Laminate and method for producing same

Abstract

This laminate includes: a base material; a first thermoconductive layer provided on the base material, the first thermoconductive layer containing an epoxy resin, an epoxy resin curing agent, and first thermoconductive particles; and a second thermoconductive layer provided on the first thermoconductive layer, the second thermoconductive layer containing a curable component, a curing agent for curing the curable component, second thermoconductive particles, and a low-melting-point metal. The first thermoconductive layer does not contain the low-melting-point metal.

Description

Laminate and manufacturing method thereof

[0001] The present invention relates to a laminate and a method for manufacturing the laminate.

[0002] In large-scale integration (LSI) and the like in various 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 of LSIs and the like from rising. The thermally conductive materials can prevent the temperature of the device from rising 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] Using metals or ceramics as such thermally conductive materials presents problems such as difficulty in reducing weight, poor processability, and low flexibility. Therefore, various thermally conductive materials have been proposed that use polymeric materials such as resins or rubbers as a base material. For example, a thermally conductive adhesive has been proposed that includes a thermosetting adhesive containing a curing component and a curing agent for the curing component, and a metal filler dispersed in the thermosetting adhesive, the metal filler containing silver powder and solder powder, the solder powder having a melting temperature lower than the thermal curing temperature of the thermally conductive adhesive and reacting with the silver powder under the thermal curing conditions of the thermosetting adhesive to form a high-melting-point solder alloy having a melting point higher than the melting temperature of the solder powder, the curing agent having flux activity with respect to the metal filler, the curing component being a glycidyl ether-type epoxy resin, and the curing agent being a monoanhydride of a tricarboxylic acid (see, for example, Patent Document 1).

[0004] JP 2012-188646 A

[0005] However, when the metal filler is highly loaded to achieve high thermal conductivity and low thermal resistance, the fluidity (viscosity) of the composition containing the metal filler deteriorates. On the other hand, when the thermal conductivity is improved by using a low-melting-point metal (solder powder) and bonding particles with a low-loading metal filler, as in the prior art described in Patent Document 1, the amount of low-melting-point metal increases by volume, making it impossible to achieve high thermal conductivity and low thermal resistance. Furthermore, when a low-melting-point metal is used, the thermal conductivity can be significantly affected by the interface material, and forming a thermally conductive layer containing a low-melting-point metal on a silicon substrate increases the contact resistance with the silicon interface, resulting in a decrease in thermal conductivity.

[0006] The present invention aims to solve the above-mentioned problems in the prior art and to achieve the following object: That is, the present invention aims to provide a laminate having excellent heat resistance, thermal conductivity, and adhesiveness, and a method for producing the laminate.

[0007] Means for solving the above problems are as follows. That is, <1> A laminate comprising: a substrate; a first thermally conductive layer provided on the substrate and containing an epoxy resin, an epoxy resin curing agent, and first thermally conductive particles; and a second thermally conductive layer provided on the first thermally conductive layer and containing a curing component, a curing agent for curing the curing component, second thermally conductive particles, and a low-melting-point metal, wherein the first thermally conductive layer does not contain the low-melting-point metal. <2> The laminate according to <1>, wherein the curing agent is represented by at least one of the following general formulas (1) and (2): However, in the general formula (1), R １ ~R ３ R each independently represents a hydrogen atom, an alkyl group, or a caprolactone skeleton. ４ represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. ５ represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms. However, in the general formula (2), R １ and R ２R each independently represents a hydrogen atom, an alkyl group, or a caprolactone skeleton. ４ and R ６ R each independently represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. ５ represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms. <3> The laminate according to any one of <1> to <2>, wherein the curing component includes at least one of an oxetane compound and an epoxy resin. <4> The laminate according to any one of <1> to <3>, wherein the first thermally conductive particles include at least one of silver particles, silver-coated particles, and silver particles. <5> The laminate according to any one of <1> to <4>, wherein the low-melting-point metal includes Sn and at least one selected from Bi, Ag, Cu, and In. <6> The laminate according to any one of <1> to <5>, wherein the base material includes at least one selected from silicon, aluminum, tungsten, molybdenum, glass, molding resin, stainless steel, and ceramics. <7> The laminate according to any one of <1> to <6>, wherein the content of the first thermally conductive particles in the first thermally conductive layer is 50% by volume or more. <8> The laminate according to any one of <1> to <7>, further comprising an opposing substrate on the second thermally conductive layer facing the substrate, wherein the opposing substrate contains at least one metal selected from the group consisting of copper, gold, platinum, palladium, silver, zinc, iron, tin, nickel, magnesium, indium, and alloys thereof. <9> A method for producing a laminate, comprising: applying, onto a substrate, a first thermally conductive layer composition containing an epoxy resin, an epoxy resin curing agent, and first thermally conductive particles; applying, onto the applied first thermally conductive layer composition, a second thermally conductive layer composition containing a curing component, a curing agent for curing the curing component, second thermally conductive particles, and low-melting-point metal particles; and heating the first thermally conductive layer composition and the second thermally conductive layer composition to form a first thermally conductive layer and a second thermally conductive layer.

[0008] According to the present invention, the above-mentioned problems in the prior art can be solved, the above-mentioned objects can be achieved, and a laminate having excellent heat resistance, thermal conductivity, and adhesiveness, and a method for manufacturing the laminate can be provided.

[0009] Fig. 1 is a schematic diagram showing an example of a process for producing a laminate according to the present embodiment. Fig. 2 is a schematic diagram showing an example of a laminate according to the present embodiment. Fig. 3 is a schematic cross-sectional view showing an example of a heat dissipation structure having the laminate according to the present embodiment.

[0010] (Laminate) The laminate of the present invention has a substrate, a first thermally conductive layer, a second thermally conductive layer, and may further have other members as required.

