Method for thermal management of chip assembly and thermal distribution device

Abstract

The invention relates to a method for thermal management of a chip assembly and a thermal distribution device. According to one aspect of the present disclosure, an example microelectronic device assembly includes a substrate, a microelectronic element electrically connected to the substrate, a stiffener element overlying the substrate, and a heat distribution device overlying a rear surface of the microelectronic element. The stiffener element may extend around the microelectronic element. The stiffener element may include a first material having a first coefficient of thermal expansion ("CTE"). A surface of the stiffener element may face the heat distribution device. The heat distribution device may include a second material having a second CTE. The first material may be different than the second material. A first CTE of a first material of the stiffener element may be greater than a second CTE of a second material of the heat distribution device.

Description

Description of the case This application is a divisional application of the patent application with application number 202110603840.7 submitted to the China Patent Office on May 31, 2021, and the invention name is "Method and heat distribution device for thermal management of chip components". CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 032,197, filed on May 29, 2020, and entitled “Methods And Heat Distribution Devices For Thermal Management Of Chip Assemblies,” and also claims the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 066,550, filed on August 17, 2020, and also entitled “Methods And Heat Distribution Devices For Thermal Management Of Chip Assemblies,” and the disclosures of all of the said U.S. Provisional Applications are hereby incorporated herein by reference. Technical Field

[0002] The present invention relates to the field of electronic devices, and more particularly to heat management and cooling of chip assemblies by utilizing heat distribution devices such as cold plates. Such heat distribution devices can be utilized within microelectronic assemblies to help reduce heat generated by microelectronic elements having the assembly and heat generated by components external to the assembly. Background Art

[0003] In addition to industry standard chip packaging, the exploration of specialized silicon is also expected to generate high-power heat sources in servers. This technology can also be applied to graphics processing units ("GPUs") and customized application-specific integrated circuits ("ASICs"). In addition, services such as imaging and artificial intelligence ("AI") will likely require high-density large-scale computer resources, with many servers in close proximity to each other. Data centers around the world are being hosted to simultaneously improve energy efficiency, consolidate operations, and reduce costs. These trends indicate the need for high-performance cooling technologies that scale well with cooling costs and energy, while being able to achieve cooling for high-density electronic devices.

[0004] In microelectronic assemblies, heat distribution devices are often used to cool and regulate the temperature of microelectronic components. Such heat distribution devices can include heat sinks, water tanks, cold plates, and combinations of one or more of these and other devices.

[0005] The coefficient of thermal expansion ("CTE") mismatch between the heat distribution device and other components in the chip assembly can stress the assembly when any of these components expand at a different rate than the other components due to temperature changes that occur during manufacture or use of the chip assembly. In a typical assembly, a one-piece heat distribution device composed of a single thermally conductive material can cover the back surface of the chip and also extend toward and be attached to the substrate. Cycling of the chip assembly through one or more reflow processes and operation of the chip assembly can also cause warping of the substrate and / or chip and other mechanical failures within the assembly due to the CTE mismatch between the substrate, the heat distribution device, and the chip. Summary of the invention

[0006] Aspects of the present disclosure provide for effectively cooling a chip assembly. For example, a method of manufacturing a chip assembly includes: providing an in-process unit; and then bonding the in-process unit to a printed circuit board. A heat distribution device can be bonded to a plurality of chips. The in-process unit can include a substrate having a top surface and an opposite bottom surface. An insert can be electrically connected to the substrate. A plurality of semiconductor chips can be overlaid on the substrate and electrically connected to the substrate via the insert. A reinforcement member can be overlaid on the substrate. Bonding the in-process unit to the printed circuit board can occur by reflowing a bonding material used to bond contacts of the substrate to contacts of the printed circuit board. Bonding the heat distribution device to the plurality of chips can be accomplished by using a highly thermally conductive thermal interface material ("TIM"), the heat distribution device including a plurality of thermally conductive fins.

[0007] In one example, the heat distribution device can be a cold plate having a base and a cover coupled to the base. The method can also include bonding the base of the cold plate to the rear surface of the plurality of chips. The base of the cold plate can also be bonded to the top surface of the stiffener. The cover can also be attached to the base of the cold plate. Additionally, an O-ring can be positioned within the base of the cold plate before coupling the cover of the cold plate to the base of the cold plate.

[0008] In another example, the reinforcement member may be spaced away from the heat distribution device.

[0009] In another example, a shim may be positioned within the stiffener to control bond wire thickness.The shim may extend circumferentially around the plurality of semiconductor chips and may occupy space within a recess of the stiffener.

[0010] In another example, the TIM may be disposed on one of the rear surface of the semiconductor device or the bottom surface of the heat distribution device before the heat distribution device is bonded to the rear surface of the semiconductor chip. In one example, the TIM may be disposed on the rear surface of the semiconductor device before the heat distribution device is bonded to the rear surface of the semiconductor chip. In another example, the TIM may be disposed on the bottom surface of the heat distribution device before the heat distribution device is bonded to the rear surface of the semiconductor chip.

[0011] In another example, the heat distribution device further comprises a plurality of heat conducting fins. A first fin length of at least some of the heat conducting fins is greater than a second fin length of the remaining fins of the heat conducting fins. A first height of at least one of the plurality of semiconductor chips is less than a second height of another of the plurality of semiconductor chips. At least some of the heat conducting fins having the first fin length are positioned to cover at least one of the plurality of semiconductor chips having the first height.

[0012] In another example, incorporating the heat distribution device includes applying pressure on the heat distribution device using an external pressure device. The pressure device may be a weight configured to cover the heat distribution device during fabrication of the chip assembly and may apply the weight to a top surface of the heat distribution device.

[0013] In another example, the pressurizing device may include a rigid plate and springs at opposite ends of the rigid plate. The rigid plate may be positioned above the rear surface of the heat distribution device and the rigid plate may be secured to the printed circuit board. In another example, the heat distribution device further includes an inlet and an outlet, and a fluid connection may be provided to connect the inlet and outlet to a fluid so as to enable the fluid to be introduced into the heat distribution device and ejected from the heat distribution device.

[0014] Providing an intermediate process unit can also include providing a plurality of intermediate process units. Providing a heat distribution device can also include providing a plurality of heat distribution devices. The method can also include: bonding the plurality of intermediate process units to a printed circuit board by reflowing a bonding material, the bonding material bonding the contacts of each of the substrates within the plurality of intermediate process units to the contacts of the printed circuit board; bonding the plurality of heat distribution devices to each of the plurality of chips in each of the plurality of intermediate process units by reflowing a highly thermally conductive thermal interface material ("TIM"), each of the heat distribution devices including a plurality of thermally conductive fins, an inlet and an outlet; and bonding the inlet and outlet of each of the heat distribution devices to each other so that the inlet and outlet of one of the plurality of intermediate process units are fluidly connected to the inlet and outlet of another of the plurality of intermediate process units.

[0015] According to various aspects of the present disclosure, a microelectronic device assembly may include a printed circuit board, a substrate covering the circuit board and electrically connected to the circuit board, and a plurality of microelectronic devices electrically connected to the substrate. The chip may have an active surface facing the substrate and a passive surface facing away from the substrate. A cavity may be positioned within at least one of the plurality of microelectronic devices, and wherein the cavity is filled with a highly thermally conductive material.

[0016] In one example, the high thermal conductivity material may be flush with or positioned lower than a rear surface of at least one of the plurality of chips.

[0017] In another example, the highly thermally conductive material extends beyond a rear surface of at least one of the plurality of chips.

[0018] In another example, the microelectronic device assembly further includes a heat distribution device including a base and a cover. The base may also include thermally conductive fins, wherein a first material forming the cold plate is different from a second material forming the thermally conductive fins.

[0019] According to various aspects of the present disclosure, a chip assembly includes a printed circuit board, a substrate, a plurality of chips and a heat distribution device. The substrate may be covered on the circuit board and electrically connected to the circuit board. The plurality of chips may be electrically connected to the substrate. Each of the plurality of semiconductor chips may have an active surface facing the substrate and a passive surface facing away from the substrate. The heat distribution device can include a plurality of fins. The length of at least some of the fins may be longer than the length of the remaining fins. The height of at least one of the plurality of semiconductor chips is different from another of the plurality of semiconductor chips. At least some of the fins cover at least one of the plurality of semiconductor chips.

[0020] According to one aspect of the present disclosure, a method for manufacturing a chip assembly includes: bonding an intermediate process unit to a printed circuit board; reflowing a bonding material disposed between the intermediate process unit and the printed circuit board and electrically connecting the intermediate process unit to the printed circuit board; and then bonding a heat distribution device to a plurality of semiconductor chips by using a thermal interface material ("TIM"). The bonding material may have a first reflow temperature, and the TIM may have a second reflow temperature lower than the first reflow temperature. The intermediate process unit may include a substrate, an insert, a plurality of semiconductor chips, and a reinforcement. The substrate may have an active surface, a passive surface, and contacts exposed at the active surface. The insert may be electrically connected to the substrate. A plurality of semiconductor chips may be covered on the substrate and electrically connected to the substrate through the insert. The reinforcement may be covered on the substrate and have an aperture extending through the substrate. A plurality of semiconductor chips may be positioned within the aperture.

[0021] In one example, the heat distribution device is a cold plate having a base and a cover. The method also includes bonding the base and the cover together, and then bonding the base to the back surface of the chip.

[0022] In another example, the TIM is disposed on the rear surfaces of the semiconductor chips before bonding the heat distribution device to the rear surfaces of the plurality of semiconductor chips.

[0023] In another example, the TIM is disposed on the bottom surface of the heat distribution device before bonding the heat distribution device to the rear surfaces of the plurality of semiconductor chips. Additionally, the TIM may include solder.

[0024] In another example, the pressurizing device applies pressure to the heat distribution device during reflow. The pressurizing device can be a weight configured to cover the heat distribution device during manufacturing of the chip assembly, and the method can also include applying the weight to the top surface of the heat distribution device. Alternatively or additionally, the pressurizing device can be a rigid plate and include springs at opposite ends of the rigid plate. The method can also include positioning the rigid plate over the rear surface of the heat distribution device and securing the rigid plate to the printed circuit board.

[0025] In another example, the heat distribution device can be a cold plate including a base and a cover. The method can also include bonding the base of the cold plate to the rear surface of the plurality of semiconductor chips before attaching the cover to the base. Additionally, the method can also include bonding the base of the cold plate to the top surface of the stiffener. The cover can also include an inlet and an outlet, and the method can also include providing a fluid connection to connect the inlet and the outlet to a fluid source so as to enable the fluid to be introduced into the heat distribution device and ejected from the heat distribution device.

[0026] Reflowing the bonding material can include reflowing the bonding material disposed between the substrate and the printed circuit board. The heat distribution device can include a base, a thermally conductive fin extending from at least a portion of the base, and a cover, wherein the base is formed of a substrate having a thermal conductivity greater than 394 W / m 2 and at least one of the cover and the thermal fins is made of a material having a thermal conductivity of 394 W / m 2 In another example, the base is made of a material with a thermal conductivity greater than 400 W / m 2 and at least one of the cover and the thermal fins is made of a material having a thermal conductivity of 400 W / m 2 or smaller materials.

[0027] In another example of this aspect, combining the intermediate process unit can also include providing a plurality of intermediate process units, and providing the heat distribution device can also include providing a plurality of heat distribution devices. The method can also include: bonding the plurality of intermediate process units to a printed circuit board by reflowing a bonding material, the bonding material bonding a contact of each of the substrates within the plurality of intermediate process units to a contact of the printed circuit board; bonding the plurality of heat distribution devices to each of the plurality of chips in each of the plurality of intermediate process units by reflowing a highly thermally conductive thermal interface material ("TIM"), each of the heat distribution devices including a plurality of thermally conductive fins, an inlet and an outlet; and bonding the inlet and outlet of each of the heat distribution devices to each other, so that the inlet and outlet of one of the plurality of intermediate process units are fluidly connected to the inlet and outlet of another of the plurality of intermediate process units.

[0028] According to another aspect of the present disclosure, a microelectronic assembly includes a substrate, a plurality of semiconductor chips covered on the substrate, a heat distribution device, a thermally conductive material, and a printed circuit board. The substrate includes an active surface, a passive surface, and contacts exposed at the active surface. The heat distribution device includes a base, thermally conductive fins extending upward from the base, and a cover covering the fins and at least partially enclosing the fins within the base. At least the base is composed of a heat dissipation device having a thermal conductivity greater than 394 W / m 2 At least one of the cover and the thermally conductive fins is formed of a first material having a first thermal conductivity of less than 394 W / m 2 The substrate may be formed of a second material having a second thermal conductivity of 100 W / m or less. The thermally conductive material may be disposed between the heat distribution device and the plurality of semiconductor chips. The thermal expansion coefficients of at least one of the plurality of semiconductor chips and the base are substantially similar or identical. The printed circuit board may be electrically connected to the substrate. In another example, at least the base is made of a material having a thermal conductivity greater than 400 W / m 2 The first material has a first thermal conductivity of less than 400 W / m 2 The second material has a second thermal conductivity of 1000MW or less.

[0029] In one example, the thickness of the TIM may be 200 microns or less.

[0030] In one example of this aspect, the thermally conductive fins are formed of a second material.

[0031] In another example, the cover may be formed from a second material.

[0032] In yet another example, both the cover and the thermally conductive fins are formed of the second material.

[0033] In another example, the cover and the thermally conductive fins are formed of a first material. Additionally, the first material may include silver diamond.

[0034] According to another aspect of the present disclosure, a microelectronic device assembly includes a substrate and a plurality of microelectronic elements connected to the substrate. The microelectronic elements may include an active surface facing the substrate and a passive surface facing away from the substrate. One or more cavities may extend through at least one surface of the plurality of microelectronic elements, and the one or more cavities may be filled with a thermally conductive material to dissipate heat from the plurality of microelectronic elements.

[0035] In one example, the thermally conductive material can be flush with or positioned below at least one surface of at least one of the plurality of microelectronic elements.

[0036] In another example, the thermally conductive material can extend beyond at least one surface of the plurality of microelectronic elements.

[0037] In yet another example, the assembly further includes a heat distribution device having a base and a cover. The base may further include thermally conductive fins. The first material forming the heat distribution device may be different from the second material forming the thermally conductive fins.

[0038] According to another aspect of the present disclosure, a chip assembly includes a substrate, a plurality of semiconductor chips electrically connected to the substrate, and a heat distribution device coupled to the plurality of semiconductor chips. Each of the plurality of semiconductor chips may have an active surface facing the substrate and a passive surface facing away from the substrate. The heat distribution device may include a plurality of heat conducting fins. The first fin length of at least some of the heat conducting fins may be greater than the second fin length of the remaining fins. The first height of at least one of the plurality of semiconductor chips may be less than the second height of another of the plurality of semiconductor chips. At least some of the heat conducting fins having the first fin length cover at least one of the plurality of semiconductor chips having the first height.

[0039] In one example, the heat distribution device may include a base covering the plurality of semiconductor chips, and a plurality of thermally conductive fins extending outwardly from the base.

[0040] In another example, at least some of the outermost tips of the thermally conductive fins are aligned with each other.

[0041] In another example, the base of the heat distribution device extends across the rear surfaces of the plurality of semiconductor chips.

