick single layer gasket 230 between the plates, with the top plate exhibiting deformation, warping, or bowing of the plate.

[0053] The deformation, warping, or curvature of the plate increases and exhibits maximum curvature at or near the fastener (i.e., bolt) locations. It may also be said that the deformation, warping, or curvature of the plate is greatest at or near the midpoint between the opposing bolts. Thus, simply increasing the thickness of the gasket would increase the curvature and make it difficult to consistently create center contact without resorting to an extremely thick gasket, which is neither a desirable nor practical solution.

[0054] In a thermal interface or joint, the plate contact area with the gasket is proportional to the plate thickness, the plate elastic modulus, and the torque of the fasteners (i.e., bolts). The plate contact area is inversely proportional to the distance between the fasteners (i.e., bolts). In a thermal interface or joint, the plate deformation, warping, or curvature is inversely proportional to the plate thickness and the plate elastic modulus. The plate deformation, warping, or curvature is proportional to the fastener (i.e., bolt) torque and increases monotonically with the distance between the fasteners (i.e., bolts). In some examples, it is possible to model parameters such as warping, contact area, pressure, and thermal conductivity of a theoretical thermal interface. This allows for the selection of properties of the stepped gasket discussed below to maximize the properties of the thermal interface or joint, such as by increasing the contact area / area and thermal conductivity between the stepped gasket and the plate as a whole.

[0055] To address the challenges posed by plate deformation, warping, or bending discussed above, the thermal interface or joint: First and second plates; a stepped gasket between the first and second plates; and One or more fasteners joining the first and second plates. Includes; at least one of the first and / or second plates exhibits plate deformation, warping, or curvature; The stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area less than the surface area of ​​the first base layer; At least a second layer of the stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates that exhibit plate deformation, warping, or curvature compared to a non-stepped single layer gasket.

[0056] 2, a cross-sectional view of a thermal interface 300 having two plates 310 (the top plate exhibits plate deformation, warping, or curvature), two fasteners 320 (i.e., bolts), and a stepped gasket 330 (having three steps) between the plates provides multiple contact areas 340 between the stepped gasket and the top plate exhibiting plate deformation, warping, or curvature. The introduction of contact areas through the use of a stepped gasket (versus a single layer gasket) counteracts the detrimental effects of gaps created by plate deformation, warping, or curvature.

[0057] A stepped gasket has at least two layers, as shown in FIG. 3A, which shows a cross-sectional view of a stepped gasket having a first base layer 410 and a second layer 420 on the first base layer. In some other examples, a stepped gasket has at least three layers, as shown in FIG. 3B, which shows a cross-sectional view of a stepped gasket having a first base layer 510, a second layer 520 on the first base layer, and a third layer 530 on the second layer. FIG. 4 shows an exemplary three-layer gasket on a base plate. Stepped gaskets with additional layers, up to a total of four or five layers, are also contemplated.

[0058] It is contemplated that each of the additional layers provides an additional area of ​​contact with at least one of the first and / or second plates that exhibits deformation, warping, or curvature of the plates, and each layer has a surface area that is smaller than the layer underneath and that is smaller than the surface area of ​​the layer underneath.

[0059] A thermal interface or joint includes two plates and a base plate (bottom plate), where the top plate typically exhibits deformation, warping, or curvature when the two plates are fastened (e.g., bolted) or during the manufacture of the plates. Either the top or base (bottom) plate is planar or substantially planar (where "substantially planar" means less than 0.25 μm deviation from flatness per mm of plate length). The top and bottom plates, such as those shown in FIG. 2, can be made of any suitable material with any suitable shape and dimensions, as well as thickness, to be used as a thermal interface. The two plates are usually made of the same material and have the same shape and dimensions, as well as the same thickness if necessary. In some cases, the first (bottom or base) and second (top) plates have a square, rectangular, circular, elliptical, or ring shape. Typically, the stepped gasket has the same overall shape as the first and second plates, at least with respect to the first base layer. In some examples, plates having a thickness of about >4 mm can be considered highly robust plates, whereas plates having a thickness of about <4 mm can be considered moderately or less robust plates. In some examples, the plates independently have a thickness in the range of about 0.5 to about 30 mm, about 0.5 to about 20 mm, or about 0.5 to about 10 mm, and subranges therein. In one particular example, both plates are ¼ inch thick plates.

[0060] In some examples, the first (bottom or base) and second (top) plates can be independently made of a material selected from aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates). In some examples, the first (bottom or base) and second (top) plates can be independently made of a plastic selected from acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate materials (such as FR4), high pressure fiberglass laminates (such as G10), fiberglass composites, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide. In yet another example, the first (bottom or base) and second (top) plates can be independently made of a ceramic selected from alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those comprised of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

[0061] The top and bottom plates of the thermal interface or joint are fastened by one or more fasteners, which join the first and second plates through one or more holes present in the top and bottom plates. There may be any number of one or more fastener holes on both plates at the same location on each plate as may be required for fasteners to join the two plates. In some examples, there are at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32 fastener holes on each plate. The fastener holes present may have any shape or size as needed. In some examples, the fastener holes are circular and may have a diameter suitable for a fastener such as a bolt. In some examples, the fastener holes may be threaded to receive a threaded fastener. The fastener holes may be spaced in any suitable relative arrangement. However, in certain instances, it is preferred that the fastener holes are on one or more edges of the plate. Typically, the fastener holes are evenly spaced on the plate. Non-limiting examples of fastener holes on a plate and their relative positions to one another are shown in FIG. 4. In some instances, the spacing between fastener holes may be between two holes that are immediately next to one another, and the distance may range from about 5 to 600 mm. In some instances, the spacing between fastener holes may be between two holes on opposing edges of the plate, and the distance may range from about 5 to 600 mm. In yet other instances, the spacing between fastener holes may be between two holes that are positioned diagonally relative to one another on the plate, and the distance may range from about 5 to 600 mm.

[0062] One or more fasteners can be used to fasten the first (base or bottom) plate and the second (top) plate through each of the possible fastener holes. The one or more fasteners can be selected from threaded fasteners, clamps, clips, push pins, rivets, air presses, hydraulic presses, or combinations thereof. Such fasteners are known in the art. The threaded fasteners can be bolts and nuts, such as those known in the art. In some other inserts, the threaded fasteners are bolts and pot inserts, such as those known in the art. The one or more fasteners of any type used can be made of any suitable material, such as a material selected from steel, titanium, aluminum, nylon, brass, bronze, and zinc. If the fasteners include bolts, the bolts may be applied using an appropriate amount of bolt torque, and the bolts may be tightened in any suitable tightening pattern to ensure uniform tightening between the two plates. Selection of appropriate bolts (and nuts), bolting torques, and bolting patterns is known in the art.

[0063] In some examples, for the described thermal interfaces and joints, at least one or more additional contact areas provided by the use of a stepped gasket results in increased temperature uniformity of the first and / or second plates that exhibit plate deformation, warping, or bowing, thereby providing an average thermal conductivity across the thermal interface that is at least 25%, 30%, 40%, or 50% higher than that of the same thermal interface having a single layer gasket that is not internally stepped. Thermal conductivity is defined as the time rate of steady-state heat flow through a unit area of ​​the thermal interface or joint induced by a unit temperature difference between the surfaces of the thermal interface.

[0064] In certain examples, for the described thermal interfaces and joints, at least one or more additional contact areas provided by the use of a stepped gasket result in an increased contact area between the stepped gasket and at least one of the first and / or second plates exhibiting plate deformation, warping, or bowing, thereby providing an average thermal conductivity across the thermal interface that is at least 25%, 30%, 40%, or 50% higher than that of the same thermal interface having a single layer gasket that is not internally stepped. Thermal conductivity is defined as the time rate of steady-state heat flow through a unit area of ​​the thermal interface or joint induced by a unit temperature difference between the surfaces of the thermal interface.

[0065] With respect to the described thermal interfaces and joints, each layer of the stepped gasket, if present, conforms to at least one surface of the first and / or second plate exhibiting deformation, warping, or curvature of the plates, at least in one or more contact areas. A. Stepped gasket

[0066] The use of a stepped gasket introduces one or more contact regions or areas between the stepped gasket and a plate that exhibits deformation or curvature (see FIG. 2) compared to the use of a single layer gasket. The stepped gasket can be designed to match or modify (improve) the thermal profile of the plate. The stepped gasket can distribute contact loads more evenly due to better overall uniformity. The number of layers of the stepped gasket (see FIGS. 3 and 4) and the relative locations of the layers present in the stepped gasket can be positioned based on interface curvature modeling to properly position or create a desired number of contact points or areas that improve the thermal performance of the thermal interface or joint.

[0067] The stepped gasket includes a first base layer and at least a second layer thereon. Additional layers, such as a third, fourth, or fifth layer, may be included. The first base layer and other layers may have any suitable shape or thickness as desired. More typically, the first base layer and other layers have the same shape (i.e., square, rectangular, circular, regular or irregular shapes, etc.). In some examples, the stepped gasket has a first base layer with dimensions that cover the entire area of ​​the plate between which it is placed. In some other examples, the stepped gasket has a first base layer with dimensions that are smaller than the entire area of ​​the plate between which it is placed, such as covering at least about 50%, 60%, 70%, 80%, 90% of the area of ​​the plate. The first base layer of the stepped gasket may include holes cut out to accommodate fastening holes present in the plate. Each subsequent layer is smaller in size (area) than the layer below it. In some examples, the overlying layer has an area between about 1% and 50% of the size of the area of ​​the layer below it. For example, the second layer may have an area of ​​about 1% to 75% or about 1% to 50% of the area of ​​the first base layer, and the third layer, if present, may be about 1% to 75% or about 1% to 50% smaller in area size than the second layer. The same applies to additional layers relative to the layer in which they are present.

[0068] The use of a stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates exhibiting plate deformation, warping, or curvature, compared to the use of a non-stepped single layer gasket. In a given stepped gasket, each included layer may provide at least one, two, three, or four independent contact areas with at least one of the first and / or second plates exhibiting plate deformation, warping, or curvature, compared to a gasket without that layer. In some examples, the one or more contact areas resulting from the use of a stepped gasket can be said to contact at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the surface of at least one of the first and / or second plates exhibiting plate deformation, warping, or curvature. In some examples, the contact area or areas resulting from the use of a stepped gasket can be said to contact at least about 5%-25%, about 5%-50%, about 5%-75%, or about 5%-90%, and subareas within ranges, of at least one surface of the first and / or second plate that exhibits deformation, warping, or bowing of the plate. The formation of the contact area or areas and the resulting increased contact area between the gasket and the plate results in an increased overall thermal conductivity of the thermal interface or joint.

[0069] In some cases, the maximum warpage / deformation height of the fastened plates can be determined or simulated, which allows for the formation of a stepped gasket having a combined height (i.e., the sum of all layers that may be present) that preferably matches or exceeds the maximum warpage / deformation height of the fastened plates. In some cases, each of the layers of the stepped gasket, if present, can have a thickness that ranges between about 50 μm and about 500 μm, independently. Further, in some cases, the increase in height between layers of the stepped gasket is selected to be less than about 500 μm, less than about 250 μm, less than about 150 μm, or less than about 75 μm. In some cases, the increase in height between layers of the stepped gasket can be determined based on theoretical warpage from the contact surface under fastener load, as predicted by using Euler-Bernoulli beam theory, Timoshenko beam theory, or Kirchhoff-Love plate theory, while considering the gasket layers as compressible and elastic foundations.

[0070] In certain cases, the peripheral location of the second layer of the stepped gasket is selected and sized to intersect the theoretical deflection of the contact surface under fastener load as predicted by Euler-Bernoulli beam theory, Timoshenko beam theory, or Kirchhoff-Love plate theory, considering the gasket as a compressible and elastic base and considering the deformation of the first layer of the stepped gasket near the fastener. In some cases, the peripheral location of the third layer of the stepped gasket is sized to intersect the theoretical deflection of the contact surface under fastener load as predicted by Euler-Bernoulli beam theory, Timoshenko beam theory, or Kirchhoff-Love plate theory, considering the deformation of the first layer of the stepped gasket near the fastener, if present, and the deformation of the first and second layers in the area where the second layer contacts the second surface. In yet another example, the peripheral location of the fourth layer of the stepped gasket is sized to intersect the theoretical deflection of the contact surfaces under the fastener load as predicted by Euler-Bernoulli beam theory, Timoshenko beam theory, or Kirchhoff-Love plate theory, taking into account the deformation of the first layer of the stepped gasket near the fastener, if present, the deformation of the first and second layers in the area where the second layer contacts the second surface, and the deformation of the first, second, and third layers in the area where the third layer contacts the second surface.

[0071] In some cases, the additional layers may be on top of each of the previous layers (i.e., a second layer on top of a first base layer, a third layer on top of a second layer, etc.) Additionally or alternatively, the additional layers may be adjacent to each other on the previous layers, for example a first base layer having a second and third layer adjacent to each other on the base layer, but the third layer is not in contact with or on the second layer.

[0072] In some examples, each of the layers of the stepped gasket, if present, can each independently exhibit a modulus of elasticity in the range of between about 0.1 MPa and about 50 MPa, about 0.1 MPa and about 100 MPa, about 0.1 MPa and about 150 MPa, or about 0.1 MPa and about 200 MPa. In some examples, each of the layers of the stepped gasket, if present, can each independently exhibit a modulus of elasticity in the range of between about 0.05 cm 2 ·℃ / W~approx. 1cm 2 ·℃ / W, 0.05cm 2 ·℃ / W~approx.5cm 2 ·℃ / W, 0.05cm 2 ·℃ / W ~ approx. 2cm 2 ·℃ / W, 0.05cm 2 ·℃ / W ~ approx. 3cm 2 ·℃ / W, 0.05cm 2 ·℃ / W ~ approx. 4cm 2 °C / W or 0.05cm 2 ·℃ / W~approx.5cm 2 ·°C / W.

[0073] In some examples, each of the multiple layers of the stepped gasket is independently made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic. Typically, each stepped gasket having at least two layers is made with layers made of the same material, where appropriate the number of layers and their respective thicknesses may vary. In some examples, layers of different material types may be used. Additionally, in some examples, the material making up each layer of the stepped gasket may further include thermally conductive and / or electrically conductive fillers as known in the art.

[0074] In some cases, the first base layer of the stepped gasket provides a ground path through the stepped gasket, preferably near one or more fasteners. In still other cases, the first base layer can include an adhesive (i.e., a pressure sensitive adhesive or a heat sensitive adhesive), preferably on a side that does not have any additional layers thereon. For example, adhesive may be present on the bottom of the first base layer shown in Figures 2, 3A, or 3B to adhere to a bottom (base) plate.

