Thermally-conductive sheet and thermally-conductive sheet production method

Abstract

This thermally-conductive sheet has a metal part having a metal layer and metal projection parts on at least a first surface of the metal layer, and has an adhesive part on the first surface. The area proportion of the metal projection parts exposed to the first surface of the thermally conductive sheet to the first surface is 20-80%. The ratio (Tm / TM) of the average thickness (Tm) of the metal projection parts to the average thickness (TM) of the metal layer is 0.125-8.

Description

Thermally conductive sheet and method for manufacturing the thermally conductive sheet

[0001] The present invention relates to a thermally conductive sheet and a method for manufacturing the thermally conductive sheet.

[0002] With the miniaturization of electronic devices such as power modules, image sensors, and high-performance computing (HPC), and the increase in information processing volume, the problem of heat generation has become more pronounced, and heat diffusion from the heat source has become increasingly important. In the case of LSIs and other electronic devices, if the LSI itself is exposed to high temperatures for a long period of time due to heat generated by the elements used, this may lead to malfunction or failure. For this reason, thermally conductive materials are widely used to prevent the temperature rise of LSIs and other devices. The thermally conductive materials can prevent the temperature rise of the device by diffusing the heat generated by the elements or by conducting it to a heat dissipation member for release outside the system, such as to the atmosphere.

[0003] Previously, a thermally conductive sheet has been reported in which graphite layers containing anisotropic graphite particles are laminated and the graphite layers are bonded together with resin layers (see, for example, Patent Document 1). Also, a thermally conductive insulating sheet has been reported that contains a thermally conductive insulating filler and an uncured and / or semi-cured thermosetting binder resin and has a thickness of 25 μm or more (see, for example, Patent Document 2).

[0004] JP 2009-055021 A JP 2019-029269 A

[0005] However, the conventional thermal conductive sheet described in Patent Document 1 has a graphite layer that is anisotropic and further includes a resin layer, which limits the heat path, resulting in problems such as insufficient thermal conductivity and poor adhesion between the graphite and metal. Furthermore, the conventional thermal conductive insulating sheet described in Patent Document 2 has insulating properties, but has problems such as insufficient thermal conductivity.

[0006] The present invention aims to solve the above-mentioned conventional problems and achieve the following object: That is, the present invention aims to provide a thermally conductive sheet that can achieve both high thermal conductivity and reliability.

[0007] The means for solving the above problems are as follows: <1> A thermally conductive sheet having a metal layer, a metal portion having metal convex portions on at least a first surface of the metal layer, and an adhesive portion on the first surface, wherein the area ratio of the metal convex portions exposed on the first surface of the thermally conductive sheet to the first surface is 20% or more and 80% or less, and the average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ ) is 0.125 or more and 8 or less. <2> The thermal conductive sheet according to <1>, further comprising metal convex portions and adhesive portions on a second surface of the metal layer opposite to the first surface, and the area ratio of the metal convex portions exposed on the second surface of the thermal conductive sheet to the second surface is 20% or more and 80% or less. <3> The thermal conductive sheet according to <1> or <2>, wherein the area ratio of the metal portions exposed on the first surface of the thermal conductive sheet to the first surface is 30% or more and 70% or less. <4> The average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ) is 0.2 or more and 4 or less. <5> The thermal conductive sheet according to any one of <1> to <4>, wherein the thermal conductivity of the metal layer is 50 W / (m·K) or more. <6> The thermal conductive sheet according to any one of <1> to <5>, wherein the metal layer contains at least one of gold, silver, copper, aluminum, and nickel. <7> The thermal conductive sheet according to any one of <1> to <6>, wherein the metal convex portions are metal formed by electrolytic plating. <8> The thermal conductive sheet according to any one of <1> to <7>, wherein the adhesive portion contains at least one of a modified acrylate compound, an epoxy resin, an unsaturated polyester resin, a polyurethane resin, a bismaleimide resin, an alkyd resin, a phenolic resin, and a melamine resin. <9> A method for producing a thermal conductive sheet, comprising: providing a protective portion on at least a first surface of a metal layer; and forming metal convex portions on exposed surfaces of the metal layer not provided with the protective portion. <10> The method for producing a thermal conductive sheet according to claim 9, further comprising the steps of: removing the protective portion; and filling an adhesive portion onto the exposed surface of the metal layer from which the protective portion has been removed. <11> The method for producing a thermal conductive sheet according to <9> or <10>, wherein the step of providing the protective portion is a step of providing a protective portion onto the first surface of the metal layer and a second surface opposite to the first surface.

[0008] According to the present invention, it is possible to solve the above-mentioned problems in the prior art, achieve the above-mentioned object, and provide a thermally conductive sheet that can achieve both high thermal conductivity and reliability.

[0009] FIG. 1 is a schematic cross-sectional view showing an example of a thermally conductive sheet of the present embodiment. FIG. 2A is an A-A' cross-sectional view of the thermally conductive sheet of FIG. 1. FIG. 2B is an A-A' cross-sectional view of another example of a thermally conductive sheet of the present embodiment. FIG. 3A is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 3B is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 3C is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 3D is a schematic cross-sectional view showing an example of a thermally conductive sheet of a comparative embodiment. FIG. 3E is a schematic cross-sectional view showing an example of a thermally conductive sheet of a comparative embodiment. FIG. 4A is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 4B is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 4C is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 4D is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 4E is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 5A is a schematic cross-sectional view showing another example of a thermally conductive sheet of the present embodiment. FIG. 5B is a schematic cross-sectional view showing another example of the thermal conduction sheet of this embodiment. FIG. 5C is a schematic cross-sectional view showing another example of the thermal conduction sheet of this embodiment. FIG. 5D is a schematic cross-sectional view showing another example of the thermal conduction sheet of this embodiment. FIG. 5E is a schematic cross-sectional view showing another example of the thermal conduction sheet of this embodiment. FIG. 5F is a schematic cross-sectional view showing another example of the thermal conduction sheet of this embodiment. FIG. 6A is a schematic cross-sectional view showing an example of a process for manufacturing the thermal conduction sheet of this embodiment (Part 1). FIG. 6B is a schematic cross-sectional view showing an example of a process for manufacturing the thermal conduction sheet of this embodiment (Part 2). FIG. 6C is a schematic cross-sectional view showing an example of a process for manufacturing the thermal conduction sheet of this embodiment (Part 3). FIG. 6D is a schematic cross-sectional view showing an example of a process for manufacturing the thermal conduction sheet of this embodiment (Part 4). FIG. 6E is a schematic cross-sectional view showing an example of a process for manufacturing the thermal conduction sheet of this embodiment (Part 5). FIG. 6F is a schematic cross-sectional view showing an example of a process for manufacturing the thermal conduction sheet of this embodiment (Part 6). FIG. 7A is a schematic cross-sectional view showing another example of a process for manufacturing the thermal conduction sheet of this embodiment (Part 1).Fig. 7B is a schematic cross-sectional view showing another example of the process of the method for manufacturing a thermal conductive sheet of this embodiment (part 2). Fig. 7C is a schematic cross-sectional view showing another example of the process of the method for manufacturing a thermal conductive sheet of this embodiment (part 3). Fig. 8 is a schematic cross-sectional view showing an example of the heat dissipation structure of this embodiment.