[0042] In yet another example, the assembly may further include a printed circuit board electrically connected to the plurality of semiconductor chips.

[0043] In yet another example, the plurality of semiconductor chips include at least one of the plurality of chips and two directly adjacent chips positioned on opposite sides of the at least one of the plurality of chips. The bottom surface of the base may include a protrusion extending adjacent to the top surface of the at least one chip to accommodate different heights of the at least one of the plurality of semiconductor chips.

[0044] According to another aspect, a method of assembling a cooling circuit assembly to an intermediate process unit includes: coupling a plurality of intermediate process units to a circuit board; coupling a plurality of heat distribution devices to corresponding intermediate process units in the plurality of intermediate process units, wherein each of the plurality of heat distribution devices includes an inlet and an outlet; and joining the cooling circuit assembly to the inlet and outlet of each of the plurality of heat distribution devices. Each intermediate process unit may include a substrate and at least one microelectronic element electrically connected to the substrate, wherein the microelectronic element may have an active front surface facing the substrate and an opposite rear surface facing away from the substrate. The cooling circuit assembly may include a network of fluid lines connected to each inlet and each outlet.

[0045] In one example, a plurality of heat distribution devices may be coupled to a corresponding plurality of intermediate process units prior to joining the cooling circuit assembly to each of the heat distribution devices. Additionally, each of the plurality of heat distribution devices may include a base and a cover. An inlet and an outlet of each of the heat distribution devices may extend from the cover. Before joining the cover of each of the plurality of heat distribution devices to the base and prior to joining the cooling circuit assembly, the base of each of the plurality of heat distribution devices may be coupled to a corresponding intermediate process unit of the plurality of intermediate process units. Additionally, a bottom surface of each base of each of the plurality of heat distribution devices may be attached to a rear surface of at least one microelectronic element of a corresponding intermediate process unit of the plurality of intermediate process units. Additionally, a thermal interface material may be used to couple the bottom surface of the base to a rear surface of at least one microelectronic element of each of the plurality of intermediate process units.

[0046] According to another example, each of the plurality of intermediate process units may further include a stiffener covering the substrate and extending around at least a portion of at least one microelectronic element of each of the plurality of intermediate process units. The bonding of the heat distribution device may further include bonding the bottom surface of the base to the stiffener.

[0047] In another example, a cooling circuit assembly may be coupled to the inlet and outlet of each respective heat distribution device prior to coupling the cover to the base.

[0048] According to another example, the cooling circuit assembly may be coupled to the inlet and outlet of each of the heat distribution devices by one of quill fittings, barbs, or brazing.

[0049] According to another example, the heat distribution device may be attached to the intermediate process unit before the cooling circuit assembly is coupled to the heat distribution device.

[0050] According to another example, the intermediate process unit further includes an interposer electrically connected to the substrate. At least one semiconductor chip may be covered on the substrate and may be electrically connected to the substrate through the interposer.

[0051] According to another example, at least one microelectronic component of at least one intermediate process unit includes a plurality of microelectronic components, and at least one of the plurality of microelectronic components has been thinned to have a different height than at least another of the plurality of microelectronic components. The shape of the heat distribution device can be configured to accommodate the different heights of the thinned microelectronic components.

[0052] According to one aspect of the present disclosure, an example microelectronic device assembly includes a substrate, a microelectronic element electrically connected to the substrate, a stiffener element overlying the substrate, and a heat distribution device overlying a rear surface of the microelectronic element. The microelectronic element may have an active surface facing the substrate and a rear surface facing away from the substrate. The stiffener element may extend around the microelectronic element. The stiffener element may include a first material having a first coefficient of thermal expansion ("CTE"). A surface of the stiffener element may face the heat distribution device. The heat distribution device may include a second material having a second CTE. The first material may be different from the second material. The first CTE of the first material of the stiffener element may be greater than the second CTE of the second material of the heat distribution device.

[0053] According to an example of this aspect, the assembly may also include a first adhesive that bonds the reinforcement element to the substrate, and a second adhesive that bonds the reinforcement element to the heat distribution device. The first adhesive may have a first elastic modulus that is different from the second elastic modulus of the second adhesive. In addition, the first elastic modulus of the first adhesive may be greater than the second elastic modulus of the second adhesive. In addition, the first elastic modulus may range from 10 MPa to 100 MPa, and the second elastic modulus may range from 0.10 MPa to 10 MPa. The first elastic modulus and the second elastic modulus are different.

[0054] According to another example of this aspect, the first CTE of the first material can be at least 50% greater than the second CTE of the second material of the heat distribution device. Additionally, in some examples, the first CTE can be at least 17 ppm / WK at 20°C.

[0055] According to yet another example of this aspect, the first material of the reinforcement element further comprises a first thermal conductivity, and the second material of the heat distribution device may comprise a second thermal conductivity. The second thermal conductivity of the second material may be less than the first thermal conductivity of the first material. Additionally, in some examples, the first thermal conductivity may be greater than 394 W / mK at 20°C.

[0056] According to another example of this aspect, the first material may include copper. Alternatively, the second material may include silver diamond (AgD).

[0057] According to one example of this aspect, the first material includes copper, and the second material includes AgD (silver diamond).

[0058] According to another example of this aspect, the stiffener element and the heat distribution device can be separate structures coupled together. Additionally, the heat distribution device can include a planar surface extending across an entire surface of the stiffener element and an entire rear surface of the microelectronic element.

[0059] According to yet another example of this aspect, the heat distribution device includes a top surface, an opposite bottom surface, and an edge surface extending between the top surface and the opposite bottom surface. The surface of the reinforcement member can be a top surface facing the bottom surface of the heat distribution device. The opposite bottom surface of the reinforcement member can face the substrate. The edge of the reinforcement member can extend between the top surface and the bottom surface of the reinforcement member.

[0060] Additionally, the heat distribution device may be laterally spaced away from the edge of the stiffener element. Alternatively, the edge of the heat distribution device may be vertically aligned with the edge of the stiffener element. In yet another alternative example, the edge of the heat distribution device may be an inner edge extending around the aperture.

[0061] Additionally, according to another example of this aspect, in the case where the edge of the heat distribution device can be an inner edge extending around an aperture, the aperture can be a first aperture. The edge of the reinforcement can be an inner reinforcement edge extending around a second aperture of the reinforcement. The inner edge of the heat distribution device can extend beyond the inner reinforcement edge of the reinforcement element so that the first aperture and the second aperture are aligned.

[0062] According to another aspect of the present disclosure, an example microelectronic device assembly includes a substrate, a microelectronic element electrically connected to the substrate, a heat distribution device overlying the substrate, the heat distribution device overlying the rear surface of the microelectronic device, and a thermally conductive interface material that bonds the heat distribution device to the rear surface of the microelectronic element. The microelectronic element can have an active surface facing the substrate and a passive surface facing away from the substrate. A stiffener element can extend around the microelectronic element. The stiffener element can have a first CTE and the heat distribution device can have a second CTE. The heat distribution device can be composed of a first material that is different from a second material that constitutes the stiffener element. The first CTE can be at least 50% greater than the second CTE.

[0063] According to another example of this aspect, the assembly may further include a first adhesive bonding the stiffener element to the substrate, and a second adhesive bonding the stiffener element to the heat distribution device. The first adhesive has a different elastic modulus than the second adhesive. Additionally, the elastic modulus of the second adhesive may be less than the elastic modulus of the first adhesive.

[0064] In one example of this aspect, the first material of the stiffener element has a first thermal conductivity and the second material of the heat distribution device has a second thermal conductivity, the second thermal conductivity of the heat distribution device being greater than the first thermal conductivity of the stiffener element.

[0065] In another example of this aspect, the heat distribution device is comprised of silver diamond and the stiffener element is comprised of copper.

[0066] In another example of this aspect, the heat distribution device includes a planar surface extending across the entire rear surface of the stiffener element and the microelectronic device.

[0067] In yet another example, the heat distribution device includes a top surface and an opposite bottom surface and an edge surface extending between the top surface and the opposite bottom surface. The stiffener element includes a top surface facing the bottom surface of the heat distribution device, an opposite bottom surface, and an edge surface extending between the top surface and the bottom surface. The edge of the heat distribution device is laterally spaced away from the edge of the stiffener element. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The accompanying drawings are not intended to be drawn to scale. In the various drawings, like reference numerals and names indicate like elements. For the purpose of clarity, not every component may be labeled in every drawing.

[0069] Figure 1 is a schematic cross-sectional view of an example chip assembly according to aspects of the present disclosure.

[0070] Figure 2 yes Figure 1 A perspective view of example components of a chip assembly.

[0071] Figure 3A yes Figure 1 A perspective view of example components of a chip assembly.

[0072] Figure 3B-1 yes Figure 1 A perspective view of another example component of a chip assembly.

[0073] Figure 3B-2 yes Figure 3B-1 An enlarged portion of an example component.

[0074] Figure 3C yes Figure 1 A perspective view of another example component of a chip assembly.

[0075] Figure 4 is a schematic cross-sectional view of an example chip assembly according to aspects of the present disclosure.

[0076] Figure 5 yes Figure 4 A perspective view of example components of an example chip assembly.

[0077] Figure 6 is a schematic cross-sectional view of an example chip assembly according to aspects of the present disclosure.

[0078] Figure 7 is a perspective view of another example chip assembly according to aspects of the present disclosure.

[0079] Figure 8 yes Figure 7 A cross-sectional view taken along plane 8-8;

[0080] Fig. 9 yes Figure 7 An exploded perspective view of an example chip assembly.

[0081] Fig. 10A Is from Figure 7 Another example set of components of a combination.

[0082] Fig. 10B yes Fig. 10A The enlarged part.

[0083] Fig.11A is a schematic cross-sectional view of an example chip assembly according to one aspect of the present disclosure.

[0084] Fig. 11B yes Fig.11A Components of an example chip assembly.

[0085] Figures 12A-12H Is manufacturing Figure 1 An example method of chip assembly.

[0086] Fig.12I is used to Figures 12A-12H Example methods and structures for connecting chip components to pipeline systems.

[0087] Figure 12H-1 Is manufacturing Figure 1 Alternative assembly methods for chip components.

[0088] Figures 13A-13H Is manufacturing Figure 4 An example method of chip assembly.

[0089] Fig.14A is a schematic cross-sectional view of an example intermediate process unit according to aspects of the present disclosure.

[0090] Fig. 14B is a perspective view of a plurality of intermediate process units attached to an example server tray in accordance with aspects of the present disclosure.

[0091] Fig. 14C is an exploded view of an example chip assembly according to aspects of the present disclosure.

[0092] Fig.15 is a perspective view of a server tray utilizing different example pressurization components in accordance with aspects of the present disclosure.

[0093] Figures 16A-16B and Figures 17A-17B Example pressurized components according to aspects of the present disclosure are illustrated.

[0094] Fig.18 Another example pressurizing component according to aspects of the present disclosure is illustrated.

[0095] Fig.19 yes Fig.12I Schematic top plan view of a chip assembly.

[0096] Fig. 20 is a schematic top plan view showing example cooling circuit connections.

[0097] Fig.21 yes Fig. 20 A side plan view of the example components shown.

[0098] Fig. 22 is a schematic top plan view of example cold plates incorporated together in an example cooling loop according to aspects of the present disclosure.

[0099] Fig.23A is an exploded view of example components of an example cooling assembly according to aspects of the present disclosure prior to engagement with an example chip package.

[0100] Fig. 23Bis an exploded view of example components of an example cooling assembly according to aspects of the present disclosure prior to engagement with an example chip package.

[0101] Fig.23C is an exploded view of example components of an example cooling assembly according to aspects of the present disclosure prior to engagement with an example chip package.

[0102] Fig.23D is an exploded view of example components of an example cooling assembly according to aspects of the present disclosure prior to engagement with an example chip package.

[0103] Fig.24A is an exploded view of example components of an example cooling assembly according to aspects of the present disclosure prior to engagement with an example chip package.

[0104] Fig. 24B is an exploded view of example components of an example cooling assembly according to aspects of the present disclosure prior to engagement with an example chip package.

[0105] Fig.25 is a diagram of example components of an example cooling assembly prior to engagement with an example chip package according to aspects of the present disclosure.

[0106] Fig.26 is a graph providing the results of the simulation.

[0107] Fig. 27 are example illustrative sub-components according to aspects of the present disclosure.

[0108] Fig.28 are example illustrative sub-components according to aspects of the present disclosure.

[0109] Fig.29 are example schematic components according to aspects of the present disclosure.

[0110] Fig.30 are example illustrative sub-components according to aspects of the present disclosure.

[0111] Fig.31 are example schematic components according to aspects of the present disclosure.

[0112] Fig.32 are example schematic components according to aspects of the present disclosure.

[0113] Fig.33 are example schematic components according to aspects of the present disclosure.

[0114] Fig.34 are example schematic components according to aspects of the present disclosure.

[0115] Fig.35 are example schematic components according to aspects of the present disclosure.

[0116] Fig.36 is an example chart showing substrate warpage comparison and corresponding devices.

[0117] Fig.37 are example schematic components according to aspects of the present disclosure.

[0118] Fig.38 are example schematic components according to aspects of the present disclosure.

[0119] Fig.39 are example schematic components according to aspects of the present disclosure.

[0120] Fig.40 yes Fig.39 The example in FIG. 1 illustrates a top plan view of an assembly. DETAILED DESCRIPTION Overview

[0121] Various aspects of the present disclosure disclose a chip assembly incorporating a heat distribution device, such as a cold plate, that is bonded to the chip using highly thermally conductive materials and optimized manufacturing methods. Additionally, the structures and methods disclosed herein allow for greater control over bond wire thickness, which is critical for controlling heat generated by high power devices.

[0122] The heat generated by each chip can further cause a hot spot to be created at the central portion of the chip, which may be difficult to access, especially when multiple chips are provided in an array. Various aspects of the present disclosure address the increased heat by thinning one or more portions of the chip and / or modifying the structure of the heat distribution device to accommodate the size changes of the chip. In one example, the bottom surface of the heat distribution device is adapted to accommodate the different thicknesses of one or more chips that may have been thinned. The heat distribution device may include one or more protrusions extending from its bottom surface, the bottom surface of which can be overlaid on a chip that may be thinner than an adjacent chip and in closer proximity to it. This can improve the effectiveness of the heat distribution device. In another example, the die or chip can be thinned by providing multiple cavities in the back surface of the die or chip. The cavity can be filled with a high thermal conductivity ("K") material to obtain enhanced heat distribution. In another example, multiple cavities remain open and can be occupied by extended heat fins from a cold plate.

[0123] The material or combination of materials selected to make the cold plate can also enhance the thermal conductivity and performance of the heat distribution device within the chip assembly. According to another aspect of the present disclosure, an ultra-high thermal conductivity material can be selected to form one or more portions of the heat distribution device. For example, the base or fins of the heat distribution device can be formed of an ultra-high thermal conductivity material such as silver diamond.