[0011] The laminate of this embodiment has a first thermally conductive layer and a second thermally conductive layer in this order on a substrate, and since the first thermally conductive layer does not contain a low-melting point metal, it is possible to provide a laminate with excellent heat resistance, thermal conductivity, and adhesiveness.

[0012] <Substrate> The shape, structure, size, material, etc. of the substrate are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the substrate include a plate shape and a sheet shape. Examples of the structure of the substrate include a single-layer structure and a laminated structure. The size of the substrate can be appropriately selected depending on the application, etc.

[0013] The material of the substrate can be selected from materials that are difficult to wet with solder because the first thermally conductive layer in contact with the substrate does not contain a low-melting-point metal, and suitable examples include silicon, aluminum, tungsten, molybdenum, glass, molded resin, stainless steel, and ceramics. Examples of the ceramics include aluminum nitride, silicon carbide, alumina, and gallium nitride. Examples of the molded resin include epoxy resin, silicone resin, urethane resin, and acrylic resin. The substrate preferably contains silicon.

[0014] The average thickness of the substrate is not particularly limited and can be appropriately selected depending on the purpose. The substrate may be the heat-generating body (electronic component) itself in the heat dissipation structure.

[0015] <First Thermally Conductive Layer> The first thermally conductive layer is preferably formed on the substrate and in contact with the substrate. The first thermally conductive layer contains an epoxy resin, an epoxy resin curing agent that cures the epoxy resin, and first thermally conductive particles, and may further contain other components as necessary. The first thermally conductive layer does not contain a low-melting-point metal.

[0016] -Epoxy Resin- The epoxy resin is a resin having epoxy groups (oxirane rings) within the polymer and is a thermosetting resin that can be cured by crosslinking via the epoxy groups. By including an epoxy resin in the first thermally conductive layer, flexibility can be imparted, and thermal conductivity and adhesiveness, particularly after reflow treatment, can be achieved, thereby achieving excellent heat resistance. Examples of the epoxy resin include glycidyl ether epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, trisphenol epoxy resins, tetraphenol epoxy resins, phenol-xylylene epoxy resins, naphthol-xylylene epoxy resins, phenol-naphthol epoxy resins, phenol-dicyclopentadiene epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins. These may be used alone or in combination of two or more.

[0017] Among the epoxy resins, glycidyl ether type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, phenol-dicyclopentadiene type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, and aliphatic epoxy resins are preferred. Suitable examples of commercially available bisphenol A type epoxy resins include EPICLON (registered trademark) EXA-850CRP (manufactured by DIC Corporation).

[0018] The content of the epoxy resin is preferably 5% by volume or more and 50% by volume or less, more preferably 10% by volume or more and 40% by volume or less, and even more preferably 20% by volume or more and 40% by volume or less, relative to the total amount of the first thermal conductive layer.

[0019] -Epoxy Resin Curing Agent- The epoxy resin curing agent is a curing agent that cures the epoxy resin, and examples thereof include polyaddition-type curing agents such as 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.

[0020] Commercially available imidazole curing agents can be used, and examples of the commercially available products include HX-3941HP, HXA3922HP, HXA3792, HXA3932HP, HXA3042HP, HXA9322HP, HXA9382HP, HXA5052HP, and HXA3542HP from the Novacure (registered trademark) series sold by Asahi Chemical Industry Co., Ltd. The Novacure (registered trademark) series is a microcapsule-type liquid latent curing agent for epoxy resins, and by varying the capsule thickness and capsule particle size, it is possible to adjust the curing initiation temperature, reaction rate, and solvent resistance of the first thermally conductive layer composition for forming the first thermally conductive layer. The Novacure® series also contains uncured bisphenol A and bisphenol F epoxy resins, and when the temperature rises (around 150°C), the curing agent is released from the capsules into the bulk (liquid epoxy resin), causing the curing to proceed. The curing initiation temperature of the epoxy resin curing agent is preferably 120°C or higher.

[0021] The content of the epoxy resin curing agent is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 0.1 vol% or more and 30 vol% or less, more preferably 1 vol% or more and 20 vol% or less, and even more preferably 3 vol% or more and 15 vol% or less, relative to the total amount of the first thermal conductive layer.

[0022] -First thermally conductive particles- The first thermally conductive particles are preferably at least one of copper particles, silver-coated particles, and silver particles, with silver particles being more preferred. Examples of the silver-coated particles include silver-coated copper particles, silver-coated nickel particles, and silver-coated aluminum particles. The shape of the first thermally conductive particles is not particularly limited and can be appropriately selected depending on the purpose, and examples include spherical, flat, granular, and acicular shapes.

[0023] The content of the first thermally conductive particles in the first thermally conductive layer is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of achieving high packing and increasing thermal conductivity, the content is preferably 40% by volume or more, more preferably 45% by volume or more, and even more preferably 50% by volume or more.

[0024] The volume average particle size of the first thermally conductive particles 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. When the volume average particle size of the thermally conductive particles is 0.3 μm or more and 30 μm or less, the volume ratio of the first thermally conductive particles to the low-melting-point metal particles can be increased, and the laminate can achieve excellent heat resistance, thermal conductivity, and adhesiveness. The volume average particle size can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer (product name: Microtrac MT3300EXII).

[0025] -Low-melting-point metal- The first thermally conductive layer does not contain a low-melting-point metal. Here, the low-melting-point metal refers to the low-melting-point metal particles described in the second thermally conductive layer composition in the laminate manufacturing method described below, and the low-melting-point metal formed by melting and solidifying the low-melting-point metal particles. The method for confirming that the first thermally conductive layer does not contain the low-melting-point metal is not particularly limited and can be modified as appropriate depending on the purpose. For example, a method of polishing a cut surface of the laminate and observing the polished surface with a scanning electron microscope (e.g., S-3000N, manufactured by Hitachi, Ltd.) or a method of analyzing using the analytical method described in Japanese Industrial Standard JIS Z 3910:2017 Solder Analysis Methods can be used.

