Thermally conductive sheet, heat dissipation device, and method for manufacturing thermally conductive sheet

Abstract

The purpose of the present invention is to provide a thermally conductive sheet having excellent adhesion to an adherend. This thermally conductive sheet is provided with: a thermally conductive layer containing a carbon-based material (A); and an adhesive layer containing a resin component and a thermally conductive filler, the adhesive layer being located on at least a portion of a main surface of the thermally conductive layer, the surface roughness of the adhesive layer being 7.0 [mu] m or less.

Description

Technical Field

[0001] This disclosure relates to thermally conductive sheets, heat dissipation devices, and methods for manufacturing thermally conductive sheets. Background Technology

[0002] In recent years, the increased heat generation caused by the high density of wiring and electronic components in semiconductor packages using multilayer wiring boards, as well as the increased heat generation per unit area due to the high integration of semiconductor elements, has led to the desire to improve the heat dissipation of semiconductor packages.

[0003] Between heat-generating components such as semiconductor packages and heat sinks such as aluminum or copper, a simple heat dissipation device is typically used that dissipates heat by clamping and sealing thermal grease or thermally conductive sheets. Generally, thermally conductive sheets are more maneuverable than thermal grease when assembling heat dissipation devices.

[0004] In recent years, CPU (Central Processing Unit) chips have tended to be larger in area due to multi-chip design and increasing chip size. Additionally, there is a trend towards reducing the pressure required for bonding the CPU (as a heat source) to the heat sink. Therefore, the thermal conductive sheet is required to be flexible during bonding. Furthermore, the thermal conductive sheet is required to have excellent thermal conductivity so that even if the sheet becomes thicker due to chip variations, it still exhibits low thermal resistance.

[0005] As a thermally conductive sheet, resin sheets filled with thermally conductive fillers are also known. As a resin sheet with excellent thermal conductivity filled with thermally conductive fillers, various resin sheets have been proposed in which highly thermally conductive inorganic particles are selected as thermally conductive fillers and the inorganic particles are oriented perpendicularly to the sheet surface.

[0006] For example, thermally conductive sheets with thermally conductive filler (boron nitride) oriented in a direction substantially perpendicular to the sheet surface have been proposed (e.g., see Patent Document 1), and thermally conductive sheets with a structure in which carbon fibers dispersed in a gel-like substance are oriented perpendicular to the sheet surface (e.g., see Patent Document 2).

[0007] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2002-26202 Patent Document 2: Japanese Patent Application Publication No. 2001-250894 Summary of the Invention

[0008] The problem that the invention aims to solve Patent documents 1 and 2 investigated methods to suppress thermal resistance by orienting thermally conductive fillers, carbon fibers, etc., in a direction perpendicular to the sheet surface. Furthermore, they investigated a method where, when a thermally conductive sheet is adhered to a substrate, an adhesive layer is provided on a thermally conductive layer containing thermally conductive fillers, etc., and the sheet is adhered to the substrate via the adhesive layer. In this case, sometimes a release film, such as a PET film, is provided on the side opposite to the substrate, and this release film is peeled off to transfer the thermally conductive sheet to the substrate. However, thermally conductive sheets with large surface irregularities sometimes exhibit poor transferability; for example, when peeling off the release film, there are problems such as reduced adhesion to the substrate, or the thermally conductive sheet peeling off from the substrate instead of the release film.

[0009] One aspect of the present invention aims to provide a thermally conductive sheet with excellent adhesion to the bonded body, a heat dissipation device having the thermally conductive sheet, and a method for manufacturing the thermally conductive sheet capable of producing a thermally conductive sheet with low thermal resistance.

[0010] Methods for solving problems The specific means to solve the above problems include the following methods.

[0011] <1> A thermally conductive sheet, comprising: A thermally conductive layer containing a carbon-based material (A); and An adhesive layer comprising a resin component and a thermally conductive filler, wherein the adhesive layer is located on at least a portion of the main surface of the thermally conductive layer. The surface roughness of the adhesive layer is below 7.0 μm.

[0012] <2> A thermally conductive sheet, comprising: A thermally conductive layer containing a carbon-based material (A); and An adhesive layer comprising a resin component and a thermally conductive filler, wherein the adhesive layer is located on at least a portion of the main surface of the thermally conductive layer. The average particle size of the thermally conductive filler in the adhesive layer is less than 8.0 μm.

[0013] <3> according to <1> or <2> The thermally conductive sheet, wherein the resin component comprises at least one selected from curable resin components, pressure-sensitive adhesive resin components, and thermoplastic resin components.

[0014] <4> according to <3> The thermally conductive sheet, wherein the resin component is a curable resin component, and the adhesive layer is in a semi-cured state.

[0015] <5> according to <3> The thermally conductive sheet, wherein the resin component comprises a thermoplastic resin component.

[0016] <6> according to <5> The thermally conductive sheet, wherein the thermoplastic resin component comprises thermoplastic epoxy resin.

[0017] <7> according to <1> ~ <6> The thermally conductive sheet as described in any one of the following, wherein the thermally conductive filler is a particle selected from at least one of silver, copper, aluminum, aluminum oxide, aluminum hydroxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, silicon carbide, silicon dioxide, aluminum fluoride, calcium fluoride, and zinc oxide.

[0018] <8> according to <7> The thermally conductive sheet, wherein the thermally conductive filler is silver particles.

[0019] <9> according to <1> ~ <8> The thermally conductive sheet according to any one of the following, wherein the content of the thermally conductive filler is 70% to 99% by mass relative to the total amount of the adhesive layer.

[0020] <10> according to <1> ~ <9> The thermally conductive sheet according to any one of the following methods, wherein the average thickness of the adhesive layer is 2μm to 50μm.

[0021] <11> according to <1> ~ <10> The thermally conductive sheet according to any one of the following methods, wherein the ratio of the average particle size of the thermally conductive filler to the average thickness of the adhesive layer, i.e., the average particle size / average thickness, is 0.01 to 0.8.

[0022] <12> A heat dissipation device comprising: Heating element; Heat sink; and Displaced between the heating element and the heat sink <1> ~ <11> The thermally conductive sheet described in any one of the following statements, The adhesive layer is located on at least a portion of at least one of the main surfaces of the thermally conductive layer located on the heating element side and the main surface located on the heat sink side.

[0023] <13> A method for manufacturing a thermally conductive sheet, which involves manufacturing... <1> ~ <11> The method for manufacturing the thermally conductive sheet according to any one of the following methods comprises: A process for preparing a composition containing the carbon-based material (A); The process of forming the thermally conductive layer using the composition; and The process of forming an adhesive layer on at least a portion of the main surface of the thermally conductive layer.

[0024] Invention Effects According to this disclosure, a thermally conductive sheet with excellent adhesion to the bonded body, a heat dissipation device having the thermally conductive sheet, and a method for manufacturing a thermally conductive sheet capable of producing a thermally conductive sheet with low thermal resistance can be provided. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the thermally conductive sheet according to one embodiment of the present invention.

[0026] Figure 2 This is a schematic cross-sectional view of a heat dissipation device in which the heating element is a semiconductor chip and the heat sink is a heat sink, as one embodiment of the present invention. Detailed Implementation

[0027] The following describes in detail the methods for implementing the present invention. However, the present invention is not limited to the following embodiments. In the following embodiments, except as specifically stated, the constituent elements (including element steps, etc.) are not essential. The same applies to numerical values ​​and their ranges, which are not limiting to the present invention.

[0028] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that, when they cannot be clearly distinguished from other processes, as long as they can achieve the purpose of the process.

[0029] In this disclosure, within the numerical range represented by "~", the values ​​recorded before and after "~" are included as the minimum and maximum values, respectively.

[0030] In the numerical ranges described in this disclosure in stages, the upper or lower limit value described in one numerical range can be replaced with the upper or lower limit value of other numerical ranges described in stages. Furthermore, the upper or lower limit value of the numerical ranges described in this disclosure can be replaced with the values ​​shown in the embodiments.

[0031] In this disclosure, each component may contain multiple substances equivalent to it. In the presence of multiple substances equivalent to each component in the composition, unless otherwise specified, the content or percentage of each component refers to the total content or percentage of the multiple substances present in the composition.

[0032] In this disclosure, the particles corresponding to each component may comprise multiple types. When multiple particles corresponding to each component are present in the composition, unless otherwise specified, the particle size of each component refers to a value relating to a mixture of the multiple particles present in the composition.

[0033] In this disclosure, the terms "layer" or "film" include, in addition to the case where the layer or film is formed on the whole of the region where it is observed, the case where it is formed on only a part of the region.

[0034] In this disclosure, the term "layering" refers to overlapping layers, where two or more layers can be combined together or can be detachable.

[0035] [Thermal conductive sheet] (First Implementation) The thermally conductive sheet of the first embodiment of this disclosure includes an adhesive layer containing a carbon-based material (A), and the surface roughness of the adhesive layer is 7.0 μm or less.

[0036] In the thermally conductive sheet of the first embodiment of this disclosure, a thermally conductive layer and an adhesive layer are provided, and the surface roughness of the adhesive layer is 7.0 μm or less. By making the surface roughness of the adhesive layer less than or equal to the above value, the adhesion to the adhered body is improved. For example, when a release film such as a PET film is provided on the surface of the thermally conductive sheet opposite to the adhered body side, when the release film needs to be peeled off, the adhesion to the adhered body can be properly ensured, and the peeling of the thermally conductive sheet from the adhered body can be suppressed.

[0037] Furthermore, it is believed that the thermally conductive sheet disclosed herein exhibits low thermal resistance due to its excellent adhesion to the bonded body.