[0124] A stiffener and heat distribution device extending across the rear surface of a microelectronic element can be used in a chip assembly to enhance thermal conductivity and warpage control. This configuration can replace a one-piece and u-shaped heat distribution device that extends both around and along the rear surface of the chip assembly and is directly attached to the substrate and is made of a single material such as copper alone. This configuration can be similarly used to replace a two-piece structure formed of the same material. In addition, the use of a selected combination of materials for the heat distribution device and the stiffener (alone or in combination with a selected adhesive) can also optimize thermal conductivity and warpage control within the chip assembly. For example, the elastic modulus of the adhesive used to bond the stiffener to the substrate can be different from the elastic modulus of the second adhesive used to bond the stiffener to the heat distribution device. In one example, selecting silver diamond (e.g., AgD) as a high thermal conductivity material for the heat distribution device and selecting copper (e.g., Cu, Cu-OFE, CuOHF) for the stiffener can achieve enhanced thermal conductivity and warpage control. It is also possible to achieve better bond line thickness control of the thermal interface material by using this combination. Additionally, using copper to form the stiffener saves the cost of forming a monolithic heat distribution device formed entirely from high cost silver diamond material or other ultra high thermal conductivity material.

[0125] It should be understood that examples of microelectronic elements may include microelectronic chips, semiconductor chips, non-semiconductor chips, MEMs, ASICs, etc. Additionally, discussion of the heat distribution apparatus will often be made herein with reference to a "chip," but it should be understood that the heat distribution apparatus disclosed herein is not limited to use with chips or any particular type of chip, and may include any microelectronic element or device that can benefit from the heat distribution apparatus. Example Package

[0126] Figure 1A schematic cross-sectional view of a microelectronic component assembly 100 according to aspects of the present disclosure is illustrated. In this example, the assembly 100 is supported by a printed circuit board 110 and a substrate 120 overlying the printed circuit board 110. The active front surfaces 142A, 142B, 142C of the respective chips 140A, 140B, 140C can face forward and be bonded to the substrate 120 in a ball grid array. Metallization (not shown) can also be provided on the rear surfaces 144A, 144B, 144C of the chips 140A, 140B, 140C. The chips 140A, 140B, 140C can be electrically interconnected with the substrate 120 by an interposer 126, but as will be shown in other examples herein, an interposer is not necessary. Bonding material such as solder balls 127B may be used to electrically interconnect the chips 140A, 140B, 140C with the interposer 126, and bonding material such as solder balls 127A may be used to electrically interconnect and bond the interposer 126 with the substrate 120. A cold plate 150 overlies the back surfaces 144A, 144B, 144C of the respective chips 140A, 140B, 140C, and a stiffener 130 extends between a bottom surface 162 of a base 160 of the cold plate 150 and a top surface 124 of the substrate 120. The bottom surface 122 of the substrate 120 may be bonded to another device, such as a printed circuit board 110, by another set of solder balls 127C.

[0127] The cold plate 150 may include two components: a cold plate base 160 and a cold plate cover 170 that are joined together. Figure 2 3, an example base 160 and cover 170 are shown. Base 160 may include a bottom surface 162 and an opposite top surface 164. Similarly, cover 170 may include a bottom surface 172 and an opposite top surface 174, from which an inlet 176A and two outlets 176B may extend. In other examples, the configuration of the inlet and outlet can vary, such as having two outlets directly adjacent to each other, or having two inlets and one outlet, or having any desired configuration of the inlet and outlet. Molding, machining and similar processes may be used to manufacture base 160 and cover 170.

[0128] The base 160 may include: a plurality of thermally conductive fins 166 that help promote cooling of the assembly 100; and a recess 168A extending around the fins 166. The fins may be longitudinal structures extending outward from the surface of the base, such as those known in the art. The fins may be integrally formed with the base or may be attached to the base by welding, adhesives, etc. In this example, the fins 166 are integrally formed with the base.

[0129] The cover 170 overlies the base 160 such that the bottom surface 172 of the cover 170 is directly adjacent to the top surface 164 of the base 160. Although not required and as Figure 1168A to form a seal between the base 160 and the cover 170. When combined together, the base 160 and the cover 170 allow fluids and gases to enter the cold plate 150 through the inlet 176A and flow out of the cold plate 150 through the outlet 176B. Additional O-rings 178 ( Figure 1 ) to provide a seal between the inlet 176A and the outlet 176B and components that may be connected to them.

[0130] The base 160 and the cover 170 can be formed of known heat dissipation materials such as aluminum, copper, silver, and metal alloys. In this example, the base 160 and the cover 170 are formed of the same material, but in other examples, and as will be discussed in more detail below, the materials constituting the base and the cover may be different.

[0131] refer to Figure 1 and Figure 3A , a stiffener ring such as stiffener 130 may extend circumferentially around chips 140A, 140B, and 140C. Stiffener 130 includes a bottom surface 132, an opposite top surface 134, and an aperture 136 extending through top surface 132 and bottom surface 134. Bottom surface 132 of stiffener 130 can be attached to top surface 124 of substrate 120, and top surface 134 of stiffener 130 can be attached to bottom surface 162 of cold plate base 160 with a bonding material (not shown) such as an adhesive. Aperture 136 may be approximately centered relative to the outer perimeter of stiffener 130, but in other examples, the position of aperture 136 may be adjusted. For example, the size and shape and position of aperture 136 may be adapted based on the arrangement of circuitry or chips 140A, 140B, 140C of underlying substrate 120 and insert 126 within aperture 136 to be exposed through aperture 136.

[0132] The stiffener 130 can be constructed of a variety of materials. In one example, the stiffener is formed of copper and is later plated with electroless nickel (or a similar metal to promote bonding to the substrate 120).

[0133] The reinforcement member can be further modified to provide a ridge 137-1 extending along at least one edge of the reinforcement member 130-1. For example, Figure 3B-1 and Figure 3B-2 A ridge 137-1 is shown extending around all four edges of the reinforcement 130-1, and partially between the top surface 134-1 and the opposing bottom surface 132-1. The ridge 137-1 allows gas to vent during the reflow process. The reinforcement 130-1 can alternatively include an aperture extending completely through the thickness of the reinforcement along at least one edge of the reinforcement. For example, Figure 3CApertures 139 - 2 are shown extending around all four edges of the stiffener 130 - 2 and between the top surface 134 - 2 and the bottom surface 132 - 2 , although any number of apertures can extend around one or more edges.

[0134] Return to reference Figure 1 , a thermal interface material ("TIM") having a high thermal conductivity ("k") may be used to directly bond or couple the cold plate 150 to the chips 140A, 140B, and 140C. In this example, the bottom surface 162 of the base 160 of the cold plate 150 is directly bonded to the back surfaces 144A, 144B, 144C of the respective chips 140A, 140B, 140C using a TIM 180. The TIM 180 may be a high-k TIM, which may also be a metal with a low melting temperature, including a metal or graphite such as nanosilver or indium, but other high-k TIM materials may be implemented. Thus, direct soldering is one example for directly bonding the cold plate 150 to the chips 140A, 140B, 140C. Additionally, in some embodiments, it may be desirable to use an ultra-high-K material for the TIM, as will be discussed herein. However, the methods and structures disclosed herein can also be utilized with a low-k TIM having a reduced level of thermal conductivity.

[0135] The TIM may be provided in any desired form such as liquid, solid, semi-solid, etc. For example, the TIM may be applied in a liquid form that will later solidify and remain as a soft elastomer. In other examples, the TIM may be a grease, a film, or a solder.

[0136] The insert 126 may be a conventional insert configured to provide electrical interface routing between the bonding pads 146 of the chips 140A-140C and the contacts 128 disposed at the surface of the substrate 120 to which the chips 140A-140C are attached. It should be understood that throughout the disclosure, contacts exposed at the surface of the substrate, disposed at the surface of the substrate, or at the surface of the substrate are understood to mean having a surface exposed for electrical interconnection. The contacts themselves may be partially above or below the surface of the substrate, may be completely disposed at the top surface of the substrate, or may be any contact configuration that allows electrical interconnection. The insert 126 may include contacts 128 at its top surface 125, contacts 129 at its bottom surface 127, and conductive vias (not shown) extending between the top and bottom surfaces. The bonding pads 146 of the chips 140A-140C may be directly bonded and soldered to the contacts at the insert in a ball grid array pattern. The bond pads of the chips 140A- 140C will be electrically connected to contacts on the substrate 120 through conductive vias.

[0137] The interposer may be joined to the printed circuit board 110 by using an array of solder balls 127C. Solder balls may first be applied to contacts of the interposer 126 or printed circuit board 110. The printed circuit board may be any known circuit board adapted for use alone or in conjunction with another device. In some examples, the printed circuit board may be a server tray.

[0138] Figure 4 is with Figure 1 Another example assembly 200 is the same except that it also includes a spring 290 covering the stiffener 230. As shown, the assembly 200 includes a substrate 220 and chips 240A, 240B, and 240C electrically connected to the substrate 220 through an insert 226, all of which are attached to a printed circuit board 210. A cold plate 250 is provided within the assembly to distribute the heat generated by the chips 240A, 240B, and 240C. The cold plate 250 also includes a base 260 and a cover 270. The base 260 may include a recess 268 and a fin 266 disposed within the recess 268. The base 260 may directly overlie the back surface 244A, 244B, 244C of the chip 240A, 240B, 240 and be attached to the back surface 244A, 244B, 244C of the chip 240A, 240B, 240 through a TIM 280 such as a high-K TIM and other TIMs discussed previously herein. The base 260 may also directly overlie the stiffener 230 and the spring 290.

[0139] The spring 290 may be positioned between the bottom surface 262 of the base 260 and the top surface 234 of the reinforcement member 230. Figure 5 As shown, pillars 292 may be positioned at the corners of stiffener 230 and extend outwardly from top surface 234 of stiffener 230. Springs 290 may be wrapped around pillars 292. Springs 290 can provide additional pressure to the substrate to minimize warping of the assembly, as well as achieve greater control over bond line thickness of TIM 280.

[0140] Figure 6Another example assembly 300 is provided in accordance with aspects of the present disclosure. Assembly 300 is similar to the prior examples in that the assembly generally includes a substrate 320, a stiffener 330, an insert 326, and a cold plate 350, all of which can be overlaid on a printed circuit board 310 and electrically interconnected therewith. The cold plate also includes: a base 360 ​​having fins 366; and a cover 370, which includes at least one inlet. In this example, a single inlet 376A and two outlets 376B are provided. Additionally, a thermal TIM 380 including a high-K TIM discussed previously herein can be used to bond the cold plate base 360 ​​to the chips 340A, 340B, 340C. Assembly 200 differs from the prior examples due to the arrangement of the cold plate 350. As shown, the cold plate 350 only overlies the chips 340A, 340B, 340C, and not the stiffener 330. The top surface 334 of the stiffener 330 instead remains exposed because it no longer supports the cold plate 350. In this arrangement, the weight of the stiffener 330 alone becomes one of the primary forces for maintaining warpage control for the substrate 220 and the printed circuit board 310 of the assembly 300 .

[0141] Figure 7-9 Another example assembly 400 is illustrated. Figure 7 A perspective view of the assembly 400 is shown and Figure 8 This assembly 400 is similar to the previously disclosed assemblies except that the microelectronic element is attached directly to the substrate without an interposer and the pad 412 is located below the printed circuit board 410. Fig. 9 As seen in FIG. 4 , an exploded perspective view of subassembly 400-A of assembly 400 is illustrated without the printed circuit board and backing plate 412. Subassembly 400-A (also shown in FIG. Figure 8 4) can include a plurality of chips, a stiffener 430, a TIM 480, a cold plate 450 (which in this example includes a base 460 with fins 466 and a cover 470), and an O-ring 468, such as the examples previously disclosed herein, although many variations of the examples provided herein can be utilized. The TIM can include at least a high-K TIM or an ultra-high-K TIM, as previously described herein. In this example, four chips are disposed in a face-down position, but any number of chips may be implemented. Figure 8As shown, the cold plate base 460 and the cold plate cover 470 are joined together by screws 494. The bottom surface 462 of the base 460 is bonded to the back surface 444A-E of the corresponding chip 440A-440E with a TIM 480, such as disclosed herein. The chips 440A-440E are directly bonded to the substrate 420. Although not shown, the bonding pads on the chips 440A-440E can be bonded to contacts on the substrate 420 through solder connections such as a ball grid array. The stiffener 430 overlies the substrate 420. The chips 440A-440E and a portion of the bottom surface 462 of the base 460 are positioned within the aperture 436 of the stiffener 430. In this example, the base 460 overlies the stiffener 430, but is not directly attached to the stiffener 430. There is a gap G ( Figure 8 ), so that the cold plate 450 does not apply direct pressure to the reinforcement member 430.

[0142] Figures 10A-10B Another example arrangement of a stiffener 430, a substrate 420, and chips 440A-440E in an aperture 436 of the stiffener 430 is shown, which can be implemented into any of the aforementioned assemblies. As shown, a shim 438 can be provided in the aperture 436 of the stiffener 430. The shim 438 can extend around the outermost edge surface of the chips 440A-440E. As shown in the enlarged perspective view of FIG. 11, the stiffener ring 430 can be attached to the substrate 420. As shown, the chips 440A-440E are directly attached to the substrate 420.

[0143] Fig.11A Another example assembly 400' is shown. This assembly would otherwise be identical to assembly 400, except that the cold plate base and stiffeners are formed as a single monolithic cold plate base and stiffener unit. Fig. 11B , an example monolithic cold plate and stiffener unit 486 is shown. The monolithic cold plate and stiffener unit 486 includes a body 461' having fins 466' and rigid stiffener legs 463'. A recess 465' is provided between the stiffener legs 463'. Return to Reference Fig.11A, the chips 440A', 440B', 440C' can be coupled or attached to an interposer 426' (such as, for example, a silicon interposer) and a substrate 420', all of which can be coupled or attached to a printed circuit board 410'. The monolithic cold plate and stiffener unit 486 can then be attached to the top surface 424' of the substrate 420'. For example, the TIM 480' can be used to attach the monolithic unit 486' to the back surfaces 444A', 444B', and 444C' of the chips 440A', 440B', 440C'. The TIM can be any TIM, including a high-K TIM or an ultra-high-K TIM. Additionally, an adhesive or the like can be used to attach the bottom surface 432' of the stiffener leg 463' to the top surface 424' of the substrate 420'. The chips 440A', 440B', 440C', insert 426' will be positioned within the recess 465'. Once the monolithic cold plate and stiffener unit 486 is in place, the cold plate cover 470' can then be attached to and overly the monolithic cold plate and stiffener unit 486. In other examples, the cold plate cover 470' can be pre-attached to the monolithic cold plate and stiffener unit 486, and then the two components can be attached to the rest of the assembly. Similarly, the cover 470 can be integrally formed with the stiffeners and cold plate cover to form a monolithic unit consisting of the combination of the cover, stiffeners and cold plate.

[0144] This configuration can provide additional warpage benefits due to the additional structural rigidity of the stiffener 430' created by the addition of the base 460'.This allows the cold plate assembly to be completed at the package level, so that little or no additional thermal processing steps are required at the printed circuit board level. Example Manufacturing Method

[0145] When manufacturing any of the foregoing example assemblies and variations thereof, various methods can be implemented to achieve high thermal conductivity and heat distribution within the package, including controlling bond wire thickness and the number of times reflow occurs.