[0010] (Thermal Conduction Sheet) The thermal conduction sheet of the present invention is a thermal conduction sheet having a metal layer, a metal portion having metal protrusions on at least a first surface of the metal layer, and an adhesive portion on the first surface. The area ratio of the metal protrusions exposed on the first surface of the thermal conduction sheet to the first surface is 20% or more and 80% or less, and the average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ ) is 0.125 or more and 8 or less. The thermally conductive sheet preferably further has metal convex portions and adhesive portions on a second surface of the metal layer opposite to the first surface. Here, the area ratio of the metal convex portions exposed on the second surface of the thermally conductive sheet to the second surface is 20% or more and 80% or less.

[0011] In the thermal conductive sheet of the present embodiment, the metal portion is continuous in the thickness direction and the planar direction of the thermal conductive sheet, and the average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ ) is 8 or less, the thermal conductive sheet has thermal conductivity not only in the thickness direction but also in the planar direction, and has excellent thermal conductivity. In addition, the thermal conductive sheet has an adhesive portion on at least the first surface, the area ratio of the metal convex portions exposed on the first surface of the thermal conductive sheet to the first surface is 20% or more and 80% or less, and the average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ) is 0.125 or more, in a laminate in which a thermally conductive sheet is provided between substrates such as a heat generating element and a heat dissipating member, lifting, peeling, and void generation from the substrate can be reduced, and the laminate has excellent adhesion to the substrate and excellent reliability. Therefore, by providing a thermally conductive sheet between the heat generating element and the heat dissipating member, heat generated from the heat generating element can be efficiently dissipated through the thermally conductive sheet, and a thermally conductive sheet that can achieve both high thermal conductivity and reliability can be provided.

[0012] 1 and 2A are schematic cross-sectional views showing an example of a thermally conductive sheet according to this embodiment, and a schematic cross-sectional view taken along the A-A' cross section. FIG. 1 is a schematic cross-sectional view taken along the B-B' cross section of FIG. 2A. The thermally conductive sheet 10 shown in FIGS. 1 and 2A has a metal portion 11 and an adhesive portion 12, with metal protrusions 11b and adhesive portions 12 on both sides of the thermally conductive sheet 10. The metal portion 11 has a metal layer 11a and a plurality of metal protrusions 11b on a first surface of the metal layer 11a and a second surface opposite the first surface. The thermally conductive sheet 10 has adhesive portions 12 on the first and second surfaces of the metal layer 11, filling the areas other than those where the metal protrusions 11b are provided. As shown in the cross-sectional view of FIG. 1, a pattern of the metal protrusions 11b and adhesive portions 12 is formed. The thermally conductive sheet 10 has a pattern of metal protrusions 11b and adhesive portions 12 on the first and second surfaces (exposed surfaces) in the same pattern as the cross-sectional view of FIG. 1. The area ratio of the metal protrusions 11b exposed on the first surface of the thermally conductive sheet 10 to the first surface is 20% or more and 80% or less, and the area ratio of the metal protrusions 11b exposed on the second surface of the thermally conductive sheet 10 to the second surface is 20% or more and 80% or less. On each of the first and second surfaces of the thermally conductive sheet 10, the average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ ) is 0.125 or more and 8 or less.

[0013] As shown in FIG. 2B , which is an A-A′ cross-sectional view of another example of the thermally conductive sheet of this embodiment, the thermally conductive sheet 10 may have metal convex portions 11 b and adhesive portions 12 on the first surface (only one surface). The thermally conductive sheet 10 shown in FIG. 2B has a metal portion 11 and an adhesive portion 12. The metal portion 11 has a metal layer 11 a and a plurality of metal convex portions 11 b on the first surface of the metal layer 11 a. The thermally conductive sheet 10 has adhesive portions 12 filling the first surface of the metal layer 11 a except for the portions where the metal convex portions 11 b are provided. The patterns of the metal convex portions 11 b and adhesive portions 12 on the planar cross-section and exposed surface of the thermally conductive sheet 10 in FIG. 2B are the same as those in the cross-sectional view of FIG. 1. The area ratio of the metal convex portions 11 b exposed on the first surface of the thermally conductive sheet 10 to the first surface is 20% or more and 80% or less. In addition, the average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ ) is 0.125 or more and 8 or less.

[0014] <Metal Portion> The metal portion has a metal layer and metal protrusions on at least a first surface of the metal layer. The metal portion preferably has metal protrusions on each of the first and second surfaces of the metal layer. As described in the manufacturing method of the thermal conductive sheet below, the metal portion may be a metal layer to which metal protrusions have been imparted by plating or the like, or may be a metal portion obtained by cutting out metal protrusions from a metal plate by processing such as edging.

[0015] <<Metal Layer>> The material of the metal layer preferably contains a metal with high thermal conductivity, and more preferably consists of the metal. From the viewpoints of thermal conductivity and safety, the metal is preferably aluminum, nickel, iron, gold, silver, copper, zinc, or tin, and more preferably gold, silver, copper, aluminum, or nickel.

[0016] The thermal conductivity of the metal layer is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of thermal conductivity, it is preferably 50 W / (m K) or more, more preferably 100 W / (m K) or more. The thermal conductivity of the metal is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of thermal conductivity, it is preferably 50 W / (m K) or more, more preferably 100 W / (m K) or more, even more preferably 200 W / (m K) or more.

[0017] <<Metal Convex Portion>> The metal convex portion is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include metal formed by plating such as electrolytic plating or electroless plating; a metal material filled with a filler as needed; and a metal layer cut out from a metal plate, made of the same material. Among these, metal formed by electrolytic plating is preferred. The metal formed by electrolytic plating is not particularly limited and can be appropriately selected from the above metals depending on the purpose.