[0038] Even when the surface of the bonded object, such as a heat-generating element or heat sink, is uneven, contact thermal resistance can easily occur. In such cases, it is difficult to reduce the thermal resistance by adjusting the orientation of the thermally conductive filler or the like contained in the thermally conductive sheet. However, by using the thermally conductive sheet of this disclosure, the thermally conductive sheet can be tightly bonded to the bonded object with an uneven surface through an adhesive layer. At this time, the gaps generated when the thermally conductive sheet and the bonded object are heated and pressed together (e.g., gaps originating from the unevenness of the bonded object) are filled by the adhesive layer, thus significantly reducing the contact thermal resistance.

[0039] The thermally conductive sheet disclosed herein includes a thermally conductive layer comprising at least a carbon-based material (A), and may also include the components described later, to the extent necessary to achieve the effects of this disclosure. The materials used in the thermally conductive layer of this disclosure will be described below.

[0040] <Carbon-based materials (A)> The thermally conductive layer contained in the thermally conductive sheet contains carbon-based materials (A). It is believed that carbon-based materials (A) primarily function as highly thermally conductive fillers. As for carbon-based materials (A), there are no particular limitations as long as the material mainly contains carbon atoms; examples include artificial graphite, flake graphite, ellipsoidal graphite, rod-shaped graphite, sheet graphite, natural graphite, acid-treated graphite, expanded graphite, expanded graphite, etc.; carbon black; diamond particles; graphene; fullerene; carbon nanotubes; carbon nanofibers; and other carbon-based fibers.

[0041] Carbon-based materials (A) can be used alone or in combination with two or more.

[0042] "Mainly containing carbon atoms" means that the proportion of carbon atoms in the constituent atoms of carbon-based materials (A) is more than 50 atomic percent.

[0043] The shape of carbon-based materials (A) is not particularly limited; they can be in the form of particles or non-particle forms such as fibers.

[0044] Carbon-based materials (A) may contain graphite particles.

[0045] When the carbon-based material (A) contains graphite particles, the graphite particles can be at least one selected from flake-shaped particles, ellipsoidal particles, and rod-shaped particles. Furthermore, in the case of flake-shaped particles, the facet direction is oriented in the thickness direction; in the case of ellipsoidal particles, the long axis direction is oriented in the thickness direction; and in the case of rod-shaped particles, the long axis direction is oriented in the thickness direction. Additionally, it is preferable that in the case of flake-shaped particles, the six-membered ring facets in the crystal are oriented in the facet direction; in the case of ellipsoidal particles, the six-membered ring facets in the crystal are oriented in the long axis direction; and in the case of rod-shaped particles, the six-membered ring facets in the crystal are oriented in the long axis direction. A six-membered ring facet is a facet in a hexagonal crystal system in which a six-membered ring is formed, specifically the (0001) crystal facet.

[0046] Furthermore, it is believed that the thermally conductive sheet exhibits lower thermal resistance by having both a thermally conductive layer containing graphite particles oriented in the thickness direction and the aforementioned adhesive layer. The reasoning is as follows. However, this disclosure is not limited to the following assumption. In a thermally conductive sheet where graphite particles are oriented in the thickness direction, there are uneven surfaces on the surface in contact with the bonded object. A large portion of the thermal resistance originates from the resistance (also called "contact thermal resistance") caused by the gaps created when the thermally conductive sheet contacts the bonded object, such as a heat-generating element or heat-dissipating element. In the thermally conductive sheet of this disclosure, by disposing an adhesive layer containing resin components and thermally conductive fillers on at least a portion of the main surface of the thermally conductive layer, when the thermally conductive sheet is heated and pressed against the bonded object, such as a heat-generating element or heat-dissipating element, the adhesive layer softens and deforms due to heat and pressure. Through this softening and deformation of the adhesive layer, the gaps created when the thermally conductive sheet is heated and pressed against the bonded object (e.g., gaps originating from the unevenness of the thermally conductive sheet) are filled by the adhesive layer. This reduces the gap between the thermally conductive sheet and the adhered body, and the adhesive layer ensures a tight seal between the thermally conductive sheet and the adhered body, thus significantly reducing the contact thermal resistance.

[0047] The graphite particles are more preferably flaky in shape. By selecting flaky graphite particles, there is a tendency for further improvement in thermal conductivity. This can be attributed to the fact that, for example, flaky graphite particles are more likely to orient themselves in a predetermined direction within the thermally conductive layer.

[0048] X-ray diffraction can be used to determine whether the six-membered toroidal planes in graphite crystals are oriented along the plane of flake-like particles, the long axis of ellipsoidal particles, or the long axis of rod-like particles. Specifically, the orientation of the six-membered toroidal planes in graphite crystals is determined by the following method.

[0049] First, a sample sheet for measurement is prepared in which the plane orientation of the flake-shaped graphite particles, the long axis orientation of the ellipsoidal particles, or the long axis orientation of the rod-shaped graphite particles is aligned with the plane orientation of the sheet. Specific methods for preparing the sample sheet for measurement include the following.

[0050] A sheet is made by mixing a resin with graphite particles in an amount of 10% by volume or more relative to the resin. The term "resin" is not particularly limited to any material that does not produce peaks that interfere with X-ray diffraction and is capable of forming a sheet. Specifically, amorphous resins with cohesive properties, such as acrylic rubber, NBR (acrylonitrile butadiene rubber), and SIBS (styrene-isobutylene-styrene copolymer), can be used.

[0051] The mixture is pressed into a sheet to a thickness of less than 1 / 10 of its original thickness, and multiple sheets of the pressed sheet are stacked to form a laminate. This process of further pressing the laminate to less than 1 / 10 of its original thickness is repeated at least three times to obtain a sample sheet for testing. Through this process, the graphite particles in the sample sheet are oriented in the following ways: in the case of flake-shaped particles, the surface direction is aligned with the surface direction of the sample sheet; in the case of elliptical-shaped particles, the long axis direction is aligned with the surface direction of the sample sheet; and in the case of rod-shaped particles, the long axis direction is aligned with the surface direction of the sample sheet.

[0052] X-ray diffraction measurements were performed on the surface of the sample sheet prepared as described above. The heights H1 of the peak corresponding to the (110) plane of graphite appearing near 2θ = 77° and H2 of the peak corresponding to the (002) plane of graphite appearing near 2θ = 27° were measured. In the sample sheet prepared in this way, the value obtained by dividing H1 by H2 is 0 to 0.02.

[0053] Therefore, "the six-membered toroidal surface in the crystal of graphite particles is oriented in the planar direction in the case of flake-shaped particles, in the case of ellipsoidal particles, and in the case of rod-shaped particles" refers to the state where the height of the peak corresponding to the (110) plane of the graphite particle that appears near 2θ=77° is divided by the height of the peak corresponding to the (002) plane of the graphite particle that appears near 2θ=27°, and the value obtained is 0~0.02.

[0054] In this disclosure, X-ray diffraction measurements are performed under the following conditions.

[0055] Device: For example, Bruker AXS Co., Ltd. "D8DISCOVER" X-ray source: CuKα with a wavelength of 1.5406 nm, 40 kV, 40 mA Step size (measured step length): 0.01° Step time: 720 sec Here, "the orientation of graphite particles in the thickness direction of the heat-conducting layer in the case of flake-shaped particles, the orientation of the major axis in the thickness direction of the heat-conducting layer in the case of ellipsoidal particles, and the orientation of the major axis in the thickness direction of the heat-conducting layer in the case of rod-shaped particles" means that the angle (hereinafter also referred to as "orientation angle") between the surface direction and the surface (main surface) of the heat-conducting layer is 60° or more in the case of flake-shaped particles, the angle (hereinafter also referred to as "orientation angle") between the major axis and the surface (main surface) of the heat-conducting layer is 60° or more in the case of ellipsoidal particles, and the angle (hereinafter also referred to as "orientation angle") between the major axis and the surface (main surface) of the heat-conducting layer is 60° or more in the case of rod-shaped particles. The orientation angle is preferably 80° or more, more preferably 85° or more, and even more preferably 88° or more.

[0056] Orientation angle is the average value of the angle between the surface direction of the heat-conducting layer and the surface (main surface) of the heat-conducting layer when observing the cross section of the heat-conducting layer using SEM (scanning electron microscope), for any 50 graphite particles. The angles are: the angle between the surface direction of the flaky particles and the surface (main surface) of the heat-conducting layer; the angle between the long axis direction of the ellipsoidal particles and the surface (main surface) of the heat-conducting layer; and the angle between the long axis direction of the rod-shaped particles and the surface (main surface) of the heat-conducting layer.

[0057] The particle size (preferably the particle size of graphite particles) of the particulate carbon-based material (A) is not particularly limited. The average particle size of the particulate carbon-based material (A), measured by mass-average particle size, is preferably more than half and less than the average thickness of the heat-conducting layer. If the mass-average particle size of the particulate carbon-based material (A) is more than half the average thickness of the heat-conducting layer, an effective heat-conducting path can be formed in the heat-conducting layer, tending to improve thermal conductivity. If the mass-average particle size of the particulate carbon-based material is less than or equal to the average thickness of the heat-conducting layer, the protrusion of the carbon-based material (A) from the surface of the heat-conducting layer can be suppressed, tending to result in excellent surface adhesion of the heat-conducting layer.