[0146] Figures 12A-12H Diagram for manufacturing Figure 1 An example method of the assembly 100 shown. Fig. 12A As shown, interposer 526 can be combined with substrate 520. Interposer 526 can include contacts 529 at its bottom surface 527, which can be aligned with contacts 516 exposed at top surface 524 of substrate 520. Solder balls 527A can be disposed on substrate 520 or interposer 526. Fig. 12BAs shown, microelectronic elements such as chips 540A, 540B, 540C can be bonded to the interposer 526 by using solder balls 527B. The chips 540A, 540B, 540C include bonding pads 546 that can be aligned with contacts 528 at the top surface 515 of the interposer 526. The solder balls 527B can be pre-attached to the bonding pads 546 of the chips 540A, 540B, 540C or the contacts 528 of the interposer 526. The package can then be reflowed to secure the bonding connections between the chips 540A, 540B, 540C and the interposer 526 and between the interposer 526 and the substrate 520. Alternatively, a first reflow process can occur to reflow the solder balls 527A and bond the interposer 526 and the substrate 520. A second reflow process can then occur to reflow the solder balls 527B to bond the chips 540A, 540B, 540C to the interposer 526 .

[0147] exist Fig. 12C , a stiffener 530 can be attached to a top surface 524 of a substrate 520. An adhesive (not shown) can be used to bond the stiffener 530 to the substrate 520. The stiffener 530 can extend circumferentially around the chips 540A, 540B, 540C and the insert 526. The combination of the stiffener 530, the substrate 520, and the insert 526 can be sputter coated with a combination of metals such as titanium, NiV, and gold. In one example, three materials having the following thicknesses can be applied as follows: 1000A Ti, 3500A NiV, and 1000A Au. In other examples, one or more of these same or different materials can be applied at the same or different thicknesses. This can help promote chemical bonding between the package and the TIM material. In other examples, the stiffener 530 can be omitted.

[0148] Fig. 12C The resulting subassembly shown is an intermediate process unit 500-1 that can be manufactured by, for example, an outsourced semiconductor assembly and test (OSAT) market company. This arrangement of the first assembly intermediate process unit 500-1 can allow an OSAT manufacturer or the like to manufacture a bare die package and supply it to a contract manufacturer or the like, which can incorporate the intermediate process unit 500-1 into a particular device or application.

[0149] Now turn to Fig.12D, the intermediate process unit 500-1 can be attached to a printed circuit board 510, etc. As shown, the contacts 518 at the bottom surface 522 of the substrate 520 can be aligned with the contacts 506 exposed at the top surface 508 of the printed circuit board 510. The solder balls 527C in the grid array can be used to attach the substrate 520 to the printed circuit board 510. The package can be reflowed at this stage to create a bonding connection. The solder balls 527C can be made of a high melting point solder. In one example, the solder can have a reflow temperature of 260°C, but in other examples, the temperature can be higher or lower. Additionally, different types of solder or different bonding materials can be utilized.

[0150] like Fig.12E As shown, TIM 580 can be applied to the rear surface of chips 540A-540B, 540C. The TIM can be any high-k TIM material disclosed herein, or alternatively any known TIM. Various methods can be used to apply the TIM. In an example where the TIM is a paste, the TIM can be applied directly to the rear surface 544A, 544B, 544C of the chip, after which the TIM is cured and hardened. In another example, the TIM can be pre-reattached to a cold plate, such as a cold plate base 560, by reflowing the TIM 580 (before a secondary reflow to the chip). TIM 580 can alternatively be attached to the cold plate 550 by an adhesive or similar material that can fix the TIM 580 in place before reflow.

[0151] refer to Fig.12F , the base 560 of the cold plate 550 can be attached to the rear surfaces 544A, 544B, 544C of the chips 540A, 540B, 540C and the top surface 534 of the stiffener 530. A TIM 580, such as a high-K or ultra-high-K TIM, can be positioned between the cold plate base 560 and the rear surfaces 544A, 544B, 544C. The TIM 580 can help dissipate the heat generated by the chips 540A, 540B, and 540C. Once the base 560 is positioned over the rear surface and stiffener, the TIM can be reflowed to ensure connection between the cold plate and the chips 540A, 540B, 540C. In some examples, the TIM can be selected so that its reflow temperature is lower than the reflow temperature of the bonding material used to bond the intermediate process unit to the printed circuit board. This may also be beneficial because when the TIM reflows, the bonding material (eg, solder balls 527C) between the printed circuit board 510 and the substrate 520 may not reflow.

[0152] like Figure 12G As shown, an O-ring 568 can optionally be disposed within a recess (not shown) of the cold plate base 560 of the cold plate 550 to accommodate the cover 570 . Fig.12HThe final assembly 500 is shown. The cover 570 including the inlet 576A and the outlet 576B can be attached to the base 560 by using various forms of attachments. In one example, the cover 570 can be screwed together with the base 560, but any known attachment means can be used. In another example, the cover 570 and the base 560 can first be combined together and then attached to the intermediate process unit 500-1 as a completed cold plate assembly.

[0153] Fig.12I The addition of a conduit 582 is shown, which can allow cooling of the chip assembly. In this regard, the conduit can route cooling fluid only to a single chip assembly 500, or can be combined with one or more other chip assemblies (such as will be described in detail in the accompanying drawings). Figure 19-22 576A). As shown, the pipe 582 can be directly connected to the inlet 576A. Additionally, the pipe 582 is connected to the outlet 576B. During operation, this allows water or other liquid to flow into the inlet 576A and the cold plate 550 through the pipe 582, and then flow out of the outlet 576B on the opposite side of the inlet 576A.

[0154] It should be noted that, as discussed above, first preparing the intermediate process unit 500-1 and then subsequently attaching the cold plate base with the TIM can allow for the omission of one or more reflow processes, wherein the reflow temperature of the TIM is lower than the reflow temperature of the bonding material used to bond the intermediate process unit 500-1 to the printed circuit board. This process prevents the TIM material from having to undergo an additional reflow step, which can provide good reliability.

[0155] In another example, the cold plate can alternatively be assembled as part of the intermediate process unit before the intermediate process unit is mounted and bonded to the printed circuit board. Figure 12H-1 As shown, the cold plate base 560-1 is pre-assembled as part of the processing unit 500-1A. Thereafter, the intermediate process unit 500-1A can be mounted to a printed circuit board and a cover (not shown) can be bonded to the base 560. In this example, the TIM used to bond the cold plate base 560-1 to the back surfaces 544A, 544B, 544C of the chips 540A-1, 540B01, 540C-1 and the stiffener 530-1 can be a TIM that is not affected by the reflow process used to bond the intermediate process unit 500-1A to the board. For example, the TIM can be selected to have a higher reflow temperature than the bonding material used to bond the chip to the board.

[0156] refer to Figures 13A-13H , showing the manufacture of a chip assembly such as 200 ( Figure 4 ) chip assembly method. In addition to adding the spring, the manufacturing method is similar to Figures 12A-12I The same approach is discussed in . As in the previous example, Figures 13A-13B The assembly of the chips 640A, 640B, 640C to the interposer 626 and the assembly of the chips 640A, 640B, 640C and the interposer 626 to the substrate 620 are shown. As previously mentioned, the reflow to allow the bonding of the chips 640A, 640B, 640C, the interposer 626 and the substrate 620 can occur in one step (once the chips, interposer and substrate are aligned with each other) or in two steps (first the interposer to substrate solder reflow and then the interposer to chips solder reflow). Additionally, the chips can alternatively be attached to the interposer 626 first and then the chips 640A, 640B, 640C can be attached to the substrate 620 together with the interposer 626.

[0157] refer to Fig. 13C , a stiffener 630 may be provided on the top surface of the substrate 620 and around the chips 640A, 640B, 640C and the insert 626. The pillars 692 may be integrally formed with the stiffener 630 or subsequently added to the top surface of the stiffener 630. (See, e.g. Figure 5 .)like Fig.13D As shown, a biasing mechanism such as spring 690 may be added to support 692. This creates intermediate process unit 600-1.

[0158] Now turn to Fig.13E , the intermediate process unit 600-1 can be attached to a printed circuit board 610 or the like. As shown, contacts 618 at the bottom surface 622 of the substrate 620 can be aligned with contacts 606 at the top surface 608 of the printed circuit board 610. Solder balls 627C arranged in a grid array can be used to attach the substrate 620 to the printed circuit board 610. The package and solder can be reflowed to form a bonding connection.

[0159] like Fig.13F As shown, a TIM 680 can be applied to the back surface 644A, 644B, 644C of the respective chips 640A, 640B, 640C. The TIM 680 can be any TIM material disclosed herein or any known TIM. Various methods can be used to apply the TIM. In an example where the high-K TIM is a paste, the TIM can be deposited directly onto the back surface of the chips 640A, 640B, 640C, and then the TIM is cured and hardened.

[0160] refer to Figure 13G, a base 660 of a cold plate including fins 666 can be attached to the intermediate process unit 600-1 and the printed circuit board. In particular, the base 660 can be attached to the rear surfaces 644A, 644B, 644C of the chips 640A, 640B, 640C, and the top surface 634 of the stiffener 630 including the spring 690. In this example, a TIM 580 can be positioned between the cold plate base 660 and the rear surfaces 644A, 644B, 644C. The TIM will help dissipate the heat generated by the chips 640A, 640B, and 640C. Once the base 660 is positioned over one or more rear surfaces 644A, 644B, 644C and the stiffener 630, the TIM can be reflowed to ensure the connection between the cold plate 650 and the chips 640A, 640B, 640C. The spring 690 can help secure against the pressure of the reinforcement 630 and the base plate 620 by the counterweight of the base 660 and the cover 670. An O-ring 668 can also be disposed within a recess (not shown) of the base 660.

[0161] Fig.13H The final assembly 600 is shown. Various forms of attachments can be used to attach the cover 670 to the base 660. In one example, the cover 670 can be screwed together with the base 660, but in other examples, adhesives or other joining materials can be utilized. As disclosed herein, further loops and conduits can be added to the assembly 600.

[0162] In one exemplary assembly method, Fig.13D As shown, the intermediate process unit 600-1 can be prepared by one manufacturer, such as an OSAT manufacturer, etc. The intermediate process unit 600-1 can then be further packaged by a second contractor, etc., which will then perform Figures 13E-13H Alternatively, Fig.13A All steps in -H can be formed by one entity. In still other examples, the chip can be bonded to the interposer 626 first, and then the combination of the interposer and the chips 640A- 640C can be bonded to the substrate 620 . Methods of attaching TIM materials

[0163] FIG. 14A to FIG. 18 Various methods and variations thereof of attaching TIM material to form the assemblies described herein at the server tray level are illustrated. Fig.14A Graphics and Fig. 12CThe intermediate process unit 700-1 is the same as the intermediate process unit shown. As previously discussed, the intermediate process unit 700-1 can include a substrate 720, an insert 726, and chips 740A, 740B, 740C attached to the insert 726. The reinforcement ring 730 can extend circumferentially around the chips 740A-740C and the insert 726. In other examples, as previously discussed, the intermediate process unit can include different features. For example, the insert 726 and / or the reinforcement 730 can be omitted. The omission of the insert 726 will allow the chips 740A, 740B, 740C to be directly connected to the substrate 720.

[0164] After forming the intermediate process unit 700-1, package metallization can be performed. The intermediate process unit 700-1 can be sputter coated with a combination of metals including, for example, titanium, NIV, and gold. This will help promote chemical bonding between the intermediate process unit 700-1 and the TIM 780 (as will be discussed in more detail below).

[0165] A plurality of intermediate process units 700-1 can be applied to a printed circuit board, such as a server tray 710. In one example, Fig. 14B As shown, after metallization, each intermediate process unit 700 - 1 may be reformed into solder balls and then reflowed to attach and bond each intermediate process unit 700 - 1 to the server tray 710 .

[0166] As previously discussed, the next stage of the process is to attach a cold plate to each of the respective intermediate process units 700 - 1 . Fig. 14C An exploded view of an example completed assembly 700 is illustrated to facilitate discussion. In one example, a TIM 780, such as a high-K TIM disclosed herein, can be applied directly to the back surface 744A, 744B, 744C of the chip 740A, 740B, 740C, and then the cold plate 750 (which in this example can include a cold plate base 760 and a cold plate cover 770) can be attached to the intermediate process unit 700-1. In another example, the TIM 780 can be pre-reattached to the cold plate base 760 by reflowing the TIM 780 (before secondary reflow to the chip), or alternatively attaching the TIM 780 to the cold plate base 760 by an adhesive or similar material that can fix the TIM 780 in place before reflow. Other methods can also be implemented. Some example attachment methods will be discussed in more detail below.

[0167] Different methods can be used to provide a TIM on the back surface 744A, 744B, 744C of the respective chips 740A, 740B, 740C. Fig.15A server tray 710 is illustrated showing two example pressurization methods and example structures ( 754 , 756 ) for attaching a cold plate to an intermediate process unit 700 - 1 .

[0168] In one example 756, a weight 758 may be applied above the intermediate process unit 700-1 (or any unit undergoing reflow), which would allow the weight of the weight to provide pressure on the TIM 780 during reflow ( Fig. 14C ).like Fig. 16B and the counterweight 758 is shown in transparent form for illustration and discussion purposes. Fig.16A As shown in the enlarged view of , the counterweight 758 can be a solid single piece of material block. The counterweight 758 can be alternatively formed by a plurality of parts combined together, and / or include a part that is not solid. The counterweight can be in various shapes, sizes and configurations. In one example, the counterweight 758 includes a top surface 759A, which is shown as a continuous plane surface in this example, but in other examples, the top surface 759A can vary. The opposite bottom surface 759B of the counterweight 758 can also include an extension portion EP centrally located along the bottom surface 759B. The extension portion EP can extend beyond the two lower portions LP. The extension portion EP can be substantially planar so as to allow uniform force or pressure to be applied to the intermediate process unit 700-1. In other examples, the extension portion EP can be omitted so that the resulting bottom surface of the counterweight 758 can be a continuous and substantially planar surface. In still other examples, the extension portion EP may not extend across the entire rear surface of the intermediate process unit 700-1, but can be alternatively configured so that it only covers some parts of the intermediate process unit. The counterweight 758 can be constructed of a variety of materials, but in one example, the counterweight 758 is formed of stainless steel. The counterweight 758 can be any specified or desired amount of counterweight, but in one example, the counterweight is 5 kg. In other examples, the counterweight can be greater or less than 5 kg. The counterweight 758 may include a recess 750A configured to accommodate an orifice or post 750B that can be disposed on the cold plate and extend away from the cold plate. The orifice or post 750B can guide the counterweight 758 to ensure that the counterweight 758 is properly placed above the intermediate process unit 700-1. Additionally, as in Fig.17A and Fig. 17B As seen better in FIG. 7 , a fixture 752 can also be provided directly adjacent to the base of the counterweight 758 and the intermediate process unit 700 - 1 . The fixture 752 can include a recess 755 adapted to receive a spacer or bolt on the tray 710 .

[0169] The counterweight may be removable or mechanically attached to the circuit board. For example, the counterweight may be directly attached to the circuit board with a mechanical fastener (not shown) such as a screw or bolt. Additionally or alternatively, the counterweight may be coupled or attached to an auxiliary fixture that can control the movement and positioning of the counterweight. In such an example, the auxiliary fixture can position the counterweight to overlie the chip assembly and then apply pressure to the counterweight and chip assembly during the reflow process.