[0018] The metal convex portions may be filled with a metal material or a mixture of a metal material and an optional filler. The type of metal material is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoints of thermal conductivity and safety, aluminum, aluminum oxide, aluminum nitride, boron nitride, carbon resin, nickel, iron, gold, silver, copper, zinc, and tin are preferred, and gold, silver, copper, and nickel are more preferred. These may be used alone or in combination of two or more.

[0019] The shape of the metal material is not particularly limited and can be appropriately selected depending on the purpose. Examples include particles, plates, rods, wires, and the like.

[0020] From the viewpoint of thermal conductivity, the content of the metal material relative to the metal convex portion is preferably 50% by mass or more, more preferably any one of 60% by mass or more, 70% by mass or more, and 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 99% by mass or more.

[0021] The filler is not particularly limited and can be appropriately selected depending on the purpose. Examples of the filler include dispersants, surfactants, and binder resins.

[0022] <<Adhesive Portion>> The adhesive portion is not particularly limited as long as it has adhesive properties and can be appropriately selected depending on the purpose, but is preferably a resin having adhesive properties. The resin is preferably a polymerized composition containing a curing component and a curing agent, and further containing other components such as a metal filler as necessary.

[0023] The resin is not particularly limited and can be appropriately selected depending on the purpose, but modified acrylate compounds, epoxy resins, unsaturated polyester resins, polyurethane resins, bismaleimide resins, alkyd resins, phenolic resins, and melamine resins are preferred. These may be used alone or in combination of two or more.

[0024] -Curing Component- It is preferable to use at least one of an oxirane ring compound and an oxetane compound as the curing component. The oxirane ring compound is a compound having an oxirane ring, and examples thereof include epoxy resins. The epoxy resin is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include glycidyl ether type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A type epoxy resins, trisphenol type epoxy resins, tetraphenol type epoxy resins, phenol-xylylene type epoxy resins, naphthol-xylylene type epoxy resins, phenol-naphthol type epoxy resins, phenol-dicyclopentadiene type epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. These may be used alone or in combination of two or more.

[0025] -Curing Agent- The curing agent is a curing agent corresponding to the curing component, and examples thereof include polyaddition-type curing agents such as polyfunctional carboxylic acids, acid anhydride-based curing agents, aliphatic amine-based curing agents, aromatic amine-based curing agents (e.g., imidazole-based curing agents), phenol-based curing agents, and mercaptan-based curing agents, and catalyst-type curing agents such as imidazole. These may be used alone or in combination of two or more. Among these, aromatic amine-based curing agents are preferred, and imidazole-based curing agents are more preferred.

[0026] -Metal Filler- The adhesive portion may further contain a metal filler. The metal filler is preferably at least one of copper particles, silver-coated particles, and silver particles, and more preferably silver particles. Examples of the silver-coated particles include silver-coated copper particles, silver-coated nickel particles, and silver-coated aluminum particles. The shape of the metal filler is not particularly limited and can be appropriately selected depending on the purpose, and examples include spherical, flat, granular, and acicular shapes.

[0027] When the adhesive joint contains the metal filler, the content of the metal filler in the adhesive joint is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoint of increasing the thermal conductivity without impairing the adhesiveness of the adhesive joint, the content of the metal filler is preferably more than 0 vol% and not more than 90 vol%, more preferably 40 vol% or more and 80 vol% or less, and even more preferably 50 vol% or more and 70 vol% or less.

[0028] The volume average particle size of the metal filler is preferably 0.3 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 10 μm or less. The volume average particle size can be measured, for example, by a laser diffraction / scattering particle size distribution measuring device (Microtrac MT3300EXII).

[0029] [Area Ratio] The area ratio of the metal convex portions exposed on the first surface (exposed surface) of the thermal conductive sheet to the first surface is 20% or more and 80% or less, preferably 30% or more and 70% or less, in order to reduce lifting, peeling, and void generation from the substrate, and to achieve excellent adhesion to the substrate and excellent reliability.

[0030] [Pattern] The pattern of the metal convex portions 11b and adhesive portions 12 is not particularly limited as long as it satisfies the above-mentioned area ratio and can be appropriately selected depending on the purpose. For example, a pattern in which multiple shapes are arranged is exemplified. Among these, a pattern in which multiple shapes are regularly arranged is preferred from the viewpoint of uniform thermal conductivity. Furthermore, a pattern in which the adhesive portions are connected in the planar direction is more preferred from the viewpoint of improving adhesion. From the viewpoint of improving thermal conductivity, a pattern in which the metal convex portions are connected in the planar direction is more preferred. Alternatively, a pattern in which both the metal convex portions and adhesive portions are connected in the planar direction, such as an interdigital electrode, may be used. In either case, the pattern can be appropriately selected depending on the desired aspect. Examples of the pattern include the 45° staggered pattern ( FIGS. 3A-C , 5F ), 60° staggered pattern ( FIGS. 4A and 5A ), square parallel patterns ( FIGS. 4B and 5B ), regular hexagonal 60° staggered pattern ( FIGS. 4C and 5C ), equilateral triangle arrangement ( FIGS. 4D and 5D ), and alternating rectangles ( FIGS. 4E and 5E ).

[0031] The patterns and area ratios of the metal protrusions 11b and adhesive portions 12 are described with reference to Figures 3A to 3E. Figures 3A to 3C are schematic cross-sectional views showing another example of the thermally conductive sheet of this embodiment. Figures 3D to 3E are schematic cross-sectional views showing an example of a thermally conductive sheet of a comparative embodiment. These cross-sectional views are taken along the planar direction of the thermally conductive sheet, but the pattern on the exposed surface of the thermally conductive sheet is similar. The patterns shown in Figures 3A to 3E are patterns in which multiple circular metal protrusions 11b are arranged at 45° angles to each other (a so-called 45° staggered pattern, also referred to as "45° staggered"). The area ratio can be adjusted by appropriately adjusting the distance between the multiple circles (e.g., the distance between the centers of adjacent circles). The patterns shown in Figures 3A to 3E have metal protrusion:adhesive area ratios of 80:20, 50:50, 20:80, 90:10, and 10:90, respectively, and the area ratios of the metal protrusions are 80%, 50%, 20%, 90%, and 10%. 3A to 3C in which the area ratio is in the range of 20% to 80% correspond to Examples 1 to 3 (and Examples 4 to 6), respectively, of the Examples described later. Also, the comparative embodiments in FIGS. 3D to 3E in which the area ratio is outside the range of 20% to 80% correspond to Comparative Examples 1 and 2, respectively, of the Examples described later.