[0026] Other Components The first thermally conductive layer may contain other components as long as the effects of the present invention are not impaired. The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples of the other components include thermally conductive particles other than metals (e.g., aluminum nitride, alumina, carbon fiber, etc.), additives (e.g., antioxidants, ultraviolet absorbers, curing accelerators, silane coupling agents, leveling agents, flame retardants, etc.), and resins other than epoxy resins.

[0027] The resin other than the epoxy resin is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include polymers having at least one structure selected from a phenoxy structure, a polybutadiene structure, a polysiloxane structure, a poly(meth)acrylate structure, a polyalkylene structure, a polyalkyleneoxy structure, a polyisoprene structure, a polyisobutylene structure, a polyamide structure, and a polycarbonate structure in the molecule.

[0028] The first thermally conductive layer composition for forming the first thermally conductive layer can be prepared by uniformly mixing the epoxy resin, the epoxy resin curing agent, the first thermally conductive particles, and other components as necessary using a conventional method.

[0029] The average thickness of the first thermally conductive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less.

[0030] <Second Thermally Conductive Layer> The second thermally conductive layer contains a curing component, a curing agent that cures the curing component, second thermally conductive particles, and a low-melting point metal, and may further contain other components as necessary.

[0031] -Curing Component- The curing component preferably contains at least one of an oxetane compound and an epoxy resin, and more preferably contains an oxetane compound and an epoxy resin.

[0032] --Oxetane Compound-- The oxetane compound is a compound having an oxetanyl group, and may be an aliphatic compound, an alicyclic compound, or an aromatic compound. The oxetane compound may be a monofunctional oxetane compound having only one oxetanyl group, or a polyfunctional oxetane compound having two or more oxetanyl groups.

[0033] The oxetane compound is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include 3,7-bis(3-oxetanyl)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, tetraethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, 1,4 1,6-bis(3-ethyl-3-oxetanylmethoxy)butane, 1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane, 3-ethyl-3-(phenoxy)methyloxetane, 3-ethyl-3-(cyclohexyloxymethyl)oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(chloromethyl)oxetane, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, xylylenebisoxetane, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl (OXBP), and the like. These may be used alone or in combination of two or more.

[0034] As the oxetane compound, commercially available products can be used, and examples of the commercially available products include the "Aron Oxetane (registered trademark)" series sold by Toagosei Co., Ltd. and the "ETERNACOLL (registered trademark)" series sold by Ube Industries, Ltd. Among these, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl (ETERNACOLL (registered trademark) OXBP) is preferred.

[0035] --Epoxy Resin-- The epoxy resin is not particularly limited and can be appropriately selected depending on the purpose, and 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, aliphatic epoxy resins, etc. These may be used alone or in combination of two or more.

[0036] The content of the curing component is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 0.5% by volume to 60% by volume based on the total amount of the second thermally conductive layer.

[0037] - 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 acid, acid anhydride type curing agent, aliphatic amine type curing agent, aromatic amine type curing agent, phenol type curing agent, mercaptan type curing agent, etc., catalyst type curing agent such as imidazole, etc. These may be used alone or in combination of two or more types.

[0038] Among these, polyfunctional carboxylic acids are preferred, and polyfunctional carboxylic acids represented by at least one of the following general formulas (1) and (2) are more preferred.

[0039] However, in the general formula (1), R １ ~R ３ R each independently represents a hydrogen atom, an alkyl group, or a caprolactone skeleton. ４ represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. ５ represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms.

[0040] However, in the general formula (2), R １ and R ２R each independently represents a hydrogen atom, an alkyl group, or a caprolactone skeleton. ４ and R ６ R each independently represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. ５ represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms.

[0041] R in the general formula (1) １ ~R ３ and R in general formula (2) １ and R ２ In the general formula (1), the alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a tert-octyl group, and a cyclohexyl group. １ ~R ３ and R in general formula (2) １ and R ２ The caprolactone skeleton in the above formula (i) is represented by the following general formula (i): In the general formula (i), n represents an integer of 1 or more, preferably 1 to 10, and m represents an integer of 2 or more, preferably 2 to 5.

[0042] R ４ and R ６ Examples of the alkyl group optionally substituted with a hydroxyl group in the formula (I) include a methyl group, an ethyl group, a propyl group, a -(CH ２ ) —OH, —(CH ２ ) ２ -OH, -(CH ２ ) ３ -OH and the like.

[0043] R ５ Examples of the alkyl group having 1 to 3 carbon atoms in R include a methyl group, an ethyl group, a propyl group, and an isopropyl group. ５ Examples of the alkenyl group having 2 to 3 carbon atoms include a vinyl group, a 1-propenyl group, and an allyl group (2-propenyl group). ５is preferably either an alkyl group having 2 to 3 carbon atoms or an alkenyl group having 2 carbon atoms, in view of achieving both excellent flux activity and curability.

[0044] The polyfunctional carboxylic acid represented by at least one of the general formula (1) and the general formula (2) can be synthesized by reacting a specific acid anhydride with a specific polyfunctional alcohol, as described below.

[0045] [Method for producing polyfunctional carboxylic acid] The method for producing the polyfunctional carboxylic acid includes a step of esterifying an acid anhydride with a polyfunctional alcohol, and may further include other steps as necessary. The esterification reaction between the acid anhydride and the polyfunctional alcohol is not particularly limited and can be appropriately selected depending on the purpose.

[0046] Examples of the acid anhydride include succinic anhydride, glutaric anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, and oxalic anhydride. These may be used alone or in combination of two or more. Among these, succinic anhydride, glutaric anhydride, and maleic anhydride are preferred.

[0047] The polyfunctional alcohol is preferably difunctional or higher, and more preferably difunctional or higher and tetrafunctional or lower. Examples of the polyfunctional alcohol include caprolactone derivatives, glycerin, ethylene glycol, and propylene glycol. These may be used alone or in combination of two or more. Among these, caprolactone derivatives and glycerin are preferred.