[0170] At the end of the reflow process, the weight can be removed.

[0171] Utilizing weights 758 to secure the high-k TIM to the back surfaces 744A, 744B, 744C of the chips 740A-740C can help provide even load distribution, large thermal mass, and consistent loading during reflow. The weights 758 can then be removed at the end of reflow.

[0172] In another example 754, reference Fig.15 and Fig.18 , a pressurized plate 761 with a spring connection 792 can be used to help provide pressure during reflow. Fig.18 As best shown in the enlarged view of , the pressure plate 761 is a plate that covers an intermediate process unit such as the intermediate process unit 700-1 and applies force to it. The pressure plate 761 can be a rigid plate that is machined to provide the desired thread offset. The pressure plate 761 can be of various shapes and sizes, as long as the pressure plate 761 can apply pressure to the intermediate process unit 700-1. Four spring assemblies can be positioned at each of the four corners of the pressure plate 761. Spring 792 can help accommodate differences in force. The pressure plate 761 can similarly include an aperture 750B-1, which is configured to accommodate an orifice or post 750A-1, which places the pressure plate 761 in an appropriate position to cover the intermediate process chip assembly and also prevents the pressure plate 761 from moving in a lateral direction. Example Pallet-Level Cooling Circuit

[0173] refer to Fig.19 (and return reference Figures 12A-12I ), shows a schematic top view of four chip assemblies 500-A, 500-B, 500-C, 500-D mounted on a printed circuit board such as a server tray 510-1. The configuration of the assemblies 500-A, 500-B, 500-C, 500-D can be similar to Fig.12HThe chip assembly 500 shown is the same, except that the printed circuit board is instead a larger circuit board, such as server tray 510-1, and is configured to accommodate multiple rows and columns of chip assemblies 500-A, 500-B, 500-C, 500-D. As shown, each cold plate cover 570A, 570B, 570C, 570D includes an inlet and a pair of outlets. For example, cold plate cover 570A includes an inlet 576-AA and an outlet 576B-A on the opposite side of the inlet 576-AA. In this example, only four chip assemblies are shown, but any number of chip assemblies can be used and arranged on server tray 510-1.

[0174] When configuring chip assemblies 500-A, 500-B, 500-C, 500-D, in one example, the cold plate base of each of chip assemblies 500-A, 500-B, 500-C, 500-D can first be joined (not shown) to a corresponding chip assembly or intermediate process unit, which is attached to server tray 510-1. In one example, the final assembly of the cold plate cover can occur sequentially. For example, cold plate cover 570A can first be attached to the cold plate base (not shown) within assembly 500-A. Cold plate cover 570B can then be attached to the cold plate base (not shown) of assembly 500-B; cold plate cover 570C can then be attached to the corresponding cold plate base (not shown) within assembly 500-C; and finally, cold plate cover 570D can then be attached to its corresponding cold plate base (not shown) within assembly 500-D. The order of assembly can of course vary. Alternatively, two or more of the cold plate covers 570A, 570B, 570C, 570D can be attached simultaneously. In still other examples, the cold plate covers 570A, 570B, 570C, 570D can be attached in any order.

[0175] Once the corresponding cold plate covers are attached, they can be connected together in the piping and cooling circuits. Fig. 20 , the cold plate covers 570A, 570B, 570C, 570D can be connected together via a continuous piping loop or cooling loop 582, which allows a fluid, such as water, to flow through the cold plate system. For example, referring to component 500-A, loop 582 is first connected to inlet 576A-A, which will allow a fluid, such as water, to flow into the cold plate of component 570A and then exit component 570A through outlet 576B-A on the opposite side of inlet 576A-A. This same pattern of loop 582 will continue through each of the remaining components 500-B, 500-C, and 500-D. Fig.21 An example three-dimensional side view of loop 582 overlaid on components 500-C and 500-D is illustrated in FIG.

[0176] exist Fig. 22 In another example shown, the cooling loop 582 can first be attached to each of the cold plate covers 570A, 570B, 570C, 570D before attaching the cold plate covers 570A, 570B, 570C, 570D to their respective cold plate bases. This allows the formation of a cooling loop unit 582A including the cold plate covers 570A, 570B, 570C, 570D and the cooling loop 582, which can then be attached to the respective cold plate base 560. Once the entire pre-connected loop assembly 582 is formed, the pre-connected loops and cold plate covers 570A, 570B, 570C, 570D can be directly attached to the respective cold plate bases to complete the respective chip assemblies.

[0177] In yet another example, rather than first attaching the cold plate base to the back surface of the TIM and chip, the cold plate base and cold plate cover 570A, 570B, 570C, 570D can first be joined together along with the pre-assembled cold plate loop 582. Once assembled, the combination of the cold plate base, cold plate cover, and cold plate loop can be directly attached to the back of the chips 540A-540D as a single unit.

[0178] exist Fig.23A -C. Fig.24A -B and Fig.25 Additional three-dimensional (3D) views and examples of cooling circuit assemblies are shown in . These figures illustrate the components of the system prior to reflowing and attaching the cold plate cover to the intermediate process unit. In particular, the assembly illustrates the components of the cold plate and cooling circuit assembly and the pressurization device prior to welding the cold plate base to the assembly. In each example, the example intermediate process unit, such as previously discussed herein, has been shown as being welded to a circuit board (see, e.g. Fig.12D ), such as server tray assemblies. Figure 23A-25 An example assembly method is shown in which a cold plate base is assembled and attached to an intermediate process unit and circuit board. In some examples, the cold plate base can be bonded to the intermediate process unit and circuit board by using a high thermal conductivity material before attaching the cold plate cover and cooling circuit. Alternatively, the cold plate base can be attached to either or both of the cold plate cover and / or cooling circuit before being bonded to the intermediate process unit and circuit board. For ease of discussion, the cold plate base will be assembled and attached to the intermediate process unit and circuit board. Fig.23A -C. Fig.24A -B and Fig.25 In each of the drawings, the same reference numerals are used throughout to discuss the same components.

[0179] Fig.23AAn example exploded view showing the components of the system prior to reflowing and attaching the cold plate to the intermediate process unit is provided. In this example, each cold plate base is first bonded (not shown) to the intermediate process unit including the chip and circuit board using any thermally conductive material (including solder); thereafter, a cold plate cover can be assembled to the cold plate base and chip; and then a cooling loop can be assembled to each respective cold plate cover.

[0180] As previously discussed herein, the cold plate base can first be joined to the intermediate process unit. For example, each cold plate base 860 can be attached to each of the corresponding intermediate process units 800-A, 800-B, 800-C, 800-D using a highly thermally conductive material such as solder, which may be obtained by directly attaching the cold plate base 860 to the rear surface of the chip (not shown) of each intermediate process unit 800-A, 800-B, 800-C, 800-D. The joining can occur by using any desired material. In one example, a highly thermally conductive material or an ultra-high thermally conductive material, such as those discussed herein or to be discussed herein, can be utilized. Thereafter, the remainder of the cold plate assembly can be mounted to the base. For example, each cold plate cover 870 can be attached to the base 860 together with the pressurized plate assembly 867, thereby covering each corresponding intermediate process unit 800-A to 800-D, and the pressurized plate assembly also includes a pressurized plate 861, a spring 892 and an opening 863 to accommodate the connection to the cooling circuit 882. Thereafter, the cooling circuit 882 can be attached. As shown, the cooling circuit 882 can include a flexible hose 882A and an interconnecting sealing tube and fittings 883, such as British standard cylindrical pipe ("BSPP") threaded fittings with O-ring face seals. An enlarged view of an example fitting 883 is also shown. Other fittings, configurations, etc. can be utilized in conjunction with this manufacturing process.

[0181] In addition to the method and order of assembling the parts, Fig. 23B and Fig.23A same. Fig. 23B Another example is provided in which the cold plate base 860 is first joined (not shown) to each of the corresponding intermediate process units 800-A, 800-B, 800-C, 800-D, and then the corresponding cold plate cover 870, cooling circuit 882 and pressurization plate assembly 867 (which includes pressurization plate 861 and spring 892) are attached thereafter. However, in this example, the cooling circuit 882 can first be pre-attached directly to the inlet and outlet of the cold plate cover 870 to form a subassembly 895, which includes the cover 870, the cooling circuit assembly 882 and the pressurization plate assembly 867. The subassembly 895 can then be attached directly to each cold plate base 860, which has already been attached to the corresponding intermediate process unit 800-A, 800-B, 800-C, 800-D. Alternatively, in conjunction with Fig.23Aand Fig. 23B In the otherwise identical configuration, Fig.23C An example utilizing barb fittings 883B rather than BSPP fittings is illustrated. The remaining components can be the same as the previous examples, as indicated by similar reference numerals. In still other examples, different types of fittings may be utilized to form connections between the cooling circuit and the inlet and outlet of the cold plate.

[0182] Fig.23D 800-A, 800-B, 800-C, 800-D. The subassemblies including the cold plate cover 870, the pressurization assembly 867, and the cooling circuit 882 may be first and additionally attached together as a module unit or subassembly 850, which is then attached to the cold plate base 860 as a completed subassembly 850. This example is otherwise similar to Fig.23C : The cover 870 and cooling circuit 882 are pre-assembled together before being attached to the cold plate base 860. However, in this example, the cooling circuit 882 (along with the pressurization assembly 867) is brazed to the cold plate cover 870 and then bonded to the cold plate base 860. In other examples, various alternative methods and configurations may be used to attach the cooling circuit 882 to the cold plate cover 870.

[0183] Fig.24A The illustration first combines the cold plate cover 870, the cold plate base 860, and the pressurization assembly 867 as an example of the subassembly 850. As in the previous example, this can optionally include an assembly of an O-ring 868. Each subassembly 850 can then be joined to the intermediate process unit 800-C and the tray 810 by using a thermally conductive interface material, including using solder to solder the subassembly 850 to each of the intermediate process units 800-A, 800-B, 800-C, 800-D. In one example, as previously discussed, each base 860 of each subassembly 850 can be joined to the corresponding intermediate process unit 800-A, 800-B, 800-C, 800-D by using a high thermally conductive interface material as previously discussed herein. Thereafter, the cooling and piping loop 882 can be attached to the cover 870. In other examples, the cold plate can be a single integral cold plate with both the cover and the base formed without separation.

[0184] Fig. 24B and Fig.24A800-A, 800-B, 800-C, 800-D, as previously discussed. The cooling circuit 882 can then be coupled to the subassembly 850.

[0185] Fig.25 An example exploded view is shown in which the entire cooling circuit 882, the cold plate assembly 850 (including the cold plate cover 870 and the cold plate base 860), and the pressurized plate assembly 867 are pre-attached together to form a completed cooling unit 899. In this example, the cooling circuit 882 is brazed to the cold plate cover to form the completed cooling unit 899, but other forms of connection are contemplated within the scope of the present disclosure. Each of the cooling circuit 882 and the cold plate base can then be attached and joined to each of the corresponding intermediate process units 800-A, 800-B, 800-D, 800-C, 800-D.

[0186] It should be understood that in these examples, different types of intermediate process units and components may be attached to circuit board 810 . Example Materials That Make Up a Cold Plate

[0187] As an alternative to the methods and structures described above and to be described below, or in addition to the methods and structures described above or to be discussed below, forming a cold plate by selecting a material can improve heat distribution. For example, selecting an ultra-high thermal conductivity (k) material to form a cold plate can provide the best results. In some examples, an ultra-high thermal conductivity (k) material having a coefficient of thermal expansion ("CTE") that matches the silicon in a semiconductor chip can be used to make a cold plate or portions of a cold plate. In other examples, selecting a material with a thermal conductivity greater than copper (394 W / mk at 20°C) can help provide optimal heat distribution. For example, silver diamond (AgD) (900 W / mK), which has a thermal conductivity significantly greater than that of copper (394 W / mk), is an example of an ultra-high thermal conductivity (k) material. In other examples, other ultra-high thermal conductivity materials having a thermal conductivity greater than that of copper (394 W / mk) can be utilized. The ultra-high thermal conductivity materials selected for constructing the cold plate, alone or in combination with TIMs and / or structures such as those disclosed herein, can help provide optimal heat distribution in the chip assembly.

[0188] For ease of discussion, we will refer to Figure 1Example chip assembly, wherein the cold plate 150 is attached to the chips 140A, 140B, 140C via the TIM 180. However, it should be understood that the choice of materials for the components is not limited to Figure 1 For example, the cold plate may be a single piece cold plate base and lid combined together; the cold plate base may not include fins and may be capable of utilizing less than three chips or more than three chips within the chip package.

[0189] In one example, the cold plate base 160 is formed of an ultra-high-k thermally conductive material having a CTE that matches at least one of the semiconductor chips 140A, 140B, 140C. The high-k material can achieve greater thermal performance by dissipating heat. The fins 166 of the base 160 of the cold plate can be made using this same material. To attach the base 160 of the cold plate 150 to the chips 140A-140C, as previously discussed, the base 160 of the cold plate 150 can be attached to the back of the chips 140A, 140B, 140C with a TIM such as grease, solder, or other material.

[0190] In another example, the cold plate base 160 can be made of an ultra-high thermal conductivity material. In some examples, the ultra-high thermal conductivity material can have a thermal conductivity greater than copper (394 W / mk at 20°C). Such materials can include AgD or any other ultra-high K material or a combination of these materials. The fins 166 and the cover 170 can be formed of different materials with lower thermal conductivity than the ultra-high thermal conductivity material used to form the cold plate base 160. In some examples, the fins 166 can be soldered, plated, or 3D printed onto the base 160. In order to attach the cold plate base 160 to the chips 140A-140C, as previously discussed, the base 160 of the cold plate 150 can be attached to the back of the chips 140A, 140B, 140C with a TIM such as grease, solder, or other material.

[0191] In another example, the cold plate base 160 and the fins 166 are formed of the same ultra-high-k thermally conductive material. In some examples, the ultra-high thermally conductive material can have a thermal conductivity greater than copper (394 W / mk at 20°C). Such materials can include AgD or any other ultra-high-K material or a combination of these materials. For example, the base 160 and the fins 166 can be an integral unit. The cover 170 can alternatively be formed of a different material. To attach the cold plate base 160 to the chips 140A-140C, as previously discussed, the cold plate base 160 can be attached to the back of the chips 140A, 140B, 140C with a TIM such as grease, solder, or other material.

[0192] Simulations were performed in which the thickness of the TIM used to attach the cold plate to the chips 140A-140C and the materials used to form the cold plate base and cold plate fins were varied. The best results were achieved by using an ultra-high-k or thermally conductive cold plate base formed of silver diamond bonded to the chips 140A, 140B, 140C with a TIM 180 having a thickness of 200 microns. This configuration was able to support 7.2 W / mm at a junction temperature of 95 degrees Celsius 2 The chip heat flux. Fig.26 Other examples and combinations of using silver diamond as a material for forming at least a portion of a cold plate are shown in the chart of FIG.