[0032] Variations in the patterns of the metal protrusions 11b and adhesive portions 12 are described with reference to Figures 4A to 4E. Figures 4A to 4E are schematic cross-sectional views showing another example of the thermally conductive sheet of this embodiment. The pattern shown in Figure 4A is a pattern in which multiple circular metal protrusions 11b are arranged at 60° angles to each other (referred to as "60° staggered"). The pattern shown in Figure 4B is a pattern in which multiple square metal protrusions 11b are arranged in parallel (90° angles) to each other (referred to as "square parallel"). The pattern shown in Figure 4C is a pattern in which multiple regular hexagonal metal protrusions 11b are arranged at 60° angles to each other (referred to as "regular hexagonal 60° staggered"). The pattern shown in Figure 4D is a pattern in which multiple equilateral triangular metal protrusions 11b are arranged at 60° angles to each other (referred to as "equilateral triangle arrangement"). 4E is a pattern in which a plurality of rectangular metal protrusions 11b are arranged alternately, i.e., the metal protrusions are arranged in the long-side direction of the rectangles, with a shift of half the length of the long sides (referred to as "alternate rectangles"). The area ratio of the metal protrusions can be adjusted in the same manner as in the 45° staggered pattern (FIGS. 3A to 3C). Specifically, the area ratio can be adjusted by appropriately adjusting the distance between the plurality of shapes (for example, the distance between the centers of adjacent shapes).

[0033] While the above describes a pattern in which the metal convex portions 11b are arranged as multiple figures, a pattern in which the arrangement of the metal convex portions 11b and the adhesive portions 12 is interchanged and the adhesive portions 12 are arranged as multiple figures can also be suitably employed. Figures 5A to 5F are schematic cross-sectional views showing another example of the thermal conductive sheet of this embodiment, and are the same as Figures 4A to 4E and 3B, respectively, except that the arrangement of the metal convex portions 11b and the adhesive portions 12 is interchanged in Figures 4A to 4E and 3B.

[0034] The size of the figure of the metal convex portion 11b in the pattern is not particularly limited and can be selected appropriately depending on the purpose, but the length of the long side of the figure is preferably 10 μm or more and 1,000 μm or less, and more preferably 50 μm or more and 500 μm or less.

[0035] The thermal conductivity of the thermally conductive sheet is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoint of thermal conductivity, however, it is preferably 20 W / (m·K) or more, more preferably 30 W / (m·K) or more, and even more preferably 50 W / (m·K) or more.

[0036] The average thickness of the heat conductive sheet is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.2 μm to 100 μm, more preferably 1 μm to 50 μm, and even more preferably 5 μm to 30 μm.

[0037] The average thickness of the metal layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.1 μm to 50 μm, more preferably 0.5 μm to 25 μm, and even more preferably 2.5 μm to 20 μm.

[0038] The average thickness (T Ｍ ) the average thickness (T ｍ ) ratio (T ｍ / T Ｍ ) is not particularly limited and can be appropriately selected depending on the purpose, but is 0.125 or more and 8 or less, and from the viewpoint of further improving thermal conductivity and reliability, it is preferably 0.2 or more and 4 or less, and more preferably 0.5 or more and 2 or less.

[0039] In the case where the heat conductive sheet has metal convex portions on both the first surface and the second surface, the ratio (T ｍ / T Ｍ ) can be set, and the ratio of the first surface (T ｍ / T Ｍ ) and the ratio of the second surface (T ｍ / T Ｍ ) may be different from or the same as.

[0040] By manufacturing a thermal conductive sheet by the thermal conductive sheet manufacturing method described later, the desired area ratio and the ratio (T ｍ / T Ｍ In addition, the adhesive portion can be filled into the gaps of the metal protrusions without leaving any gaps.

[0041] On the other hand, if voids (also called bubbles) remain in the thermally conductive sheet, the thermally conductive sheet may be heated by heat conduction from the heating element, causing the voids (bubbles) to expand and burst, crack, or otherwise impair the reliability of the thermally conductive sheet. Furthermore, because voids (bubbles) have high insulating properties, the thermal conductivity of the resulting thermally conductive sheet may be reduced. Furthermore, in a laminate in which a thermally conductive sheet is provided between substrates such as a heating element or a heat dissipation member, if the sheet lifts or peels off from the substrate or voids occur, adhesion to the substrate may be reduced, potentially impairing the reliability of the thermally conductive sheet.

[0042] Methods for confirming the reliability of the thermally conductive sheet include: evaluating the presence or absence of voids in the thermally conductive sheet using an ultrasonic imaging system (SAT) for the laminate after compression; evaluating the adhesion to the substrate and the presence or absence of voids using an ultrasonic imaging system (SAT) for the laminate after compression after an accelerated life test (e.g., 130°C, 85% humidity, 192 hours); indirectly estimating the adhesion to the substrate and the presence or absence of voids by comparing the ratio (%) of the thermal conductivity of the manufactured thermally conductive sheet to the thermal conductivity of the metal layer used; and combinations of these methods.

[0043] Because the adhesive portion of the thermally conductive sheet is exposed on its surface, it has excellent adhesion and can suppress the occurrence of voids when attached to other components, such as a heat generating element or a heat dissipation component. Therefore, it also has excellent reliability after heat treatment (accelerated life test). The thermally conductive sheet has metal portions that communicate in the thickness direction and in the planar direction of the thermally conductive sheet, which can relieve stress. Furthermore, this eliminates the problem of the film itself becoming brittle and collapsing during high-temperature tests, which is common with thermally conductive sheets in which thermally conductive materials are bound with a binder resin, and effectively prevents the thermally conductive sheet from collapsing.

[0044] (Method for manufacturing thermally conductive sheet) The method for manufacturing the thermally conductive sheet of the present invention is not particularly limited and can be appropriately selected depending on the purpose. Examples include a method of forming metal convex portions and adhesive portions on a metal layer (first embodiment); a method of cutting out a metal portion in which the metal layer and metal convex portions are integrated by edging a metal plate (second embodiment); and a method of bonding a layer having pre-formed metal convex portions and adhesive portions to a metal layer (third embodiment).

[0045] [First embodiment] A method for manufacturing a thermally conductive sheet according to a first embodiment includes a protective portion providing step and a metal convex portion forming step, and preferably includes a protective portion removing step and an adhesive portion filling step, and further includes other steps such as a polishing step as necessary. The thermally conductive sheet manufacturing method according to the first embodiment can suitably manufacture the thermally conductive sheet of the present invention described above.