[0048] Examples of the caprolactone derivative include compounds having a caprolactone skeleton represented by the general formula (i). Commercially available caprolactone derivatives can be used, and examples of the commercially available products include PLACCEL 205, PLACCEL 205U, PLACCEL 303, and PLACCEL 410 (all manufactured by Daicel Corporation).

[0049] An example of the esterification reaction between a specific acid anhydride and a trifunctional alcohol is shown below. However, in the above reaction formula, R １ ~R ３ represents a hydrogen atom, an alkyl group, or a caprolactone skeleton. ４ represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. ５ represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms.

[0050] The other steps are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a concentration step and a separation and purification step.

[0051] The polyfunctional carboxylic acid represented by at least one of the general formulas (1) and (2) can simultaneously exhibit a good flux effect and a good curing agent function. That is, the polyfunctional carboxylic acid represented by at least one of the general formulas (1) and (2) remains liquid from room temperature to high temperature, and does not undergo any reaction during film formation, thereby improving the wettability of the coating liquid. When heated in stages, the first heating stage exerts a flux effect, and then the second heating stage has a heat curing start switch function, in which curing begins with the curing components that were blended together. The first heating stage is preferably 120°C to 150°C, for example. The second heating stage is preferably 150°C to 190°C, for example.

[0052] The polyfunctional carboxylic acid is preferably liquid at 25°C and 150°C. Here, being liquid means having fluidity that allows application. Whether the polyfunctional carboxylic acid is liquid at 25°C and 150°C can be confirmed, for example, by visually confirming the fluidity at 25°C (room temperature) and by the presence or absence of an absorption peak up to 150°C by DSC. In terms of being liquid, the molecular weight of the polyfunctional carboxylic acid is preferably 800 g / mol or less, and more preferably 400 g / mol or more and 700 g / mol or less. The molecular weight of the polyfunctional carboxylic acid can be measured, for example, using Shodex (registered trademark) GPC-101 (product of Showa Denko K.K.).

[0053] The polyfunctional carboxylic acid is a curing agent having flux activity. The first-stage heating process provides the polyfunctional carboxylic acid with flux activity, thereby improving the wettability of the molten low-melting-point metal to the second thermally conductive particles contained in the second thermally conductive layer. The second-stage heating process then allows the polyfunctional carboxylic acid to harden the curing component in the second thermally conductive layer. The lower first thermally conductive layer contains an epoxy resin hardener and hardens faster than the upper second thermally conductive layer. Therefore, by appropriately adjusting the heating conditions and other factors, the first and second thermally conductive layers can be formed without the molten low-melting-point metal flowing into the first thermally conductive layer.

[0054] When the curing component is an epoxy resin, the acid anhydride curing agent is preferred because it does not generate gas during thermal curing, can achieve a long pot life when mixed with the epoxy resin, and can achieve a good balance between the electrical properties, chemical properties, and mechanical properties of the resulting cured product.

[0055] Examples of the acid anhydride curing agent include cyclohexane-1,2-dicarboxylic acid anhydride and mono-acid anhydrides of tricarboxylic acids. Examples of the mono-acid anhydrides of tricarboxylic acids include cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride.

[0056] The curing agent preferably has flux activity in order to improve the wettability of the molten low-melting-point metal to the thermally conductive particles. Examples of methods for imparting flux activity to the curing agent include introducing a protonic acid group, such as a carboxyl group, a sulfonyl group, or a phosphate group, into the curing agent by a known method. Among these, introducing a carboxyl group is preferred in terms of reactivity with the epoxy resin or oxetane compound used as the curing component. Examples include carboxyl group-containing organic acids such as glutaric acid and succinic acid. Alternatively, compounds modified from glutaric anhydride or succinic anhydride, or metal salts of organic acids such as silver glutarate, may also be used.

[0057] The content of the curing agent in the second thermally conductive layer can be appropriately selected so that it is an amount necessary to form the second thermally conductive layer, which is the upper layer, and does not flow into the first thermally conductive layer composition for forming the lower layer. The content is preferably 0.5% by volume or more and 10% by volume or less, and more preferably 0.5% by volume or more and 7% by volume or less, relative to the total amount of the second thermally conductive layer.

[0058] -Second Thermally Conductive Particles- The second thermally conductive particles are preferably at least one of copper particles, silver-coated particles, and silver particles, with silver-coated particles being more preferred. Examples of the silver-coated particles include silver-coated copper particles, silver-coated nickel particles, and silver-coated aluminum particles. The shape of the second thermally conductive particles is not particularly limited and can be appropriately selected depending on the purpose, and examples include spherical, flat, granular, and acicular shapes.

[0059] The volume average particle size of the second thermally conductive particles is preferably 1 μm or more and 100 μm or less, more preferably 5 μm or more and 70 μm or less, and even more preferably 5 μm or more and 50 μm or less. When the volume average particle size of the second thermally conductive particles is 1 μm or more and 100 μm or less, excellent thermal conductivity can be achieved. The volume average particle size of the second thermally conductive particles can be measured in the same manner as the volume average particle size of the first thermally conductive particles.

[0060] The low-melting-point metal refers to the low-melting-point metal particles and the low-melting-point metal formed by melting and solidifying the low-melting-point metal particles. As the low-melting-point metal particles, solder particles specified in JIS Z3282-1999 are preferably used.

[0061] Examples of the solder particles include Sn—Pb solder particles, Pb—Sn—Sb solder particles, Sn—Sb solder particles, Sn—Pb—Bi solder particles, Sn—Bi solder particles, Sn—Bi—Ag solder particles, Sn—Cu solder particles, Sn—Pb—Cu solder particles, Sn—In solder particles, Sn—Ag solder particles, Sn—Pb—Ag solder particles, Pb—Ag solder particles, Sn—Ag—Cu solder particles, etc. These may be used alone or in combination of two or more. Among these, solder particles containing Sn and at least one selected from Bi, Ag, Cu, and In are preferred, Sn—Bi solder particles, Sn—Bi—Ag solder particles, Sn—Ag—Cu solder particles, and Sn—In solder particles are more preferred, and Sn—Bi solder particles containing Sn and Bi are even more preferred.