[0058] There are no particular limitations on the method of fabricating a thermally conductive layer by aligning the surface direction in the thickness direction for flake-shaped particles, the long axis direction in the thickness direction for elliptical particles, and the long axis direction in the thickness direction for rod-shaped particles. For example, the method described in Japanese Patent Application Publication No. 2008-280496 can be used. Specifically, the following method can be used: a sheet is made using a composition, the sheet is stacked to form a laminate, and the side end face of the laminate (for example, at an angle of 0° to 30° relative to the normal from the main surface of the laminate) is sliced ​​(hereinafter also referred to as "laminated slicing method").

[0059] Furthermore, when using the above-described stacked slicing method, the particle size of the graphite particles used as raw material is preferably at least 1 / 2 times the average thickness of the heat-conducting layer, and may also exceed the average thickness, in terms of mass-average particle size. The reason for allowing the particle size of the graphite particles used as raw material to exceed the average thickness of the heat-conducting layer is that, for example, even if graphite particles with a particle size exceeding the average thickness of the heat-conducting layer are included, since the heat-conducting layer is formed by slicing together with the graphite particles, the graphite particles will not protrude from the surface of the heat-conducting layer. Additionally, if slicing is performed together with the graphite particles in this manner, multiple graphite particles penetrating in the thickness direction of the heat-conducting layer are generated, forming extremely efficient heat-conducting paths and tending to further improve thermal conductivity.

[0060] When using the stacked slicing method, the particle size of the graphite particles used as raw material, in terms of mass-average particle size, is more preferably 1 to 5 times the average thickness of the heat-conducting layer, and even more preferably 2 to 4 times. If the mass-average particle size of the graphite particles is more than 1 times the average thickness of the heat-conducting layer, a more efficient heat conduction path can be formed, and the thermal conductivity can be further improved. If it is less than 5 times the average thickness of the heat-conducting layer, the area occupied by the graphite particles on the surface can be prevented from becoming too large, and the reduction in adhesion can be suppressed.

[0061] The mass-average particle size (D50) of particulate carbon-based material (A) was measured using a laser diffraction particle size distribution device (e.g., Nikkiso Corporation's "Microtrac series MT3300") suitable for laser diffraction-scattering method. The particle size corresponding to the mass accumulation of 50% when plotting the mass accumulation particle size distribution curve from the small particle size side was measured.

[0062] As graphite particles, flake-shaped particles are preferred. From the viewpoint that it is easy to obtain flakes with high crystallinity and large particle size, flake-shaped expanded graphite particles obtained by crushing expanded graphite that has been made into sheets are preferred.

[0063] For example, from the perspective of balancing thermal conductivity and sealing, the content of carbon-based material (A) in the thermally conductive layer is preferably 15% to 50% by volume, more preferably 20% to 45% by volume, and even more preferably 25% to 40% by volume.

[0064] When the content of carbon-based material (A) is 15% by volume or more, it tends to improve thermal conductivity. In addition, when the content of carbon-based material (A) is 50% by volume or less, it tends to suppress the decrease in adhesion and bonding properties.

[0065] The content (volume %) of carbon-based material (A) is calculated using the following formula.

[0066] The content (volume %) of carbon-based material (A) = [(Aw / Ad) / {(Aw / Ad)+(Xw / Xd)}]×100 Aw: Mass composition (mass%) of carbon-based materials (A) Xw: Mass composition (mass%) of any other component Ad: Density of carbon-based material (A) (When carbon-based material (A) is graphite particles, Ad is calculated as 2.1.) Xd: Density of any other component <Component B, which is liquid at 25°C> The thermally conductive layer included in the thermally conductive sheet of this disclosure may contain a component that is liquid at 25°C (hereinafter also referred to as "liquid component (B)"). In this disclosure, "liquid at 25°C" means a substance that exhibits fluidity and viscosity at 25°C, and whose viscosity, as a measure of viscosity, is 0.0001 Pa·s to 1000 Pa·s at 25°C. In this disclosure, "viscosity" is defined as the viscosity measured using a rheometer at 25°C at a rate of 5.0 s⁻¹. -1 The value is the shear rate measured. Specifically, "viscosity" is the shear viscosity, measured using a rotary shear viscometer fitted with a cone plate (40 mm in diameter, 0° cone angle) at 25°C.

[0067] The viscosity of the liquid component (B) at 25°C is preferably 0.001 Pa·s to 100 Pa·s, more preferably 0.01 Pa·s to 10 Pa·s.

[0068] The liquid component (B) is not particularly limited as long as it is liquid at 25°C, and is preferably a polymer. Examples of liquid components (B) include polybutene, polyisoprene, polysulfides, acrylonitrile rubber, silicone rubber, hydrocarbon resins, terpene resins, and acrylic resins. From the viewpoint of heat resistance, liquid component (B) preferably contains polybutene. Liquid component (B) can be used alone or in combination with two or more components.

[0069] Here, polybutene refers to a polymer obtained by polymerizing isobutene or n-butene. It also includes polymers obtained by copolymerizing isobutene and n-butene. As a structure, it refers to a polymer having structural units represented by "-CH2-C(CH3)2-" or "-CH2-CH(CH2CH3)-". It is sometimes also called polyisobutylene. Polybutene only needs to contain the above-mentioned structures; there are no particular restrictions on other structures.

[0070] Examples of polybutene include homopolymers of butene and copolymers of butene with other monomeric components. Examples of copolymers with other monomeric components include copolymers of isobutylene and styrene or copolymers of isobutylene and ethylene. The copolymer can be any of random copolymers, block copolymers, and graft copolymers.

[0071] As an example of polybutene, Nippon Yuko Co., Ltd.'s "Nippon Yuko Polybutene" is a good example. TM •EMAWET (registered trademark), JXTG Energy Corporation's "Polybutene", JXTG Energy Corporation's "Tetrax", JXTG Energy Corporation's "Himol", and Bako Industries Co., Ltd.'s "Polyisobutylene".

[0072] It is believed that the liquid component (B) functions primarily as a stress reliever and thickener, possessing excellent heat and moisture resistance. Furthermore, when used in conjunction with the hot melt agent (D) described later, it tends to further enhance cohesiveness and flowability upon heating.

[0073] From the viewpoint of further improving adhesive strength, sealing, sheet strength, and hydrolysis resistance, the content of liquid component (B) in the thermal conductive layer is preferably 10% to 55% by volume, more preferably 15% to 50% by volume, and even more preferably 20% to 50% by volume.

[0074] If the content of liquid component (B) is 10% by volume or more, there is a tendency for further improvement in adhesion and bonding properties. If the content of liquid component (B) is 55% by volume or less, there is a tendency for more effective suppression of the reduction in sheet strength and thermal conductivity.

[0075] <Acrylic Polymer (C)> The thermally conductive layer contained in the thermally conductive sheet may contain acrylate polymers (C). It is believed that acrylate polymers (C) function primarily as tackifiers and elastic agents to restore thickness in response to warpage.

[0076] The preferred acrylic polymer (C) is an acrylic polymer (so-called acrylic rubber) made primarily of butyl acrylate, ethyl acrylate, acrylonitrile, acrylic acid, glycidyl methacrylate, 2-ethylhexyl acrylate, etc., and copolymerized with methyl acrylate as needed. The acrylic polymer (C) can be used alone or in combination with two or more types.

[0077] The weight-average molecular weight (C) of the acrylate polymer is preferably 100,000 to 1,000,000, more preferably 250,000 to 700,000, and even more preferably 400,000 to 600,000. When the weight-average molecular weight is 100,000 or higher, it tends to have excellent film strength, and when it is 1,000,000 or lower, it tends to have excellent flexibility.

[0078] Weight-average molecular weight can be determined by gel permeation chromatography using a standard curve of standard polystyrene.

[0079] The glass transition temperature (Tg) of the acrylate polymer (C) is preferably below 20°C, more preferably -70°C to 0°C, and even more preferably -50°C to -20°C. When the glass transition temperature is below 20°C, it tends to have excellent flexibility and adhesion.

[0080] The glass transition temperature (Tg) can be calculated by performing a dynamic viscoelasticity determination based on tension and then deriving tanδ from it.

[0081] Acrylic polymers (C) can be present throughout the thermally conductive layer by internal addition, or locally on the surface by coating or impregnation. In particular, coating or impregnation on one side imparts strong adhesion only to that side, thus being preferred from the perspective of obtaining a sheet with good workability.

[0082] In the thermally conductive layer, the content of acrylate polymer (C) is preferably 3% to 25% by volume, more preferably 5% to 20% by volume, and even more preferably 7% to 15% by volume.

[0083] <Hot Melt Fluid (D)> The thermally conductive layer contained in the thermally conductive sheet may contain a hot melt flux (D). The hot melt flux (D) has the effect of improving the strength of the thermally conductive layer and improving its fluidity during heating.

[0084] Examples of hot melt agents (D) include aromatic petroleum resins, terpene phenolic resins, and cyclopentadiene petroleum resins. Alternatively, hot melt agents (D) can also be hydrogenated aromatic petroleum resins or hydrogenated terpene phenolic resins. Hot melt agents (D) can be used alone or in combination with two or more.

[0085] When polybutene is used as the liquid component (B), the hot melt agent (D) preferably includes at least one selected from hydrogenated aromatic petroleum resins and hydrogenated terpene phenolic resins. These hot melt agents (D) have high stability and excellent compatibility with polybutene, and therefore tend to achieve better thermal conductivity, flexibility and operability when forming a thermally conductive layer.

[0086] Examples of commercially available hydrogenated aromatic petroleum resins include "ARKON" from Arakawa Chemical Industry Co., Ltd. and "I-MARV" from Idemitsu Kosan Co., Ltd. Examples of commercially available hydrogenated terpene phenolic resins include "Clearon" from Yasuhara Chemical Co., Ltd. Examples of commercially available cyclopentadiene petroleum resins include "Quintone" from Zeon Co., Ltd. and "Marcarez" from Maruzen Petrochemical Co., Ltd.