[0046] 6A-6F are schematic cross-sectional views illustrating an example of a process for manufacturing a thermally conductive sheet according to the first embodiment. This embodiment involves forming metal convex portions on both the first and second surfaces of a metal layer. First, a metal layer 11a is prepared (FIG. 6A). A protective portion 13 is formed on the first surface of the metal layer 11a (FIG. 6B, protective portion application step). Optionally, a protective portion 13 is also formed on the second surface of the metal layer 11a (FIG. 6C). Next, metal convex portions 11b are formed on the exposed surface of the metal layer 11a to which the protective portion 13 is not applied (FIG. 6D, metal convex portion formation step). When the protective portion 13 is an adhesive portion 12, the thermally conductive sheet 10 can be manufactured in this manner.

[0047] If the protective portion 13 is not the adhesive portion 12, the protective portion 13 is removed ( FIG. 6E , protective portion removal step), yielding a metal portion 11 having a metal layer 11a and metal protrusions 11b on the first and second surfaces of the metal layer 11a. Next, adhesive portions 12 are filled onto the exposed surface of the metal layer 11a from which the protective portion 13 has been removed ( FIG. 6F , adhesive portion filling step). This allows the production of a thermally conductive sheet 10 having a metal portion 11 having a metal layer 11a and metal protrusions 11b on the first and second surfaces of the metal layer 11a, and adhesive portions 12 on the first and second surfaces of the metal layer 11a. Each step is described in detail below.

[0048] <Protective part providing step> The protective part providing step is a step of providing a protective part on at least the first surface of the metal layer, and can be suitably performed by a protective part providing means. When producing a thermal conductive sheet having metal convex parts and adhesive parts on both surfaces thereof, the protective part providing step is a step of providing a protective part on the first surface and the second surface of the metal layer.

[0049] The pattern of the protective portion provided in the protective portion providing step can be the same as the pattern of the adhesive portion in the intended thermal conductive sheet. The protective portion may be the adhesive portion or a member different from the adhesive portion, and can be suitably selected depending on the intended embodiment.

[0050] The method for providing a protective portion is not particularly limited and can be appropriately selected depending on the purpose. Examples include a method for providing a protective portion having a desired pattern by imprinting; a method for providing a protective portion having a desired pattern by inkjet printing, screen printing, or the like; and a method for forming a protective portion having a desired pattern using a resist. Examples of the method for forming a protective portion having a desired pattern using a resist include a method for providing a resist on at least the first surface of a metal layer, exposing and developing the resist to a desired pattern, and, if necessary, performing heating after exposure or development to form a protective portion. The resist may be a negative type in which exposed portions remain after development, or a positive type in which unexposed portions remain after development.

[0051] <Metal Convex Portion Forming Process> The metal convex portion forming process is a process of forming metal convex portions on the exposed surface of the metal layer to which the protective portion is not applied, and can be suitably carried out by a metal convex portion forming means. The method for forming the metal convex portions is not particularly limited and can be appropriately selected depending on the purpose. Examples include a method for forming metal convex portions by plating, such as electrolytic plating or electroless plating; a method for forming metal convex portions by filling a composition containing a metal material; and a method for forming metal convex portions by sputtering or vapor deposition. These methods may be performed in a single process, multiple processes, or a combination of multiple processes. The metal, metal material, filler, and other factors for the metal convex portions can be appropriately selected from those described above for the metal convex portions of the thermal conductive sheet of the present invention.

[0052] The plating may be either electrolytic plating or electroless plating (chemical plating), but electrolytic plating is preferred from the viewpoint of throughput. The metal to be filled by plating is not particularly limited and can be appropriately selected depending on the purpose, but preferably contains at least one of nickel, gold, silver, and copper, and more preferably at least one of nickel, gold, silver, and copper.

[0053] The composition containing the metal material contains the metal material and, if necessary, further contains a filler and a solvent. The content of the metal material in the composition is preferably 50% by mass or more, more preferably 60% by mass or more, 70% by mass or more, or 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the solid content of the composition.

[0054] The solvent is not particularly limited and can be appropriately selected depending on the purpose. Examples of the solvent include terpineol, butyl carbitol, butyl carbitol acetate, and texanol.

[0055] The composition can be prepared by mixing and dispersing the metal material and, if necessary, a filler and a solvent. Commercially available products may be used as the composition, and examples of the composition include H 9890-6A (a thermosetting conductive adhesive, silver paste, manufactured by Namics Corporation) as a metal paste containing metal particles.

[0056] The method for filling the voids in the metal convex portions of the metal part with the composition is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a dipping method, an inkjet method, a dispensing method, a spray coating method, a slit coating method, and a spin coating method.

[0057] When the protective portion is an adhesive portion, the thermal conductive sheet can be suitably manufactured by the protective portion providing step and the metal convex portion forming step. Furthermore, if necessary, other steps such as a polishing step may be further included. When the protective portion is not an adhesive portion, it is preferable to further include a protective portion removing step and an adhesive portion filling step in addition to the protective portion providing step and the metal convex portion forming step. Furthermore, if necessary, other steps such as a polishing step may be further included.

[0058] The protective part removing step is a step of removing the protective part, and can be suitably performed by a protective part removing means. The method for removing the protective part is not particularly limited and can be appropriately selected depending on the purpose. For example, a method of removing the adhesive part by treatment with high temperature, strong alkali, organic solvent, etc. can be mentioned.

[0059] The adhesive filling step is a step of filling the adhesive onto the exposed surface of the metal layer from which the protective portion has been removed, and can be suitably carried out by an adhesive filling means. The method for filling the adhesive is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a dipping method, an inkjet method, a dispensing method, a spray coating method, a slit coating method, and a spin coating method.

[0060] <Polishing step> The polishing step may be a step of polishing the surface of the metal layer on which the metal convex portions are formed following the metal convex portion forming step or the protective portion removing step, or may be a step of polishing the surface of the metal layer on which the metal convex portions and the adhesive portions are formed following the metal convex portion forming step or the adhesive portion filling step. The method for polishing the surface of the metal layer is not particularly limited, and a known method can be appropriately selected depending on the purpose.

[0061] By the polishing step, the metal convex portions and adhesive portions are exposed on the surface of the obtained thermally conductive sheet, which provides excellent adhesion to other members, excellent reliability of the thermally conductive sheet, and excellent electrical conductivity.

[0062] [Second Embodiment] A method for manufacturing a thermal conductive sheet according to a second embodiment includes a metal portion forming step and an adhesive portion filling step, and further includes other steps such as the polishing step, as necessary. The metal portion forming step is a step of edging a metal plate to form a metal portion having a metal layer and metal protrusions on at least a first surface of the metal layer. The adhesive portion filling step is a step of filling an adhesive portion on an exposed surface of the metal layer.