[0062] The shape of the low-melting-point metal particles is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include spherical, flat, granular, acicular, etc. The melting point of the low-melting-point metal particles is preferably 100°C or higher and 250°C or lower, more preferably 120°C or higher and 200°C or lower.

[0063] The melting point of the low-melting-point metal particles is preferably lower than the thermal curing temperature (second-stage heating) of the first thermal conductive layer composition and the second thermal conductive layer composition. This allows for the formation of a second thermal conductive layer in which a network (a continuous metal phase) is formed via the second thermal conductive particles by the low-melting-point metal molten in the cured product of the second thermal conductive layer composition. Therefore, a laminate with excellent heat resistance, thermal conductivity, and adhesiveness can be realized. The thermal curing of the first thermal conductive layer composition is performed, for example, at a temperature of 150°C to 190°C for 30 minutes to 2 hours.

[0064] The volume average particle size of the low-melting-point metal particles is preferably 10 μm or less, and more preferably 1 μm or more and 5 μm or less. When the volume average particle size of the low-melting-point metal particles is 10 μm or less, the volume ratio of the low-melting-point metal particles to the second thermal conductive particles can be reduced, thereby achieving high thermal conductivity and low thermal resistance of the second thermal conductive layer. The volume average particle size of the low-melting-point metal particles can be measured in the same manner as the volume average particle size of the first thermal conductive particles.

[0065] The volume average particle size of the second thermally conductive particles is larger than the volume average particle size of the low-melting-point metal particles, and the volume average particle size ratio (A / B) of the second thermally conductive particles A to the low-melting-point metal particles B is preferably 2 or more, more preferably 3 or more, and even more preferably 5 or more. The upper limit of the volume average particle size ratio (A / B) is preferably 20 or less, more preferably 10 or less. By using low-melting-point metal particles having a volume average particle size smaller than that of the second thermally conductive particles, the second thermally conductive particles become the main component in the second thermally conductive layer composition, and the low-melting-point metal particles present between the second thermally conductive particles and the second thermally conductive particles melt when heated and alloy with the second thermally conductive particles to form a network, thereby achieving high thermal conductivity and low thermal resistance.

[0066] In the second thermal conductive layer composition for forming the second thermal conductive layer, the volume ratio (A / B) of the second thermal conductive particles A to the low-melting point metal particles B is preferably at least 1, more preferably at least 1.5, and even more preferably at least 2. The upper limit of the volume ratio (A / B) is preferably at most 5, more preferably at most 4, and even more preferably at most 3.

[0067] The average thickness of the second thermally conductive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 20 μm or more and 300 μm or less, and more preferably 50 μm or more and 200 μm or less.

[0068] <Facing substrate> The facing substrate is disposed opposite the substrate, and its shape, structure, size, material, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of the shape of the facing substrate include a plate shape and a sheet shape. Examples of the structure of the facing substrate include a single-layer structure and a laminated structure. The size of the facing substrate can be appropriately selected depending on the application, etc. The material of the facing substrate is a material that is easily wetted by solder, and includes at least one selected from copper, gold, platinum, palladium, silver, zinc, iron, tin, nickel, magnesium, indium, and alloys thereof. The average thickness of the facing substrate is not particularly limited and can be appropriately selected depending on the purpose. The facing substrate may be the heat spreader itself in the heat dissipation structure.

[0069] <Other Components> The other components are not particularly limited and can be appropriately selected depending on the purpose. For example, a protective layer can be mentioned.

[0070] (Method for Producing Laminate) The method for producing a laminate of the present invention includes a first applying step, a second applying step, and a heating step, and may further include other steps as necessary.

[0071] <First Application Step> The first application step is a step of applying a first thermally conductive layer composition onto the substrate. The first thermally conductive layer composition contains an epoxy resin, an epoxy resin curing agent, and first thermally conductive particles, does not contain a low-melting-point metal, and may further contain other components as necessary. The substrate, epoxy resin, epoxy resin curing agent, first thermally conductive particles, other components, and low-melting-point metal can be appropriately selected from the items described for the laminate of this embodiment.

[0072] Examples of methods for applying the first thermal conductive layer composition to the substrate include inkjet coating, blade coating, gravure coating, gravure offset coating, bar coating, roll coating, knife coating, air knife coating, comma coating, U comma coating, AKKU coating, smoothing coating, microgravure coating, reverse roll coating, four-roll coating, five-roll coating, dip coating, curtain coating, slide coating, and die coating.

[0073] <Second Application Step> The second application step is a step of applying a second thermally conductive layer composition onto the applied first thermally conductive layer composition. The second thermally conductive layer composition contains a curing component, a curing agent that cures the curing component, second thermally conductive particles, and low-melting-point metal particles, and may further contain other components as necessary. The second curing component, the second curing agent, the second thermally conductive particles, and the low-melting-point metal particles can be appropriately selected from the items described for the laminate of this embodiment.

[0074] Examples of methods for applying the second thermal conductive layer composition onto the applied first thermal conductive layer composition include inkjet method, blade coating method, gravure coating method, gravure offset coating method, bar coating method, roll coating method, knife coating method, air knife coating method, comma coating method, U comma coating method, AKKU coating method, smoothing coating method, microgravure coating method, reverse roll coating method, four-roll coating method, five-roll coating method, dip coating method, curtain coating method, slide coating method, and die coating method.

[0075] <Heating Step> The curing step is a step of heating the first thermally conductive layer composition and the second thermally conductive layer composition to form a first thermally conductive layer and a second thermally conductive layer.

