Thermosetting resin composition, heat dissipation sheet, heat dissipation plate, method for manufacturing a heat dissipation sheet, and method for manufacturing a heat dissipation plate.

Abstract

This thermosetting resin composition contains an epoxy resin, a curing agent, an acrylic copolymer having a functional group in a side chain thereof, boron nitride, and a filler. The average particle diameter (D50) of the boron nitride is 7.0-60 μm. The average particle diameter (D50) of the filler is 0.5-5.0 μm. The volume fraction of the boron nitride is 55-70 vol% with respect to 100 vol% of the thermosetting resin composition. The volume fraction of the filler is 0.3-2.0 vol% with respect to 100 vol% of the thermosetting resin composition.

Description

Technical Field

[0001] The present invention relates to a thermosetting resin composition, a heat dissipation sheet, a heat dissipation plate, a method for manufacturing a heat dissipation sheet, and a method for manufacturing a heat dissipation plate.

Background Art

[0002] When driving a device on which a large number of electronic components such as IC chips and transistors are mounted, a lot of heat is generated from the electronic components. At this time, if heat dissipation is not sufficient, the functions of the electronic components deteriorate due to the influence of heat, and the device malfunctions. In order to dissipate heat efficiently, the substrate on which the electronic components are installed is provided with a metal heat dissipation plate having a high thermal conductivity through a heat dissipation sheet having insulation properties.

[0003] Patent Document 1 and Patent Document 2 disclose a heat dissipation sheet having insulation properties and a thermally conductive resin composition constituting the heat dissipation sheet.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the heat dissipation sheets described in Patent Document 1 and Patent Document 2 are excellent in heat dissipation, they are likely to cause dielectric breakdown when a high voltage is applied. Therefore, for example, it is difficult to use such a heat dissipation sheet as a heat dissipation sheet having long-term withstand voltage characteristics used together with a power semiconductor mounted on an electric vehicle. The long-term withstand voltage characteristics refer to characteristics in which dielectric breakdown is unlikely to occur even when a constant voltage is applied for a long time. The evaluation of this characteristic is performed, for example, under the conditions of 150°C, 1 kV, and 10 years.

[0006] This invention has been made in view of the above circumstances, and aims to provide a heat dissipation sheet and a heat sink that are excellent in heat dissipation and long-term withstand voltage characteristics, a thermosetting resin composition constituting them, a method for manufacturing a heat dissipation sheet, and a method for manufacturing a heat sink. [Means for solving the problem]

[0007] The present invention is as follows: [1] The thermosetting resin composition according to the present invention comprises an epoxy resin, a curing agent, an acrylic copolymer having a functional group in its side chain, boron nitride, and a filler, wherein the average particle size (D50) of the boron nitride is 7.0 μm or more and 60 μm or less, the average particle size (D50) of the filler is 0.5 μm or more and 5.0 μm or less, the volume percentage of the boron nitride is 55% or more and 70% or less per 100% by volume of the thermosetting resin composition, and the volume percentage of the filler is 0.3% or more and 2.0% or less per 100% by volume of the thermosetting resin composition.

[0008] Furthermore, [2] the filler may consist of at least one selected from the group consisting of silica, alumina, boron nitride, magnesium oxide, aluminum hydroxide, magnesium hydroxide, zinc oxide, silicon nitride, silicon carbide, gallium nitride, and talc.

[0009] Furthermore, [3] the shape of the filler may be spherical.

[0010] Furthermore, [4] the boron nitride may consist of at least one selected from the group consisting of boron nitride having a flaky shape and aggregated boron nitride in which a plurality of boron nitrides are aggregated.

[0011] Furthermore, [5] the functional group may have at least one functional group selected from the group consisting of carboxyl groups, hydroxyl groups, and epoxy groups.

[0012] Furthermore, [6] the heat dissipation sheet according to the present invention is composed of a resin layer, the resin layer is composed of any one of the thermosetting resin compositions described in [1] to [5].

[0013] Furthermore, [7] the curing state of the resin layer may be a semi-cured state.

[0014] Furthermore, [8] the heat sink according to the present invention comprises a metal plate and a resin layer made of a thermosetting resin composition according to any one of [1] to [5], wherein the resin layer is laminated on at least one surface of the metal plate.

[0015] Furthermore, [9] the curing state of the resin layer may be a semi-cured state.