[0075] In some examples, the stepped gasket can be made of a multi-layer or multi-tiered structure comprising carbon nanotube arrays or sheets. For example, the stepped gasket can be made of: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The laminate may be a multi-layer or multi-stage laminate comprising: At least a first layer or step and at least a second layer or step are stacked such that the vertically aligned carbon nanotubes of the at least a first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least a second layer or step that interface with one another. Such stepped gaskets are described in more detail below. i. Stepped gaskets having multi-layer or multi-stage layer structures

[0076] Multi-layer or multi-tiered structures comprising carbon nanotube arrays or sheets can be used to form stepped gaskets as described below. a. Carbon nanotube arrays and carbon nanotube sheets

[0077] Carbon nanotube (CNT) arrays are described herein. The arrays comprise a plurality of carbon nanotubes supported on or attached to the surface of an inert substrate / support, such as one made of metal (e.g., Al or Au) foil or of a metal alloy (i.e., steel). In some embodiments, the substrate / support can be a flexible, electrically and thermally conductive substrate, such as graphite or other carbon-based materials. In yet other embodiments, the substrate / support can be an electrically insulating substrate, such as a flexible ceramic. CNT arrays can be formed using the methods described below. The CNTs are vertically aligned on the substrate / support. CNTs are said to be "vertically aligned" when they are substantially perpendicular to the surface on which they are supported or attached. Nanotubes are said to be substantially vertical when they are oriented within an average of 30, 25, 20, 15, 10, or 5 degrees from the surface normal.

[0078] Generally, the carbon nanotubes are present in a sufficient density such that the nanotubes are free-standing and adopt a substantially perpendicular orientation to the surface of the multi-layer substrate. Preferably, the nanotubes are spaced an optimal distance from one another and are of uniform height to minimize heat transfer losses, thereby maximizing collective thermal diffusivity. In some embodiments, the carbon nanotube density on the substrate surface is greater than or equal to 1 mm 2 Approximately 1 x 10 7 ~1×10 11 Nanotubes, mm 2 Approximately 1 x 10 8 ~1×10 10 Nanotubes, or mm 2 Approximately 1 x 10 9 ~1×10 10 This is the range of nanotubes.

[0079] A CNT array comprises nanotubes continuous from the top of the array (i.e., the surface formed by the distal ends of the carbon nanotubes when aligned vertically on the multilayer substrate) to the bottom of the array (i.e., the surface of the multilayer substrate). CNT arrays may be formed from multi-walled carbon nanotubes (MWNTs), which generally refer to nanotubes having between about 4 and about 10 walls. Arrays may also be formed from few-walled nanotubes (FWNTs), which generally refer to nanotubes having between about 1 and 3 walls. FWNTs include single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), and triple-walled carbon nanotubes (TWNTs). In certain embodiments, the nanotubes are MWNTs. In some embodiments, the diameter of the MWNTs in the array ranges from 10 to 40 nm, more preferably 15 to 30 nm, and most preferably about 20 nm. The length of the CNTs in the array can range from 1 to 5,000 micrometers, preferably from 5 to 5000 micrometers, preferably from 5 to 2500 micrometers, more preferably from 5 to 2000 micrometers, more preferably from 5 to 1000 micrometers. In some embodiments, the length of the CNTs in the array can range from 1 to 500 micrometers, even more preferably from 1 to 100 micrometers.

[0080] CNTs exhibit strong adhesion to multilayer substrates. In certain embodiments, CNT arrays or sheets remain substantially intact after being immersed in a solvent such as ethanol and sonicated for at least 5 minutes. In certain embodiments, at least about 90%, 95%, 96%, 97%, 98%, 99%, or 99.9% of the CNTs remain on the surface after sonication in ethanol.

[0081] Carbon nanotube sheets are also described herein. The sheets comprise a plurality of carbon nanotubes that support each other through strong van der Waals force interactions and mechanical entanglement to form a free-standing material. CNT sheets can be formed using the methods described below. The CNTs form a free-standing sheet and are aligned in the same plane as the surface of the sheet. The CNTs are said to be "planarly aligned" when they are substantially parallel to the surface of the sheet they form. The nanotubes are said to be substantially parallel when they are oriented, on average, greater than 40, 50, 60, 70, 80, or 85 degrees from the surface normal of the sheet.

[0082] Generally, the nanotubes are present in a sufficient density so that they are free-standing and adopt a substantially parallel orientation to the surface of the sheet. Preferably, the nanotubes are spaced an optimal distance from one another and are of uniform length to minimize heat transfer losses, thereby maximizing collective thermal diffusivity.

[0083] The CNT sheets may be formed from multi-walled carbon nanotubes (MWNTs), which generally refer to nanotubes with between about 4 and about 10 walls. The sheets may also be formed from few-walled nanotubes (FWNTs), which generally refer to nanotubes with between about 1 and 3 walls. FWNTs include single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), and triple-walled carbon nanotubes (TWNTs). In certain embodiments, the nanotubes are MWNTs. In some embodiments, the diameter of the MWNTs in the array ranges from 10 to 40 nm, more preferably from 15 to 30 nm, and most preferably about 20 nm. The length of the CNTs in the sheet may range from 1 to 5,000 micrometers, preferably from 100 to 5000 micrometers, preferably from 500 to 5000 micrometers, and more preferably from 1000 to 5000 micrometers. In some embodiments, the length of the CNTs in the sheet may range from 1 to 500 micrometers, and even more preferably from 1 to 100 micrometers.

[0084] The CNT arrays or sheets described above can include a coating or coating material (the terms can be used interchangeably) that adheres or bonds to the CNTs inside. The coating / coating material can be applied as described below. In some embodiments, the coating contains one or more oligomeric materials, polymeric materials, waxes, or combinations thereof. In other embodiments, the coating contains one or more non-polymeric materials. In some embodiments, the coating can contain a mixture of oligomers, waxes, and / or polymeric materials, as well as non-polymeric materials.

[0085] In certain embodiments, the coating material(s) act as binder(s) that can bond, for example chemically, the carbon nanotubes of the stacked array or sheet. Without limitation, coating materials that can act as binder(s) can be selected from adhesives (i.e., acrylate adhesives) and phase change materials (i.e., wax(es)).

[0086] In some embodiments, the coating that adheres or bonds to the CNTs of the array is applied before two or more CNT arrays or sheets are stacked, while in other embodiments, the coating that adheres or bonds to the CNTs of the array is applied after stacking of two or more CNT arrays or sheets. In still other embodiments, the coating infiltrates or backfills within the multi- or multi-tiered layered structure formed by stacking the CNT arrays or sheets, and adheres or bonds to the CNTs of the array forming the structure. As used herein, "infiltrate" or "infiltrated" refers to the coating material(s) that has infiltrated through at least a portion of the carbon nanotubes of the array or sheets that are stacked to form the multi- or multi-tiered layered structure. In some embodiments, the degree of infiltration ranges from 0.1 to 99.9% of the volumetric space between the carbon nanotubes of the array or sheet. In some embodiments, the infiltrated coating material at least partially fills the interstitial spaces between the carbon nanotubes, while in some other embodiments, the infiltrated coating coats at least a portion of the surface(s) of the carbon nanotubes, or both. In some embodiments, the infiltrated coating material fills all or substantially all (i.e., at least about 95%, 96%, 97%, 98%, or 99%) of the interstitial spaces between carbon nanotubes present within a layer or tier of a structure formed by stacking of CNT arrays or sheets.

[0087] Various materials can be coated onto the CNT array or sheet before, during, or after lamination. In certain embodiments, the coating can cause a decrease in the thermal resistance of the CNTs of the array or sheet of structures having multiple layers or tiers as defined herein. The coating can be conformally deposited to coat the tips and / or sidewalls of the CNTs. It is also desirable for the coating to be reflowable, as the interface is assembled using, for example, a solvent, heat, or some other source that is easy to deposit. The polymer used as the coating should be thermally stable up to at least 130° C. In some embodiments, the coating is easily removable, such as by dissolving in heat or a solvent, to allow for "reworking" of the interface. "Reworking" as used herein refers to the disruption of the interface (i.e., removal of the coating) by application of a solvent or heat.

[0088] In some embodiments, the coating is or contains one or more polymeric materials. The polymer or polymer coating can contain conjugated polymers, such as aromatic, heteroaromatic, or non-aromatic polymers, or non-conjugated polymers.

[0089] Suitable classes of conjugated polymers include polyaromatics and polyheteroaromatics, including, but not limited to, polythiophenes (including alkyl-substituted polythiophenes), polystyrene, polypyrrole, polyacetylene, polyaniline, polyfluorene, polyphenylene, polypyrene, polyazulene, polynaphthalene, polycarbazole, polyindole, polyazepine, poly(3,4-ethylenedioxythiophene), poly(p-phenylsulfide), and poly(p-phenylenevinylene). Suitable non-aromatic conjugated polymers include, but are not limited to, polyacetylene and polydiacetylene. The classes of polymers listed above include substituted polymers, where the polymer backbone is substituted with one or more functional groups, such as alkyl groups. In some embodiments, the polymer is polystyrene (PS). In other embodiments, the polymer is poly(3-hexythiophene) (P3HT). In other embodiments, the polymer is poly(3,4-ethylenedioxythiophene) (PEDOT) or poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS).

[0090] In other embodiments, the polymer is a non-conjugated polymer. Suitable non-conjugated polymers include, but are not limited to, polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS), polyurethane, silicone, acrylic, and combinations (blends) thereof.

[0091] In other embodiments, the polymer is a paraffin wax. In other embodiments, the polymer is a synthetic wax, such as a Fischer-Tropsch wax or a polyethylene wax. In other embodiments, the polymer is a wax having a melting temperature above 80, 90, 100, 110, or 120° C., preferably above 130° C.

[0092] In other embodiments, the polymer is an adhesive, such as, but not limited to, a hot glue or hot melt adhesive that combines wax, adhesive, and polymer base to provide improved adhesive properties to one or more surfaces. In some embodiments, the adhesive is a pressure-sensitive adhesive. In certain other embodiments, the adhesive is a monomer that polymerizes upon contact with air or water, such as cyanoacrylate. In still other embodiments, the adhesive is a combination of a pressure-sensitive adhesive and a heat-activated (or activatable) adhesive polymer, which enhances the ease of adhesion to the surface(s) of the multi-layer or multi-stage layered structure described herein, including such combinations of coatings, by the pressure-sensitive adhesive, as well as additional and more permanent or semi-permanent adhesion by the heat-sensitive adhesive.

[0093] The CNT array or sheet can be further coated with one or more metal nanoparticles. The one or more metal nanoparticles can be adsorbed on the distal ends and / or sidewalls of the CNTs to bond them to the surface, reduce the thermal resistance between the CNT array or sheet and the surface, or a combination thereof. The metal nanoparticles can be attached to the CNT array or sheet using various methods known in the art. Examples of suitable metal nanoparticles include palladium, gold, silver, titanium, iron, nickel, copper, and combinations thereof. a1. Flowable or phase change materials

[0094] In certain embodiments, the flowable or phase change material is applied to the above-mentioned CNT array or sheet before, during, or after lamination. The flowable or phase change material may be added to the CNT array or sheet to replace the air between the CNTs and improve the contact between the distal ends and / or sidewalls of the CNTs and the surface, thereby reducing the thermal resistance of the array or sheet and the contact between the array or sheet and the surface, or a combination thereof. The flowable or phase change material can be applied to the CNT array using various methods known in the art.

[0095] Examples of suitable flowable or phase change materials generally include paraffin wax, polyethylene wax, hydrocarbon-based wax, and blends thereof. Other examples of suitable flowable or phase change materials that are not waxes or polymers include liquid metals, oils, organic-inorganic and inorganic-inorganic eutectics, and blends thereof. In some embodiments, the coating material, such as the non-polymeric coating material and the flowable or phase change material, is the same material or materials. b. Stacked CNT arrays or sheets

[0096] The above CNT arrays or sheets are laminated according to the methods described below to provide a stepped gasket that is a multi-layered or multi-tiered structure. In some examples, the stepped gasket is formed by contacting / laminating two CNT arrays or sheets of carbon nanotubes that are at least partially interdigitated and may be optionally coated with a suitable coating material as described herein. In some other examples, each layer of the stepped gasket may be formed from multiple CNT arrays or sheets that are laminated. For example, the base layer may include a multi-layered or multi-tiered structure formed from at least two CNT arrays or sheets that are laminated, a second smaller layer on the first base layer may also be a multi-layered or multi-tiered structure formed from at least two or CNT arrays or sheets, and an optional third even smaller layer on the second layer may also be a multi-layered or multi-tiered structure formed from at least two or CNT arrays or sheets. By including more CNT arrays or sheets, the thickness of each layer formed from a multi-layered or multi-tiered structure may be modified as needed. In yet another example, the layers of the stepped gasket may be formed from multiple CNT arrays or sheets stacked together, with the top layer being formed from a single CNT array or sheet forming a layer by itself. Such combination layer types are contemplated.

[0097] In some embodiments, the multi-layer or multi-tiered structure can further include a coating, a coating of metal nanoparticles, and / or a coating of flowable or phase-change material on the nanostructured elements, such as the CNTs of the array, such as coatings, metal nanoparticles, and / or flowable or phase-change material coatings as described above.

[0098] In some examples, the stepped gasket comprises at least two CNT arrays or sheets that are stacked and form a multi-layered or multi-tiered structure. By including more CNT arrays or sheets, the thickness of the multi-layered or multi-tiered stepped gasket can be increased as needed. In some embodiments, up to 3, 4, 5, 10, 15, 20, 25, 30, or more CNT arrays or sheets can be stacked according to the methods described below. For example, a stepped gasket with at least two layers can be formed by stacking two CNT arrays or sheets. A stepped gasket with at least three layers can be formed by stacking three CNT arrays or sheets. It is further understood that one CNT array or sheet acts as a first base layer. A second CNT array or sheet is stacked on the first base layer, as in FIG. 3A, and has a smaller size and surface area than the base layer. In some cases, a third CNT array or sheet can be stacked on the second layer, as in FIG. 3B, and has a smaller size and surface area than the second layer. In some cases, the overlying layer has an area between about 1%-50% of the size of the area of ​​the layer below it. For example, the second layer may have an area of ​​about 1%-75% or about 1%-50% of the area of ​​the first base layer, and the third layer, if present, may have an area size of about 1%-75% or about 1%-50% smaller than that of the second layer. The same applies to additional layers relative to the layer in which they are present.

[0099] The first base layer and the other layers made of CNT arrays or sheets can have the same shape (i.e., square, rectangular, circular, regular or irregular shapes, etc.) The first base layer of the stepped gasket may include holes cut out to accommodate fastening holes present in the plate.

[0100] In a non-limiting embodiment, at least two vertically aligned arrays or sheets formed on a support / substrate are stacked / contacted such that the nanostructured elements, such as CNTs, of the arrays are at least partially interdigitated by contact. In one embodiment, complete interdigitation of the nanostructured elements of the arrays occurs with each other when stacked. In other embodiments, the arrays may interdigitate only at the tips of the nanostructured elements, such as CNTs. In still other embodiments, individual nanostructures may progress through the nanostructures of adjacent arrays during the interdigitation process, and the nanostructured elements of the individual arrays, such as CNTs or portions thereof, are completely or substantially interdigitated with each other; as used herein, "substantially" refers to at least 95%, 96%, 97%, 98%, or 99% interdigitation between the nanostructured elements of the individual arrays. In some embodiments, the degree of interdigitation ranges from about 0.1% to 99%, or is at least about 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%.