[0063] 7A-7C are schematic cross-sectional views illustrating an example of a process for manufacturing a thermally conductive sheet according to the second embodiment. This embodiment involves forming metal protrusions on the first and second surfaces (both surfaces) of a metal layer. First, a metal plate 11' serving as a precursor for the metal portion 11 is prepared (FIG. 7A). Regions corresponding to the pattern of the adhesive portions 12 are removed from the metal plate 11' by etching, resulting in a metal portion 11 integrally comprising a metal layer 11a and metal protrusions 11b on the first and second surfaces of the metal layer 11a (FIG. 7B, metal portion forming step). Next, the adhesive portions 12 are filled onto the exposed surface of the metal layer 11a (FIG. 7C, adhesive portion filling step). This allows for the production of a thermally conductive sheet 10 having a metal portion 11 having a metal layer 11a and metal protrusions 11b on the first and second surfaces of the metal layer 11a, and adhesive portions 12 on the first and second surfaces of the metal layer 11a.

[0064] [Third embodiment] The manufacturing method of a thermal conductive sheet in the third embodiment preferably includes a step of forming a layer having metal convex portions and adhesive portions, and a step of bonding the obtained layer having metal convex portions and adhesive portions to a metal layer, and further includes other steps such as the polishing step as necessary.

[0065] (Heat Dissipation Structure) The heat dissipation structure of the present invention includes a heat generating element, the heat conduction sheet of the present invention described above, a heat dissipation member, and further includes other members as necessary. The heat dissipation structure includes the heat conduction sheet between the heat generating element and the heat dissipation member. The heat dissipation structure may further include an adhesive layer between each component as necessary.

[0066] The heating element is not particularly limited and can be appropriately selected depending on the purpose. Examples of the heating element include electronic components such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and a GPU (Graphics Processing Unit).

[0067] The heat dissipation member is not particularly limited as long as it is a structure that dissipates heat generated by an electronic component (heat-generating element) and can be appropriately selected depending on the purpose. Examples include a heat spreader, a heat sink, a vapor chamber, and a heat pipe. The heat spreader is a component for efficiently transferring heat from the electronic component to other components. The material of the heat spreader is not particularly limited and can be appropriately selected depending on the purpose, such as copper or aluminum. The heat spreader is typically flat. The heat sink is a component for dissipating heat from the electronic component into the air. The material of the heat sink is not particularly limited and can be appropriately selected depending on the purpose, such as copper or aluminum. The heat sink, for example, has multiple fins. The heat sink, for example, has a base and multiple fins extending in a non-parallel direction (e.g., a direction perpendicular to) one surface of the base. The heat spreader and the heat sink generally have solid structures without internal spaces. The vapor chamber is a hollow structure. A volatile liquid is sealed in the internal space of the hollow structure. Examples of the vapor chamber include a hollow structure of the heat spreader, and a plate-like hollow structure similar to the heat sink. The heat pipe is a cylindrical, approximately cylindrical, or flattened cylindrical hollow structure. A volatile liquid is sealed in the internal space of the hollow structure.

[0068] 8 is a schematic cross-sectional view showing an example of a semiconductor device as a heat dissipation structure. The thermally conductive sheet 7 of the present invention dissipates heat generated by an electronic component 3 such as a semiconductor element, and is fixed to the main surface 2a of the heat spreader 2 facing the electronic component 3, as shown in FIG. 5, and is sandwiched between the electronic component 3 and the heat spreader 2. The thermally conductive sheet 1 is sandwiched between the heat spreader 2 and a heat sink 5. The thermally conductive sheet 1 may be the thermally conductive sheet of the present invention or another thermally conductive sheet.

[0069] The heat spreader 2 is formed, for example, in the shape of a rectangular plate, and has a main surface 2a facing the electronic components 3 and side walls 2b extending along the outer periphery of the main surface 2a. The heat spreader 2 has a thermally conductive sheet 1 provided on the main surface 2a surrounded by the side walls 2b, and a heat sink 5 provided on the other surface 2c opposite the main surface 2a via the thermally conductive sheet 1. The higher the thermal conductivity of the heat spreader 2, the lower the thermal resistance and the more efficiently it absorbs heat from the electronic components 3, such as semiconductor elements. Therefore, the heat spreader 2 can be formed using, for example, copper or aluminum, which have good thermal conductivity.

[0070] The electronic component 3 is, for example, a semiconductor element such as a BGA, and is mounted on the wiring board 6. The tip surfaces of the side walls 2b of the heat spreader 2 are also mounted on the wiring board 6, so that the side walls 2b surround the electronic component 3 at a predetermined distance. The thermally conductive sheet 7 of the present invention is provided on the main surface 2a of the heat spreader 2, thereby forming a heat dissipation member that absorbs heat generated by the electronic component 3 and dissipates the heat from the heat sink 5.

[0071] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0072] Example 1 <Production of Thermally Conductive Sheet> According to the production method shown in FIGS. 6A to 6F, a thermally conductive sheet of Example 1 having the pattern of metal protrusions and adhesive portions shown in FIG. 3A was produced by the following procedure.

[0073] <<Preparation of Metal Part>> On both sides of a copper plate (size: 20 mm × 20 mm, average thickness: 18 μm, FIG. 6A ) serving as a metal layer, etching resist X-87 (manufactured by Taiyo Ink Mfg. Co., Ltd.) was screen-printed to an average thickness of 9 μm as a coating liquid for forming a protective part in the area corresponding to the adhesive part 12 shown in FIG. 3A , and the protective part was formed by heating at 100°C for 5 minutes ( FIGS. 6B-C ). Note that in the pattern (45° staggered) shown in FIG. 3A , the metal convex parts were circular with a diameter of 100 μm, and the area ratio of the metal convex parts, i.e., the area ratio of the metal convex parts exposed on each surface of the thermal conduction sheet to each surface of the thermal conduction sheet, was 80%.

[0074] The metal layer on which the protective portion was formed was plated using a nickel sulfamate bath under the following conditions: 50°C, pH 4.5, 10 mA / cm ２ The protective layer was then removed by immersion in 3% NaOH at 40°C for 15 seconds, resulting in the production of a metal part having metal projections on both sides of the metal layer (Fig. 6E).