[0016] Furthermore,

[10] The method for manufacturing a heat dissipation sheet according to the present invention includes a resin composition preparation step of preparing a thermosetting resin composition according to any one of [1] to [5], a coating step of applying the thermosetting resin composition to a film, and a heating step of heating the film to which the thermosetting resin composition has been applied.

[0017] Furthermore,

[11] the method for manufacturing a heat sink according to the present invention includes a resin composition preparation step of preparing a thermosetting resin composition according to any one of [1] to [5], a coating step of applying the thermosetting resin composition to a metal plate, and a heating step of heating the metal plate to which the thermosetting resin composition has been applied. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a heat dissipation sheet and a heat sink that are excellent in heat dissipation and long-term withstand voltage characteristics, a thermosetting resin composition that constitutes them, a method for manufacturing a heat dissipation sheet, and a method for manufacturing a heat sink. [Modes for carrying out the invention]

[0019] Hereinafter, embodiments for implementing the present invention (hereinafter referred to as embodiments) will be described in detail. The following embodiments are examples for explaining the present invention and are not intended to limit the present invention to the following content. The present invention can be appropriately modified and implemented within the scope of its gist.

[0020] [Thermosetting resin composition] The thermosetting resin composition of the embodiment is preferably used mainly as a resin composition constituting a heat dissipation sheet and a heat dissipation plate.

[0021] The thermosetting resin composition of the embodiment contains an epoxy resin, a curing agent, an acrylic copolymer having a functional group in a side chain, boron nitride, and a filler.

[0022] (Epoxy resin) The epoxy resin contained in the thermosetting resin composition of the embodiment preferably has two or more epoxy groups in one molecule and an epoxy equivalent of 100 g / eq or more and 1000 g / eq or less, more preferably 150 g / eq or more and 300 g / eq or less, from the viewpoint of enhancing the long-term withstand voltage characteristics after curing.

[0023] Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, novolac type epoxy resin, amine type epoxy resin, biphenyl type epoxy resin, alicyclic epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, naphthalene ring-containing epoxy resin, dicyclopentadiene type epoxy resin, and the like.

[0024] From the viewpoint of improving the long-term withstand voltage characteristics after curing, polyfunctional epoxy resins such as novolac-type epoxy resins, phenol novolac-type epoxy resins, and cresol novolac-type epoxy resins, alicyclic epoxy resins, and bisphenol A-type epoxy resins are preferred as epoxy resins. It is preferable to use two or more types of epoxy resins. Furthermore, the epoxy resin may be pre-dissolved in an organic solvent to facilitate mixing with other materials contained in the thermosetting resin composition.

[0025] From the viewpoint of improving the long-term withstand voltage characteristics after curing and increasing the thermal conductivity, the epoxy resin content is preferably 14 to 23 parts by weight, and more preferably 14 to 21 parts by weight, per 100 parts by weight of the thermosetting resin composition. Here, the parts by weight used in the embodiment refers to the weight of the resin only, excluding volatile components such as organic solvents contained in the resin.

[0026] (Hardening agent) The curing agent cures the epoxy resin. Examples of curing agents include diaminodiphenylmethane (DDM), diaminodiphenylsulfone (DDS), diaminodiphenyl ether (DDE), hexamethylenediamine, dicyandiamide, and phenol novolac type epoxy resins. From the viewpoint of ease of controlling the curing reaction, dicyandiamide is preferred, and diaminodiphenylsulfone is preferred. In addition, two or more curing agents may be used in combination.

[0027] From the viewpoint of improving the long-term withstand voltage characteristics after curing and enhancing heat resistance, the curing agent content is preferably 5 to 40 parts by weight per 100 parts by weight of epoxy resin.

[0028] The equivalent amount of the curing agent is 0.3 equivalents or more and 0.8 equivalents or less relative to 1 equivalent of epoxy groups contained in the epoxy resin, and is preferably 0.3 equivalents or more and 0.6 equivalents or less from the viewpoint of improving long-term withstand voltage characteristics and heat resistance.

[0029] (Acrylic copolymer having functional groups in its side chains) Examples of acrylic copolymers having functional groups in their side chains include acrylic acid ester copolymers having functional groups in their side chains, and (meth)acrylic acid ester copolymers having functional groups in their side chains.