[0193] Fig.26 A comparison is shown between using copper (high-K) as the substrate compared to silver diamond (ultra-high-K), which has significantly greater thermal conductivity than copper, in combination with different TIM materials and thicknesses and thermal conductivities. As shown, a heat distribution device with a cold plate base and cold plate fins formed of silver diamond is able to achieve 7.2 W / mm 2 The maximum heat flux of the cold plate can be achieved by changing the materials forming the cold plate base, fins, and lid without using ultra-high thermal conductivity materials and simply relying on a high-k material such as copper to form the base, which can be sufficient in some applications. Modify cold plate structure and / or chip thickness to control heat distribution

[0194] Die thinning and modifications to the cold plate and cold plate fins can provide greater control over heat distribution. Fig. 27A schematic diagram of a portion of a package 1000 is illustrated. The package 1000 can include a printed circuit board 1010, a substrate 1020, a silicon insert 1026, three chips 1040A, 1040B, 1040C, and a cold plate base 1060 bonded to respective rear surfaces 1044A, 1044B, 1044C of the chips 1040A, 1040B, 1040C via a TIM 1080. As discussed further, the package can also include a stiffener. In this example, three chips adjacent to each other are shown. A central chip 1040B is positioned between at least two directly adjacent chips 1040A, 1040C, which are positioned on opposite sides of the central chip 1040B. The central chip 1040B can be thinned so that a thickness T1 of the chip 1040B is less than a thickness of one or more directly adjacent chips. In this example, the thickness T1 of the central chip 1040B is less than the thickness T2 of the two directly adjacent chips 1040A, 1040C. This creates a height difference between the chips 1040A, 1040C and the chip 1040B and creates a recessed area A located directly above the chip 1040B. The die thinning can be accomplished by grinding, etching, grinding, or any known die thinning method. The die thinning reduces the thermal resistance within the silicon of the chip 1040B. In some examples, the central chip 1040B can be an ASIC chip, and the directly adjacent chips 1040A, 1040B can have the same or different functions. In other examples, the central chip 1040B is another type of chip.

[0195] To accommodate the thickness variation of the chip 1040B due to die thinning, the structure of the cold plate base 560 can be modified. As shown, the bottom surface 1062 of the base 1060 is not planar, but includes a step or protrusion P that extends into the recessed area A above the chip 1040B to fill the open space created by the thinning of the die 1040B. The cold plate base 1060 thus includes at least one protrusion P. Additionally, the length L1 of the fin 1066 is greater than the length L2 of the fin 1066 covering the chips 1040A and 1040C in the cold plate base 1060. In this example, the elongated fin can have a length L1 between 0.5 mm and 5 mm, which can be optimized based on the cooling requirements of the chip, but in other examples, the length L1 can vary. In the example shown, the elongated fin extends upward from the recessed portion R of the top surface 1060A of the base 1060. As previously discussed herein, the base 1060 can be bonded to the back surface of the chips 1040A, 1040B, 1040C via a thermally conductive interface material 1080 including a low melting point metal.

[0196] Fig.28 is similar to Fig. 27Another example chip assembly 1001-1 is shown, except that the structure of the example fins 1066-1 of the cold plate base 1060-1 is different. As shown, chip 1040B is positioned between chips 1040A, 1040C. Chip 1040B has been thinned so that the overall thickness of chip 1040B is less than the thickness of directly adjacent chips 1040A, 1040C. All fins 1066-1 of the cold plate base 1060-1 have substantially equal lengths L3 because all fins 1066-1 extend from the continuously planar interior surface 1057 of the cold plate base 1060-1. The bottom surface 1062-1 of the cold plate base 1060-1 will have a substantially equal length L3. Fig. 27 The bottom surface 1062 of the cold plate base 1060 - 1 has a similar stepped profile.

[0197] Fig.29 Graphics and Fig.28 Another example chip assembly 1001-2 is similar, except that the bottom surface 1062-2 of the cold plate base 1060-2 includes a recessed portion R, which creates two protrusions P-1A and P-1B. In this example, instead of the thickness of the middle chip 1040B-2 being less than the thickness of the two adjacent chips, the thickness of the middle chip 1040B-2 is instead greater than the thickness of the two adjacent and outermost chips 1040A-2, 1040C-2. The cold plate 1060-2 accommodates the thickness variation of the chip by including a recessed portion R in the central portion of the bottom surface 1062-2. This allows the chip 1040B-2 to extend into the recessed portion R, and allows the protrusions P-1A and P-1B to cover the thinned chips 1040A-12 and 1040C-2. The cold plate base 1060 - 2 may be attached to the chips 1040A- 2 , 1040B- 2 , 1040C- 2 by using a TIM 1080 .

[0198] Fig.30 An example subassembly 1100 of a chip package is shown, which includes a substrate 1120, an interposer 1126, and chips 1140A, 1140B, 1140C mounted on a printed circuit board 1110. Rather than thinning the overall height of the chip 1140B, the chip 1140B includes a cavity 1114 directly within the chip 1140B. The cavity 1114 can be formed using any known method including milling, etching, etc.

[0199] In one example, to better distribute the heat from the chip, the cavity 1114 can be filled with a thermally conductive material for heat distribution, such as Fig.31110A is shown. In some examples, a high thermal conductivity or ultra-high thermal conductivity material 1115 can fill the cavity 1114. Examples of such materials can include copper, but other materials can also be utilized. The high thermal conductivity or ultra-high thermal conductivity material 1115 can have a top surface 1117 that is aligned with or flush with the back surface 1144B of the chip 1140B. In other examples, the top surface 1117 of the material 1115 can be recessed below the back surface 1144B of the chip 1140B, or extend beyond the back surface 1144B of the chip 1140B, as discussed below.

[0200] exist Fig.32 In another example chip assembly 1100B shown, the top surface 1117-1 of the material 1115-1 extends beyond the back surface 1144B of the chip 1140B-1 to form a protrusion or chip fin 1169. The chip fin 1169 can help distribute heat outward from the chip 1140B-1 and the entire chip assembly 1100B. High or ultra-high thermal conductive material 1115-1 can be deposited into the cavity 1114-1. The chip fin 1169 can be formed in a variety of ways. In one example, the fin can be formed by a subtractive process such as etching / laser, followed by an additive process like electroplating, physical vapor deposition, and printing. Other manufacturing methods can also be used.

[0201] Fig.33 Another exemplary chip subassembly 1200 is provided, which has a structure similar to Fig.30 1240B, except that instead of multiple cavities, a single central cavity 1214 is provided at the central portion of the chip 1240B. This is intended to address the heat generated at the center of the chip 1240B, which is typically highest at the center of the chip. Additionally, the location of the chip 1240B between the two immediately adjacent chips 1240A, 1240C makes it even more difficult to dissipate the heat at the center of the chip 1240B. Thinning the chip 1240B can help reduce the heat generated.

[0202] In this example, rather than filling the cavity 1214 with a thermally conductive material, a cold plate base 1260 can be attached and bonded to the back surfaces 1244A, 1244B, 1244C of the chips 1240A, 1240B, 1240C using a TIM 1280. Fig.34 As shown, the base 1260 can include a stepped and non-planar bottom surface 1262. The step or protrusion P of the base 1260 can protrude directly into the cavity 1214. It should be understood that although the base 1260 does not include fins, fins can be provided in other examples. Similarly, any of the cold plates described herein can omit fins. In addition, the central cavity 1214 can alternatively be filled with a thermally conductive material, such as, for example, a high or ultra-high thermally conductive material. Structural arrangement and material selection for optimal heat distribution and warpage control

[0203] Enhanced heat distribution within the chip assembly and enhanced warpage control can be further achieved by coordinating the selection of a material or material combination for forming a heat distribution device and a material or material combination for forming a stiffener. In an example chip assembly including a heat distribution device covering at least a portion of a stiffener, the thermal conductivity of the material used to form the heat distribution device can be higher than the thermal conductivity of the material used to form the stiffener, but the thermal expansion coefficient of the material used to form the heat distribution device can be lower than the thermal expansion coefficient of the material used to form the stiffener. Even if the material can have a relatively low coefficient of thermal expansion ("CTE"), this combination can allow the use of high thermal conductivity materials as heat sinks. In order to compensate for the low CTE of high thermal conductivity materials, stiffeners formed of materials with higher CTE can be used. For example, ultra-high thermal conductivity materials such as silver diamond (e.g., AgD) or any form of silver diamond discussed previously herein can be selected as materials for forming the heat distribution device, while copper (e.g., Cu-OFE) or any form of copper can be selected as materials for forming stiffeners. In other examples, different material combinations can be selected as discussed below. The arrangement of components within the assembly combined with the selection of materials can optimize heat distribution and warpage control of the substrate and microelectronic device.

[0204] Steering Fig.35 , an example microelectronic device assembly 2000 is illustrated. The assembly may include a substrate 2020 that supports at least the assembly 2000, a stiffener element 2030, at least one microelectronic element or chip 2040, and a heat distribution device 2050. The chip 2040 may be a semiconductor chip and may be arranged so that the active front surface 2042 faces forward and may be bonded or joined to the substrate 2020 in a ball grid array. Although only a single chip is shown in the figure, multiple chips may be present within the assembly 2000. The substrate 2020 may be a conventional single-layer or multi-layer substrate formed of a non-conductive dielectric material such as glass epoxy, silicon, polyimide, polytetrafluoroethylene, or a glass fiber epoxy laminate. A bonding material such as solder balls 2027 may be used to electrically interconnect the chip 2040 to the substrate 2020.

[0205] The stiffener element may extend around the chip 2040 and overlie the substrate 2020. The adhesive 2038A may bond the bottom surface 2032 of the stiffener element 2030 to the top surface 2024 of the substrate 220. As previously discussed, the example stiffener element 2030 may be a stiffener ring extending circumferentially around the chip 2040. The stiffener element 2030 may be circular, rectangular, or any other desired shape. As shown, the stiffener element 2030 may include a bottom surface 2032, an opposing top surface 2034, an outer edge surface 2036 extending between the bottom surface 2032 and the top surface 2034, opposing inner edge surfaces 2037 extending between the bottom surface 2032 and the top surface 2034, and an aperture 2039 extending through the top surface 2034 and the bottom surface 2032. The aperture 2039 may be approximately centered relative to the outer perimeter of the stiffener 2030, but in other examples, the position of the aperture 2039 may be adjusted. For example, the size, shape, and position of the aperture 2039 may be adapted based on the arrangement of the circuits or chips of the underlying substrate 2020 to be exposed through the aperture 2039 within the aperture 2039 .

[0206] The heat distribution device 2050 can extend over at least a portion of the stiffener 2030 and the chip 2040. In this example, the heat distribution device 2050 is a single monolithic element having a planar bottom surface 2062 and a planar top surface 2064. The example heat distribution device 2050 can include a cold plate or heat sink, and can also include thermally conductive fins or other features (not shown). Adhesive 2038B can be used to attach the heat distribution device 2050 to the stiffener element 2030. As shown, the second adhesive 2038B bonds the bottom surface 2062 of the heat distribution device 2050 to the top surface 2034 of the stiffener 2030. The heat distribution device 2050 can include a bottom surface 2062, a top surface 2064, and an outermost edge surface 2066 extending between the bottom surface 2062 and the top surface 2064. In this example, the two outermost edges 2066 of the heat distribution device 2050 are aligned with the outermost edges 2036 of the stiffener element 2030. In examples, including those to be described below, one or both edges 2066 are not aligned with outermost edge 2036 .

[0207] A thermal interface material ("TIM") having at least a high thermal conductivity ("k") can be used to directly bond the heat distribution device 2050 to the chip 2040. In this example, the bottom surface 2062 of the cold plate 2050 is directly bonded to the back surface 2044 of the chip 2040 using a TIM 2080. The TIM 2080 can be a high-k TIM, which can also be a metal with a low melting temperature, including metals or graphite, such as nanosilver or indium, but other high-k TIM materials can be implemented. The methods and structures disclosed herein can also be utilized with a low-k TIM having a reduced level of thermal conductivity.

[0208] The TIM 2080 may be provided in any desired form such as liquid, solid, semi-solid, etc. For example, the TIM may be applied in liquid form, which will then cure and remain as a soft elastomer. In other examples, the TIM may be a grease, a film, or a solder.

[0209] In some examples, the first adhesive 2038A that bonds the bottom surface of the stiffener 2030 to the substrate 2020 can be different from the second adhesive 2038B that bonds the stiffener 2030 to the heat distribution device 2050. For example, the first adhesive 2038A can optionally have different properties than the second adhesive 2038B. As will be discussed below, either alone or in combination with selecting a material to form the stiffener element 2030, selecting an adhesive can also help compensate for CTE mismatches in the overall system, including any CTE mismatches between the heat distribution device 2050 and the substrate 2020 and / or the stiffener element 2030.

[0210] Compared with the elastic modulus of the second adhesive 2038B, the first adhesive 2038A can have a higher elastic deformation resistance and a higher elastic modulus. In some examples, the first adhesive 2038A can have an elastic modulus ranging from 10 MPa to 100 MPa. In other examples, the elastic modulus of the first adhesive 2038A can be less than 10 MPa or greater than 100 MPa. The first adhesive 2038A can be in the form of a paste, but it can also be in other forms. The second adhesive 2030B can be different and have a second elastic modulus ranging from 0.1 MPa to 10 MPa. In other examples, the elastic modulus of the second adhesive 2038B can be less than 0.1 MPa or greater than 10 MPa. The second adhesive can be in the form of a liquid or a film, but in other examples, the second adhesive can be in other forms. Thus, while there is a slight overlap in the exemplary ranges of the elastic moduli of the first adhesive 2038A and the second adhesive 2038B, in examples where the elastic moduli of the first adhesive and the second adhesive are intended to be different, an exemplary embodiment would be one where the elastic modulus of the first adhesive 2038A is selected to be greater than the elastic modulus of the second adhesive 2038B. In other examples, the same or similar elastic moduli may be selected for the first adhesive 2038A and the second adhesive 2038B in order to minimize warpage of the chip package, either alone or in combination with other components of the package, relying on the properties selected for the stiffener 2030 and the heat distribution device 2050.

[0211] Different adhesives can also help achieve enhanced warpage control and compensate for CTE mismatches between the reinforcement and the heat sink and / or the substrate or other components within the assembly. In some examples, as long as the first elastic modulus is greater than the second elastic modulus, the selected elastic modulus can be within or outside the example ranges noted above. In this example, a first adhesive in the form of a paste, compared to a second adhesive in the form of a liquid, can also help CTE mismatches in the assembly depending on the materials selected for the reinforcement and the heat sink. In other examples, the second adhesive 2038B can have a larger elastic modulus than the first adhesive 2038A. In still other examples, depending on the materials selected for the heat sink 2050 and the reinforcement element 2030, the first adhesive 2038A and the second adhesive 2038B can be the same or substantially the same, or have corresponding elastic moduli that are not significantly different.

[0212] The first adhesive and the second adhesive may be dielectric or insulating adhesives. For example, the first adhesive and the second adhesive may be epoxy or other types of materials. The selective adhesive may be thermally conductive or non-conductive and have high reliability to both thermal cycling and mechanical shock and vibration.