[0087] The hot melt agent (D) is preferably solid at 25°C and has a softening temperature of 40°C to 150°C. When a thermoplastic resin is used as the hot melt agent (D), the softening fluidity during hot pressing is improved, resulting in a tendency for improved adhesion. Furthermore, when the softening temperature is above 40°C, cohesion can be maintained near room temperature, resulting in a tendency to easily obtain the desired sheet strength and excellent workability. When the softening temperature is below 150°C, the softening fluidity during hot pressing becomes higher, resulting in a tendency for improved adhesion. A softening temperature of 60°C to 120°C is more preferred. Furthermore, the softening temperature is determined by the ring and ball method (JIS K 2207:1996).

[0088] From the viewpoint of improving adhesive strength, sealing, sheet strength, etc., the content of hot melt flux (D) in the thermal conductive layer is preferably 3% to 25% by volume, more preferably 5% to 20% by volume, and even more preferably 5% to 15% by volume.

[0089] When the content of hot melt flux (D) is 3% by volume or more, it tends to have sufficient adhesive strength, heat flowability and sheet strength, while when it is 25% by volume or less, it tends to have sufficient softness, excellent workability and heat cycle resistance.

[0090] Antioxidant (E) To impart thermal stability, for example, at high temperatures, the thermally conductive layer included in the thermally conductive sheet may contain an antioxidant (E). Examples of antioxidants (E) include phenolic antioxidants, phosphorus-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, hydrazine-based antioxidants, and amide-based antioxidants. The antioxidant (E) can be appropriately selected depending on the temperature conditions used, with phenolic antioxidants being more preferred. Antioxidant (E) can be used alone or in combination with two or more.

[0091] Commercially available phenolic antioxidants include, for example, ADK STAB AO-50, ADK STAB AO-60, and ADK STAB AO-80 from ADEKA Co., Ltd.

[0092] The content of antioxidant (E) in the thermally conductive layer is not particularly limited, but is preferably 0.1 vol% to 5 vol%, more preferably 0.2 vol% to 3 vol% or less, and even more preferably 0.3 vol% to 1 vol% or less. When the content of antioxidant (E) is 0.1 vol% or more, there is a tendency to obtain sufficient antioxidant effect. When the content of antioxidant (E) is 5 vol% or less, there is a tendency to suppress the reduction of strength of the thermally conductive layer.

[0093] <Other Ingredients> The thermally conductive layer contained in the thermally conductive sheet may contain components other than carbon-based materials (A), liquid components (B), acrylate-based polymers (C), hot melt agents (D), and antioxidants (E), depending on the intended purpose. For example, from a flame-retardant perspective, the thermally conductive layer may contain flame retardants. There are no particular limitations on the flame retardant; it can be appropriately selected from commonly used flame retardants. Examples include red phosphorus-based flame retardants and phosphate-based flame retardants. From the viewpoint of superior safety and improved adhesion through plasticizing effects, phosphate-based flame retardants are preferred.

[0094] As red phosphorus flame retardants, in addition to pure red phosphorus particles, red phosphorus flame retardants with various coatings or masterbatches can also be used to improve safety or stability. Specifically, examples include Nova Red, Nova Excel, Nova Quel, and Nova Pellet (all trade names) from Phosphochemicals Co., Ltd.

[0095] Examples of phosphate ester-based flame retardants include aliphatic phosphates such as trimethyl phosphate, triethyl phosphate, and tributyl phosphate; aromatic phosphates such as triphenyl phosphate, tricresyl phosphate, toluyl diphenyl phosphate, tri(xylyl) phosphate, toluyl di(2,6-xylyl) phosphate, tri(tert-butylphenyl) phosphate, tri(isopropylphenyl) phosphate, and triaryl isopropyl phosphate; and aromatic condensed phosphates such as resorcinol bis(xylyl) phosphate, bisphenol A bis(xylyl) phosphate, and resorcinol bis(xylyl) phosphate.

[0096] Among them, bisphenol A bis(diphenyl phosphate) is preferred from the viewpoint that it has excellent hydrolysis resistance and excellent effect of improving the tightness through plasticization.

[0097] There is no limit to the content of flame retardant in the heat-conducting layer. It can be used in an amount that exerts flame retardancy, preferably about 30% by volume or less. From the viewpoint of suppressing the deterioration of thermal resistance caused by the seepage of flame retardant components to the surface of the heat-conducting layer, it is preferably 20% by volume or less.

[0098] The average thickness of the thermally conductive layer is not particularly limited and can be appropriately selected according to the purpose. The thickness of the thermally conductive layer can be appropriately selected according to the specifications of the semiconductor package, etc. used. There is a tendency for smaller thickness to reduce thermal resistance, and a tendency for larger thickness to improve warpage followability. The average thickness of the thermally conductive layer can be 20μm to 3000μm, and from the viewpoint of thermal conductivity and sealing, 30μm to 500μm is preferred, and 50 to 400μm is more preferred.

[0099] The average thickness of the heat-conducting layer is given as the arithmetic mean by observing the cross-section of the object using an electron microscope or by randomly measuring the thickness at three locations using a micrometer.

[0100] <Adhesive Layer> The thermally conductive sheet disclosed herein includes an adhesive layer comprising a resin component and a thermally conductive filler, and located on at least a portion of the main surface of the thermally conductive layer, wherein the surface roughness of the adhesive layer is less than 7.0 μm.

[0101] The surface roughness of the adhesive layer can be 0.5μm~6.0μm, 0.8μm~5.0μm, or 1.0μm~4.0μm.

[0102] The surface roughness of the adhesive layer refers to the arithmetic mean roughness (Ra) specified in JIS B 0601 (2001).

[0103] The surface roughness of the adhesive layer can be adjusted, for example, by changing the thickness of the adhesive layer or the composition of the adhesive layer.

[0104] Examples of resin components include curable resin components, pressure-sensitive adhesive resin components, and thermoplastic resin components. Examples of curable resin components include thermosetting resin components and light-curing resin components. A resin component may contain one or more curable resin components, one or more pressure-sensitive adhesive resin components, or one or more thermoplastic resin components. Furthermore, a resin component may be a mixture of two or more resin components.

[0105] Examples of curable resin components include epoxy resin, phenolic resin, melamine resin, urea-formaldehyde resin, unsaturated polyester resin, alkyd resin, polyurethane resin, bismaleimide resin, polyimide resin, polyamide resin, polyamide-imide resin, silicone resin, and thermosetting (meth)acrylic resin. From the viewpoint of adhesion, epoxy resin is preferred.

[0106] Examples of resin components used in pressure-sensitive adhesives, such as thermoplastic resin components, include polyethylene (PE), polypropylene (PP), polycarbonate (PC), polystyrene, polyvinyl chloride, vinyl polymers, polyesters, polyamides, acrylonitrile-butadiene-styrene copolymer resins (ABS resin), thermoplastic (meth)acrylic resins, acrylonitrile-ethylene-propylene-diene-styrene copolymer resins (AES resin), thermoplastic epoxy resins, phenoxy resins, and thermoplastic elastomers. By using thermoplastic resin components, the adhesive layer can be easily softened and melted by heating, resulting in excellent recyclability and repairability. Furthermore, thermally conductive sheets using thermoplastic resin components exhibit superior storage stability compared to thermally conductive sheets using curable resin components (especially thermosetting resin components), and can also be stored at room temperature. Among these, thermoplastic resin components can achieve low viscosity through heating; from the viewpoint of further reducing the gap between the bonded material and the thermally conductive sheet, thermoplastic epoxy resins are preferred.

[0107] The thermoplastic resin component can be an amorphous thermoplastic resin, such as at least one of thermoplastic epoxy resin and phenoxy resin. An amorphous thermoplastic resin refers to a resin that, although possessing a melting point (Tm), exhibits an endothermic peak accompanying melting that is not clearly identified as an endothermic peak in measurements using a differential scanning calorimeter (DSC), or such endothermic peak is very small.

[0108] The heat of fusion of the amorphous thermoplastic resin is preferably 15 J / g or less, more preferably 11 J / g or less, even more preferably 7 J / g or less, particularly preferably 4 J / g or less, and most preferably the melting peak is below the detection limit.

[0109] The heat of fusion is calculated from the area of ​​the endothermic peak of the DSC (differential scanning calorimeter) and the mass of the thermoplastic resin component. In this case, the heat of fusion is calculated using the mass of the thermoplastic resin component other than the components contained in the adhesive layer such as thermally conductive fillers.

[0110] For example, the heat of fusion can be calculated as follows.

[0111] First, weigh 2 mg to 10 mg of the sample and place it in an aluminum pan. Use a DSC (e.g., Rigaku DSC8231) to heat the sample to over 200 °C at a rate of 10 °C / min to obtain a DSC curve. Then, calculate the heat of fusion based on the area of ​​the endothermic peak at melting obtained from the DSC curve and the aforementioned weighing value.

[0112] The thermoplastic epoxy resin is preferably a polymer of (a) a difunctional epoxy resin monomer or oligomer and (b) a difunctional compound containing two functional groups selected from phenolic hydroxyl, carboxyl, mercapto, isocyanate, and cyanate groups, which may be the same or different. The polymer can be generated by heating components (a) and (b) in the presence of a catalyst such as an imidazole catalyst.