[0030] Acrylic acid ester copolymers having functional groups in their side chains, and (meth)acrylic acid ester copolymers having functional groups in their side chains, may be composed of a single monomer or of two or more monomers. Examples of monomers constituting these copolymers include acrylic acid ester monomers, carboxyl group-containing monomers, anhydrides of carboxyl group-containing monomers, amide group-containing monomers, aromatic vinyl monomers, cyano group-containing monomers, and the like.

[0031] Examples of acrylic acid ester monomers include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; alkyl acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; hydroxyalkyl acrylates such as hydroxyethyl acrylate; hydroxyalkyl acrylates such as hydroxyethyl (meth)acrylate; N,N-dimethylaminoalkyl acrylates such as N,N-dimethylaminomethyl acrylate; N,N-dimethylaminoalkyl acrylates such as N,N-dimethylaminomethyl meth)acrylate; epoxy group-containing acrylic acid esters such as glycidyl acrylate; and epoxy group-containing (meth)acrylic acid esters such as glycidyl acrylate.

[0032] Examples of carboxyl group-containing monomers include acrylic acid, (meth)acrylic acid, fumaric acid, maleic acid, and maleic anhydride.

[0033] Examples of carboxyl group-containing monomer anhydrides include acrylic acid, (meth)acrylic acid, fumaric acid, maleic acid, and maleic anhydride.

[0034] Examples of monomers containing an amide group include acrylamide.

[0035] Examples of aromatic vinyl monomers include styrene and methylstyrene.

[0036] Examples of cyano group-containing monomers include acrylonitrile.

[0037] The weight-average molecular weight of the acrylic acid ester copolymer having a functional group in its side chain, and the (meth)acrylic acid ester copolymer having a functional group in its side chain, is preferably between 100,000 and 400,000, and more preferably between 150,000 and 300,000, from the viewpoint of processability. Here, the weight-average molecular weight is the molecular weight measured by gel permeation chromatography (GPC) using standard polystyrene with an average molecular weight of approximately 500 to approximately 1,000,000.

[0038] From the viewpoint of improving the long-term withstand voltage characteristics after curing, the content of the acrylic copolymer having functional groups in its side chains is 10 parts by weight or more and 40 parts by weight or less, preferably 10 parts by weight or more and 30 parts by weight or less, per 100 parts by weight of epoxy resin.

[0039] Acrylic copolymers having functional groups in their side chains have at least one functional group selected from the group consisting of carboxyl groups, hydroxyl groups, and epoxy groups. From the viewpoint of improving long-term withstand voltage characteristics after curing, the functional group is preferably a carboxyl group. Acrylic copolymers having functional groups in their side chains may have two or more functional groups.

[0040] When the functional group is, for example, a carboxyl group, the acid value is preferably 3 KOH mg / g to 20 KOH mg / g, and more preferably 10 KOH mg / g to 20 KOH mg / g, from the viewpoint of improving the long-term withstand voltage characteristics after curing. The acid value was measured by titration with a 0.1 N potassium hydroxide aqueous solution.

[0041] Examples of commercially available acrylic copolymers having functional groups in their side chains include Knoxtite (manufactured by Nippon Oilseal Co., Ltd.), Nipol (registered trademark, manufactured by Nippon Zeon Co., Ltd.), Vamac (registered trademark, manufactured by DuPont), Leocote (manufactured by Toray Coatex Co., Ltd.), and Paracron (registered trademark, manufactured by Shin Nakamura Chemical Co., Ltd.).

[0042] (Boron nitride) The average particle size (D50) of boron nitride (BN) is 7.0 μm or more and 60 μm or less. For boron nitride with a flaky shape, the average particle size (D50) is preferably 7.0 μm or more and 15 μm or less from the viewpoint of good dispersibility. For aggregated boron nitride, the average particle size (D50) is preferably 10 μm or more and 40 μm or less from the viewpoint of good dispersibility.

[0043] Here, the average particle diameter (D50) refers to the particle diameter at which the sum of the smallest and largest particles in a volume-based particle size distribution reaches 50% of the total volume. The particle diameter is measured by dynamic light scattering. The average particle diameter (D50) is also called the median diameter.

[0044] From the viewpoint of increasing thermal conductivity and maintaining a high dielectric breakdown voltage, the volume percentage of boron nitride is preferably 55% to 70% and more, and more preferably 55% to 65% per 100% volume of the thermosetting resin composition.