[0101] In some embodiments, the at least partially interdigitated stacked CNT arrays or sheets nanostructures may also be formed into larger superstructures, such as, but not limited to, bundles, clamps, or rows. These superstructures may be formed through mechanisms such as capillary clamping, or by the deposition of polymer coatings before, during, or after the stacking process.

[0102] In some embodiments, the above-mentioned polymer coating and / or adhesive, or other coating, is applied to the CNT array(s) that are subsequently laminated. In such embodiments, the thickness of the above-mentioned coating and / or adhesive, or other coating, is about 1-1000 nm, more preferably 1-500 nm, and most preferably 1-100 nm.

[0103] In addition to the above, the favorable deformation dynamics of CNTs present in multi- or multi-layered structures allows them to efficiently accommodate the irregularities of adjacent surfaces, resulting in high contact areas at the interfaces. b1. Reduction of thermal resistance

[0104] Stepped gaskets formed by lamination of the CNT arrays or sheets described herein exhibit reduced interfacial thermal resistance, which can be measured using a variety of techniques known in the art, such as the protected hot plate method.

[0105] In one embodiment, the thermal resistance of a multi-layer or multi-tiered structure formed by stacking such CNT arrays or sheets is reduced by at least about 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or more compared to a single tiered structure, as measured, for example, using a bolted joint equipped with thermocouples on the hot and cold sides of the joint. In certain embodiments, the CNT arrays or sheets, and multi-layer or multi-tiered structures formed by stacking such CNT arrays or sheets, have a thermal resistance of about 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1 cm. 2 In such embodiments, the thermal resistance is about 0.4, preferably about 0.3 cm 2These thermal resistances are measured locally using methods such as those described in ASTM D-5470. The actual composite thermal resistance of the thermal interface or portions thereof will depend on the actual part geometry and materials and may not fall within this range. In certain embodiments, CNT arrays or sheets, and multi- or multi-tiered structures formed by stacking such CNT arrays or sheets, have a thermal resistance of about 2.0 to 0.1 cm 2 In such embodiments, the thermal resistance is between about 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1 cm 2 In some embodiments, the thermal resistance value of a multi-layer or multi-tiered structure formed by stacking CNT arrays or sheets is the same or does not change substantially compared to the value(s) of the single layer array used to form the stack; as used herein, "substantially" refers to less than 10%, 5%, 4%, 3%, 2%, or 1% change.

[0106] In one example, the apparent thermal conductivity of a multi-layer or multi-level layered structure formed by stacking CNT arrays or sheets to form a stepped gasket is increased by at least about 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or more compared to a single level layered structure. In some embodiments, the multi-layer or multi-tiered gasket structure exhibits a conductivity value in the range of about 1-2500 W / m·K, 1-2000 W / m·K, 1-1500 W / m·K, 1-1000 W / m·K, 1-500 W / m·K, 5-500 W / m·K, 5-400 W / m·K, 5-300 W / m·K, 5-200 W / m·K, 5-150 W / m·K, 5-100 W / m·K, or 3-30 W / m·K.

[0107] In some cases, coatings may be applied to CNT arrays or sheets before, during, or after lamination as required to form multi-layer or multi-tiered structures formed by stacking such CNT arrays or sheets. Coating(s) have been shown to be an effective means of increasing the contact area and reducing the thermal resistance of the CNT forest thermal interface. The bonding process added by including nanoscale coatings around individual CNT contacts includes, for example, drawing additional CNTs near the interface through capillary action to increase the contact area.

[0108] In some examples, the multi-layer or multi-stage layered structures can exhibit excellent elastic recovery properties after one or more repeated deformations, typically compression, at various pressures up to about 30, 50, 100, 200, 300, 400, 500 psi or more. The elastic recovery of the multi-layer or multi-stage layered structures, expressed as a percentage value after one or more compressions, can be greater than about 50%, 60%, 70%, 80%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%. In some examples, the described multi-layer or multi-stage layered structures also exhibit compression set properties after one or more repeated deformations, typically compression, at various pressures up to about 30, 50, 100, 200, 300, 400, 500 psi or more. The compression set of the multi-layer or multi-stage layered structure, expressed as a percentage value after one or more compressions, can be less than about 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%. ii. Shim

[0109] The thermal interfaces and joints described above may also include one or more shims thereon, as shown in Figures 5A, 5B, 6A, and 6B. The shim may be placed on top of the stepped gasket, as shown in Figure 5A. Alternatively, the shim may be placed so that it does not contact the stepped gasket, as shown in Figure 5B.

[0110] The shim or shims can be placed or positioned around, near, and / or behind one or more fasteners or fastener holes present in the plate, as shown in Figures 6A and 6B. In some examples, the shim or shims have a height selected to be equal to the height of the first layer of the stepped gasket. In some examples, the shim or shims are positioned as far back as possible from the fastener holes and fasteners, such as at the very edge of the plate.

[0111] The shims can have any suitable shape. In some examples, one or more shims preferably have an annulus or semi-annulus shape, which may be circular, square, or rectangular. Such semi-annulus shaped shims can be 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annulus shaped shims. Additionally or alternatively, shims having a square or rectangular shape can be used that are disposed or positioned around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plates, as shown in FIG. 6B.

[0112] In some examples, the shim is made of a metal foil, preferably aluminum or copper foil, hi some other examples, the shim is made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic.

[0113] In yet another example, the shim: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The present invention is made of a multi-layer or multi-stage layered structure comprising: At least a first layer or step and at least a second layer or step are stacked such that the vertically aligned carbon nanotubes of the at least a first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least a second layer or step that interface with each other. Such multi-layer or multi-step layered structures, and methods for making them, are as described above and in Section VI below.

[0114] The one or more shims can independently have any suitable range. In some examples, the shims have a thickness ranging between about 25 μm and about 500 μm. In some examples, the shims each independently exhibit an elastic modulus ranging between about 5 MPa and about 130 GPa. III. Thermal Interfaces or Joints Including Shims

[0115] As described, a thermal interface or joint formed of at least two plates fastened by nuts and bolts or the like and having a compressible material, such as a gasket, between the plates has at least one plate that undergoes undesirable plate deformation, warping, or bending that can cause the formation of a gap(s) that reduces and / or limits the contact area between the plate and the gasket, thereby adversely affecting the ability of the thermal interface to efficiently conduct heat.

[0116] In some cases, it is possible to offset the effects of plate deformation, warping, or bowing by including one or more shims in the thermal interface or joint with a single layer gasket inside.

[0117] To address challenges arising from plate deformation, warping, or curvature, thermal interfaces or joints: First and second plates; a single layer gasket between the first and second plates; and One or more fasteners joining the first and second plates. may include at least one of the first and / or second plates exhibits plate deformation, warping, or curvature; The one or more shims are present around, near, and / or behind the one or more fasteners to reduce and / or mitigate deformation, warping, or bowing of the first and / or second plates.

[0118] A thermal interface or joint includes two plates, a base plate (bottom plate) and a top plate, one or both of which typically exhibit deformation, warping, or curvature when the two plates are fastened (i.e., bolted). At least one of the plates is planar or substantially planar ("substantially planar" means less than 0.25 μm deviation from flatness per mm of plate length). The top and bottom plates as shown in FIG. 2 can be made of any suitable material with any suitable shape and dimensions and thickness to be used as a thermal interface. The two plates are usually made of the same material and have the same shape and dimensions, and optionally the same thickness. In some cases, the first (bottom or base) and second (top) plates have a square, rectangular, circular, elliptical, or ring shape. Typically, a single layer gasket has the same overall shape as the first and second plates, at least with respect to the first base layer. In some examples, plates having a thickness of about >4 mm can be considered highly robust plates, whereas plates having a thickness of about <4 mm can be considered moderately or less robust plates. In some examples, the plates independently have a thickness in the range of about 0.5 to about 30 mm, about 0.5 to about 20 mm, or about 0.5 to about 10 mm, and subranges therein. In one particular example, both plates are 1 / 4 inch thick plates.

[0119] In some examples, the first (bottom or base) and second (top) plates can be independently made of a material selected from aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates). In some examples, the first (bottom or base) and second (top) plates can be independently made of a plastic selected from acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate materials (such as FR4), high pressure fiberglass laminates (such as G10), fiberglass composites, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide. In yet another example, the first (bottom or base) and second (top) plates can be independently made of a ceramic selected from alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those comprised of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

[0120] The top and bottom plates of the thermal interface or joint are fastened by one or more fasteners, which join the first and second plates through one or more holes present in the top and bottom plates. There may be any number of one or more fastener holes in both plates at the same location on each plate as may be required for fasteners to join the two plates. In some examples, there are at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32 fastener holes in each plate. The fastener holes present may have any shape or size as needed. In some examples, the fastener holes are circular and may have a diameter suitable for a fastener such as a bolt. In some examples, the fastener holes may be threaded to receive a threaded fastener. The fastener holes may be spaced in any suitable relative arrangement. However, in certain instances, it is preferred that the fastener holes are on one or more edges of the plate. Typically, the fastener holes are evenly spaced on the plate. Non-limiting examples of fastener holes on a plate and their relative positions to one another are shown in FIG. 4. In some instances, the spacing between fastener holes can be between two holes that are immediately next to one another, and the distance can range from about 5 to 600 mm. In some instances, the spacing between fastener holes can be between two holes on opposing edges of the plate, and the distance can range from about 5 to 600 mm. In yet other instances, the spacing between fastener holes can be between two holes that are positioned diagonally to one another on the plate, and the distance can range from about 5 to 600 mm.

[0121] One or more fasteners can be used to fasten the first (base or bottom) plate and the second (top) plate through each of the possible fastener holes. The one or more fasteners can be selected from threaded fasteners, clamps, clips, push pins, rivets, air presses, hydraulic presses, or combinations thereof. Such fasteners are known in the art. The threaded fasteners can be bolts and nuts, such as those known in the art. In some other examples, the threaded fasteners are bolts and potted inserts, such as those known in the art. In some examples, the one or more shims can reduce stress(es) on the potted insert during assembly, such as when one of the plates of the thermal interface is curved or distorted prior to fastening: the reduction in stress(es) on the potted insert is at least about 10, 20, 30, 40, 50, 60, 70, 80, or 90% compared to a thermal interface that is equivalent except for the presence of the one or more shims. The fastener or fasteners of any type used can be made of any suitable material, such as a material selected from steel, titanium, aluminum, nylon, brass, bronze, and zinc. If the fasteners include bolts, the bolts may be applied using an appropriate amount of bolt torque, and the bolts may be tightened in any suitable tightening pattern to ensure uniform fastening between the two plates. Selection of appropriate bolts (and nuts), bolting torques, and bolting patterns is known in the art.

[0122] In some examples, the single layer gasket is made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic. In some examples, the material that constitutes the single layer gasket can further include thermally conductive and / or electrically conductive fillers known in the art. The single layer gasket can have any suitable thickness. In some examples, the thickness ranges between about 50 μm and about 500 μm.

[0123] The single layer gasket can have a modulus of elasticity ranging between about 0.1 MPa and about 50 MPa, about 0.1 MPa and about 100 MPa, about 0.1 MPa and about 150 MPa, or about 0.1 MPa and about 200 MPa. In some examples, each of the layers of the stepped gasket, if present, can each independently have a modulus of elasticity of between about 0.05 cm 2 ·℃ / W~approx. 1cm 2 ·℃ / W, 0.05cm 2 ·℃ / W~approx.5cm 2 ·℃ / W, 0.05cm 2 ·℃ / W ~ approx. 2cm 2 ·℃ / W, 0.05cm 2 ·℃ / W ~ approx. 3cm 2 ·℃ / W, 0.05cm 2 ·℃ / W ~ approx. 4cm 2 °C / W or 0.05cm 2 ·℃ / W~approx.5cm 2 ·°C / W.

[0124] In some cases, the single layer gasket can include an adhesive (i.e., a pressure sensitive adhesive or a heat sensitive adhesive), preferably on the side that contacts the bottom (base) plate, for adhering to the bottom (base) plate.

[0125] The use of one or more shims around, near, and / or behind one or more fasteners can reduce and / or mitigate deformation, warping, or bending of the first and / or second plates. The shims provide an increased contact area between the monolayer gasket and at least one of the first and / or second plates that exhibit plate deformation, warping, or bending. For example, FIGS. 5A and 5B show that the presence of a shim induces an increased contact area between the monolayer gasket and the top plate that exhibits bending. In some examples, the increased contact area provides an average thermal conductivity across the thermal interface that is at least 25%, 30%, 40%, or 50% higher than that of the same thermal interface without the shim present. Thermal conductivity is defined as the time rate of steady-state heat flow through a unit area of ​​a thermal interface or joint induced by a unit temperature difference between the surfaces of the thermal interface. In some other examples, the shims can also provide an increased uniformity of temperature of the first and / or second plates of the thermal interface or joint.

[0126] The shim may be placed on top of the monolayer gasket. Alternatively, the shim may be placed in such a manner that it does not contact the monolayer gasket. The shim or shims may be placed or positioned around, near, and / or behind one or more fasteners or fastener holes present in the plate(s). In some examples, the shim or shims have a height selected to be equal to the height of the monolayer gasket. In some examples, the shim or shims are positioned as far back as possible from the fastener holes and fasteners, such as at the very edge of the plate.

[0127] The shims can have any suitable shape. In some examples, one or more shims preferably have an annulus or semi-annulus shape and may be circular, square, or rectangular. Such semi-annulus shaped shims can be 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annulus shaped shims. Additionally or alternatively, shims having a square or rectangular shape can be used that are positioned or positioned around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plates, as shown in FIG. 6B.

[0128] In some examples, the shim is made of a metal foil, preferably aluminum or copper foil, hi some other examples, the shim is made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic.

[0129] In yet another example, the shim: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The present invention is made of a multi-layer or multi-stage layered structure comprising: At least a first layer or step and at least a second layer or step are stacked such that the vertically aligned carbon nanotubes of the at least a first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least a second layer or step that interface with each other. Such multi-layer or multi-step layered structures, and methods for making them, are as described above and in Section VI below.

[0130] The one or more shims can independently have any suitable range. In some examples, the shims have a thickness ranging between about 25 μm and about 500 μm. In some examples, the shims each independently exhibit an elastic modulus ranging between about 5 MPa and about 130 GPa. IV. Methods for Preparing a Thermal Interface or Joint Having a Stepped Gasket

[0131] Thermal interfaces or joints with an internal stepped gasket: (1) providing a first and a second plate; (2) preparing a stepped gasket; (3) placing a stepped gasket between the first and second plates; (4) joining the first and second plates with one or more fasteners; 1. A method comprising: at least one of the first and / or second plates exhibits deformation, warping, or bowing of the plate when joined by the one or more fasteners; The stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area less than the surface area of ​​the first base layer; at least a second layer of the stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates that exhibit plate deformation, warping, or bowing when compared to a non-stepped single layer gasket; It can be prepared according to the method.

[0132] Typically, one or more fasteners join the first and second plates through one or more fastener holes present in the first and second plates.