[0213] In order to allow for enhanced heat distribution within the assembly and enhanced warpage control to prevent warpage and other mechanical failures of the chip and / or substrate, the materials used to form the heat distribution device 2050 and the stiffener element 2030 can be additionally or alternatively coordinated to compensate for each other. The heat distribution device 2050 (and TIM 2080) can control heat distribution within the assembly 2000, making the heat distribution device formed of a high thermal conductivity material desirable. The stiffener element 2030 can control the warpage of the substrate 2020 and components within the assembly, making the stiffener element 2030 formed of a material with a high CTE desirable. Additionally, the stiffener element 2030 combined with the first adhesive 2038A having a higher elastic modulus than the elastic modulus of the second adhesive 2038B can also provide greater warpage control of the substrate 2020 and components within the assembly. In one example, the material or combination of materials used to form the heat distribution device 2050 can be different from the material or combination of materials used to form the stiffener 2030. For example, the thermal conductivity of the material used to form the heat distribution device 2050 can be higher than the thermal conductivity of the material used to form the stiffener element 2030, but the CTE of the material used to form the heat distribution device 2050 can be lower than the CTE of the material used to form the stiffener 2030. In some examples, the thermal conductivity of the material used to form the heat distribution device 2050 can be at least 50% greater than the thermal conductivity of the material used to form the stiffener element 2030. Additionally, the CTE of the material used to form the stiffener 2030 can be at least 50% greater than the CTE of the material used to form the heat distribution device 2050. In still other examples, the CTE of the stiffener element can be at least twice the CTE of the heat distribution device 2050.

[0214] Table 1 below lists the CTE and thermal conductivity of several common materials.

[0215] The materials identified on this chart indicate that a stiffener element 2030 formed of copper, which will help control warpage, can be paired with a heat distribution device 2050 formed of silver diamond (e.g., AgD), the combination of which will help achieve the highest thermally conductive assembly 2000. Additionally, in combination with a first adhesive 2038A that bonds the stiffener element to the substrate and a second adhesive 2038B that bonds the stiffener element to the heat distribution device 2050, the stiffener 2030 can also help compensate for the CTE mismatch of the heat distribution device and the stiffener element and the substrate 2020. As noted from Table 1 above, silver diamond is one of the highest thermal conductivity at 900 Wm / K, but has the lowest CTE of 6.5 ppm / K. While silver diamond is highly effective at distributing or transferring heat, its ability to control warpage is low. Therefore, while it may be desirable to select silver diamond due to its high thermal conductivity properties, using silver diamond alone results in possible warping of the substrate and other mechanical failures within the assembly, depending on the application and structure of the assembly. Selecting a material with a greater CTE than silver diamond in at least the structures disclosed herein can better help control warpage. In one example, a copper material (e.g., Cu, CuOFE) with a CTE of 17.7 ppm / K and a thermal conductivity of 394 w / mK can be selected. The high CTE of copper can offset the low CTE of silver diamond. In addition, copper is one of the highest thermal conductivity of the remaining components on the chart, and has the additional advantage of distributing heat within the chip assembly 2000. Therefore, the combination of copper reinforcement element 2030 and silver diamond heat distribution device 2050 can help achieve optimal thermal conductivity and warpage control in chip packaging. Other material combinations are contemplated within the scope of the present disclosure, examples of which are discussed in more detail below.

[0216] refer to Fig.36 , results from a test chip assembly are shown in a graph. The graph illustrates how the best results can be achieved using a silver diamond heat distribution device and a copper reinforcement compared to a monolithic heat distribution device. A monolithic heat distribution device can be formed of a single material and the structure of the heat distribution device and the reinforcement are combined into an integral heat distribution device within the assembly. The graph highlights the resulting warping of the substrate due to the CTE mismatch between the substrate and the heat distribution device / reinforcement. In particular, the graph shows the warping results of a substrate A1 attached to a heat distribution device A2 formed entirely of copper or silver diamond in a chip assembly. Similarly, the warping results of a substrate B1 within an assembly B are shown, in which the heat distribution device B2 is formed of silver diamond and a separate reinforcement B3 is formed of copper.

[0217] At room temperature of 20°C, the warpage of substrate A1 in assembly A resulting from the use of "u-shaped" all-copper heat distribution device A2 is about 120 microns. The warpage of substrate A1 in assembly A resulting from the use of "u-shaped" all-silver diamond heat distribution device A2 is about 201 microns. The warpage of substrate B1 in assembly B resulting from the use of a combined planar silver diamond heat distribution device B2 in combination with copper reinforcement B3 and first adhesive B1A and second adhesive B1B is about 133 microns. In this simulation, the elastic modulus of the first adhesive 2038A is greater than the elastic modulus of the second adhesive 2038B. Similar results at a high temperature of 260°C show similarity in the warpage of substrate B2 in assembly B using silver diamond heat distribution device B2 and copper reinforcement B3, compared to the warpage of substrate A1 in assembly A using all-copper and "u-shaped" heat distribution device.

[0218] These test results reveal several improvements resulting from the use of such a combined silver diamond heat distribution device and copper reinforcement. The combined silver diamond heat distribution device 2050 with copper reinforcement 2030 exhibits similar warpage properties to an all-copper heat distribution device. This is advantageous because enhanced warpage control is possible with the silver diamond / copper combination while still allowing the greatly enhanced thermal conductivity properties of the silver diamond heat distribution device to be achieved. Additionally, as a pure metal, copper already possesses one of the highest thermal conductivity properties, making copper a desirable material to further aid thermal conductivity in the assembly.

[0219] Costs can be reduced by using a combined silver diamond heat distribution device and copper reinforcement. Silver diamond is an expensive material. Using copper as the material to form reinforcement element 2030 replaces the traditional "u-shaped" all silver diamond heat distribution device (such as heat distribution device A1; Fig.36 ), allowing the material volume of silver diamond necessary to form the component to be reduced. This in turn minimizes overall cost.

[0220] Ease of manufacturing is also achieved through the combination of silver diamond and copper. By using a planar heat distribution device 2050, rather than a "u-shaped" heat distribution device, it is easier to attach the heat distribution device 2050 to the chip 2040. Better bond wire thickness control of the TIM 2080 between the chip 2040 and the heat distribution device 2050 can be achieved. For example, consistent bond wire thicknesses of 75 microns and 100 microns can be obtained.

[0221] Additional material combinations can be considered to achieve both enhanced warpage control and thermal conductivity. It is possible to consider obtaining the best results through a material combination with a thermal conductivity of at least the same or greater than copper. For example, although silver diamond may be preferred due to its inherent properties as one of the highest thermal conductivity materials, it is possible to obtain the best warpage and thermal conductivity by selecting a copper material for the reinforcement and a copper diamond or aluminum diamond material for the heat distribution device. In still other examples, different materials can be selected for the reinforcement to compensate for the thermal expansion differences of the package. For example, when it is desired to offset the low CTE of the material used to form the heat sink and help maintain the warpage control of the substrate and the overall package, a reinforcement with a high CTE can be selected, and the high CTE can match or exceed the CTE of the material forming the heat sink. This can help compensate for the low CTE of the material forming the heat sink. Additionally, the reinforcement is combined with the first adhesive and the second adhesive to help compensate for the CTE mismatch. Other material combinations that achieve similar results can also be obtained based on various aspects of the present disclosure, including metal alloys or other material combinations not listed here.

[0222] According to aspects of the present disclosure, another example structure is configured to achieve optimal heat distribution and warpage control. Fig.37 As shown, the microelectronic device assembly 2100 includes a substrate 2120 supporting the assembly 2100, a stiffener element 2130, at least one microelectronic element or chip 2140, and a heat distribution device 2150. A first adhesive 2138A bonds a bottom surface 2132 of the stiffener 2130 to a top surface 2124 of the substrate 2120. A second adhesive 2138B bonds a top surface 2134 of the stiffener 2130 to a bottom surface 2162 of the heat distribution device 2150.

[0223] The components in assembly 2100 have the same Fig.35 2168B. The heat distribution device 2150 of FIG. 2160 has the same characteristics as the assembly 2000 in FIG. 2161 , differing only in the configuration of the heat distribution device 2150. As shown, the outermost edge 2166 of the heat distribution device 2150 is laterally spaced from the edge 2136 of the stiffener element 2130 by distances 2168A and 2168B. In this example, the distances 2168A and 2168B are the same, but in other examples, the distances 2168A and 2168B may be different. In yet another example, only one edge 2166 of the heat distribution device 2150 may be laterally spaced from the outer edge 2136 of the stiffener 2130, and another edge 2166 of the heat distribution device may be aligned with the edge 2136 of the stiffener element 2130.

[0224] Turning to aspects of the present disclosure Fig.38, the example microelectronic device assembly 2200 includes a substrate 2220 supporting the assembly 2200, a stiffener element 2230, at least one microelectronic element or chip 2240, a TIM 2280, and a heat distribution device 2250. A first adhesive 2238A can bond the bottom surface 2232 of the stiffener 2230 to the top surface 2224 of the substrate 2220. A second adhesive 2238B can bond and join the top surface 2234 of the stiffener 2230 to the bottom surface 2262 of the heat distribution device 2250. As in the previous embodiments, the components in the assembly 2200 have similarities with other components in the assembly, such as Fig.35 2240 and the heat distribution device 2250. The heat distribution device 2250 has the same characteristics as the assembly 2000 in FIG. 2240, differing only in the height of the chip 2240 and the configuration of the heat distribution device 2250. As shown, the chip 2240 can be thinned by grinding, etching, milling, or any known die thinning method. As a result, the height H10 of the chip 2240 is less than the height H12 of the stiffener 2230. To compensate for this height difference, the heat distribution device 2250 may include a central portion 2282 extending away from the main bottom surface 2262 of the heat distribution device. The central portion 2282 is sized to completely cover the back surface 2244 of the chip 2240 and extend across it, but in other examples, only a portion of the bottom surface 2262 may be covered. The edge 2266 of the heat distribution device 2250 can be aligned with the edge 2236 of the stiffener 2230. In other examples, one or more heat distribution devices 22250 may be laterally offset from the edge 2236 of the stiffener element 2230.

[0225] Figure 39-40 Another example microelectronic device assembly 2300 according to aspects of the present disclosure is provided. The device assembly includes a substrate 2320 supporting the assembly 2300, a stiffener element 2330, at least one microelectronic element or chip 2340, and a heat distribution device 2350. The chip 2340 can have a rear surface 2344. A first adhesive 2338A can bond a bottom surface 2332 of the stiffener 2130 to a top surface 2324 of the substrate 2120. A second adhesive 2338B can bond a top surface 2334 of the stiffener 2330 to a bottom surface 2362 of the heat distribution device 2350.

[0226] The components in assembly 2300 have the same Fig.35 The components 2000 have the same characteristics as in the embodiment of the present invention, differing only in the configuration of the heat distribution device 2350.

[0227] The heat distribution device 2350 includes a top surface 2364, a bottom surface 2362, and an inner peripheral edge 2372 extending between the top surface 2364 and the bottom surface 2362. The inner peripheral edge extends around the aperture 2339A. Another aperture 2339B extends through the top surface 2364 and the bottom surface 2362 and is defined by the inner peripheral edge 2372. The inner peripheral edge 2372 of the heat distribution device 2350 extends beyond the inner edge 2337 of the reinforcement element 2330 so that in the case of a heat distribution device such as Fig.39 In the top plan view shown, only the microelectronic element 2340 and the substrate 2320 are visible through the aperture 2339. The stiffener element 2330 is not visible from the top plan view. Additionally, the aperture 2339A and the aperture 2339B are aligned with each other.

[0228] Can be Figure 37-40 In any of the additional chip assemblies disclosed in and any of the assemblies previously disclosed herein, enhanced heat distribution and enhanced warpage control can be further achieved by coordinating the selection of a material or combination of materials used to form the stiffener with the selection of a material or combination of materials used to form the heat distribution device. As discussed, the thermal conductivity of the material used to form any of the heat distribution devices in these examples can be higher than the thermal conductivity of the material used to form the stiffener, but the coefficient of thermal expansion of the material used to form the heat distribution device can be lower than the coefficient of thermal expansion of the material used to form the stiffener. This can allow for optimal heat distribution and warpage control in the package. In one example, optimal results can be achieved by using a silver diamond material to form the heat distribution device and a copper material to form the stiffener, but other combinations are available according to aspects of the present disclosure.

[0229] In summary, according to a first aspect of the present disclosure, a method for manufacturing a chip assembly includes bonding an intermediate process unit to a printed circuit board, the intermediate process unit including: a substrate having an active surface, an inactive surface, and contacts exposed at the active surface; an insert electrically connected to the substrate; a plurality of semiconductor chips covered on the substrate and electrically connected to the substrate through the insert; and a stiffener covered on the substrate and having an aperture extending through the substrate, the plurality of semiconductor chips being positioned within the aperture; reflowing a bonding material disposed between the intermediate process unit and the printed circuit board and electrically connecting the intermediate process unit to the printed circuit board, the bonding material having a first reflow temperature; and then bonding a heat distribution device to the plurality of semiconductor chips by using a thermal interface material ("TIM"), the TIM having a second reflow temperature lower than the first reflow temperature; and / or wherein the heat distribution device comprises a cold plate having a base and a cover coupled to the base, the method further comprising bonding the base of the cold plate to the rear surfaces of the plurality of semiconductor chips before coupling the cover to the base; and / or bonding the base of the cold plate to the top surface of the stiffener; and / or The heat distribution device includes a cold plate having a base and a cover coupled to the base, the method further comprising bonding the base and the cover together, and then bonding the base to the rear surfaces of the plurality of semiconductor chips; and / or Reflowing the bonding material includes reflowing the bonding material disposed between the substrate and the printed circuit board, wherein the heat distribution device includes a base, a plurality of thermally conductive fins extending from at least a portion of the base, and a cover, wherein the base is formed of a substrate having a thermal conductivity greater than 394 W / m 2 The cover and at least one of the plurality of thermally conductive fins are made of a material having a thermal conductivity of 394 W / m 2 or smaller; and / or Before bonding the heat distribution device to the rear surfaces of the plurality of semiconductor chips, disposing the TIM on one of the rear surfaces of the semiconductor chips or the bottom surface of the heat distribution device; and / or The heat distribution device also includes a plurality of thermally conductive fins, wherein a first fin length of at least some of the plurality of thermally conductive fins is greater than a second fin length of remaining fins of the plurality of thermally conductive fins, wherein a first height of at least one of the plurality of semiconductor chips is less than a second height of another of the plurality of semiconductor chips, and wherein the method further includes positioning at least some of the plurality of thermally conductive fins having the first fin length to overlie at least one of the plurality of semiconductor chips having the first height; and / or The pressurizing device applies pressure to the heat distribution device during reflow; and / or The pressurizing device is a weight configured to cover the heat distribution device during the manufacture of the chip assembly, the method further comprising applying the weight to the top surface of the heat distribution device; and / or The pressurizing device includes a rigid plate and springs at opposite ends of the rigid plate, the method further comprising positioning the rigid plate over a rear surface of the heat distribution device and securing the rigid plate to the printed circuit board; and / or The heat distribution device further comprises an inlet and an outlet, and wherein the method further comprises providing a fluid connection to connect the inlet and the outlet to a fluid source to enable the fluid to be introduced into the heat distribution device and ejected from the heat distribution device; and / or Providing the intermediate process unit further comprises providing a plurality of intermediate process units, and wherein providing the heat distribution device further comprises providing a plurality of heat distribution devices, the method further comprising: bonding the plurality of intermediate process units to a printed circuit board by reflowing a bonding material, the bonding material bonding a contact of each of the substrates within the plurality of intermediate process units to a contact of the printed circuit board; bonding each of the plurality of heat distribution devices to a corresponding one of the plurality of semiconductor chips of the plurality of intermediate process units by reflowing a highly thermally conductive thermal interface material ("TIM"), each of the plurality of heat distribution devices comprising a plurality of thermally conductive fins, an inlet, and an outlet; and combining inlets and outlets of the plurality of heat distribution devices with each other so that the inlet and outlet of one of the plurality of heat distribution devices are fluidly connected to the inlet and outlet of another of the plurality of heat distribution devices; and / or TIM is solder.