[0113] The above (a) 2-functional epoxy resin monomers or oligomers refer to epoxy resin monomers or oligomers with two epoxy groups in the molecule.

[0114] As specific examples of (a) above, examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, difunctional phenolic varnish type epoxy resin, bisphenol AD ​​type epoxy resin, biphenyl type epoxy resin, difunctional naphthalene type epoxy resin, difunctional alicyclic epoxy resin, difunctional glycidyl ester type epoxy resin (e.g., diglycidyl phthalate, tetrahydrodiglycidyl phthalate and dimeric acid diglycidyl ester), difunctional glycidylamine type epoxy resin (e.g., diglycidyl aniline and diglycidyl toluidine), difunctional heterocyclic epoxy resin, difunctional diaryl sulfone type epoxy resin, and hydroquinone type epoxy resin (e.g., hydroquinone diglycidyl ether, 2,5-di-tert-butylhydrogen ether). The compounds include quinone diglycidyl ethers and resorcinol diglycidyl ethers, difunctional alkylene glycidyl ether compounds (e.g., butanediol diglycidyl ether, butenediol diglycidyl ether, and butynediol diglycidyl ether), difunctional hydantoin compounds containing glycidyl groups (e.g., 1,3-diglycidyl-5,5-dialkylhydantoin and 1-glycidyl-3-(epoxypropoxyalkyl)-5,5-dialkylhydantoin), difunctional siloxanes containing glycidyl groups (e.g., 1,3-bis(3-epoxypropoxypropyl)-1,1,3,3-tetramethyldisiloxane and α,β-bis(3-epoxypropoxypropyl)polydimethylsiloxane), and modified versions thereof. From the viewpoint of reactivity and operability, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and biphenyl type epoxy resins are preferred.

[0115] Examples of the difunctional compounds containing phenolic hydroxyl groups mentioned in (b) above include mononuclear aromatic dihydroxy compounds with a single benzene ring such as catechol, resorcinol, and hydroquinone; bisphenols such as bis(4-hydroxyphenyl)propane (bisphenol A), bis(4-hydroxyphenyl)methane (bisphenol F), bis(4-hydroxyphenyl)ethane (bisphenol AD), and bis(4-hydroxyphenyl)sulfone (bisphenol S); compounds with fused rings such as dihydroxynaphthalene; difunctional phenolic compounds with allyl groups such as diallyl resorcinol, diallyl bisphenol A, and triallyl dihydroxybiphenyl; and dibutyl bisphenol A.

[0116] Examples of the difunctional compounds containing a carboxyl group mentioned in (b) above include adipic acid, succinic acid, malonic acid, cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, and terephthalic acid.

[0117] Examples of thiol-containing difunctional compounds in (b) above include ethylene glycol dithioglycolate and ethylene glycol dithiopropionate.

[0118] Examples of difunctional compounds containing isocyanate groups as described in (b) above include diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HMDI), toluene diisocyanate (TDI), etc.

[0119] Examples of the difunctional compounds containing cyanate groups in (b) above include 2,2-bis(4-cyanophenyl)propane, 1,1-bis(4-cyanophenyl)ethane, and bis(4-cyanophenyl)methane.

[0120] In (b) above, from the viewpoint of obtaining a thermoplastic polymer, a difunctional compound containing phenolic hydroxyl groups is preferred; from the viewpoint of heat resistance and adhesion, a difunctional compound containing two phenolic hydroxyl groups and containing a bisphenol structure or a biphenyl structure is preferred; and from the viewpoint of heat resistance and cost, bisphenol A, bisphenol F, or bisphenol S is preferred.

[0121] When (a) above refers to bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, or biphenyl type epoxy resin, and (b) above refers to bisphenol A, bisphenol F, or bisphenol S, the polymer obtained by polymerization of (a) and (b) above preferably has a main chain with a p-phenylene structure and ether bonds as the main backbone and them linked by alkylene groups, and hydroxyl groups generated by addition polymerization configured in the side chain.

[0122] The linear structure formed by the p-phenylene backbone enhances the mechanical strength of the polymer after polymerization, and the hydroxyl groups configured in the side chains improve adhesion. As a result, high adhesive strength can be achieved while maintaining the workability of the thermosetting resin.

[0123] The epoxy equivalent (molecular weight / number of epoxy groups) of thermoplastic epoxy resin can be above 1600 g / eq, above 2000 g / eq, above 5000 g / eq, or above 9000 g / eq.

[0124] The epoxy equivalent of the epoxy resin was determined by a method based on JIS K 7236:2009.

[0125] The adhesive layer may contain phenoxy resin as a thermoplastic resin component.

[0126] Phenoxy resins, for example, are polyhydroxy polyethers synthesized from bisphenols and epichlorohydrin, and are thermoplastic.

[0127] In the manufacture of phenoxy resins, methods are known to involve the direct reaction of diphenols with epichlorohydrin and the addition polymerization of diphenols with diglycidyl ethers. In the case of the direct reaction of diphenols with epichlorohydrin, examples of diphenols include phenols such as bisphenol A, bisphenol F, bisphenol S, biphenol, biphenylene glycol, and fluorene diphenyl; and aliphatic glycols such as ethylene glycol, propylene glycol, and diethylene glycol. Among these, bisphenol A, bisphenol F, and bisphenol S are preferred from the perspectives of cost, adhesion, viscosity, and heat resistance. They can be used individually or in combination of two or more.

[0128] Phenoxy resins preferably contain a chemical structure similar to that of epoxy resins, including a main chain consisting of a p-phenylene structure and ether bonds as the main backbone and linking them together, and hydroxyl groups configured in the side chains.

[0129] Regarding thermoplastic epoxy resins and phenoxy resins, the weight-average molecular weight (MAM) of polystyrene, determined by GPC (gel permeation chromatography), is preferably 10,000 to 500,000, more preferably 18,000 to 300,000, and even more preferably 20,000 to 200,000. The MAM is calculated based on the elution peak position detected by GPC and represents the MAM value converted from standard polystyrene. When the MAM is within this range, a good balance between thermoplasticity and heat resistance is achieved. A MAM of 10,000 or higher exhibits excellent heat resistance, while a MAM of 500,000 or lower results in low viscosity at melt and high adhesion.

[0130] Examples of thermally conductive fillers include those containing metal particles and non-metal particles, which exhibit excellent thermal conductivity. Examples include metals, metal oxides, metal nitrides, metal hydroxides, metal carbides, metal fluorides, and carbon. Thermally conductive fillers can have a thermal conductivity of 10 W / (m·K) or higher. Thermally conductive fillers can be either insulating or conductive.

[0131] The thermally conductive filler can be particles selected from at least one of silver, copper, aluminum, alumina, aluminum hydroxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, silicon carbide, silicon dioxide, aluminum fluoride, calcium fluoride, and zinc oxide. Among these, silver particles are preferred from the viewpoint of thermal conductivity.

[0132] Boron nitride is preferred for applications requiring insulation due to its insulating properties. However, boron nitride has a flaky shape, exhibits anisotropic thermal conductivity, and tends to align along its surface, resulting in a tendency for its thermal conductivity to decrease in the thickness direction. Therefore, from a thermal conductivity perspective, when using boron nitride, it is necessary to form an adhesive layer with the boron nitride oriented in the thickness direction, which can easily complicate the adhesive layer formation process.

[0133] On the other hand, compared with ceramic fillers such as boron nitride, metal particles such as silver, copper, and aluminum have higher thermal conductivity and less anisotropy in thermal conductivity. Therefore, when forming the adhesive layer, it is not necessary to orient the metal particles in the thickness direction, and an adhesive layer with excellent thermal conductivity can be easily formed, resulting in a significant reduction in the thermal resistance of the thermally conductive sheet. Furthermore, by using silver particles as the metal particles, the particles are sintered together at a relatively low temperature. Therefore, the network of silver particles formed by sintering tends to have higher thermal conductivity compared with other thermally conductive fillers. In addition, the sintered silver particles have excellent adhesion to the bonded body such as the heating element and the heat sink, thus tending to further reduce the thermal resistance.

[0134] The thermally conductive filler preferably contains silver particles. When the thermally conductive filler contains silver particles, the content of silver particles relative to 100% by mass of the thermally conductive filler can be 50% to 100% by mass, 80% to 100% by mass, or 90% to 100% by mass.

[0135] From the viewpoint of excellent thermal conductivity and further reducing the gap between the adherend and the thermally conductive sheet, the average particle size of the thermally conductive filler is preferably 8.0 μm or less, more preferably 7.0 μm or less, and even more preferably 6.0 μm or less. The lower limit of the average particle size of the thermally conductive filler is not particularly limited; for example, it can be 0.5 μm or more, or 1.0 μm or more.

[0136] The average particle size of the thermally conductive filler was measured using a laser diffraction particle size distribution device adapted to laser diffraction-scattering method (e.g., the "Microtrac series MT3300" manufactured by Nikkiso Corporation). When plotting the mass-cumulative particle size distribution curve from the small particle size side, the particle size corresponding to the mass-cumulative 50% (D50) was measured.

[0137] In the thermally conductive sheet disclosed herein, the adhesive layer only needs to be located on at least a portion of the main surface of the thermally conductive layer. The adhesive layer can be located on the entire main surface, or it can be located on a portion of the main surface (e.g., the portion that is in contact with the heat-generating element, heat-dissipating element, or other bonded body).

[0138] The adhesive layer can be located on one main surface or on two main surfaces.

[0139] From the perspective of balancing thermal conductivity and adhesion, for example, the content of resin component in the adhesive layer is preferably 1% to 30% by mass relative to the total amount of the adhesive layer, more preferably 3% to 25% by mass, and even more preferably 5% to 20% by mass.