[0133] In some examples of the method, the two plates are typically made of the same material and have the same shape and dimensions, and optionally the same thickness. In some examples, the first (bottom or base) and second (top) plates have a square, rectangular, circular, oval, or ring shape. Typically, the stepped gasket has the same overall shape as the first and second plates, at least with respect to the first base layer. In some examples, a plate having a thickness of about >4 mm can be considered a highly robust plate, whereas a plate having a thickness of about <4 mm can be considered a moderately or lowly robust plate. In some examples, the plates independently have a thickness in the range of about 0.5 to about 30 mm, about 0.5 to about 20 mm, or about 0.5 to about 10 mm, and subranges therein. In one particular example, both plates are 1 / 4 inch thick plates.

[0134] In some examples, the first (bottom or base) and second (top) plates can be independently made of a material selected from aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates). In some examples, the first (bottom or base) and second (top) plates can be independently made of a plastic selected from acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate materials (such as FR4), high pressure fiberglass laminates (such as G10), fiberglass composites, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide. In yet another example, the first (bottom or base) and second (top) plates can be independently made of a ceramic selected from alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those comprised of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

[0135] The top and bottom plates of the thermal interface or joint are fastened by one or more fasteners, which join the first and second plates through one or more holes present in the top and bottom plates. There may be any number of one or more fastener holes on both plates at the same location on each plate as may be required to join the two plates with fasteners. In some examples, there are at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32 fastener holes on each plate. The fastener holes present may have any shape or size as needed. In some examples, the fastener holes may be circular and have a diameter suitable for a fastener such as a bolt. In some examples, the fastener holes may be threaded to receive a threaded fastener. The fastener holes may be spaced in any suitable relative arrangement. However, in certain instances, it is preferred that the fastener holes are present on one or more edges of the plate. Typically, the fastener holes are evenly spaced on the plate. In some instances, the spacing between the fastener holes may be between two holes that are immediately next to each other, and the distance may range from about 5 to 600 mm. In some instances, the spacing between the fastener holes may be between two holes that are on opposing edges of the plate, and the distance may range from about 5 to 600 mm. In yet other instances, the spacing between the fastener holes may be between two holes that are positioned diagonally to each other on the plate, and the distance may range from about 5 to 600 mm.

[0136] One or more fasteners can be used to fasten the first (base or bottom) plate and the second (top) plate through each of the possible fastener holes. The one or more fasteners can be selected from threaded fasteners, clamps, clips, push pins, rivets, air presses, hydraulic presses, or combinations thereof. Such fasteners are known in the art. The threaded fasteners can be bolts and nuts, such as those known in the art. In some other examples, the threaded fasteners are bolts and pot inserts, such as those known in the art. The one or more fasteners of any type used can be made of any suitable material, such as a material selected from steel, titanium, aluminum, nylon, brass, bronze, and zinc. If the fasteners include bolts, the bolts may be applied using an appropriate amount of bolt torque, and the bolts may be tightened in any suitable tightening pattern to ensure uniform fastening between the two plates. Selection of appropriate bolts (and nuts), bolting torques, and bolting patterns is known in the art.

[0137] The stepped gasket used in the above-mentioned method includes a first base layer and at least a second layer thereon. Additional layers, such as a third, fourth, or fifth layer, may be included. The first base layer and the other layers may have any suitable shape or thickness as needed. More typically, the first base layer and the other layers have the same shape (i.e., square, rectangular, circular, regular or irregular shape, etc.). In some examples, the stepped gasket has a first base layer with dimensions that cover the entire area of ​​the plate between which it is placed. In some other examples, the stepped gasket has a first base layer with dimensions that are smaller than the entire area of ​​the plate between which it is placed, such as covering at least about 50%, 60%, 70%, 80%, 90% of the area of ​​the plate. The first base layer of the stepped gasket may include holes cut out to accommodate fastening holes present in the plate. Each subsequent layer is smaller in size (area) than the layer below it. In some cases, the overlying layer has an area between about 1% and 50% of the size of the area of ​​the layer below it. For example, the second layer may have an area between about 1% and 75% or about 1% and 50% of the area of ​​the first base layer, and the third layer, if present, may be about 1% and 75% or about 1% and 50% smaller in area size than the second layer. The same applies to additional layers relative to the layer in which they are present. In some cases, each of the layers of the stepped gasket, if present, can each independently have a thickness ranging between about 50 μm and about 500 μm. Furthermore, in some cases, the height increase between the layers of the stepped gasket is selected to be less than about 500 μm, less than about 250 μm, less than about 150 μm, or less than about 75 μm. In some cases, the height increase between layers of a stepped gasket can be determined based on theoretical deflection from the contact surface under fastener load, as predicted by using Euler-Bernoulli beam theory, Timoshenko beam theory, or Kirchhoff-Love plate theory, while considering the gasket layers as compressible and elastic foundations.

[0138] In some examples of the method, each of the multiple layers of the stepped gasket can be independently made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic. Typically, each stepped gasket having at least two layers is made of layers made of the same material, where appropriate the number of layers and their respective thicknesses may vary. In some examples, layers of different material types can be used. Additionally, in some examples, the material making up each layer of the stepped gasket can further include thermally conductive and / or electrically conductive fillers as known in the art.

[0139] In still other cases, the first base layer may include an adhesive (ie, a pressure sensitive adhesive or a heat sensitive adhesive), preferably on the side that does not have any additional layers thereon.

[0140] In some cases, the stepped gasket can be made of a multi-layer or multi-tiered structure comprising carbon nanotube arrays or sheets. For example, the stepped gasket can be made of: at least a first layer or tier comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The structure may be a multi-layer or multi-stage layered structure comprising: At least a first layer or step and at least a second layer or step are stacked such that the vertically aligned carbon nanotubes of the at least a first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least a second layer or step that interface with each other. Such stepped gaskets made of multi-layer or multi-step layered structures and methods for making them are as described above and in Sections II and VI.

[0141] In some examples, the method further includes placing one or more shims between the first and second plates prior to step (4). In some cases, the shims are placed during, before, or after step (3). The one or more shims can be placed or positioned around, near, and / or behind one or more fasteners or fastener holes present in the plates.

[0142] The shims can have any suitable shape. In some examples, the shim or shims preferably have an annulus or semi-annulus shape, which may be circular, square, or rectangular. Such semi-annulus shaped shims can be 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annulus shaped shims. Additionally or alternatively, shims having a square or rectangular shape can be used that are positioned or positioned around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plate. In some examples, the shim or shims have a height selected to be equal to the height of the first layer of the stepped gasket. In some examples, the shim or shims are positioned as far back as possible from the fastener holes and fasteners, such as at the very edge of the plate.

[0143] In some examples of the method, the shim is made of a metal foil, preferably aluminum foil or copper foil, hi some other examples, the shim is made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic.

[0144] In yet another example, the shim: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The present invention is made of a multi-layer or multi-stage layered structure comprising: At least a first layer or step and at least a second layer or step are stacked such that the vertically aligned carbon nanotubes of the at least a first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least a second layer or step that interface with each other. Such multi-layer or multi-step layered structures, and methods for making them, are as described above and in Section VI below.

[0145] The one or more shims can independently have any suitable range. In some examples, the shims have a thickness ranging between about 25 μm and about 500 μm. In some examples, the shims each independently exhibit an elastic modulus ranging between about 5 MPa and about 130 GPa. V. Methods for Preparing a Thermal Interface or Joint with a Shim

[0146] Thermal interfaces or joints with internal shims: (1) providing a first and a second plate; (2) providing a single layer gasket; (3) disposing a single layer gasket between the first and second plates; (4) disposing one or more shims between the first and second plates; (5) joining the first and second plates with one or more fasteners. 1. A method comprising: at least one of the first and / or second plates exhibits deformation, warping, or bowing of the plate when joined by the one or more fasteners; one or more shims are present around, near, and / or behind one or more fasteners to reduce and / or mitigate deformation, warping, or curvature of the first and / or second plates; It can be prepared according to the method.

[0147] In some cases, steps (3) and (4) may be combined into a single step.

[0148] For the described method, the two plates are typically made of the same material and have the same shape and dimensions, and optionally the same thickness. In some examples, the first (bottom or base) and second (top) plates have a square, rectangular, circular, oval, or ring shape. Typically, the single layer gasket has the same overall shape as the first and second plates, at least with respect to the first base layer. In some examples, a plate having a thickness of about >4 mm can be considered a highly robust plate, whereas a plate having a thickness of about <4 mm can be considered a moderately or lowly robust plate. In some examples, the plates independently have a thickness in the range of about 0.5 to about 30 mm, about 0.5 to about 20 mm, or about 0.5 to about 10 mm, and subranges within those ranges. In one particular example, both plates are ¼ inch thick plates.

[0149] In some examples, the first (bottom or base) and second (top) plates can be independently made of a material selected from aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates). In some examples, the first (bottom or base) and second (top) plates can be independently made of a plastic selected from acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate materials (such as FR4), high pressure fiberglass laminates (such as G10), fiberglass composites, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide. In yet another example, the first (bottom or base) and second (top) plates can be independently made of a ceramic selected from alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those comprised of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

[0150] The top and bottom plates of the thermal interface or joint are fastened by one or more fasteners that join the first and second plates through one or more holes present in the top and bottom plates. There may be any number of one or more fastener holes on both plates at the same location on each plate as may be required for fasteners to join the two plates. In some examples, there are at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, or 32 fastener holes in each plate. The fastener holes present may have any shape or size as needed. In some examples, the fastener holes are circular and may have a diameter suitable for a fastener such as a bolt. In some examples, the fastener holes may be threaded to receive a threaded fastener. The fastener holes may be spaced in any suitable relative arrangement. However, in certain instances, it is preferred that the fastener holes are on one or more edges of the plate. Typically, the fastener holes are evenly spaced on the plate. Non-limiting examples of fastener holes on a plate and their relative positions to one another are shown in FIG. 4. In some instances, the spacing between fastener holes may be between two holes that are immediately next to one another, and the distance may range from about 5 to 600 mm. In some instances, the spacing between fastener holes may be between two holes on opposing edges of the plate, and the distance may range from about 5 to 600 mm. In yet other instances, the spacing between fastener holes may be between two holes that are positioned diagonally to one another on the plate, and the distance may range from about 5 to 600 mm.

[0151] One or more fasteners can be used to fasten the first (base or bottom) plate and the second (top) plate through each of the possible fastener holes. The one or more fasteners can be selected from threaded fasteners, clamps, clips, push pins, rivets, air presses, hydraulic presses, or combinations thereof. Such fasteners are known in the art. The threaded fasteners can be bolts and nuts, such as those known in the art. In some other examples, the threaded fasteners are bolts and pot inserts, such as those known in the art. Any type of fastener or fasteners used can be made of any suitable material, such as a material selected from steel, titanium, aluminum, nylon, brass, bronze, and zinc. In the case where the fasteners include bolts, the bolts may be applied using an appropriate amount of bolt torque, and the bolts may be tightened in any suitable tightening pattern to ensure uniform fastening between the two plates. Selection of appropriate bolts (and nuts), bolting torques, and bolting patterns is known in the art.

[0152] In some examples of the method, the single layer gasket is made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic. In some further examples, the material that constitutes the single layer gasket can further include thermally conductive and / or electrically conductive fillers known in the art. The single layer gasket can have any suitable thickness. In some examples, the thickness ranges between about 50 μm and about 500 μm.

[0153] In some cases, the single layer gasket may include an adhesive (i.e., a pressure sensitive adhesive or a heat sensitive adhesive), preferably on the side that contacts the bottom (base) plate, for adhering to the bottom (base) plate.

[0154] The use of one or more shims around, near, and / or behind one or more fasteners can reduce and / or mitigate deformation, warping, or bending of the first and / or second plates. The shims provide an increased contact area between the monolayer gasket and at least one of the first and / or second plates that exhibits plate deformation, warping, or bending. For example, Figures 5A and 5B show that the presence of a shim induces an increased contact area between the monolayer gasket and the top plate that exhibits bending.

[0155] The shim may be placed on top of the monolayer gasket. Alternatively, the shim may be placed in such a manner that it does not contact the monolayer gasket. The shim or shims may also be placed or positioned around, near, and / or behind one or more fasteners or fastener holes present in the plate. In some examples, the shim or shims have a height selected to be equal to the height of the monolayer gasket. In some examples, the shim or shims are positioned as far back as possible from the fastener holes and fasteners, such as at the very edge of the plate.

[0156] The shims can have any suitable shape. In some examples, one or more shims preferably have an annulus or semi-annulus shape, which may be circular, square, or rectangular. Such semi-annulus shaped shims can be 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annulus shaped shims. Additionally or alternatively, shims having a square or rectangular shape can be used that are positioned or positioned around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plates, as shown in FIG. 6B.

[0157] In some examples, the shim is made of a metal foil, preferably aluminum or copper foil, hi some other examples, the shim is made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic.

[0158] In yet another example, the shim: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The present invention is made of a multi-layer or multi-stage layered structure comprising: At least a first layer or step and at least a second layer or step are stacked such that the vertically aligned carbon nanotubes of the at least a first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least a second layer or step that interface with each other. Such multi-layer or multi-step layered structures, and methods for their fabrication, are as described in Sections II and VI below. VI. Methods for preparing multi-layer or multi-layered structures

[0159] Multi-layer or multi-tiered structures made of stacked carbon nanotube arrays or sheets as discussed above can be prepared as follows. These multi-layer or multi-tiered structures can be used as stepped gaskets or can form one or more layers of stepped gaskets as well as shims as described elsewhere. A. Carbon Nanotube Arrays

[0160] Carbon nanotube arrays can be prepared using techniques well known in the art. In one embodiment, the arrays are prepared as described in US Publication No. 2014-0015158-A1, which is incorporated herein by reference. This method includes the use of a multi-layer substrate to promote the growth of dense, vertically aligned CNT arrays and provide excellent adhesion between the CNTs and the metal surface.

[0161] The multi-layer substrate comprises three or more layers deposited on an inert support, such as a metal surface. Generally, the multi-layer substrate comprises an adhesion layer, an interface layer, and a catalyst layer deposited on the surface of the inert support. Generally, the support is at least partially formed of a metal, such as aluminum, platinum, gold, nickel, iron, tin, lead, silver, titanium, indium, copper, or a combination thereof. In a particular example, the support is a metal foil, such as an aluminum foil or a copper foil. The support may also be a surface of a device, such as a conventional heat sink or heat spreader used in heat exchange applications.

[0162] The adhesion layer is formed of a material that improves the adhesion of the interface layer to the support. In a particular embodiment, the adhesion layer is a thin film of iron. In general, the adhesion layer must be thick enough to remain a continuous film at the high temperatures used to form CNTs. The adhesion layer also generally provides resistance to the formation of oxides and carbides during CNT synthesis at high temperatures.

[0163] The interfacial layer is preferably formed from a metal that is oxidized under the conditions of nanotube synthesis or during exposure to air after nanotube synthesis to form a suitable metal oxide. Examples of suitable materials include aluminum. Alternatively, the interfacial layer may be formed from a metal oxide, such as aluminum oxide or silicon oxide. Generally, the interfacial layer is thin enough to allow the catalyst layer and adhesion layer to diffuse through the interfacial layer. In some embodiments where the catalyst layer and adhesion layer have the same composition, this reduces migration of the catalyst into the interfacial layer and improves catalyst lifetime during nanotube growth.