[0230] According to a second aspect of the present disclosure, a microelectronic assembly includes: a substrate having an active surface, a passive surface, and contacts exposed at the active surface; a plurality of semiconductor chips covered on the substrate; a heat distribution device including a base, heat-conducting fins extending upward from the base, and a cover covering the plurality of heat-conducting fins and at least partially enclosing the plurality of heat-conducting fins within the base, wherein at least the base is made of a heat-conducting fin having a heat-conducting capacity greater than 394 W / m 2 The cover and the plurality of thermally conductive fins are formed of a first material having a first thermal conductivity of less than 394 W / m 2 a thermal interface material (TIM) disposed between the heat distribution device and the plurality of semiconductor chips, wherein the thermal expansion coefficients of at least one of the plurality of semiconductor chips and the base are substantially similar or identical; and a printed circuit board electrically connected to the substrate; and / or The plurality of thermally conductive fins are formed of a second material; and / or the cover is formed from a second material; and / or The cover and the plurality of thermally conductive fins are both formed of a second material; and / or The base and the plurality of thermally conductive fins are formed of a first material; and / or The first material is silver diamond; and / or The thickness of the TIM is 200 microns or less.

[0231] According to a third aspect of the present disclosure, a microelectronic device assembly includes: a substrate; and a plurality of microelectronic elements connected to the substrate, the microelectronic elements having an active surface facing the substrate and a passive surface facing away from the substrate, wherein one or more cavities extend through at least one surface of the plurality of microelectronic elements, and wherein the one or more cavities are filled with a thermally conductive material to dissipate heat from the plurality of microelectronic elements; and / or The thermally conductive material is flush with or positioned below at least one surface of at least one of the plurality of microelectronic elements; and / or The thermally conductive material extends beyond at least one surface of the plurality of microelectronic elements; and / or The assembly also includes a heat distribution device having a base and a cover, wherein the base further includes a plurality of thermally conductive fins, and wherein a first material forming the heat distribution device is different than a second material forming the plurality of thermally conductive fins.

[0232] According to a fourth aspect of the present disclosure, a chip assembly includes: a substrate; a plurality of semiconductor chips electrically connected to the substrate, each of the plurality of semiconductor chips having an active surface facing the substrate and a passive surface facing away from the substrate; and a heat distribution device coupled to the plurality of semiconductor chips, the heat distribution device including a plurality of heat-conducting fins, wherein a first fin length of at least some of the plurality of heat-conducting fins is greater than a second fin length of the remaining fins of the plurality of heat-conducting fins, wherein a first height of at least one of the plurality of semiconductor chips is less than a second height of another of the plurality of semiconductor chips, and wherein at least some of the plurality of heat-conducting fins having the first fin length cover the plurality of semiconductor chips having the first height; and / or Wherein, the heat distribution device comprises a base covering the plurality of semiconductor chips, and the plurality of heat conducting fins extend away from the base; and / or At least some of the outermost tips of the plurality of thermally conductive fins are aligned with each other; and / or The base of the heat distribution device extends across the rear surfaces of the plurality of semiconductor chips; and / or The printed circuit board is electrically connected to the plurality of semiconductor chips; and / or The plurality of semiconductor chips include at least one of the plurality of semiconductor chips and two directly adjacent chips positioned on opposite sides of the at least one of the plurality of semiconductor chips, and wherein the bottom surface of the base includes a protrusion extending adjacent to the top surface of the at least one chip to accommodate different heights of the at least one of the plurality of semiconductor chips.

[0233] According to a fifth aspect of the present disclosure, a method of assembling a cooling circuit assembly to an intermediate process unit comprises: bonding a plurality of intermediate process units to a circuit board, each intermediate process unit comprising: a substrate; at least one microelectronic element electrically connected to the substrate, the microelectronic element having an active front surface facing the substrate and an opposite rear surface facing away from the substrate; bonding a corresponding plurality of heat distribution devices to the plurality of intermediate process units, each of the corresponding plurality of heat distribution devices comprising an inlet and an outlet; and engaging a cooling circuit assembly to the inlet and outlet of each of the corresponding plurality of heat distribution devices, the cooling circuit assembly comprising a network of fluid lines connected to each inlet and each outlet; and / or before coupling the cooling circuit assembly to each of the corresponding plurality of heat distribution devices, coupling the corresponding plurality of heat distribution devices to the plurality of intermediate process units; and / or Each of the corresponding plurality of heat distribution devices comprises a base and a cover, an inlet and an outlet of each of the corresponding plurality of heat distribution devices extending from the cover; and / or before coupling the cover of each of the corresponding plurality of heat distribution devices to the base and before engagement of the cooling circuit assembly, coupling the base of each of the corresponding plurality of heat distribution devices to a corresponding intermediate process unit of the plurality of intermediate process units; and / or attaching a bottom surface of a base corresponding to each of the plurality of heat distribution devices to a rear surface of at least one microelectronic element of each of the plurality of intermediate process units; and / or using a thermal interface material to bond the bottom surface of the base to a rear surface of at least one microelectronic element of each of the plurality of intermediate process units; and / or Each of the plurality of intermediate process units further comprises a stiffener overlying the substrate and extending around at least a portion of at least one microelectronic element of each of the plurality of intermediate process units, and wherein the bonding of each of the corresponding plurality of heat distribution devices comprises bonding a bottom surface of a base of each of the corresponding plurality of heat distribution devices to the stiffener; and / or A cooling circuit assembly is coupled to the inlet and outlet of each of the plurality of heat distribution devices prior to coupling the cover to the base; and / or Joining the cooling circuit components to the inlet and outlet via one of briquettes, barbs, or brazing; and / or The heat distribution device is attached to the intermediate process unit prior to joining the cooling circuit assembly to each of the corresponding plurality of heat distribution devices; and / or The intermediate process unit further comprises an interposer electrically connected to the substrate, and the method further comprises electrically connecting at least one microelectronic element to the substrate through the interposer; and / or At least one microelectronic element of at least one intermediate process unit comprises a plurality of microelectronic elements, and wherein at least one of the plurality of microelectronic elements has been thinned to have a different height than at least another of the plurality of microelectronic elements, and wherein a shape of the heat distribution device is configured to accommodate the different heights of the thinned microelectronic elements.

[0234] According to a sixth aspect of the present disclosure, a microelectronic device assembly includes: a substrate; a microelectronic element electrically connected to the substrate, the microelectronic element having an active surface facing the substrate and a rear surface facing away from the substrate; a stiffener element overlying the substrate and extending around the microelectronic element, the stiffener element being composed of a first material having a first coefficient of thermal expansion (“CTE”); and a heat distribution device overlying the rear surface of the microelectronic element and a surface of the stiffener element facing the heat distribution device, the heat distribution device being composed of a second material having a second CTE; and wherein the first material is different from the second material, wherein a first CTE of the first material of the stiffener element is greater than a second CTE of the second material of the heat distribution device; and / or The reinforcement element is bonded to the base with a first adhesive and the reinforcement element is bonded to the heat distribution device with a second adhesive, wherein the first adhesive has a first elastic modulus different from a second elastic modulus of the second adhesive; and / or The first elastic modulus of the first adhesive is greater than the second elastic modulus of the second adhesive; and / or The first elastic modulus ranges from 10 MPa to 100 MPa, and the second elastic modulus ranges from 0.10 MPa to 10 MPa; and / or A first CTE of the first material is at least 50% greater than a second CTE of the second material of the heat distribution device; and / or The first CTE is at least 17 ppm / WK at 20°C; and / or The first material of the reinforcement element further comprises a first thermal conductivity, and wherein the second material of the heat distribution device further comprises a second thermal conductivity, and wherein the second thermal conductivity of the second material is less than the first thermal conductivity of the first material; and / or The first thermal conductivity is greater than 394 W / mK at 20°C; and / or The first material comprises copper; and / or The second material comprises silver diamond; and / or The first material comprises copper and the second material comprises silver diamond; and / or The reinforcement element and the heat distribution device are separate structures coupled together; and / or The heat distribution device includes a planar surface extending across the entire surface of the stiffener element and the entire rear surface of the microelectronic element; and / or The heat distribution device includes a top surface, an opposite bottom surface, and an edge surface extending between the top surface and the opposite bottom surface, wherein the surface of the stiffener element is the top surface facing the bottom surface of the heat distribution device, wherein the stiffener element also includes an opposite bottom surface facing the substrate, and wherein the edge of the stiffener element extends between the top surface and the bottom surface of the stiffener element; and / or The edge of the heat distribution device is laterally spaced away from the edge of the reinforcement element; and / or The edges of the heat distributor are vertically aligned with the edges of the reinforcement element; and / or The edge of the heat distribution means is an inner edge extending around the aperture; and / or The aperture is a first aperture, the edge of the stiffener element is an inner stiffener edge extending around a second aperture of the stiffener element, and the inner edge of the heat distribution device extends beyond the inner stiffener edge of the stiffener element such that the first and second apertures are aligned.

[0235] According to a seventh aspect of the present disclosure, a microelectronic device assembly includes: a substrate; a microelectronic element electrically connected to the substrate, the microelectronic element having an active surface facing the substrate and a passive surface facing away from the substrate; a stiffener element overlying the substrate and extending around the microelectronic element, the stiffener element having a first CTE; a heat distribution device overlying a rear surface of the microelectronic element and the stiffener element, the heat distribution device having a second CTE; and a thermally conductive interface material that bonds the heat distribution device to the rear surface of the microelectronic element, wherein the heat distribution device is composed of a first material different from a second material constituting the stiffener element, and wherein the first CTE is at least 50% greater than the second CTE; and / or The assembly further comprises bonding the stiffener element to the substrate with a first adhesive and bonding the stiffener element to the heat distribution device with a second adhesive, wherein the first adhesive has a different modulus of elasticity than the second adhesive; and / or The first adhesive has a modulus of elasticity greater than the modulus of elasticity of the second adhesive; and / or The first material of the stiffener element has a first thermal conductivity and the second material of the heat distribution device has a second thermal conductivity, the second thermal conductivity of the heat distribution device being greater than the first thermal conductivity of the stiffener element; and / or The heat distribution device is composed of silver diamond and the reinforcement element is composed of copper; and / or The heat distribution device includes a planar surface extending across the entire rear surface of the stiffener element and the microelectronic element; and / or The heat distribution device includes a top surface and an opposite bottom surface, and an edge surface extending between the top surface and the opposite bottom surface, wherein the stiffener element includes a top surface facing the bottom surface of the heat distribution device, an opposite bottom surface, and an edge surface extending between the top surface and the bottom surface of the stiffener element, wherein an edge of the heat distribution device is laterally spaced away from the edge surface of the stiffener element.

[0236] Unless otherwise stated, the foregoing alternative examples are not mutually exclusive, but can be implemented in various combinations to achieve unique advantages. Since these and other variations and combinations of the features discussed above can be utilized without departing from the subject matter defined by the claims, the foregoing description should be made by way of illustration rather than by way of limitation of the subject matter defined by the claims. In addition, the examples described herein and the provision of phrases such as "such as", "including", etc. should not be interpreted as limiting the subject matter of the claims to specific examples; on the contrary, the examples are intended to illustrate only one of many possible implementations. In addition, the same reference numerals in different figures can identify the same or similar elements.

Claims

1. A microelectronic device assembly comprising: substrate; a microelectronic element electrically connected to the substrate, the microelectronic element having an active surface facing the substrate and a rear surface facing away from the substrate; a stiffener element overlying the substrate and extending around the microelectronic element, the stiffener element being comprised of a first material having a first coefficient of thermal expansion "CTE"; as well as a heat distribution device overlying the rear surface of the microelectronic element and a surface of the stiffener element facing the heat distribution device, the heat distribution device being comprised of a second material having a second CTE; and Wherein the first material is different from the second material, wherein the first CTE of the first material of the stiffener element is greater than the second CTE of the second material of the heat distribution device.

2. The microelectronic device assembly according to claim 1, wherein: The stiffener element is bonded to the substrate with a first adhesive and the stiffener element is bonded to the heat distribution device with a second adhesive, wherein the first adhesive has a first elastic modulus different from a second elastic modulus of the second adhesive.

3. The microelectronic device assembly according to claim 2, wherein: A first elastic modulus of the first adhesive is greater than a second elastic modulus of the second adhesive.

4. The microelectronic device assembly according to claim 3, wherein: The first elastic modulus ranges from 10 MPa to 100 MPa, and the second elastic modulus ranges from 0.10 MPa to 10 MPa.

5. The microelectronic device assembly according to claim 1, wherein: The first CTE of the first material is at least 50% greater than the second CTE of the second material of the heat distribution device.

6. The microelectronic device assembly according to claim 5, wherein: The first CTE is at least 17 ppm / WK at 20°C.

7. The microelectronic device assembly according to claim 1, wherein: The first material of the reinforcement element further comprises a first thermal conductivity, and wherein the second material of the heat distribution device further comprises a second thermal conductivity, and wherein the second thermal conductivity of the second material is less than the first thermal conductivity of the first material.

8. The microelectronic device assembly according to claim 7, wherein: The first thermal conductivity is greater than 394 W / mK at 20°C.

9. The microelectronic device assembly of claim 1, wherein: The first material includes copper.

10. The microelectronic device assembly of claim 1, wherein: The second material includes silver diamond.

11. The microelectronic device assembly of claim 1 , wherein: The first material includes copper and the second material includes silver diamond.

12. The microelectronic device assembly of claim 1, wherein: The reinforcement element and the heat distribution device are separate structures coupled together.

13. The microelectronic device assembly of claim 12, wherein: The heat distribution device includes a planar surface extending across an entire surface of the stiffener element and an entire rear surface of the microelectronic element.

14. The microelectronic device assembly of claim 12, wherein: The heat distribution device includes a top surface, an opposite bottom surface, and an edge surface extending between the top surface and the opposite bottom surface, wherein the surface of the stiffener element is a top surface facing the bottom surface of the heat distribution device, wherein the stiffener element also includes an opposite bottom surface facing the substrate, and wherein the edge surface of the stiffener element extends between the top surface and the bottom surface of the stiffener element.

15. The microelectronic device assembly of claim 14, wherein: An edge surface of the heat distribution device is laterally spaced away from an edge surface of the stiffener element.

16. The microelectronic device assembly of claim 14, wherein: An edge surface of the heat distribution device is vertically aligned with an edge surface of the stiffener element.

17. The microelectronic device assembly of claim 14, wherein: The edge surface of the heat distribution device is an inner edge extending around the aperture.

18. The microelectronic device assembly of claim 17, wherein: The aperture is a first aperture, the edge surface of the stiffener element is an inner stiffener edge extending around a second aperture of the stiffener element, and the inner edge of the heat distribution device extends beyond the inner stiffener edge of the stiffener element such that the first and second apertures are aligned.

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