[0076] The heating conditions preferably include (1) a first-stage heating in which the flux activity of the curing agent is expressed, improving the wettability of the curing agent and the dissolved low-melting-point metal with the second thermally conductive particles, and (2) a second-stage heating in which the curing activity of the curing agent is expressed, curing each layer. The heating may be performed, for example, by continuously increasing the temperature, followed by the second-stage heating, or the two-stage heating conditions may be performed sequentially. The first-stage heating is preferably performed, for example, at 120°C to 150°C for 1 minute to 30 minutes. The second-stage heating is preferably performed, for example, at 150°C to 190°C for 30 minutes to 2 hours.

[0077] The second thermally conductive layer composition is applied onto the first thermally conductive layer composition while still in the liquid phase, and then the flux activity of the curing agent is expressed by the first heating step, thereby improving the wettability of the curing agent and the dissolved low-melting point metal with the second thermally conductive particles, and also improving the adhesiveness of the resulting first thermally conductive layer and second thermally conductive layer.

[0078] Then, the first thermally conductive layer composition and the second thermally conductive layer composition are cured by a second stage of heating to form the first thermally conductive layer and the second thermally conductive layer, respectively.

[0079] The curing initiation temperature of the epoxy resin curing agent is preferably 120°C or higher. When the curing initiation temperature is 120°C or higher, after the second application step and during the first stage of heating in the heating step, the first thermal conductive layer composition and the second thermal conductive layer composition do not start to harden, and the flux activity of the curing agent is exerted, thereby improving the wettability between the molten low-melting point metal and the second thermal conductive particles. The subsequent second stage of heating hardens each layer.

[0080] <Other Steps> The other steps are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a protective layer forming step and an opposing substrate laminating step.

[0081] Here, the laminate manufacturing method of the present invention and the laminate embodiment will be described in detail with reference to the drawings. Note that in each drawing, the same components are given the same reference numerals, and duplicated explanations may be omitted. Furthermore, the number, position, shape, etc. of the following components are not limited to the present embodiment, and may be the number, position, shape, etc. that are preferable for implementing the present invention.

[0082] Fig. 1 is a schematic diagram showing an example of a process for producing a laminate according to an embodiment. The uncured laminate 10a shown in Fig. 1 is a wet-on-wet uncured laminate after the second application step and before the heating step, and specifically includes a first thermally conductive layer composition 12a containing first thermally conductive particles 12b on a substrate 11, a second thermally conductive layer composition 14a containing second thermally conductive particles 14b and low-melting-point metal particles 14c on the first thermally conductive layer composition 12a, and an opposing substrate 15 on the second thermally conductive layer composition 14a.

[0083] Fig. 2 is a schematic diagram showing an example of a laminate according to an embodiment. The laminate 10 shown in Fig. 2 includes a first thermally conductive layer 12 containing first thermally conductive particles 12b on a substrate 11, a second thermally conductive layer 14 containing second thermally conductive particles 14b and a low-melting-point metal 14d on the first thermally conductive layer 12, and an opposing substrate 15 on the second thermally conductive layer 14.

[0084] The laminate of the present invention can be suitably used, for example, when forming a power LED module or a power IC module by bonding a thermal interface material (TIM), which fills the minute gap between a heat source such as an LSI and a heat sink to allow heat to flow smoothly between them, or a heat dissipation substrate on which an LED chip or an IC chip is mounted, to a heat sink. Here, power LED modules include those of the wire bonding mounting type and those of the flip chip mounting type, and power IC modules include those of the wire bonding mounting type.

[0085] (Heat Dissipation Structure) The heat dissipation structure of this embodiment includes a heat generating element, the laminate of the present invention described above, and a heat dissipation member, and further includes other members as necessary.

[0086] 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).

[0087] 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.

[0088] 3 is a schematic cross-sectional view showing an example of a semiconductor device as a heat dissipation structure. The laminate 7 of the present invention dissipates heat generated by an electronic component 3 such as a semiconductor element, and as shown in FIG. 3, is fixed to the main surface 2a of the heat spreader 2 facing the electronic component 3, 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.

[0089] 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.

[0090] 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 laminate 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 through the heat sink 5.

[0091] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0092] <Synthesis of Curing Agent> A polyfunctional carboxylic acid represented by the general formula (1) was synthesized as a curing agent and identified according to the following procedure. 50 parts by mass of glycerin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was weighed into a three-necked glass flask equipped with a thermocouple, a stirrer, a condenser, and a heater. 43.3 parts by mass of methyl ethyl ketone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added thereto and thoroughly stirred to achieve complete dissolution. Next, 1 part by mass of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as a catalyst and further thoroughly stirred. After complete dissolution, 50 parts by mass of glutaric anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) represented by the following structural formula was added dropwise in powder form to the three-necked flask using a funnel. The mixture was kept at a constant temperature of 60°C and stirred for 24 hours until the reaction was completely completed. The synthesized product was cooled to room temperature, transferred to a recovery flask, concentrated with an evaporator, and then dried under reduced pressure (at 60°C for 24 hours) to obtain the target polyfunctional carboxylic acid in a yield of 90%. The obtained polyfunctional carboxylic acid was in a liquid state.

[0093] The resulting polyfunctional carboxylic acid was identified by FT-IR measurement. FT-IR measurement was performed using a Nicolet iS10 (manufactured by Thermo Fisher Scientific Co., Ltd.) by the ATR method. The FTIR absorption of the resulting polyfunctional carboxylic acid is shown below. －１ , 868 cm －１ , 1016 cm －１ , 1065 cm －１ , 1097 cm －１ , 1138 cm －１ , 1268 cm －１ , 1410 cm －１ , 1703 cm －１ , 1730 cm －１ and 2700 cm －１ ~3700cm －１ .