[0164] The catalyst layer is typically a thin film formed from a transition metal capable of catalyzing the formation of carbon nanotubes via chemical vapor deposition. Examples of suitable materials that can be used to form the catalyst layer include iron, nickel, cobalt, rhodium, palladium, and combinations thereof. In some embodiments, the catalyst layer is formed from iron. The catalyst layer is of a thickness suitable to form catalytic nanoparticles or aggregates under the annealing conditions used during nanotube formation.

[0165] In other embodiments, the multilayer substrate serves as a catalytic surface for the growth of the CNT array. In these examples, the process of CNT growth using chemical vapor deposition changes the morphology of the multilayer substrate. Specifically, upon heating, the interfacial layer is converted to metal oxide, forming a layer or partial layer of metal oxide nanoparticles or aggregates that are deposited on the adhesion layer. The catalyst layer in turn forms a series of catalyst nanoparticles or aggregates that are deposited on the metal oxide nanoparticles or aggregates. During CNT growth, the CNTs arise from the catalyst nanoparticles or aggregates. The resulting CNT array comprises CNTs anchored to the inert support via the adhesion layer, the metal oxide nanoparticles or aggregates, and / or the catalyst nanoparticles or aggregates.

[0166] In a particular embodiment, the multilayer substrate is formed from an iron adhesion layer about 30 nm thick, an aluminum or alumina interfacial layer about 10 nm thick, and an iron catalyst layer about 3 nm thick, deposited on a metal surface. In this embodiment, the iron adhesion layer adheres to both the metal surface and the Al (alumina nanoparticles or aggregates after growth) or Al2O3 interfacial layer. The iron catalyst layer forms iron nanoparticles or aggregates from which the CNTs grow. These iron nanoparticles or aggregates are also bonded to the underlying alumina.

[0167] As a result, a well-bonded interface exists on both sides of the oxide interface material. Of the metal / metal oxide interfaces, the iron-alumina interface is known to be one of the strongest in terms of bonding and chemical interactions. Furthermore, metals (e.g., iron adhesion layers and metal surfaces) tend to bond well to each other due to strong electronic coupling. As a result, CNTs are strongly anchored to the metal surface.

[0168] Additionally, subsurface diffusion of iron from the catalyst layer during nanotube growth is reduced because the same metal is on both sides of the oxide support, which balances the concentration gradient that would normally drive diffusion. Thus, the catalyst is not depleted during growth, improving the growth rate, density, and yield of nanotubes in the array.

[0169] In some embodiments, the CNT array is formed by vertically aligning a plurality of CNTs on the multi-layer substrate described above. This can be achieved, for example, by transferring an array of CNTs to the distal end of a CNT grown on the multi-layer substrate. In some embodiments, a tall CNT array is transferred to the distal end of a very short CNT on the multi-layer substrate. This technique improves the bonding strength by increasing the surface area for bonding.

[0170] The inert support for the CNT array or sheet can be a piece of metal foil, such as aluminum foil. In these cases, the CNTs are attached to the surface of the metal foil via an adhesive layer, metal oxide nanoparticles or aggregates, and catalytic nanoparticles or aggregates. In some cases, only one surface (i.e., side) of the metal foil comprises an array or sheet of aligned CNTs attached to the surface. In other cases, both surfaces (i.e., sides) of the metal foil comprise an array or sheet of aligned CNTs attached to the surface. In other embodiments, the inert support for the CNT array or sheet is the surface of a conventional metal heat sink or heat spreader. In these cases, the CNTs are attached to the surface of the heat sink or heat spreader via an adhesive layer, metal oxide nanoparticles or aggregates, and catalytic nanoparticles or aggregates. This functionalized heat sink or heat spreader may then be adjacent to or attached to a heat source, such as an integrated circuit package. B. Carbon nanotube sheet

[0171] Carbon nanotube sheets can be prepared using techniques well known in the art. In one embodiment, the sheets are prepared as described in U.S. Pat. No. 7,993,620. In this embodiment, CNT agglomerates are collected into sheets on a metal foil substrate in-situ in a growth chamber. The sheets can then be densified by removing the solvent. In another embodiment, the CNT sheets are made by vacuum filtration of CNT agglomerates dispersed in a solvent. C. Coated Nanotube Arrays and Sheets 1. Polymer coating

[0172] The polymer to be coated can be dissolved in one or more solvents and sprayed or dip coated or chemically or electrochemically deposited on the vertical CNT forest or array or sheet grown on the substrate as described above. The coating material can also be spray coated in powder form on top of the vertical CNT forest or array grown on the substrate or on the CNT sheet as described above. The coating comprises a polymer or molecule that binds to the CNTs by van der Waals bonds, π-π stacking, mechanical wrapping, and / or covalent bonds, and that binds to the metal, metal oxide, or semiconductor material surface by van der Waals bonds, π-π stacking, and / or covalent bonds.

[0173] For spray or dip coating, the coating solution can be prepared by sonicating or stirring the coating material in a suitable solvent for a suitable length of time. The solvent is typically an organic solvent or solvents, and should be one that is easily removed, for example, by evaporation at room temperature or at elevated temperatures. Suitable solvents include, but are not limited to, chloroform, xylene, hexane, pyridine, tetrahydrofuran, ethyl acetate, and combinations thereof. The polymer can also be spray coated in dry form using powders with micron-scale particle sizes, i.e., particles with diameters of less than about 100, 50, 40, 20, 10 micrometers. In this embodiment, the polymer powder may need to be immersed in a solvent or heated to a liquid melt to further spread the powder particles into a continuous coating after being spray deposited.

[0174] The coating thickness is generally between 1 and 1000 nm, preferably between 1 and 500 nm, more preferably between 1 and 100 nm, and most preferably between 1 and 50 nm. In some embodiments, the coating thickness is less than 500, 450, 400, 350, 300, 250, 200, 150, 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10 nm.

[0175] The spray coating process limits the deposition of the coating on the CNT tips and limits clumping due to capillary forces associated with drying of the solvent. The amount of coating found on the CNT array increases with the number of sprays. Alternative techniques, including techniques more suitable for coating on a commercial scale, can be used to spray coat the coating material onto the CNT array.

[0176] In another embodiment demonstrating the coating process, CNT sheets are immersed in a coating solution or molten coating to coat the CNTs throughout the thickness of the sheet and increase the thermal conductivity of the sheet by more than 20, 30, 50, or 70% in the transplanar direction. These coated sheets are then placed between a chip and a heat sink or heat spreader by application of a solvent or heat to reflow the polymer and bond the CNT sheet between the chip and the heat sink or spreader, reducing the thermal resistance between the chip and the heat sink or spreader.

[0177] In other embodiments, the coating material can be deposited on the CNT array or sheet using deposition techniques known in the art, such as chemical deposition (e.g., chemical vapor deposition (CVD)), aerosol spray deposition, and electrochemical deposition.

[0178] In one embodiment, the polymer coating can be applied by electrochemical deposition. In electrochemical deposition, a monomer of the polymer is dissolved in an electrolyte and the CNT array or sheet is used as a working electrode opposite a counter electrode. A potential is applied between the working and counter electrodes relative to a third reference electrode. The monomer is electrooxidized at the tip of the CNT array or the sheet sidewall facing the electrolyte as a result of the applied potential. The thickness of the deposited polymer layer is controlled by controlling the total time the potential is applied.

[0179] In some embodiments, the coating material is or contains one or more oligomeric and / or polymeric materials. In certain embodiments, the polymer can be a conjugated polymer, including aromatic and non-aromatic conjugated polymers. Suitable classes of conjugated polymers include polyaromatic and polyheteroaromatic, including but not limited to polythiophenes (including alkyl-substituted polythiophenes), polystyrene, polypyrrole, polyacetylene, polyaniline, polyfluorene, polyphenylene, polypyrene, polyazulene, polynaphthalene, polycarbazole, polyindole, polyacepine, poly(3,4-ethylenedioxythiophene), poly(p-phenylsulfide), and poly(p-phenylenevinylene). Suitable non-aromatic polymers include, but are not limited to, polyacetylene and polydiacetylene. The classes of polymers listed above include substituted polymers, in which the polymer backbone is substituted with one or more functional groups, such as alkyl groups. In some embodiments, the polymer is polystyrene (PS). In other embodiments, the polymer is poly(3-hexythiophene) (P3HT).

[0180] In other embodiments, the polymer is a non-conjugated polymer. Suitable non-conjugated polymers include, but are not limited to, polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polysiloxane, polyurethane, polydimethylsiloxane (PDMS), and combinations (blends) thereof.

[0181] In other embodiments, the polymer is a paraffin wax. In other embodiments, the polymer is a synthetic wax, such as Fischer-Tropsch wax or polyethylene wax. In other embodiments, the polymer is a wax having a melting temperature above 80, 90, 100, 110, and 120° C., preferably above 130° C.

[0182] In some other embodiments, the polymer is an adhesive, such as, but not limited to, a hot glue or hot melt adhesive that combines wax, adhesive, and polymer base to provide improved surface adhesion. In some embodiments, the adhesive is a pressure-sensitive adhesive. In certain other embodiments, the adhesive is a monomer that polymerizes upon contact with air or water, such as cyanoacrylate. In still other embodiments, the adhesive is a combination of a pressure-sensitive adhesive polymer and a heat-activated (or activatable) adhesive polymer, which enhances the ease of adhesion to the surface(s) of the multi-layer or multi-stage layered structure described herein, including such combinations of coatings, by the pressure-sensitive adhesive, as well as additional and more permanent or semi-permanent adhesion by the heat-sensitive adhesive. 2. Metal nanoparticles

[0183] The CNT array or sheet can be coated with one or more metal nanoparticles. The one or more metal nanoparticles may be adsorbed on the distal ends and / or sidewalls of the CNTs to bond the distal ends of the CNTs to the surface, to reduce the thermal resistance between the CNT array or sheet and the surface, or a combination thereof. The metal nanoparticles can be attached to the CNT array or sheet using various methods known in the art. For example, a solution of a metal thiolate, such as palladium hexadecanethiolate, can be sprayed or spin coated on the distal ends and / or sidewalls of the CNTs, and the organics can be baked off to leave the palladium nanoparticles. In another example, electron beam or sputter deposition can be used to coat metal nanoparticles or connected "film-like" assemblies of nanoparticles on the distal ends and / or sidewalls of the CNTs. The metal particles can be coated simultaneously with the coating or before or after the coating.

[0184] Examples of suitable metal nanoparticles include palladium, gold, silver, titanium, iron, nickel, copper, and combinations thereof. 3. Flowable or Phase Change Materials

[0185] In certain embodiments, a flowable or phase change material can be attached to the CNT array or sheet. The flowable or phase change material can be added to the CNT array or sheet to replace the air between the CNTs and improve the contact between the distal ends of the CNTs and the surface, resulting in a reduced thermal resistance of the array or sheet and the contact between the array or sheet and the surface, or a combination thereof. The flowable or phase change material can be attached to the CNT array or sheet using various methods known in the art. For example, the flowable or phase change materials in their liquid state can be drawn into the CNT array or sheet by placing the CNT array or sheet in partial or complete contact with the liquid.

[0186] Examples of suitable flowable or phase change materials generally include paraffin wax, polyethylene wax, hydrocarbon-based wax, and blends thereof. Other examples of suitable flowable or phase change materials that are not waxes or polymers include liquid metals, oils, organic-inorganic and inorganic-inorganic eutectics, and blends thereof. In some embodiments, the coating material(s) and the flowable or phase change material are the same.

[0187] The above-mentioned coatings, metal particles, and / or flow or phase change materials can be applied directly to the CNT array or sheet, and the coated CNT array or sheet can be subsequently stacked to form a multi-layer or multi-tiered layered structure. In certain other embodiments, the above-mentioned coatings, metal particles, and / or flow or phase change materials are applied during stacking of two or more CNT arrays or sheets. In still other embodiments, the above-mentioned coatings, metal particles, and / or flow or phase change materials are applied subsequent to stacking of two or more CNT arrays or sheets. In a non-limiting embodiment, the multi-layer or multi-tiered layered structure(s) are formed by first stacking two or more CNT arrays or sheets, and then infiltrating at least partially interdigitating tiers of the formed structure with one or more coatings, metal particles, and / or flow or phase change materials, or combinations thereof. The introduction of such coatings / materials to at least partially interdigitating layers of a multi-layer or multi-tiered layered structure(s) before, during, or after lamination can be used to modify and / or enhance the heat transport or heat resistance properties of the multi-layer or multi-tiered structure resulting from the lamination of CNT arrays or sheets. D. Multi-layer or multi-stage layered structures

[0188] In embodiments described herein, multi-layer or multi-tiered structures that can be used as stepped gaskets and shims are formed by stacking CNT arrays or sheets: (1) providing at least two or more CNT arrays or sheets; (2) stacking at least a CNT array or sheet; A method comprising: The step of stacking results in an array or sheet of nanostructures, at least partial interdigitation of the CNTs; In some embodiments, the method of making the multi-layer or multi-tiered structure further comprises the step of depositing or infiltrating the coating, metal nanoparticle coating, and / or flowable or phase change material coating described above. In some embodiments, the step of depositing or infiltrating the coating, metal nanoparticle coating, and / or flowable or phase change material coating occurs before, during, or after lamination. In still other embodiments, the method includes applying pressure during the lamination step. The applied pressure may be in the range of about 1-100 psi, 1-50 psi, 1-30 psi, more preferably about 1-20 psi, and most preferably about 1-15 psi. In some embodiments, the pressure is about 15 psi. Pressure may be applied continuously until adjacent tiered layers are bonded if a coating material(s) capable of acting as a binder, such as an adhesive or phase change material, is used. Pressure may be applied for any suitable length of time. In some embodiments, if no binder is used, only a short time, such as less than a minute, is used.

[0189] At least two CNT arrays or sheets can be stacked to form a multi-layered or multi-stage layered structure. For example, FIG. 2 shows a stack of three CNT arrays (right side). The thickness of the multi-layered or multi-stage layered structure can be increased as needed by using more CNT arrays. In some embodiments, up to 5, 10, 15, 20, 25, 30, or more CNT arrays or sheets can be stacked according to the above-mentioned method. The thickness of the formed multi-layered or multi-stage layered structure obtained by stacking can be in the range of 1 to 10,000 microns or more.

[0190] In certain embodiments, multi-layer or multi-tiered structures can be formed by stacking multiple tiers of CNT arrays in a stepped, offset, and / or other non-uniform manner to allow conformance to complex surfaces.

[0191] In a non-limiting embodiment, at least two vertically aligned arrays or sheets formed on a support / substrate are stacked / contacted such that the nanostructured elements, such as CNTs, of the arrays at least partially interdigitate upon contact. In one embodiment, full interdigitation of the nanostructured elements of the arrays occurs with one another when stacked. In other embodiments, the arrays may interdigitate only at the tips of the nanostructured elements, such as CNTs. In yet other embodiments, individual nanostructures can progress through the nanostructures of adjacent arrays during the interdigitation process.

[0192] In some embodiments, the nanostructures of the at least partially interdigitated stacked arrays may also be formed into larger superstructures, such as, but not limited to, bundles, clamps, or rows. These superstructures may be formed through mechanisms such as capillary clamping or by the deposition of a polymer coating before, during, or after the stacking process.