[0075] <<Filling of Adhesive Portions and Production of Thermally Conductive Sheet>> A coating liquid for forming adhesive portions was applied between the plurality of metal protrusions on each surface of the metal layer of the obtained metal portion, containing 25 mass % of bisphenol F type epoxy resin (EPICRON 830 (registered trademark), manufactured by DIC Corporation), 5 mass % of 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MHZ-PW, manufactured by Shikoku Chemicals Corporation), and 5 mass % of phenoxy resin (Phenototo An epoxy resin composition containing 70% by mass of YP-50 (registered trademark, manufactured by Nippon Steel Chemical & Material Co., Ltd.) was filled using a comma knife bar coater (FJ-TADK104, manufactured by Fuji Seiki Co., Ltd.) to a thickness equivalent to that of the metal convex portions, and the mixture was sandwiched between a nickel-plated copper plate (25 mm x 25 mm, average thickness 1.00 mm) and a silicon plate (20 mm x 20 mm, average thickness 0.76 mm). The mixture was then heated and pressed for 2 minutes using a mini press under conditions of an upper plate temperature on the copper plate side of 170°C, a lower plate temperature on the silicon plate side of 170°C, and a set air pressure of 0.11 MPa (40 psi equivalent pressure), followed by natural cooling and then releasing, to produce the thermally conductive sheet of Example 1.

[0076] (Example 2) A thermal conductive sheet of Example 2 was obtained in the same manner as Example 1, except that in Example 1, the pattern shown in FIG. 3A was changed to the pattern shown in FIG. 3B and the area ratio of the metal convex portions was changed to 50%.

[0077] (Example 3) A thermal conductive sheet of Example 3 was obtained in the same manner as Example 1, except that in Example 1, the pattern shown in FIG. 3A was changed to the pattern shown in FIG. 3C and the area ratio of the metal convex portions was changed to 20%.

[0078] (Examples 4 to 6) In Examples 1 to 3, the thermal conductive sheets of Examples 4 to 6 were obtained in the same manner as in Examples 1 to 3, except that the diameter of the metal convex portions in the patterns (45° staggered) shown in Figures 3A to 3C was changed from 100 μm to 500 μm, respectively.

[0079] (Example 7) A thermal conductive sheet of Example 7 was obtained in the same manner as Example 1, except that the pattern shown in Figure 3A (45° staggered) in Example 1 was changed to the pattern shown in Figure 4A (60° staggered).

[0080] Example 8 A thermal conductive sheet of Example 8 was obtained in the same manner as Example 1, except that the pattern shown in FIG. 3A (45° staggered) was changed to the pattern shown in FIG. 4B (parallel squares).

[0081] (Example 9) A thermal conductive sheet of Example 9 was obtained in the same manner as Example 1, except that the pattern shown in Figure 3A (45° staggered) was changed to the pattern shown in Figure 4C (regular hexagonal 60° staggered).

[0082] Example 10 A thermally conductive sheet of Example 10 was obtained in the same manner as in Example 1, except that in Example 2, the diameter of the metal convex portions shown in FIG. 3B was changed from 100 μm to 1000 μm.

[0083] Example 11 In Example 2, the average thickness T of the metal layer Ｍ The average thickness of the metal projections is T ｍ 9 μm to 4.5 μm, and the average thickness of the metal layer T Ｍ Average thickness T of the metal projections ｍ The ratio (T ｍ / T Ｍ A thermal conductive sheet of Example 11 was obtained in the same manner as in Example 1, except that the ratio of the thickness of the heat-transfer layer to the thickness of the heat-transfer layer was changed from 1 to 1 / 8.

[0084] (Example 12) In Example 2, the average thickness T of the metal layer Ｍ 18 μm to 6 μm, and the average thickness T ｍ 9 μm to 48 μm, and the average thickness T Ｍ Average thickness T of the metal projections ｍ The ratio (T ｍ / TＭ A thermally conductive sheet of Example 12 was obtained in the same manner as in Example 1, except that the number of the particles was changed from 1 to 8.

[0085] (Comparative Example 1) A thermal conductive sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that in Example 1, the pattern shown in FIG. 3A was changed to the pattern shown in FIG. 3D and the area ratio of the metal convex portions was changed to 90%.

[0086] (Comparative Example 2) A thermal conductive sheet of Comparative Example 2 was obtained in the same manner as in Example 1, except that in Example 1, the pattern shown in FIG. 3A was changed to the pattern shown in FIG. 3E and the area ratio of the metal convex portions was changed to 10%.

[0087] (Comparative Examples 3 to 4) In Example 4, the pattern shown in FIG. 3A was changed to the pattern shown in FIG. 3D or the pattern shown in FIG. 3E, and the area ratio of the metal convex portions was changed to 90% or 10%, and the thermal conductive sheets of Comparative Examples 3 and 4 were obtained in the same manner as in Example 4.

[0088] Comparative Example 5 In Example 1, the average thickness T Ｍ The average thickness of the metal projections is T ｍ 9 μm to 4 μm, and the average thickness T Ｍ Average thickness T of the metal projections ｍ The ratio (T ｍ / T Ｍ The thermal conductive sheets of Comparative Examples 5 and 6 were obtained in the same manner as in Example 1, except that the ratio of the thickness of the sheet to the thickness of the substrate was changed from 1 to 1 / 9.

[0089] Comparative Example 6 In Example 1, the average thickness T Ｍ 18 μm to 6 μm, and the average thickness T ｍ 9 μm to 54 μm, and the average thickness T Ｍ Average thickness T of the metal projections ｍ The ratio (T ｍ / T Ｍ A thermal conductive sheet of Comparative Example 6 was obtained in the same manner as in Example 1, except that the number of the particles was changed from 1 to 9.

[0090] (Comparative Example 7) Instead of the thermally conductive sheet of Example 1, indium (Pure Indium Heat-Spring Kit (2.00 inches x 2.00 inches, thickness 0.004 inches), manufactured by Indium Corporation) was used. A nickel-plated copper plate (25 mm x 25 mm, average thickness 1.00 mm) and a silicon plate (20 mm x 20 mm, average thickness 0.76 mm) were used. Indium was provided between them, and a shim tape (manufactured by Misumi Group Holdings Co., Ltd.) having an average thickness of 50 μm was sandwiched around it. Then, the upper plate temperature on the copper plate side was 170 ° C. in a mini press, the lower plate temperature on the silicon plate side was 170 ° C., and the set air pressure was 0.11 MPa (40 psi in pressure equivalent). After heating and pressing for 2 minutes, the sheet was allowed to cool naturally, and the shim tape was removed to form an indium layer having an average thickness of 100 μm. This was used as the thermally conductive sheet of Comparative Example 7.