[0140] When the adhesive layer contains a thermoplastic resin component, the content of the thermoplastic resin component relative to the total amount of resin component can be 50% or more by mass, or 60% or more by mass, or 80% or more by mass, or 90% or more by mass.

[0141] There is no particular limit to the upper limit of the content of the above-mentioned thermoplastic resin components; it can be 100% by mass or less than 95% by mass.

[0142] From the perspective of balancing thermal conductivity and adhesion, for example, the content of thermally conductive filler in the adhesive layer is preferably 70% to 99% by mass relative to the total amount of the adhesive layer, more preferably 75% to 97% by mass, and even more preferably 80% to 95% by mass.

[0143] The total content of resin components and thermally conductive fillers in the adhesive layer can be 80% to 100% by mass or 90% to 100% by mass relative to the total amount of the adhesive layer.

[0144] The adhesive layer may contain components other than resin components and thermally conductive fillers, or it may not contain components other than resin components and thermally conductive fillers. Examples of components other than resin components and thermally conductive fillers include hot melt flux (D), antioxidant (E), and other components described in the above-mentioned thermally conductive layer section.

[0145] When the adhesive layer contains a thermosetting resin component, from the viewpoint of improving processability, the adhesive layer is preferably in a semi-cured state. For example, an adhesive layer in a semi-cured state can be obtained by subjecting a resin composition containing a thermosetting resin component and a thermally conductive filler to heating, drying, or other treatments.

[0146] In this disclosure, the semi-cured state refers to the adhesive layer having a viscosity of 10 at room temperature (25~30℃). 4 Pa·s~10 6 Pa·s. In addition, the above viscosity was measured by DMA (Dynamic Viscoelasticity Measurement Apparatus; frequency 1 Hz, load 10 g; heating rate 20 °C / min).

[0147] There are no particular limitations on the method for obtaining the adhesive layer in a semi-cured state. For example, a resin composition containing a thermosetting resin component, a thermally conductive filler, a solvent, etc., can be applied to the main surface of the thermally conductive layer, and the applied resin composition can be heated and dried. Alternatively, a resin composition can be applied to a release film, followed by heating and drying, and then the adhesive layer formed from the heated and dried resin composition can be hot-rolled onto the main surface of the thermally conductive layer. Examples of heating and drying methods include hot vacuum pressing and hot roll lamination.

[0148] The average thickness of the adhesive layer is preferably 2 μm to 50 μm, more preferably 2 μm to 30 μm, and even more preferably 2 μm to 20 μm. By making the average thickness of the adhesive layer 2 μm or more, there is a tendency to further reduce the gap between the bonded body and the thermally conductive sheet, thereby further reducing the contact thermal resistance. By making the average thickness of the adhesive layer 50 μm or less, there is a tendency for the thermal conductivity of the thermally conductive sheet to be even better.

[0149] Alternatively, an electron microscope can be used to observe the cross-section of the thermally conductive layer being measured, and the thickness at three random locations can be measured. The arithmetic mean of these measurements can be taken as the average thickness of the adhesive layer. Alternatively, for both thermally conductive layers without an adhesive layer and thermally conductive sheets with an adhesive layer, the thickness at three random locations can be measured using a micrometer, and the arithmetic mean of these measurements can be taken as the average thickness of the thermally conductive layer and the average thickness of the thermally conductive sheet. Then, the average thickness of the adhesive layer can be calculated by subtracting the average thickness of the thermally conductive layer from the average thickness of the thermally conductive sheet.

[0150] When adhesive layers are formed on the two main surfaces of the heat-conducting layer, the average thickness of the adhesive layer refers to the sum of the thicknesses of the adhesive layers formed on the two main surfaces.

[0151] The ratio of the average particle size of the thermally conductive filler to the average thickness of the adhesive layer, i.e., average particle size / average thickness, can be 0.01~0.8, 0.05~0.7, or 0.10~0.6.

[0152] In the thermally conductive sheet, the thermal conductivity in the thickness direction of the thermally conductive layer is preferably greater than that in the thickness direction of the adhesive layer. For example, the ratio of the thermal conductivity in the thickness direction of the thermally conductive layer to that in the thickness direction of the adhesive layer (thermal conductivity of the thermally conductive layer / thermal conductivity of the adhesive layer) only needs to be greater than 1. For example, it can be greater than 1 and less than 20, greater than 1 and less than 10, or 2 to 8.

[0153] The thermal conductivity in the thickness direction of the thermally conductive layer and the thermal conductivity of the adhesive layer can be determined using the xenon flash method. Furthermore, when the resin composition includes curable resin components, the thermal conductivity of the adhesive layer refers to the thermal conductivity of the cured adhesive layer.

[0154] The thermal conductivity of the adhesive layer can be above 5.0 W / (m·K), ranging from 5.0 W / (m·K) to 20 W / (m·K), or from 7.0 W / (m·K) to 15 W / (m·K).

[0155] The thermally conductive sheet may have a protective film on at least one side, preferably on both sides. This protects the adhesive surface of the thermally conductive sheet.

[0156] Protective films can be made from resins such as polyethylene, polyester, polypropylene, polyethylene terephthalate, polyimide, polyetherimide, polyether naphthalate, and methylpentene, as well as coated paper, coated fabric, and metal foils such as aluminum. These protective films can be used alone or in combination to form multilayer films. Preferably, the protective film has been surface-treated with release agents such as silicone-based or silica-based agents.

[0157] The application of the thermally conductive sheet is not particularly limited. The thermally conductive sheet disclosed herein is particularly suitable as a thermally conductive sheet (TIM1; Thermal Interface Material 1) placed between the semiconductor chip and the heat sink when the semiconductor chip is used as the heat source and the heat sink is used as the heat sink, and as a film-like adhesive material for semiconductor chips such as a chip bonding film. When the thermally conductive sheet is used as a chip bonding film, it can also be made into a die bonding film integrally formed by stacking it with a dicing tape.

[0158] [Thermal conductive sheet] (Second Implementation) The thermally conductive sheet of the second embodiment of this disclosure comprises: a thermally conductive layer containing a carbon-based material (A); and an adhesive layer containing a resin component and a thermally conductive filler, and located on at least a portion of the main surface of the thermally conductive layer, wherein the average particle size of the thermally conductive filler in the adhesive layer is 8.0 μm or less.

[0159] In the thermally conductive sheet of the first embodiment of this disclosure, a thermally conductive layer and an adhesive layer are provided, and the average particle size of the thermally conductive filler in the adhesive layer is 8.0 μm or less. By making the average particle size of the thermally conductive filler contained in the adhesive layer less than or equal to the above value, the surface roughness of the adhesive layer is reduced, and the adhesion to the bonded body is improved.

[0160] The preferred conditions for the thermally conductive sheet in the second embodiment are the same as those for the thermally conductive sheet in the first embodiment.

[0161] use Figure 1 Embodiments of the thermally conductive sheet will be described. The thermally conductive sheet disclosed herein is not limited to the following embodiments.

[0162] Figure 1 The heat-conducting sheet 1 shown includes a heat-conducting layer 11 and adhesive layers 12 and 13. The adhesive layer 12 is located on one main surface of the heat-conducting layer 11, and the adhesive layer 13 is located on the other main surface of the heat-conducting layer 11.

[0163] [Manufacturing method of thermally conductive sheet] There are no particular limitations on the manufacturing method of the thermally conductive sheet, as long as it is a method that can obtain a thermally conductive sheet having the above-described structure. The manufacturing method of the thermally conductive sheet includes: a step of preparing a composition containing the above-described carbon-based material (A) (also called a "preparation step"), a step of forming the above-described thermally conductive layer using the above-described composition (also called a "forming step"), and a step of forming an adhesive layer on at least a portion of the main surface of the above-described thermally conductive layer (also called a "adhesive layer forming step").

[0164] <Preparation Process> In the preparation process, a composition containing a carbon-based material (A) and any other components (e.g., a component that is liquid at 25°C (B), an acrylate polymer (C), a hot melt agent (D), an antioxidant (E), and other components) is prepared. As for the method of combining each component, any method can be used as long as the components can be mixed uniformly; there are no particular limitations. Alternatively, commercially available compositions can also be prepared. For details on the preparation of the composition, please refer to paragraph

[0033] of Japanese Patent Application Publication No. 2008-280496.

[0165] <Formation Process> In the forming process, the above-mentioned heat-conducting layer is formed using a composition containing a carbon-based material (A) and any other components. For example, the aforementioned composition can be molded into a sheet to form the heat-conducting layer.

[0166] When the carbon-based material (A) is graphite particles, the forming process preferably includes: a process of forming the above composition into a sheet to obtain a sheet (also called "sheet making process"), a process of making a laminate of the above sheet (also called "laminate making process"), and a process of slicing the side end face of the above laminate (also called "slicing process").

[0167] Sheet manufacturing process The sheet manufacturing process can be carried out by any method as long as the composition obtained in the previous process can be made into a sheet, and there are no particular limitations. For example, it is preferred to use at least one molding method selected from rolling, pressing, extrusion and coating. For details of the sheet manufacturing process, please refer to paragraph

[0034] of Japanese Patent Application Publication No. 2008-280496.

[0168] Fabrication Process of Layered Bodies The laminate manufacturing process forms a laminate of sheets obtained in previous processes. For example, a laminate can be made by stacking multiple independent sheets in sequence, by folding a single sheet, or by rolling a single sheet. For details of the laminate manufacturing process, please refer to paragraphs

[0035] to

[0037] of Japanese Patent Application Publication No. 2008-280496.