[0193] In some embodiments, the polymer coating and / or adhesive, or other coating described above, is applied to the CNT array(s) and then laminated. In such embodiments, the thickness of the coating and / or adhesive, or other coating described above, is about 1-1000 nm, more preferably 1-500 nm, and most preferably 1-100 nm.

[0194] In certain embodiments of the above method, following the lamination step, the method further comprises attaching an adhesive to the resulting laminate, such as, but not limited to, a hot glue or hot melt adhesive combining wax, adhesive, and polymer base, to provide improved adhesion performance to one or the surface of the stacked / tiered CNT arrays forming the multi-layered or multi-tiered layered structure. In some embodiments, the adhesive is a pressure-sensitive adhesive. In still other embodiments, the adhesive is a combination of a pressure-sensitive adhesive polymer and a heat-activated (or activatable) adhesive polymer, which enhances the ease of adhesion to the surface(s) of the multi-layered or multi-tiered layered structure described herein, including such combinations of coatings, by the pressure-sensitive adhesive, as well as additional and more permanent or semi-permanent adhesion by the heat-sensitive adhesive.

[0195] In yet other embodiments, one or more of the tiers of the above-mentioned stacked arrays may be replaced with other materials to obtain a composite laminate. Such materials include, but are not limited to, solder, grease, adhesive, phase change material, gel, heat spreader, compliant pad, and / or (elastomeric) gap pad. Replacement of one or more of the CNT array tiers of the described multi- or multi-tiered stacks with these materials can be used to further tune the properties of the resulting composite laminate. Such composite laminates can be used in various applications described below, such as thermal interface materials (TIMs).

[0196] Yet another option is to introduce or induce the formation of a dielectric material within the layers / tiers of the stacked array to convert the resulting composite stack from a conductor into an insulator. Dielectric materials are known in the art, such as ceramic insulating materials. As an example, one or more of the substrates of the CNT array present in a multi-tiered stack formed from aluminum can be oxidized (such as by anodization) to produce an electrically insulating stack.

[0197] Once prepared according to the above method, the multi-layer or multi-step layered structure can be used as a stepped gasket and shim. The multi-layer or multi-step layered structure can have any suitable shape and size and thickness for use as a stepped gasket and / or shim. Those skilled in the art can form a multi-layer or multi-step layered structure with a desired number of layers (2, 3, 4 or more layers or steps) to function as a stepped gasket as needed to address the curvature present in the upper plate of the thermal interface or joint. Those skilled in the art can also modify the multi-layer or multi-step layered structure as needed to have a specific desired shape or size required to act as a shim. For example, the multi-layer or multi-step layered structure can be made to have an annulus or semi-annulus shape that may be circular, square, or rectangular. Additionally or alternatively, shims made of the multi-layer or multi-step layered structure and having a square or rectangular shape can be prepared. VII. Application Examples

[0198] The thermal interfaces or joints described above may form part of devices including, but not limited to, personal computers, server computers, memory modules, graphics chips, radar and radio frequency (RF) devices, disk drives, displays including light emitting diode (LED) displays, lighting systems, automotive control units, power electronics, solar cells, batteries, communications equipment such as mobile phones, thermoelectric generators, and imaging equipment including MRI.

[0199] In certain instances, the thermal interfaces or joints described throughout this specification are useful in low contact pressure and / or low pressure applications. Low pressure may refer to pressures below ambient pressure or 1 atm, such as in the range of about 0.01 to less than about 1 atm. In some instances, low pressure may refer to vacuum, such as in aerospace applications, where such thermal interfaces or joints may be used in satellites or spacecraft / systems. Under vacuum conditions, the thermal interfaces or joints are particularly useful because the additional contact points enabled by the stepped gasket can substantially increase the area involved in heat transfer across the joint, unlike applications at atmospheric pressure, where air in the separation gap between the plates may contribute to heat transfer. Furthermore, the use of thick gaskets to make contacts in space applications can be problematic, as plate deformation following a thick gasket can result in stresses on the potted insert, which can lead to the insertion being pulled out during the life of the spacecraft. In certain instances, the thermal interfaces or joints described are useful at temperatures below ambient, below freezing, or at cryogenic temperatures (such as those experienced in space).

[0200] The disclosed thermal interfaces and joints and methods of making them can be further understood through the following numbered paragraphs.

[0201] Paragraph 1. First and second plates; a stepped gasket between the first and second plates; and One or more fasteners joining the first and second plates. Including, at least one of the first and / or second plates exhibits plate deformation, warping, or curvature; The stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area less than the surface area of ​​the first base layer; at least a second layer of the stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates that exhibit plate deformation, warping, or curvature as compared to a non-stepped single layer gasket; Thermal interface.

[0202] Paragraph 2. The thermal interface of paragraph 1, wherein one or more fasteners join the first and second plates through one or more holes present in the first and second plates.

[0203] Paragraph 3. The thermal interface of paragraph 1, wherein the first and second plates are independently made of a material selected from the group consisting of aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates).

[0204] Paragraph 4. The thermal interface of paragraph 1, wherein the first and second plates are independently made of a plastic selected from the group consisting of acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate material (such as FR4), high pressure fiberglass laminate (such as G10), fiberglass composite, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide.

[0205] Paragraph 5. The thermal interface of paragraph 1, wherein the first and second plates are independently made of a ceramic selected from the group consisting of alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those made of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

[0206] Paragraph 6. The first and second plates have a square, rectangular, circular, elliptical, or annular shape; the stepped gasket has the same shape as the first and second plates; A thermal interface according to any one of paragraphs 1 to 5.

[0207] Paragraph 7. The thermal interface of any one of Paragraphs 1-6, wherein the first and second plates each independently have a thickness in a range between about 0.5 mm and about 30 mm.

[0208] Paragraph 8. The thermal interface of any one of Paragraphs 1-7, wherein the first plate is planar or substantially planar and the second plate exhibits plate deformation, warping, or curvature.

[0209] Paragraph 9. The thermal interface of any one of paragraphs 1-8, wherein the one or more fasteners are threaded fasteners, clamps, clips, push pins, rivets, pneumatic presses, hydraulic presses, or combinations thereof.

[0210] Paragraph 10. The thermal interface of paragraph 9, wherein the threaded fasteners are bolts and nuts.

[0211] Paragraph 11. The thermal interface of paragraph 9, wherein the threaded fastener is a bolt and pot type insert.

[0212] Paragraph 12. The thermal interface of any one of paragraphs 1-11, wherein the one or more fasteners are made of a material selected from the group consisting of steel, titanium, aluminum, nylon, brass, bronze, and zinc.

[0213] Paragraph 13. The thermal interface of any one of paragraphs 1-12, wherein the deformation, warping, or curvature of the plates is greatest at or near the one or more fasteners joining the first and second plates.

[0214] Paragraph 14. The thermal interface of any one of paragraphs 1-12, wherein the deformation, warping, or curvature of the plates is greatest at or near the center of the first or second plate.

[0215] Paragraph 15. The thermal interface of any one of Paragraphs 1-14, wherein the stepped gasket includes at least a third layer on top of and in contact with the second layer, the third layer providing at least one or more additional contact areas with at least one of the first and / or second plates that exhibit deformation, warping, or curvature of the plates; and the third layer has a surface area that is less than the surface area of ​​the second layer.

[0216] Paragraph 16. The thermal interface of Paragraph 15, wherein the stepped gasket includes at least a fourth layer on top of and in contact with the third layer, the fourth layer providing at least one or more additional contact areas with at least one of the first and / or second plates that exhibit deformation, warping, or curvature of the plates; and the fourth layer has a surface area that is less than the surface area of ​​the third layer.

[0217] Paragraph 17. The thermal interface of any one of paragraphs 1-16, wherein at least a second layer of the stepped gasket forms at least one, two, three, or four independent areas of contact with at least one of the first and / or second plates that exhibit deformation, warping, or curvature of the plates.

[0218] Paragraph 18. The thermal interface of Paragraph 15, wherein each of at least the second layer and / or the third layer of the stepped gasket independently forms at least one, two, three, or four independent areas of contact with at least one of the first and / or second plates that exhibit deformation, warping, or curvature of the plates.

[0219] Paragraph 19. The thermal interface of Paragraph 16, wherein each of at least the second layer, the third layer, and / or the fourth layer of the stepped gasket independently forms at least one, two, three, or four independent areas of contact with at least one of the first and / or second plates that exhibit deformation, warping, or bowing of the plates.

[0220] Paragraph 20. The thermal interface of Paragraph 15, wherein at least one or more additional contact areas from the second and / or third layers of the stepped gasket to at least one of the first and / or second plates exhibiting plate deformation, warping, or bowing, results in increased temperature uniformity of the first and / or second plates to provide an average thermal conductivity across the thermal interface that is at least 25% higher than that of the same thermal interface having a single layer gasket that is not internally stepped.

[0221] Paragraph 21. The thermal interface of Paragraph 16, wherein at least one or more additional contact areas from the second layer, third layer, and / or fourth layer of the stepped gasket to at least one of the first and / or second plates exhibiting plate deformation, warping, or bowing, results in increased temperature uniformity of the first and / or second plates to provide an average thermal conductivity across the thermal interface that is at least 25% higher than for the same thermal interface having a single layer gasket that is not internally stepped.

[0222] Paragraph 22. The thermal interface of any one of Paragraphs 1 to 21, wherein each of the layers of the stepped gasket independently exhibits a modulus of elasticity in the range of between about 0.1 MPa and about 200 MPa.

[0223] Paragraph 23. Each layer of the stepped gasket is independently spaced apart by approximately 0.05 cm. 2 ·℃ / W~approx.5cm 2 The thermal interface of any one of paragraphs 1 to 22 having a thermal interface resistance in the range of between °C / W.

[0224] Paragraph 24. The thermal interface of any one of Paragraphs 1 to 23, wherein each of the layers of the stepped gasket independently has a thickness in a range between about 50 μm and about 500 μm.

[0225] Paragraph 25. The thermal interface of any one of Paragraphs 1-23, wherein the stepped gasket has an increase in height between layers of less than about 500 μm, less than about 250 μm, less than about 150 μm, or less than about 75 μm.

[0226] Paragraph 26. The thermal interface of any one of paragraphs 1 to 25, wherein each of the multiple layers of the stepped gasket is independently made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic.

[0227] Paragraph 27. The thermal interface of Paragraph 26, wherein the material further comprises a thermally conductive and / or electrically conductive filler.

[0228] Paragraph 28. Stepped gaskets: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The present invention is made of a multi-layer or multi-stage layered structure comprising: at least a first layer or step and at least a second layer or step are stacked together, and the vertically aligned carbon nanotubes of the at least first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; A thermal interface according to any one of paragraphs 1 to 25.

[0229] Paragraph 29. The thermal interface of Paragraph 28, wherein at least a first layer or step and at least a second layer or step of the stack are bonded together by a coating material that is an adhesive, a phase change material, or a combination thereof.

[0230] Paragraph 30. The thermal interface of Paragraph 29, wherein the adhesive is a pressure sensitive adhesive.

[0231] Paragraph 31. The thermal interface of any one of Paragraphs 1 to 30, wherein at least the first base layer provides a ground path through a stepped gasket, preferably near one or more fasteners.

[0232] Paragraph 32. The thermal interface of any one of Paragraphs 1 to 26, wherein at least the first base layer further comprises an adhesive, preferably on the non-laminated side.

[0233] Paragraph 33. The thermal interface of any one of paragraphs 1 to 32, wherein at least a second layer of the stepped gasket conforms to at least one surface of the first and / or second plate exhibiting deformation, warping, or curvature of the plate, at least in one or more contact areas.

[0234] Paragraph 34. The thermal interface of Paragraph 15, wherein at least a third layer of the stepped gasket conforms to at least one surface of the first and / or second plate exhibiting deformation, warping, or curvature of the plate, at least in one or more contact areas.

[0235] Paragraph 35. The thermal interface of Paragraph 16, wherein at least a fourth layer of the stepped gasket conforms to at least one surface of the first and / or second plate exhibiting deformation, warping, or curvature of the plate, at least in one or more contact areas.

[0236] Paragraph 36. The thermal interface of any of paragraphs 1-35, further comprising one or more shims.

[0237] Paragraph 37. The thermal interface of Paragraph 36, wherein one or more shims are positioned around, near, and / or behind one or more fasteners present; and optionally, the one or more fasteners are potted inserts, and the one or more shims reduce stress on the potted insert by at least about 10, 20, 30, 40, 50, 60, 70, 80, or 90% compared to a comparable thermal interface without the one or more shims present.

[0238] Paragraph 38. The thermal interface of any one of paragraphs 36-37, wherein the one or more shims have an annulus or semi-annulus shape that may be circular, square, or rectangular.

[0239] Paragraph 39. The thermal interface of paragraph 38, wherein the semi-annular shim is a 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annular shim.

[0240] Paragraph 40. The thermal interface of Paragraph 36, wherein the one or more shims have a square or rectangular shape and are disposed around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plates.

[0241] Paragraph 41. The thermal interface of any one of Paragraphs 28 to 40, wherein the shim or shims are made of metal foil, preferably aluminum foil or copper foil.

[0242] Paragraph 42. The thermal interface of any one of paragraphs 28 to 40, wherein the one or more shims are made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic. Paragraph 43. One or more sims: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The present invention is made of a multi-layer or multi-stage layered structure comprising: at least a first layer or step and at least a second layer or step are stacked together, and the vertically aligned carbon nanotubes of the at least first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; A thermal interface according to any one of paragraphs 28 to 40.

[0243] Paragraph 44. The thermal interface of any one of Paragraphs 28 to 43, wherein the one or more shims independently have a thickness in a range between about 25 μm and about 500 μm.

[0244] Paragraph 45. The thermal interface of any one of Paragraphs 28 to 44, wherein one or more shims independently exhibit an elastic modulus in the range of between about 5 MPa and about 130 GPa.

[0245] Paragraph 46. A method of making a thermal interface of any one of Paragraphs 1 to 45, comprising: (1) providing a first and a second plate; (2) preparing a stepped gasket; (3) disposing a stepped gasket between the first and second plates; (4) joining the first and second plates with one or more fasteners; Including, at least one of the first and / or second plates exhibits deformation, warping, or bowing of the plate when joined by the one or more fasteners; The stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area less than the surface area of ​​the first base layer; at least a second layer of the stepped gasket provides at least one or more contact areas with at least one of the first and / or second plates that exhibit plate deformation, warping, or curvature as compared to a non-stepped single layer gasket; method.

[0246] Paragraph 47. The method of Paragraph 46, wherein one or more fasteners join the first and second plates through one or more holes present in the first and second plates.

[0247] Paragraph 48. The method of Paragraph 46, wherein the first and second plates are independently made of a material selected from the group consisting of aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates).

[0248] Paragraph 49. The method of Paragraph 46, wherein the first and second plates are independently made of a plastic selected from the group consisting of acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate material (such as FR4), high pressure fiberglass laminate (such as G10), fiberglass composite, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide.