[0094] As a result of FTIR absorption, broad absorption vibrations derived from carboxylic acid were observed, and therefore it was confirmed that the target compound was pentanedioic acid-1,1',1''-(1,2,3-propanetriyl) ester (molecular formula: C) having the following structure. １８ H ２６ O１２ ) was found to be obtained.

[0095]

[0096] (Example 1) <Preparation of Thermal Conductive Layer Composition> The compositions and contents shown in Table 1 were uniformly mixed using a stirring device (Awatori Rentaro Automatic Revolving Mixer, manufactured by Thinky Corporation) to prepare a first thermal conductive layer composition and a second thermal conductive layer composition. The content of each component in Table 1 is in volume %.

[0097] <Production of Laminate> Next, a first thermally conductive layer composition was applied onto a substrate (silicon substrate) measuring 20 mm × 20 mm × 0.725 mm so that the average thickness after curing would be 20 μm, and then a second thermally conductive layer composition was applied onto the first thermally conductive layer so that the average thickness after curing would be 80 μm. A counter substrate (copper) measuring 20 mm × 20 mm × 1 mm was laminated on this second thermally conductive layer composition, and the resultant was heated in two stages, at 150°C for 5 minutes and at 170°C for 60 minutes, to be cured, thereby producing the laminate of Example 1.

[0098] (Examples 2 to 3) Laminates of Examples 2 and 3 were produced in the same manner as in Example 1, except that the composition of the first thermally conductive layer composition in Example 1 was changed as shown in Table 1. Note that the Novacure (registered trademark) HX-3941HP (manufactured by Asahi Kasei E-materials Corporation) used is shown in the "epoxy resin curing agent" column, and contains an epoxy resin in addition to an epoxy resin curing agent.

[0099] Comparative Examples 1 and 2 Laminates of Comparative Examples 1 and 2 were produced in the same manner as in Example 1, except that the composition of the first thermal conductive layer composition in Example 1 was changed as shown in Table 1.

[0100] Next, for Examples 1 to 3 and Comparative Examples 1 and 2, the "measurement of the average thickness of each layer," "thermal conductivity," and "adhesion" were evaluated as follows. The results are shown in Table 1.

[0101] <Measurement of Average Thickness of Each Layer> Next, the thickness of each layer was measured from the cut surface of the laminate, and the average value of the thicknesses at any three points was calculated. It was confirmed that each of the laminates of Examples 1 to 3 had a first thermally conductive layer, a second thermally conductive layer, and an opposing substrate on a substrate in this order, corresponding to the cross-sectional view of the laminate shown in Figure 2.

[0102] As a result, in all of Examples 1 to 3 and Comparative Examples 1 and 2, the total average thickness of the first thermally conductive layer was 20 μm, and the average thickness of the second thermally conductive layer was 80 μm.

[0103] <Thermal conductivity> <<Preparation of laminate after pressure bonding>> Each laminate was sandwiched between a 20 mm × 20 mm square silicon plate (thickness 0.77 mm) and a 20 mm diameter copper plate (thickness 1.0 mm), and pressed for 5 minutes using a mini-press machine under the conditions of an upper plate temperature on the copper substrate side of 150°C, a lower plate temperature on the silicon substrate side of 150°C, and a set air pressure of 0.11 MPa (equivalent to 40 psi).

[0104] <<Preparation of Laminates After Reflow>> The low-melting point metal particles of each laminate were remelted (reflowed) by performing a treatment simulating reflow conditions, which involved heating at 260°C for 5 minutes, to obtain laminates after reflow.

[0105] <<Evaluation of Thermal Conductivity>> The thermal resistance (°C cm) of the laminate after compression bonding and the laminate after reflow (interface Cu and silicon) was measured using a method in accordance with ASTM-D5470. ２ / W) was measured. From the result, the thermal resistances of the substrate (silicon substrate) and the opposing substrate (copper substrate) were subtracted to calculate the thermal resistance of the portion of the laminate excluding the substrate and opposing substrate. The thermal conductivity (W / m·K) was calculated from this thermal resistance and the thickness (100 μm) of the portion of the laminate excluding the substrate and opposing substrate, and the thermal conductivity was evaluated according to the following criteria. [Evaluation criteria] ⊚: Thermal conductivity is 20 W / m·K or more. ◯: Thermal conductivity is 12 W / m·K or more but less than 20 W / m·K. ×: Thermal conductivity is less than 12 W / m·K.

[0106] <Adhesion> For each example, the adhesion was evaluated using the laminate after compression bonding and the laminate after reflow by the following procedure. The laminate after compression bonding and the laminate after reflow were prepared by the procedure described above in <Thermal Conductivity>. As a reliability test, a shear test was performed on the laminate after compression bonding or the laminate after reflow using a bond tester (4000Plus, manufactured by Nordson DAGE) under test conditions of a shear rate of 200 μm, a height of 150 μm, n=3, and an environment of 130°C, to evaluate the adhesion at high temperatures. [Evaluation Criteria] ○: Adhesion strength is 3 kg or more. ×: Adhesion strength is less than 3 kg.

[0107]

[0108] As a result, it was confirmed that in the laminates of Examples 1 and 2, the curing agent and the dissolved low-melting point metal in the second thermally conductive layer composition improved the wettability of the second thermally conductive particles, and the layers were laminated and cured as a liquid phase, thereby forming first and second thermally conductive layers with excellent adhesiveness. The laminates of Examples 1 and 2 had good thermal conductivity and adhesiveness after compression bonding. It was also found that the laminates after reflow also had good thermal conductivity and adhesiveness, and excellent heat resistance.

[0109] The laminate of Example 3 had good thermal conductivity and adhesiveness after compression bonding, and was particularly excellent in thermal conductivity. It was also found that the laminate after reflow also had good thermal conductivity and adhesiveness, and was also excellent in heat resistance.