[0169] Slicing Process The slicing process can be any method as long as it can slice the side end face of the laminate obtained in the previous process, and there is no particular limitation. From the viewpoint of further improving thermal conductivity by forming an extremely effective heat conduction path by graphite particles penetrating in the thickness direction of the heat-conducting layer, it is preferable to slice with a thickness of less than twice the mass-average particle size of the graphite particles. For details of the slicing process, please refer to paragraph

[0038] of Japanese Patent Application Publication No. 2008-280496.

[0170] <Adhesive Layer Formation Process> The adhesive layer forming process can be any method, without particular limitation, as long as it forms an adhesive layer on at least a portion of the main surface of the thermally conductive layer (e.g., a sliced ​​sheet obtained by slicing). For example, a resin composition containing a thermosetting resin component, a thermally conductive filler, a solvent, etc., can be applied to the main surface of the thermally conductive layer, and the applied resin composition can be heated and dried to evaporate the solvent. Alternatively, a resin composition can be applied to a release film, followed by heating, drying, etc., and then the adhesive layer formed from the heated and dried resin composition can be hot-rolled onto the main surface of the thermally conductive layer. Examples of heating, drying, etc., include hot vacuum pressing and hot roll lamination. The adhesive layer formed on the main surface of the thermally conductive layer can be in a semi-cured state.

[0171] The manufacturing method of the thermally conductive sheet may further include a step of pasting a protective film onto the thermally conductive sheet and laminating it after the adhesive layer formation step (also known as the "lamination step").

[0172] <Lamination Process> The lamination process can be carried out by any method, as long as the thermally conductive sheet obtained in the adhesive layer formation process is attached to the protective film. There are no particular restrictions.

[0173] By manufacturing thermally conductive sheets using this method, it is easy to form efficient heat conduction paths, thus tending to produce thermally conductive sheets with high thermal conductivity and excellent adhesion.

[0174] [Heat dissipation device] The heat dissipation device disclosed herein comprises a heating element, a heat sink, and a thermally conductive sheet of the present disclosure disposed between the heating element and the heat sink, wherein the adhesive layer is located on at least a portion of at least one main surface of the thermally conductive layer located on the heating element side and on the heat sink side. Preferably, the adhesive layer is located on at least a portion of the main surface of the thermally conductive layer located on the heating element side and at least a portion of the main surface of the heat sink side, respectively. More preferably, the adhesive layer is located on the region opposite the heating element on the main surface of the heating element side and the region opposite the heat sink on the main surface of the heat sink side, respectively.

[0175] Examples of heat-generating components include semiconductor chips, semiconductor packages, and power modules. Examples of heat-dissipating components include heat sinks, heat pumps, and water-cooling pipes.

[0176] The following uses Figure 2 A more specific example of a heat dissipation device will be described. A heat dissipation device using a semiconductor chip as a heat source and a heat sink as a heat sink will be described. The semiconductor chip and heat sink are examples of heat source and heat sink, respectively, and this disclosure is not limited thereto. The thermally conductive sheet 1 is used such that one side is in close contact with the semiconductor chip 2 and the other side is in close contact with the heat sink 3. The semiconductor chip 2 is fixed to the substrate 4 using a bottom filler material 5, and the heat sink 3 is fixed to the substrate 4 using a sealing material 6. Pressing improves the adhesion between the thermally conductive sheet 1 and the semiconductor chip 2 and heat sink 3. Furthermore, the heat source and heat sink do not need to be separate entities relative to one thermally conductive sheet 1. For example, multiple semiconductor chips 2 can be provided on one thermally conductive sheet 1, or one semiconductor chip 2 can be provided on multiple thermally conductive sheets 1, or multiple semiconductor chips 2 can be provided on multiple thermally conductive sheets 1. The adhesive layer is located on the main surface of the thermally conductive sheet 1 on the semiconductor chip 2 side and on the main surface of the thermally conductive sheet 1 on the heat sink 3 side. For example, in Figure 1 In the thermally conductive sheet 1 shown, adhesive layer 13 is located on the main surface of the thermally conductive sheet 1 on the side of the semiconductor chip 2, and adhesive layer 12 is located on the main surface of the thermally conductive sheet 1 on the side of the heat sink 3. Furthermore, adhesive layer 13 can contact the semiconductor chip 2, and adhesive layer 12 can contact the heat sink 3.

[0177] The heat dissipation device is formed by placing the disclosed thermally conductive sheet between a heat-generating element and a heat-dissipating element. By layering the heat-generating element and the heat-dissipating element through the thermally conductive sheet, heat from the heat-generating element can be efficiently conducted to the heat-dissipating element. This efficient heat conduction provides a heat dissipation device with an extended service life and stable function during long-term use.

[0178] The temperature range in which the thermally conductive sheet is particularly suitable can be, for example, -10℃ to 150℃, -10℃ to 100℃, or -10℃ to 80℃. Therefore, as a heat source, examples of preferred heat sources include semiconductor packages, displays, LEDs, lamps, automotive power modules, and industrial power modules.

[0179] Examples of heat sinks include heat sinks using aluminum or copper fins or plates, aluminum or copper blocks connected to heat pipes, aluminum or copper blocks that use a pump to circulate coolant internally, and Peltier elements and aluminum or copper blocks equipped with such Peltier elements.

[0180] A heat dissipation device is constructed by bringing the various surfaces of a heat-conducting sheet into contact with a heat-generating element and a heat-dissipating element. There are no particular restrictions on the method by which the heat-generating element contacts one surface of the heat-conducting sheet, or the method by which the heat-dissipating element contacts the other surface of the heat-conducting sheet, as long as the method can fix them in a sufficiently tight fit.

[0181] For example, the following methods can be used: placing a heat-conducting sheet between the heating element and the heat sink, fixing it with a clamp capable of applying pressure up to approximately 0.05 MPa to 1 MPa, and then heating the heating element in this state; or heating it to approximately 80°C to 200°C using an oven or similar device. Alternatively, a method using a press capable of heating and pressurizing at 80°C to 200°C and 0.05 MPa to 1 MPa can be used. In this method, the preferred pressure range is 0.10 MPa to 1 MPa, and the preferred temperature range is 100°C to 180°C. Setting the pressure to 0.10 MPa or higher, or the heating temperature to 100°C or higher, tends to result in excellent sealing performance. Furthermore, setting the pressure to 1 MPa or lower, or the heating temperature to 180°C or lower, tends to further improve the reliability of the seal. This is believed to be because it can prevent the heat-conducting sheet from being excessively compressed and becoming thinner, or it can prevent the strain or residual stress of surrounding components from becoming excessive.

[0182] As a thermally conductive sheet disposed between the heat-generating element and the heat-dissipating element, there are no particular limitations on the aforementioned thermally conductive sheet materials. For example, it can be... Figure 1 The heat-conducting sheet shown is positioned between the heat-generating element and the heat-dissipating element.

[0183] In use Figure 1 In the case of the heat-conducting sheet 1 shown, by heating and pressurizing the heat-conducting sheet 1 while it is positioned between the heat-generating element and the heat-dissipating element, the adhesive layers 12 and 13 on the main surface of the heat-conducting sheet 1 soften or deform. The gaps generated when the heat-conducting sheet 1 is heated and pressed together with the heat-generating element and the heat-dissipating element are filled by the softened and deformed adhesive layers. As a result, the gap between the heat-conducting sheet and the bonded body can be reduced, and the heat-conducting sheet and the bonded body can be tightly sealed through the adhesive layers.

[0184] For example, by applying an adhesive layer containing a thermosetting resin component, the adhesive layer, deformed by heating and pressing, fills the gap between the thermally conductive sheet and the bonded body, and the thermosetting resin component is cured by heating. Thus, the thermally conductive sheet and the bonded body can be tightly bonded together via the adhesive layer.

[0185] For example, by applying an adhesive layer containing thermoplastic resin components, the adhesive layer softened by heat pressing fills the gap between the thermally conductive sheet and the bonded body.

[0186] As a result, the gap between the heat-conducting sheet and the heating element or heat sink is reduced, and the contact thermal resistance is significantly reduced.

[0187] The reduction in thickness of the thermally conductive sheet after being pressed between the heat-generating element and the heat-dissipating element, relative to its initial thickness before being pressed between the heat-generating element and the heat-dissipating element (compression ratio), can be 1% to 35%.

[0188] In addition to using clips, screws, springs, and other clamps can also be used for fixing. However, from the perspective of maintaining a tight seal, it is preferable to further fix the seal using commonly used methods such as adhesives.

[0189] Example The present invention will be described in detail below through embodiments, but the present invention is not limited to these embodiments.

[0190] (Examples 1-3) The following materials were added to a kneading machine (Moriyama Co., Ltd., DS3-SGHM-E type double-arm kneading machine) in the mixing ratio (volume %) shown in Table 1 and kneaded at a temperature of 150°C to obtain the composition.

[0191] <Carbon-based materials (A)> (A)-1: Scaly expanded graphite particles (Showa Denko Materials Co., Ltd. "HGF-L", mass-average particle size: 270 μm, confirmed by the X-ray diffraction method described above, the orientation of the six-membered ring in the crystal in the plane direction of the scaly particles was observed).