[0249] Paragraph 50. The method of Paragraph 46, wherein the first and second plates are independently made of a ceramic selected from the group consisting of alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those consisting of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates). Paragraph 51. The first and second plates have a square, rectangular, circular, elliptical, or annular shape; the stepped gasket has the same shape as the first and second plates; Any one of paragraphs 46 to 50.

[0250] Paragraph 52. The method of any one of Paragraphs 46 to 51, wherein the first and second plates each independently have a thickness in the range of between about 0.5 mm and about 30 mm.

[0251] Paragraph 53. The method of any one of paragraphs 46-52, wherein the one or more fasteners are threaded fasteners, clamps, clips, push pins, rivets, pneumatic presses, hydraulic presses, or combinations thereof.

[0252] Paragraph 54. The method of paragraph 53, wherein the threaded fastener is a bolt and nut.

[0253] Paragraph 55. The method of paragraph 53, wherein the threaded fastener is a bolt and pot insert.

[0254] Paragraph 56. The method of any one of Paragraphs 46-55, wherein the one or more fasteners are made of a material selected from the group consisting of steel, titanium, aluminum, nylon, brass, bronze, and zinc.

[0255] Paragraph 57. The method of any one of Paragraphs 46-56, wherein the stepped gasket includes at least a third layer on top of and in contact with the second layer, the third layer providing at least one or more additional contact areas with at least one of the first and / or second plates exhibiting deformation, warping, or curvature of the plate; and the third layer has a surface area less than the surface area of ​​the second layer.

[0256] Paragraph 58. The method of Paragraph 57, wherein the stepped gasket includes at least a fourth layer on top of and in contact with the third layer, the fourth layer providing at least one or more additional contact areas with at least one of the first and / or second plates that exhibit plate deformation, warping, or curvature; and the fourth layer has a surface area that is less than the surface area of ​​the third layer.

[0257] Paragraph 59. The method of any one of Paragraphs 46-58, wherein each of the plurality of layers of the stepped gasket independently has a thickness in the range of between about 50 μm and about 500 μm.

[0258] Paragraph 60. The method of any one of Paragraphs 46-59, wherein each of the plurality of layers of the stepped gasket is independently made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic.

[0259] Paragraph 61. Stepped gaskets: at least a first layer or tier comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; and At least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate. The present invention is made of a multi-layer or multi-stage layered structure comprising: at least a first layer or step and at least a second layer or step are stacked together, and the vertically aligned carbon nanotubes of the at least first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; Any one of paragraphs 46 to 59.

[0260] Paragraph 62. The method of Paragraph 61, wherein at least a first layer or step and at least a second layer or step of the stack are bonded together by a coating material that is an adhesive, a phase change material, or a combination thereof.

[0261] Paragraph 63. The method of Paragraph 62, wherein the adhesive is a pressure sensitive adhesive.

[0262] Paragraph 64. The method of any of Paragraphs 46-63, wherein the method further comprises, prior to step (4), placing one or more shims between the first and second plates.

[0263] Paragraph 65. The method of Paragraph 64, wherein one or more shims are placed around, near, and / or behind one or more existing fasteners.

[0264] Paragraph 66. The method of any one of Paragraphs 64-65, wherein the one or more shims have an annulus or semi-annulus shape that may be circular, square, or rectangular.

[0265] Paragraph 67. The method of Paragraph 66, wherein the semi-annular shim is a 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annular shim.

[0266] Paragraph 68. The method of Paragraph 64, wherein the one or more shims have a square or rectangular shape and are positioned around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plate.

[0267] Paragraph 69. The method of any one of Paragraphs 64 to 68, wherein the shim or shims are made of a metal foil, preferably an aluminum foil or a copper foil.

[0268] Paragraph 70. The method of any one of Paragraphs 64 to 68, wherein the one or more shims are made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomers, rubber, and acrylic.

[0269] Paragraph 71. One or more sims: at least a first layer or tier comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; and At least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate. The present invention is made of a multi-layer or multi-stage layered structure comprising: at least a first layer or step and at least a second layer or step are stacked together, and the vertically aligned carbon nanotubes of the at least first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; Any one of the methods set out in paragraphs 64 to 68.

[0270] Paragraph 72. The method of any one of Paragraphs 64 to 71, wherein the one or more shims independently have a thickness in the range of between about 25 μm and about 500 μm.

[0271] Paragraph 73. The method of any one of Paragraphs 64 to 72, wherein one or more shims independently exhibit an elastic modulus in the range of between about 5 MPa and about 130 GPa.

[0272] Paragraph 74. First and second plates; a single layer gasket between the first and second plates; and One or more fasteners joining the first and second plates. Including, at least one of the first and / or second plates exhibits plate deformation, warping, or curvature; one or more shims are present around, near, and / or behind one or more fasteners to reduce and / or mitigate deformation, warping, or curvature of the first and / or second plates; Thermal interface.

[0273] Paragraph 75. The thermal interface of Paragraph 74, wherein one or more fasteners join the first and second plates through one or more holes present in the first and second plates.

[0274] Paragraph 76. The thermal interface of Paragraph 74, wherein the first and second plates are independently made of a material selected from the group consisting of aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates).

[0275] Paragraph 77. The thermal interface of Paragraph 74, wherein the first and second plates are independently made of a plastic selected from the group consisting of acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate material (such as FR4), high pressure fiberglass laminate (such as G10), fiberglass composite, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide.

[0276] Paragraph 78. The thermal interface of Paragraph 74, wherein the first and second plates are independently made of a ceramic selected from the group consisting of alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those made of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

[0277] Paragraph 79. The thermal interface of any one of paragraphs 74 to 78, wherein the first and second plates have a square, rectangular, circular, elliptical, or ring shape.

[0278] Paragraph 80. The thermal interface of any one of Paragraphs 74 to 79, wherein the first and second plates each independently have a thickness in the range of between about 0.5 mm and about 30 mm.

[0279] Paragraph 81. The thermal interface of any one of Paragraphs 74 to 80, wherein the first plate is planar or substantially planar and the second plate exhibits plate deformation, warping, or curvature.

[0280] Paragraph 82. The thermal interface of any one of paragraphs 74 to 81, wherein the one or more fasteners are threaded fasteners, clamps, clips, push pins, rivets, pneumatic presses, hydraulic presses, or combinations thereof.

[0281] Paragraph 83. The thermal interface of paragraph 82, wherein the threaded fasteners are bolts and nuts.

[0282] Paragraph 84. The thermal interface of paragraph 82, wherein the threaded fastener is a bolt and pot type insert.

[0283] Paragraph 85. The thermal interface of any one of paragraphs 74 to 84, wherein the one or more fasteners are made of a material selected from the group consisting of steel, titanium, aluminum, nylon, brass, bronze, and zinc.

[0284] Paragraph 86. The thermal interface of any one of Paragraphs 74 to 85, wherein the deformation, warping, or curvature of the plates is greatest at or near the one or more fasteners joining the first and second plates.

[0285] Paragraph 87. The thermal interface of any one of paragraphs 74 to 86, wherein the deformation, warping, or curvature of the plates is greatest at or near the center of the first or second plate.

[0286] Paragraph 88. The thermal interface of any one of paragraphs 74 to 87, wherein the one or more shims increase the average thermal conductivity across the thermal interface by at least about 25% over the same thermal interface without the shim being present.

[0287] Paragraph 89. The thermal interface of any one of paragraphs 74 to 88, wherein one or more shims are positioned around, near, and / or behind one or more present fasteners.

[0288] Paragraph 90. The thermal interface of any one of paragraphs 74 to 89, wherein the one or more shims have an annulus or semi-annulus shape that may be circular, square, or rectangular.

[0289] Paragraph 91. The thermal interface of Paragraph 90, wherein the semi-annular shim is a 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annular shim.

[0290] Paragraph 92. The thermal interface of any one of paragraphs 74 to 89, wherein the one or more shims have a square or rectangular shape and are positioned around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plate.

[0291] Paragraph 93. The thermal interface of any one of Paragraphs 74 to 92, wherein the shim or shims are made of metal foil, preferably aluminum foil or copper foil.

[0292] Paragraph 94. The thermal interface of any one of paragraphs 74 to 93, wherein the one or more shims are made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomer, rubber, and acrylic.

[0293] Paragraph 95. One or more sims: at least a first layer or tier comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; and At least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate. The present invention is made of a multi-layer or multi-stage layered structure comprising: at least a first layer or step and at least a second layer or step are stacked together, and the vertically aligned carbon nanotubes of the at least first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; A thermal interface according to any one of paragraphs 74 to 93.

[0294] Paragraph 96. The thermal interface of any one of Paragraphs 74 to 95, wherein the one or more shims independently have a thickness in a range between about 25 μm and about 500 μm.

[0295] Paragraph 97. The thermal interface of any one of Paragraphs 74 to 96, wherein one or more shims independently exhibit an elastic modulus in the range of between about 5 MPa and about 130 GPa.

[0296] Paragraph 98. A method of making a thermal interface according to any one of Paragraphs 74 to 97, comprising the steps of: (1) providing a first and a second plate; (2) providing a single layer gasket; (3) disposing a single layer gasket between the first and second plates; (4) disposing one or more shims between the first and second plates; and (5) joining the first and second plates with one or more fasteners. Including, at least one of the first and / or second plates exhibits deformation, warping, or bowing of the plate when joined by the one or more fasteners; one or more shims are present around, near, and / or behind one or more fasteners to reduce and / or mitigate deformation, warping, or curvature of the first and / or second plates; method.

[0297] Paragraph 99. The method of Paragraph 98, wherein one or more fasteners join the first and second plates through one or more holes present in the first and second plates.

[0298] Paragraph 100. The method of Paragraph 98, wherein the first and second plates are independently made of a material selected from the group consisting of aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates).

[0299] Paragraph 101. The method of Paragraph 98, wherein the first and second plates are independently made of a plastic selected from the group consisting of acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate material (such as FR4), high pressure fiberglass laminate (such as G10), fiberglass composite, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide.

[0300] Paragraph 102. The method of Paragraph 98, wherein the first and second plates are independently made of a ceramic selected from the group consisting of alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y2O3, TiC, SrAl2O3, ZrC, HfC, TaC, ZrB2, HfB2, Mo2B5, MoSi2TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those consisting of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

[0301] Paragraph 103. The method of any one of Paragraphs 98-102, wherein the first and second plates have a square, rectangular, circular, elliptical, or ring shape.

[0302] Paragraph 104. The method of any one of Paragraphs 98 to 103, wherein the first and second plates each independently have a thickness in the range of between about 0.5 mm and about 30 mm.

[0303] Paragraph 105. The method of any one of paragraphs 98-104, wherein the one or more fasteners are threaded fasteners, clamps, clips, push pins, rivets, pneumatic presses, hydraulic presses, or combinations thereof.

[0304] Paragraph 106. The method of Paragraph 105, wherein the threaded fastener is a bolt and nut.

[0305] Paragraph 107. The method of Paragraph 105, wherein the threaded fastener is a bolt and pot type insert.

[0306] Paragraph 108. The method of any one of Paragraphs 98-107, wherein the one or more fasteners are made of a material selected from the group consisting of steel, titanium, aluminum, nylon, brass, bronze, and zinc.

[0307] Paragraph 109. The method of any one of paragraphs 98-108, wherein one or more shims are placed around, near, and / or behind one or more existing fasteners.

[0308] Paragraph 110. The method of any one of Paragraphs 98 to 109, wherein the one or more shims have an annulus or semi-annulus shape that may be circular, square, or rectangular.

[0309] Paragraph 111. The method of Paragraph 110, wherein the semi-annular shim is a 1 / 4, 1 / 2, 1 / 3, or 3 / 4 semi-annular shim.

[0310] Paragraph 112. The method of any one of Paragraphs 98-109, wherein the one or more shims have a square or rectangular shape and are positioned around, near, and / or behind at least one corner, edge, and / or center of the first and / or second plate.

[0311] Paragraph 113. The method of any one of Paragraphs 98 to 112, wherein the shim or shims are made of a metal foil, preferably an aluminum foil or a copper foil.

[0312] Paragraph 114. The method of any one of Paragraphs 98-112, wherein the one or more shims are made of a material selected from graphite, carbon fiber, silicone, thermoplastic elastomers, rubber, and acrylic.

[0313] Paragraph 115. One or more sims: at least a first layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; The present invention is made of a multi-layer or multi-stage layered structure comprising: at least a first layer or step and at least a second layer or step are stacked together, and the vertically aligned carbon nanotubes of the at least first layer or step at least partially interdigitate with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; Any one of the methods set forth in paragraphs 98 to 112.

[0314] Paragraph 116. The method of any one of Paragraphs 98 to 115, wherein the one or more shims independently have a thickness in the range of between about 25 μm and about 500 μm.

[0315] Paragraph 117. The method of any one of Paragraphs 98 to 116, wherein one or more shims independently exhibit an elastic modulus in the range of between about 5 MPa and about 130 GPa.

[0316] Paragraph 118. A device including a thermal interface according to any one of paragraphs 1 to 45 or 74 to 97.

[0317] Paragraph 119. The device of Paragraph 118, wherein the device is selected from the group consisting of personal computers, server computers, memory modules, graphics chips, radar and radio frequency (RF) devices, disk drives, displays including light emitting diode (LED) displays, lighting systems, automobile control units, power electronics, solar cells, batteries, communications equipment such as mobile phones, thermoelectric generators, and imaging equipment.

[0318] Paragraph 120. The device of paragraph 119, wherein the device is an aerospace device selected from a satellite, a spacecraft, or a space system operating under a vacuum. EXAMPLES

[0319] Example 1 Thermal interface housing with stepped gasket material and method: Test sample The gaskets used were obtained from Carbice® Corporation. The gaskets consisted of vertically aligned carbon nanotube arrays grown on 50 μm aluminum foil and encapsulated in silicone. The thicknesses of the gasket products used were 65 μm and 125 μm, and the compressive moduli were estimated to be approximately 18 and 35 MPa, respectively. The moduli were calculated from stress-strain data collected using a Precision Thickness Gauge (Hanatek Instruments) under various loads ranging from 0.2 to 1.4 MPa.

[0320] Additionally, stepped gaskets were prepared from single layer 65 μm and 125 μm gaskets by stacking the gaskets. Thus, 1, 2, 3 and 4 layer gaskets were studied as follows: - 1 layer (single layer gasket): 500μm - 1 layer (single layer gasket): 125μm - Two layers (stepped gasket): 125μm (base layer) and 65μm (layer #3 in Table 1 below) - 3 layers (stepped gasket): 125μm and 2×(65μm - layers #2 and #3 in table 1 below) - 4 layers (stepped gasket): 125μm and 3×(65μm - layers #2, #3, and #4 in Table 1 below)

[0321] The dimensions of these layers, as mentioned above, are given in Table 1 below. [Table 1] Thermal conductivity of the sample

[0322] Thermal properties of single and stepped gaskets were recorded for each specimen thickness and for each multilayer specimen combination studied. 1 cm x 1 cm specimens were measured with a modified ASTM-D5470 stepped bar apparatus to record 1D steady-state thermal contact resistance (the inverse of conductivity). The relationship between applied contact pressure and conductivity closely follows a power law correlation that was uniquely fitted to each gasket specimen and multilayer combination used in this study (see Figure 7). These pressure-conductivity relationships are used to correlate the warped gasket pressure distribution in bolted joint predictions to the spatial distribution of thermal contact conductivity. Selection and solution of stepped gaskets.