[0110] In the laminate of Comparative Example 1, the first thermally conductive layer contained a low-melting-point metal, and therefore the thermal conductivity and adhesiveness of the laminate after compression bonding met the evaluation criteria. However, the thermal conductivity and adhesiveness after reflow were poor, resulting in poor heat resistance. In the laminate of Comparative Example 2, the first thermally conductive layer composition did not contain low-melting-point metal particles, but also did not contain an epoxy resin curing agent, resulting in poor heat resistance, thermal conductivity, and adhesiveness. In the laminates of Comparative Examples 1 and 2, the first thermally conductive layer composition did not contain an epoxy resin curing agent, so it took time for the first thermally conductive layer composition to cure. The two-layer structure of the first and second thermally conductive layers and their interface (see Figure 2), as observed in the laminate of Example 1, could not be observed in the laminates of Comparative Examples 1 and 2.

[0111] Details of each component in Table 1 are as follows:

[0112] -Epoxy resin- EPICLON (registered trademark) EXA-850CRP (manufactured by DIC Corporation)

[0113] - Epoxy resin curing agent - Epoxy resin curing agent: Novacure (registered trademark) HX-3941HP (manufactured by Asahi Kasei E-Materials Corporation, epoxy resin curing agent 30% to 40%, bisphenol A type epoxy resin 45% to 55%, bisphenol F type epoxy resin 10% to 20%)

[0114] -Curing component- Curing component (oxetane compound): ETERNACOLL (registered trademark) OXBP (manufactured by Ube Industries, Ltd.), 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl

[0115] - Curing agent - Curing agent: polyfunctional carboxylic acid represented by the general formula (1) (pentanedioic acid-1,1',1''-(1,2,3-propanetriyl) ester; molecular formula: C １８ H ２６ O １２ (Synthetic product by Dexerials Corporation)

[0116] - Low melting point metal particles (solder particles) - Sn ５８ Bi ４２ Manufactured by Mitsui Mining & Smelting Co., Ltd., volume average particle size Dv: 4 μm, melting point 139° C.

[0117] -Thermal conductive particles- Thermal conductive particles 1: Ag particles, manufactured by DOWA Electronics Co., Ltd., volume average particle size Dv: 1.9 μm Thermal conductive particles 2: Ag-coated Cu particles, manufactured by Fukuda Metal Foil & Powder Co., Ltd., volume average particle size Dv: 10 μm

[0118] - Thermoplastic resin - Thermoplastic resin: YP-50 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), a polyhydroxypolyether synthesized from bisphenols and epichlorohydrin

[0119] The laminate of the present invention can achieve excellent heat resistance, thermal conductivity, and adhesiveness as a thermal interface material (TIM), and is therefore suitable for use in, for example, the periphery of various electrical devices such as CPUs, MPUs, power transistors, LEDs, and laser diodes, where temperature can adversely affect the efficiency and lifespan of element operation.

[0120] This international application claims priority based on Japanese Patent Application No. 2023-128347, filed on August 7, 2023, the entire contents of which are incorporated herein by reference.

[0121] 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 Laminate 10 Laminate 10a Laminate before curing 11 Substrate 12 First thermally conductive layer 12a First thermally conductive layer composition 12b First thermally conductive particles 14 Second thermally conductive layer 14a Second thermally conductive layer composition 14b Second thermally conductive particles 14c Low-melting point metal particles 14d Low-melting point metal 15 Opposing substrate

Claims

1. A laminate comprising: a substrate; a first thermally conductive layer provided on the substrate and containing an epoxy resin, an epoxy resin curing agent, and first thermally conductive particles; and a second thermally conductive layer provided on the first thermally conductive layer and containing a curing component, a curing agent for curing the curing component, second thermally conductive particles, and a low-melting point metal, wherein the first thermally conductive layer does not contain the low-melting point metal.

2. The laminate according to claim 1, wherein the curing agent is represented by at least one of the following general formula (1) and general formula (2): In the above general formula (1), R １ ~R ３ R each independently represents a hydrogen atom, an alkyl group, or a caprolactone skeleton. ４ R represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. ５ represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms. In the above general formula (2), R １ and R ２ R each independently represents a hydrogen atom, an alkyl group, or a caprolactone skeleton. ４ and R ６ R each independently represents a hydrogen atom or an alkyl group which may be substituted with a hydroxyl group. ５ represents an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 3 carbon atoms.

3. The laminate according to claim 1, wherein the curing component comprises at least one of an oxetane compound and an epoxy resin.

4. The laminate according to any one of claims 1 to 3, wherein the first thermally conductive particles include at least one of silver particles, silver-coated particles, and silver particles.

5. A laminate according to any one of claims 1 to 4, wherein the low melting point metal comprises Sn and at least one selected from the group consisting of Bi, Ag, Cu, and In.

6. The laminate according to any one of claims 1 to 5, wherein the substrate comprises at least one material selected from the group consisting of silicon, aluminum, tungsten, molybdenum, glass, molding resin, stainless steel, and ceramics.

7. A laminate according to any one of claims 1 to 6, wherein the content of the first thermally conductive particles in the first thermally conductive layer is 50 volume % or more.

8. A laminate according to any one of claims 1 to 7, further comprising an opposing substrate on the second thermally conductive layer facing the substrate, the opposing substrate containing at least one metal selected from the group consisting of copper, gold, platinum, palladium, silver, zinc, iron, tin, nickel, magnesium, indium, and alloys thereof.

9. A method for producing a laminate, comprising the steps of: applying a first thermally conductive layer composition onto a substrate, the first thermally conductive layer composition containing an epoxy resin, an epoxy resin curing agent, and first thermally conductive particles, and containing no low-melting point metal; applying a second thermally conductive layer composition onto the applied first thermally conductive layer composition, the second thermally conductive layer composition containing a curing component, a curing agent for curing the curing component, second thermally conductive particles, and low-melting point metal particles; and heating the first thermally conductive layer composition and the second thermally conductive layer composition to form a first thermally conductive layer and a second thermally conductive layer.

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