[0192] <Liquid Component (B)> (B)-1: Isobutylene-n-butene copolymer (Nippon Oil Corporation "Nippon Oil Polybutene") TM ·EMAWET (registered trademark), Class 30N) (B)-2: Homopolymer of isobutylene (Tetrax 6T, Nippon Oil Co., Ltd.) <Acrylic Polymer (C)> (C)-1: Acrylic ester copolymer resin (butyl acrylate / ethyl acrylate / acrylonitrile / acrylic acid copolymer, weight average molecular weight: 530,000, Tg=-39℃) <Hot Melt Fluid (D)> (D)-1: Hydrogenated petroleum resin (ARKON P90, Arakawa Chemical Industry Co., Ltd.) Antioxidant (E) (E)-1: Hindered phenolic antioxidant (ADK STAB AO-60, ADEKA Co., Ltd.) (Fabrication of the thermal conductive layer) The compound obtained by mixing is placed in an extrusion molding machine (Parker Corporation, trade name: HKS40-15 extruder) and extruded into a flat shape with a width of 20cm and a thickness of 1.5mm to 1.6mm to obtain a primary sheet. The primary sheet is pressed and punched using a 40mm × 150mm die, and 61 sheets of the punched sheets are stacked together. With a height of 80mm, spacers of 80mm height are clamped between the stacked sheets and pressure is applied at 90°C for 30 minutes in the stacking direction to obtain a 40mm × 150mm × 80mm laminate. Next, the 80mm × 150mm side end of the laminate is sliced ​​using a woodworking slicer to obtain a thermally conductive layer with a thickness of 0.11mm.

[0193] (Fabrication of thermally conductive sheets) (Example 1) A resin composition comprising 8 parts by weight of a thermoplastic resin component (phenoxy resin), 8 parts by weight of a saturated polyester resin, 84 parts by weight of a thermally conductive filler (silver particles, 1.4 μm particle size), and 26 parts by weight of a solvent (cyclohexanone) was prepared. The prepared resin composition was coated onto a release film (material: polyethylene terephthalate), and dried in an oven at 130°C. By hot-roll laminating the two main surfaces of the thermally conductive layer obtained above at 70°C, a thermally conductive sheet with an adhesive layer (adhesive layer 1 in Table 2) formed on both main surfaces was obtained. That is, a thermally conductive sheet composed of a release film / adhesive layer / thermally conductive layer / adhesive layer / release film was obtained.

[0194] (Example 2) A resin composition comprising 8 parts by weight of a thermoplastic resin component (phenoxy resin), 8 parts by weight of a saturated polyester, 84 parts by weight of a thermally conductive filler (silver particles, 2.6 μm particle size), and 26 parts by weight of a solvent (cyclohexanone) was prepared. The prepared resin composition was coated onto a release film and dried in an oven at 130°C. By hot-roll laminating the two main surfaces of the thermally conductive layer obtained as described above at 70°C, a thermally conductive sheet with an adhesive layer (adhesive layer 2 in Table 2) formed on the two main surfaces was obtained.

[0195] (Example 3) A resin composition comprising 8 parts by weight of a thermoplastic resin component (phenoxy resin), 8 parts by weight of a saturated polyester, 84 parts by weight of a thermally conductive filler (silver particles, 5.0 μm particle size), and 26 parts by weight of a solvent (cyclohexanone) was prepared. The prepared resin composition was coated onto a release film and dried in an oven at 130°C. By hot-roll laminating the two main surfaces of the thermally conductive layer obtained as described above at 70°C, a thermally conductive sheet with an adhesive layer (adhesive layer 3 in Table 2) formed on the two main surfaces was obtained.

[0196] (Comparative Example 1) A resin composition comprising 8 parts by weight of thermoplastic resin (phenoxy resin), 8 parts by weight of saturated polyester resin, 84 parts by weight of thermally conductive filler (silver particles, 9.5 μm particle size), and 26 parts by weight of solvent (cyclohexanone) was prepared. The prepared resin composition was coated onto a release film and dried in an oven at 130°C. By hot-roll laminating the two main surfaces of the thermally conductive layer obtained as described above at 70°C, a thermally conductive sheet with an adhesive layer (adhesive layer 4 in Table 2) formed on the two main surfaces was obtained.

[0197] For the thermally conductive sheets of Examples 1-3 and Comparative Example 1, the evaluations were conducted using the following methods. The results are shown in Table 2.

[0198] (Determination of thermal resistance) Thermal resistance was measured using a benchtop xenon flash analyzer (LFA 467 Hyper Flash). Two Φ14mm thermally conductive sheets, after the release film was removed, were sandwiched between a 1mm copper plate to create a three-layer sample. Sample preparation conditions included pressurizing at 150℃ and 0.14MPa for 3 minutes, followed by heating in a 170℃ oven for 2 hours and then cooling completely at room temperature. Additionally, as a pretreatment, the copper surface was blackened using carbon spraying before measurement. The thermal conductivity λ, obtained after removing the influence of the copper plate composition from the three-layer structure, was calculated per unit area (cm²) using the following formula based on the obtained thermal conductivity λ and thickness t. 2 Thermal resistance value X (K·cm) 2 / W).

[0199] X = (10 × t) / λ t: Thickness (mm) of the thermally conductive sheet in Examples 1-3 or Comparative Example 1 λ: Thermal conductivity (W / (m·K)) (Surface roughness) For Examples 1-3 and Comparative Example 1, the arithmetic mean roughness (Ra) of the adhesive layer as specified in JIS B 0601 (2001) was determined. Additionally, the surface roughness of the thermally conductive layer prior to the formation of the adhesive layer was determined, and the result was 5 μm.

[0200] (Evaluation of thickness) For Examples 1-3 and Comparative Example 1, the thickness of the adhesive layer after hot roller lamination was measured using a micrometer.

[0201] (Evaluation of adhesion) In the measuring section of the adhesion testing machine (Adhesion Testing Machine TAC-II), the thermally conductive sheets of Examples 1-3 and Comparative Example 1 were placed with the adhesive layer exposed after the release film was peeled off facing upwards. The value obtained under the conditions of a plate temperature of 25°C, a load of 100 gf, a speed of 120 mm / min, and a pressing time of 1 sec was taken as the adhesive force (gf).

[0202] (Evaluation of transferability) Transferability is evaluated by confirming the tightness of the adhesion to the bonded substrate.

[0203] As the substrate, a 10mm × 10mm silicon wafer (material of the bonding surface: Si) with a surface roughness of 0.1μm was prepared. For the thermally conductive sheets of Examples 1-3 and Comparative Example 1, which were pre-cut into 10mm × 10mm pieces, the release film on one side was peeled off, exposing the adhesive layer to contact the substrate. The adhesive layer was then pressed together twice using a 140g hand roller. Next, the release film on the other side was peeled off, and the transferability was evaluated based on the following evaluation criteria.

[0204] -Evaluation Criteria- A: When the release film on the other side is peeled off, the thermally conductive sheet does not peel off from the bonded body.

[0205] B: When the release film on the other side is peeled off, the thermally conductive sheet separates from the bonded material.

[0206] As shown in Table 1, the thermally conductive sheets in Examples 1-3 exhibit excellent transferability to the adhered substrate.

Claims

1. A thermally conductive sheet, comprising: A thermally conductive layer containing a carbon-based material (A); and An adhesive layer comprising a resin component and a thermally conductive filler, wherein the adhesive layer is located on at least a portion of the main surface of the thermally conductive layer. in, The surface roughness of the adhesive layer is below 7.0 μm.

2. A thermally conductive sheet, comprising: A thermally conductive layer containing a carbon-based material (A); and An adhesive layer comprising a resin component and a thermally conductive filler, wherein the adhesive layer is located on at least a portion of the main surface of the thermally conductive layer. in, The average particle size of the thermally conductive filler in the adhesive layer is less than 8.0 μm.

3. The thermally conductive sheet according to claim 1, wherein, The resin component includes at least one selected from curable resin components, pressure-sensitive adhesive resin components, and thermoplastic resin components.

4. The thermally conductive sheet according to claim 3, wherein, The resin component is a curable resin component, and the adhesive layer is in a semi-cured state.

5. The thermally conductive sheet according to claim 3, wherein, The resin composition includes thermoplastic resin components.

6. The thermally conductive sheet according to claim 5, wherein, The thermoplastic resin component includes thermoplastic epoxy resin.

7. The thermally conductive sheet according to claim 1, wherein, The thermally conductive filler is a particle selected from at least one of silver, copper, aluminum, aluminum oxide, aluminum hydroxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, silicon carbide, silicon dioxide, aluminum fluoride, calcium fluoride, and zinc oxide.

8. The thermally conductive sheet according to claim 7, wherein, The thermally conductive filler is silver particles.

9. The thermally conductive sheet according to claim 1, wherein, The thermally conductive filler content is 70% to 99% by mass relative to the total amount of the adhesive layer.

10. The thermally conductive sheet according to claim 1, wherein, The average thickness of the adhesive layer is 2μm to 50μm.

11. The thermally conductive sheet according to claim 1, wherein, The ratio of the average particle size of the thermally conductive filler to the average thickness of the adhesive layer, i.e., average particle size / average thickness, is 0.01 to 0.

8.

12. A heat dissipation device, comprising: Heating element; Heat sink; and The thermally conductive sheet according to any one of claims 1 to 11 is disposed between the heating element and the heat sink. The adhesive layer is located on at least a portion of at least one of the main surfaces of the thermally conductive layer located on the heating element side and the main surface located on the heat sink side.

13. A method for manufacturing a thermally conductive sheet, comprising the method for manufacturing a thermally conductive sheet according to any one of claims 1 to 11, wherein the method comprises: A process for preparing a composition containing the carbon-based material (A); The process of forming the thermally conductive layer using the composition; and The process of forming an adhesive layer on at least a portion of the main surface of the thermally conductive layer.

Images