[0323] To achieve conformal contact with the plate surface, a stepped gasket with a pyramidal / stepped arrangement was studied as discussed above. Parameters of interest were the number of gasket layers, the thickness of each step layer, and the exact positioning of each layer in the step / stacked arrangement. For a given bolted joint configuration, various combinations of these parameters that give the best thermal performance were studied with a numerical approach outlined below.

[0324] Because these studies incorporate a selection of commercially available single layer gasket materials, the height selection was constrained to a combination of 65 μm material layers, however, it was found that using a thicker base layer of 125 μm provided easier handling and assembly without significantly affecting thermal performance.

[0325] The precise positioning of each layer was a factor influencing the contact obtained throughout the stepped gasket. Thus, due to the complexity and sensitivity of the stepped gasket, there was evidence of diminishing returns over two-layered gaskets. Nevertheless, the use of three or even four layers may be useful depending on the circumstances.

[0326] Once the multi-tier / layer structure was determined for a given bolted joint configuration, each gasket layer was laser cut to size from large sheets of material and assembled layer by layer. Numerical modelling of warping of bolted connections

[0327] The warping characteristics of a bolted joint (or interface) incorporating a stepped gasket was numerically modeled to evaluate the effect of gasket layer and location on the interfacial contact and thermal performance. First, a plate bolted at the perimeter was examined and approximated as an Euler-Bernoulli beam with a thin gasket layer(s) between the mating surfaces treated as a compressive elastic foundation. Classical beam theory then gives the following equation:

number

[0328] The predicted warpage of the bolted joint was calculated by numerically solving equation (1) while iteratively determining the gasket compression area relative to separation. The warpage characteristics provide a picture of the pressure distribution in the compressed gasket, which, according to the correlation highlighted in Figure 7, allows for an estimation of the thermal contact conductivity distribution imparted by the gasket throughout the bolted interface. The compression of the gasket can be extracted from this beam position data, which can then be used together with the measured modulus values ​​and thermal conductivity to output the pressure and, subsequently, the local thermal contact conductivity of the gasket. Experimental methods for contact and conductivity in bolted joints.

[0329] A typical setup for measuring thermal conductivity in bolted joints consisted of a stepped or single layer gasket sandwiched between a cold base plate and a heated top plate. A representative case was used to study the condition where the plate deformation was severe enough to ensure that the stepped gasket enhances the contact and thermal performance; see Figure 8: 50cm x 36cm plate size, 18mm plate thickness, 26 bolt configuration. The thickness of the top plate is chosen to represent a bending stiffness equivalent to that of honeycomb panels such as those commonly used in spacecraft construction.

[0330] The thick aluminum base plate was cooled by a steady flow of cold water circulating through a chiller at -30 to 25°C. The various gaskets mentioned above were applied with a soft rubber roller to ensure smooth adhesion to the interface. The top plate was equipped with one or more ceramic heaters to generate approximately 1 W / cm 2 A surface heat flux of the order of 1×10 was provided. Pairs of thermocouples were placed in the grooves at corresponding locations along the hot and cold plates to measure the interfacial temperature difference. Several pairs of thermocouples were distributed along the plate area at strategic locations to map the temperature gradient across the interfacial surface. An approximate temperature contour was then created through 2D interpolation of these thermocouple data points. An approximate temperature contour was then created through 2D interpolation of these thermocouple data points. These experiments were performed on a 1×10 -6 The experiments were carried out in vacuum with a target pressure of 1000 torr. Thermal Contact Conductance Calculation

[0331] From the steady-state measurements, the thermal contact conductivity h c and the thermal contact resistance R is

number

[0332] To evaluate the contact area between the bolted joint surface and the gasket, a pressure sensitive film was used (Extreme Low, Fujifilm Prescale Pressure Indicating Film). Results and Discussion: Validation of warpage model contact predictions for single and dual layer gaskets

[0333] The model prediction of beam contact to separation was first verified using a pressure sensitive film (not shown). When observing the coloration of the pressure map, the contact matched the prediction. As predicted, the contact was achieved at the second layer gasket.

[0334] The first layer of the gasket was 125 μm in height. Using a pressure sensitive film to reveal where the top plate / beam contacted the gasket, the contact area near each bolt for this single layer control test was found to be approximately 33 mm ± 2 mm. A second layer was then placed on top to form the stepped gasket. The second layer was 65 μm in height and positioned to match the expected curvature of the beam. The contact measured for the stepped gasket was 28 mm near each bolt (first layer of the stepped gasket) with an additional 10 mm on each edge of the second layer of the gasket. The total area of ​​contact was therefore found to be increased by 15% through the use of the stepped gasket as opposed to the single layer gasket. Additionally, the fact that the contact was more distributed along the length of the beam (as opposed to being localized near the bolts) had a more pronounced effect on spreading resistance, which has a significant effect on full interfacial thermal conductivity.

[0335] The two-layer case had a 33% increase in average thermal conductivity compared to the single-layer case (1,064 vs. 802 W / m 2 -°C). Thus, the use of a stepped gasket serves to increase the contact area as well as better distribute the contact area. A more even distribution of interfacial contact is advantageous due to the effect of resisting heat spreading between planar surfaces, and the better distribution also results in reduced hot spots at the thermal interface where the stepped gasket is used.

[0336] Beyond the single layer gasket control and the two layer stepped gasket discussed above, the cases of testing three and four layer stepped gaskets were also studied. In these cases, the single layer gasket (802 W / m 2 -℃), compared with 19% (957 W / m 2 -℃) and 52% (1220W / m 2 Enhanced contact is achieved which translated into an overall improvement in contact conductivity (-°C). The three-layer gasket did not show as high an increase in conductivity as the other cases, likely due to the lack of contact or proper alignment of the layers in that case.

[0337] Temperature contour maps showed qualitative agreement between ANSYS simulations performed (not shown) and the stepped gaskets tested and measured in vacuum chamber tests. Vacuum tests were performed in an evacuated chamber at pressures below 1 μTorr. ANSYS predicted that conductivity correlated to the measured thermal performance. Conclusion:

[0338] The above studies show that multi-layer structuring giving a stepped gasket can be used at thermal interfaces to enhance interfacial thermal conductivity in bolted joints, etc., where plates exhibit warping and deformation. To address the challenge of plate warping / deformation, it was shown that a stepped gasket can better conform to the curvature of naturally warped plates. Thus, a stepped gasket can enhance gasket contact and improve thermal contact conductivity at the interface, such as in bolted joints. The warping behavior of the bolted joint was modeled using Euler-Bernoulli beam theory, and this model was then used to predict the warping under a structured / step-layered gasket and optimize the geometric stepped gasket. Experiments were found to be in agreement with the model predictions. Based on the conductivity studies, it was shown that the thermal conductivity can be improved by up to 52% due to the introduction of as many as three additional layers (in the form of a stepped gasket) compared to a single layer gasket. Example 2 Thermal testing of stepped gaskets material and method:

[0339] The thermal performance of the interface (not shown) was tested by fastening an aluminum box measuring 238 mm by 279 mm to a thick base plate using sixteen #8-32 bolts. The box featured inset side walls and gussets, with the bolts fastened along the perimeter. Thermal testing was performed with multiple pairs of thermocouples affixed to various corresponding locations on the box and below the base plate. Four heater blocks were placed within the box to provide >600 W of heating. Three thermal interface material (TIM) gasket samples were tested: - Sample 1: Single layer gasket - 125μm thick and covering the entire interface of 238mm x 279mm; - Sample 2: Stepped gasket (see FIG. 9A) - a 125 μm thick base layer covering the entire interface of 238 mm x 279 mm, topped by a second layer of 65 μm thickness and measuring 104 mm x 124 mm; - Sample 3: Stepped gasket (see Figure 9B) - a 125 μm thick base layer covering the entire 238 mm x 279 mm interface, topped by a second layer measuring 66 mm x 80 mm and 65 μm thick; - Sample 4: Stepped gasket (see Figure 9B) - a 125 μm thick base layer covering the entire 238 mm x 279 mm interface, topped by a second layer measuring 38 mm x 184 mm and 65 μm thick; Results and Discussion:

[0340] For each test, each of the above samples was assembled between a base plate and a box, which was tightened to a torque of 20 in-lb and then heated at 600 W. The temperature difference measured at each thermocouple location was used to generate a thermal contour map (not shown) of the interface, which was then used to calculate the average thermal contact conductivity h avg was calculated for each test. The results of the thermal tests are shown in Table 2 below. [Table 2]

[0341] Thermal measurements showed that strategic design of the stepped gasket can be used to maximize overall performance. For example, net conductivity was increased by 15% in Sample 3, which targeted central heat dissipation.

[0342] The stepped gasket can also provide an improvement in cooling hot spot locations (center of the plate and / or near the heater location). In Sample 3, this resulted in a lower center temperature by increasing the local conductivity by 36%. See bar graph in Figure 10.

[0343] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosed invention belongs. Publications cited herein and the materials for which they are cited are specifically incorporated by reference.

[0344] Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein which equivalents are intended to be encompassed by the following claims.

Claims

1. First and second plates; a stepped gasket between the first and second plates; and one or more fasteners joining the first and second plates Including, at least one of the first and / or second plates exhibits plate deformation, warping, or curvature; the stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area smaller than the surface area of ​​the first base layer; the at least second layer of the stepped gasket provides at least one or more contact areas with the at least one of the first and / or second plates that exhibit plate deformation, warping, or bending compared to a non-stepped single layer gasket; the one or more fasteners join the first and second plates through one or more holes present in the first and second plates, or the one or more fasteners are threaded fasteners, clamps, clips, push pins, rivets, air presses, hydraulic presses, or combinations thereof; Thermal interface.

2. The first and second plates are independently made of a material selected from the group consisting of aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates); or the first and second plates are independently made of a material selected from the group consisting of acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate materials (such as FR4), high pressure fiberglass laminates (such as G10), fiberglass composites, PEEK, polyethylene, polyethylene terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene)polystyrenesulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide; or the first and second plates are independently made of a plastic selected from the group consisting of alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y ２ O ３ , TiC, SrAl ２ O ３ , ZrC, HfC, TaC, ZrB ２ , HfB ２ , Mo ２ B ５ , MoSi ２ 10. The thermal interface of claim 1, made of a ceramic selected from the group consisting of TiN, YrN, and co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), and ultra low temperature co-fired ceramics (ULTCC) including those composed of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

3. The thermal interface of claim 1 , wherein the threaded fastener is a bolt and nut, or the threaded fastener is a bolt and pot insert.

4. 10. The thermal interface of claim 1, wherein the at least one or more contact areas from the second layer of the stepped gasket to the at least one of the first and / or second plates exhibiting plate deformation, warping, or bowing results in increased temperature uniformity of the first and / or second plates, providing an average thermal conductivity across the thermal interface that is at least 25% higher than the same thermal interface having a single layer gasket that is not internally stepped.

5. 10. The thermal interface of claim 1, wherein each of the layers of the stepped gasket independently has a thickness ranging between about 50 μm and about 500 μm.

6. The stepped gasket is at least a first layer or terrace comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; made of a multi-layer or multi-stage layered structure comprising: the at least first layer or step and the at least second layer or step are stacked, and the vertically aligned carbon nanotubes of the at least first layer or step are at least partially interdigitated with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; 10. The thermal interface of claim 1.

7. The thermal interface of claim 1 , further comprising one or more shims.

8. the one or more shims: at least a first layer or terrace comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a first planar substrate; at least a second layer or layer comprising a carbon nanotube array comprising vertically aligned carbon nanotubes grown from both sides of a second planar substrate; made of a multi-layer or multi-stage layered structure comprising: the at least first layer or step and the at least second layer or step are stacked, and the vertically aligned carbon nanotubes of the at least first layer or step are at least partially interdigitated with the vertically aligned carbon nanotubes of the at least second layer or step that interface with each other; 8. The thermal interface of claim 7.

9. 10. A method of fabricating the thermal interface of claim 1, comprising: (1) providing a first and a second plate; (2) preparing a stepped gasket; (3) placing the stepped gasket between the first and second plates; (4) joining the first and second plates with one or more fasteners; Including, at least one of the first and / or second plates exhibits plate deformation, warping, or bowing when joined by the one or more fasteners; the stepped gasket includes multiple layers, including at least a first base layer and at least a second layer on top of and in contact with the first base layer, the second layer having a surface area smaller than the surface area of ​​the first base layer; the at least second layer of the stepped gasket provides at least one or more contact areas with the at least one of the first and / or second plates that exhibit plate deformation, warping, or bending compared to a non-stepped single layer gasket; the one or more fasteners join the first and second plates through one or more holes present in the first and second plates, or the one or more fasteners are threaded fasteners, clamps, clips, push pins, rivets, air presses, hydraulic presses, or combinations thereof; method.

10. The first and second plates are independently made of a material selected from the group consisting of aluminum, copper, steel, titanium, zinc, metal matrix composites (such as AlSiC or aluminum-graphite), and metal laminate structures (such as honeycomb panels or fiber metal laminates), or the first and second plates are independently made of a material selected from the group consisting of acrylonitrile butadiene styrene, polycarbonate, nylon, epoxy, glass reinforced epoxy laminate materials (such as FR4), high pressure fiberglass laminates (such as G10), fiberglass composites, PEEK, polyethylene, polyethylene terephthalate (PEK), ... terephthalate glycol, polypropylene, polyurethane, polyvinyl chloride, polyimide, polytetrafluoroethylene, polylactic acid, PEDOT:PSS (poly(3,4-ethylenedioxythiophene)polystyrenesulfonate), PARA, polyphenylene sulfide, polyamide-imide, and polyetherimide; or the first and second plates are independently made of a plastic selected from the group consisting of alumina, aluminum nitride, zirconia, zirconia alumina, beryllium oxide, carbon fiber, graphite, silicon carbide, silicon dioxide, silicon nitride, Y ２ O ３ , TiC, SrAl ２ O ３ , ZrC, HfC, TaC, ZrB ２ , HfB ２ , Mo ２ B ５ , MoSi ２ 10. The method of claim 9, wherein the ceramic is made of a ceramic selected from the group consisting of TiN, YrN, co-fired ceramics (including high temperature co-fired ceramics (HTCC), low temperature co-fired ceramics (LTCC), ultra low temperature co-fired ceramics (ULTCC) including those composed of phosphates, silicates, borates, molybdates, vanadates, tellurates, and tungstates).

11. 10. The method of claim 9, wherein the threaded fastener is a bolt and nut, or the threaded fastener is a bolt and pot insert.

12. The method of claim 9, wherein each of the plurality of layers of the stepped gasket independently has a thickness ranging between about 50 μm and about 500 μm.

13. 10. The method of claim 9, wherein the method further comprises, prior to step (4), placing one or more shims between the first and second plates.

14. A device comprising the thermal interface of claim 1.

15. The device of claim 14 , wherein the device is an aerospace device selected from a satellite, a spacecraft, or a space system operating under vacuum.

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