[0091] (Comparative Example 8) Instead of the thermally conductive sheet of Example 1, a commercially available conductive adhesive (thermally conductive RTV rubber (room temperature curing type) KE3467, manufactured by Shin-Etsu Chemical Co., Ltd.) was used. The conductive adhesive was placed between a nickel-plated copper plate (25 mm × 25 mm, average thickness 1.00 mm) and a silicon plate (20 mm × 20 mm, average thickness 0.76 mm), and a shim tape (manufactured by Misumi Group Holdings Co., Ltd.) with an average thickness of 50 μm was sandwiched around the periphery. After leaving it at room temperature for one day, the shim tape was removed to form a conductive adhesive layer with an average thickness of 50 μm, which was used as the thermally conductive sheet of Comparative Example 8.

[0092] <Evaluation> Next, the "thermal conductivity" and "reliability" were evaluated as follows for Examples 1 to 9 and Comparative Examples 1 to 8. The results are shown in Table 1.

[0093] <Thermal Conductivity> In accordance with JIS R 1611, the thermal resistance of each thermally conductive sheet was measured using a Netzsch flash thermal diffusivity / thermal conductivity measuring device (LFA467, manufactured by Netzsch-Gereithebau GmbH) with a pulse width of 20 μsec. The thermal resistance of the thermally conductive sheet was then calculated by subtracting the thermal resistance of the nickel-plated copper plate (25 mm x 25 mm, average thickness 1.00 mm) and silicon plate (20 mm x 20 mm, average thickness 0.76 mm) used as the substrates from the measured values. The thermal conductivity of the thermally conductive sheet (W / (m·K)) was then calculated by dividing the previously measured average thickness of the thermally conductive sheet by the thermal resistance. Thermal conductivity was evaluated according to the following criteria. The results are shown in Tables 1 to 3. [Evaluation Criteria] ⊚: Thermal conductivity is 20 W / m·K or greater. ◯: Thermal conductivity is 10 W / m·K or greater but less than 20 W / m·K. ×: The thermal conductivity is less than 10 W / m·K.

[0094] <Reliability> <<Preparation of laminate after compression bonding>> Each thermally conductive sheet was sandwiched between a nickel-plated copper plate (25 mm x 25 mm, average thickness 1.00 mm) and a silicon plate (20 mm x 20 mm, average thickness 0.76 mm), and heated and pressed for 5 minutes using a mini press under conditions of an upper plate temperature on the copper plate side of 150°C, a lower plate temperature on the silicon plate side of 150°C, and a set air pressure of 0.11 MPa (equivalent to 40 psi), followed by heating in an oven (Perfect Oven PHH-202, manufactured by Espec Corporation) at 150°C for 1 hour. <<Accelerated Life Test and Reliability Evaluation>> The laminated body after compression was placed in a highly accelerated life tester (EHS-212MD, manufactured by Espec Corporation) at 130°C and 85% humidity for 192 hours. After the accelerated life test, each thermally conductive sheet was observed using an ultrasonic imaging device (SAT, FS300IIIHR, manufactured by Hitachi Power Solutions Co., Ltd.) to inspect the adhesion to the substrate and the presence or absence of voids. A 50 MHz, 7 mm probe was used on the copper plate side, and a 25 MHz probe was used on the silicon plate side. The results are shown in Tables 1 to 3. [Evaluation Criteria] ⊚: No lifting, delamination, or voids of the thermally conductive sheet from the substrate. ◯: Lifting, delamination, or voids of the thermally conductive sheet from the substrate were less than 0.1% of the observed field of view, within the practical range. ×: Lifting, delamination, or voids of the thermally conductive sheet were more than 0.1% of the observed field of view, outside the practical range.

[0095]

[0096]

[0097]

[0098] This international application claims priority based on Japanese Patent Application No. 2023-205183, filed on December 5, 2023, the entire contents of which are incorporated herein by reference.

[0099] REFERENCE SIGNS LIST 1 Thermally conductive sheet 2 Heat spreader 2a Main surface 3 Heat generating element (electronic component) 3a Upper surface 5 Heat sink 6 Wiring board 7 Thermally conductive sheet 10 Thermally conductive sheet 11 Metal part 11a Metal layer 11' Metal plate before etching 11b Metal convex part 12 Adhesive part 13 Protective part

Claims

1. A thermally conductive sheet having a metal layer, a metal portion having metal protrusions on at least a first surface of the metal layer, and an adhesive portion on the first surface, wherein the area ratio of the metal protrusions exposed on the first surface of the thermally conductive sheet to the first surface is 20% or more and 80% or less, and the average thickness (T Ｍ ) to the average thickness (T ｍ ) ratio (T ｍ / T Ｍ ) is 0.125 or more and 8 or less.

2. A thermal conduction sheet as described in claim 1, further comprising a metal convex portion and an adhesive portion on a second surface of the metal layer opposite the first surface, and the area ratio of the metal convex portions exposed on the second surface of the thermal conduction sheet to the second surface is 20% or more and 80% or less.

3. A thermal conductive sheet according to claim 1 or 2, wherein the area ratio of the metal convex portions exposed on the first surface of the thermal conductive sheet to the first surface is 30% or more and 70% or less.

4. The average thickness of the metal layer (T Ｍ ) to the average thickness (T ｍ ) ratio (T ｍ / T Ｍ 4. The thermal conductive sheet according to claim 1 , wherein the coefficient of thermal expansion is 0.2 or more and 4 or less.

5. A thermally conductive sheet according to any one of claims 1 to 4, wherein the thermal conductivity of the metal layer is 50 W / (m·K) or more.

6. The thermal conductive sheet according to any one of claims 1 to 5, wherein the metal layer contains at least one of gold, silver, copper, aluminum, and nickel.

7. A thermally conductive sheet according to any one of claims 1 to 6, wherein the metal protrusions are formed by electrolytic plating.

8. A thermally conductive sheet according to any one of claims 1 to 7, wherein the adhesive portion contains at least one of a modified acrylate compound, an epoxy resin, an unsaturated polyester resin, a polyurethane resin, a bismaleimide resin, an alkyd resin, a phenolic resin, and a melamine resin.

9. A method for manufacturing a thermal conductive sheet, comprising the steps of: providing a protective portion on at least a first surface of a metal layer; and forming metal convex portions on exposed surfaces of the metal layer that do not have the protective portion.

10. A method for manufacturing a thermal conductive sheet according to claim 9, further comprising the steps of: removing the protective portion; and filling an adhesive portion onto the exposed surface of the metal layer from which the protective portion has been removed.

11. A method for manufacturing a thermal conductive sheet as described in claim 9 or 10, wherein the step of providing a protective portion is a step of providing a protective portion on the first surface of the metal layer and on a second surface opposite to the first surface.

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