[0045] From the viewpoint of increasing thermal conductivity and maintaining a high dielectric breakdown voltage, the boron nitride is preferably composed of at least one type selected from the group consisting of boron nitride having a flaky shape and aggregated boron nitride in which multiple boron nitrides are aggregated. From the viewpoint of having excellent thermal conductivity, aggregated boron nitride is preferred. The boron nitride may be composed of two or more types of boron nitride.

[0046] (Filler) From the viewpoint of maintaining a high dielectric breakdown voltage, the average particle size (D50) of the filler is preferably 0.5 μm to 5.0 μm, and more preferably 0.5 μm to 3.0 μm.

[0047] From the viewpoint of maintaining a high dielectric breakdown voltage, the volume percentage of the filler is preferably 0.3% to 2.0% per 100% volume of the thermosetting resin composition, and more preferably 0.5% to 1.5% per 1.5% volume.

[0048] The filler is insulating and consists of at least one selected from the group consisting of silica, alumina, boron nitride, magnesium oxide, aluminum hydroxide, magnesium hydroxide, zinc oxide, silicon nitride, silicon carbide, gallium nitride, and talc. From the viewpoint of improving the long-term withstand voltage characteristics after curing, silica with a low dielectric constant is preferred as the filler. The filler may consist of two or more types of fillers.

[0049] The filler has a spherical shape. This suppresses the concentration of the electric field on the filler when a voltage is applied to the thermosetting resin composition after curing, making the thermosetting resin composition less susceptible to dielectric breakdown after curing.

[0050] (Other ingredients) The thermosetting resin composition of the embodiment may further contain other additives. Other additives include 2-methylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, and N-benzyl-2-methylimidazole.Ru etc. Examples include imidazole-based curing accelerators; Lewis acid complex-based curing accelerators such as boron trifluoride monoethylamine and boron trifluoride diethylamine; curing accelerators, dispersants, softeners, heat aging inhibitors, and silane coupling agents for polyamines, melamine resins, etc.

[0051] As described above, the thermosetting resin composition of the embodiment is obtained by mixing the materials described above. An organic solvent may be added when preparing the thermosetting resin composition of the embodiment. Next, a heat dissipation sheet made from the thermosetting resin composition of the embodiment will be described.

[0052] [Heat dissipation sheet] The heat dissipation sheet of the embodiment is composed of a resin layer. The resin layer is composed of the thermosetting resin composition of the embodiment.

[0053] The thickness of the heat dissipation sheet in the embodiment is 100 μm or more and 500 μm or less.

[0054] The heat dissipation sheet of the embodiment is manufactured, for example, by the following procedure. A thermosetting resin composition is prepared by adding predetermined amounts of epoxy resin, a curing agent, an acrylic copolymer having functional groups in its side chains, boron nitride, a filler, and an organic solvent to a container (resin composition preparation step). The thermosetting resin composition is applied to a film using a coating device (coating step). Next, the film coated with the thermosetting resin composition is heated to cure the thermosetting resin composition to a semi-cured state (heating step). After cooling, a heat dissipation sheet is obtained in which a resin layer composed of the thermosetting resin composition is formed on the film. The heating conditions are 100°C to 250°C and 5 seconds to 30 minutes. The heating conditions may be adjusted according to the thickness of the applied thermosetting resin composition. The obtained heat dissipation sheet is used by peeling off the film when in use. Here, the semi-cured state refers to the state in which the curing reaction of the thermosetting resin composition has progressed partway. The semi-cured state is also called the B stage.

[0055] The thickness of the film used when manufacturing the heat dissipation sheet of the embodiment is 25 μm to 100 μm. The film thickness is determined according to the thickness of the resin layer. Examples of film materials include polyethylene, polypropylene, polyimide, polyamide, polyethylene naphthalate, polyethylene terephthalate, etc.

[0056] From the viewpoint of making the film easier to peel off, a release treatment may be applied to the surface of the film. Examples of release agents include silicone-based agents and fluorine-based agents.

[0057] From the viewpoint of improving rigidity and electrical insulation reliability, the heat dissipation sheet may have a structure in which resin layers are provided on both sides of the film. Examples of materials for this film include polyimide, polyamide, polyethylene naphthalate, and the like.

[0058] Furthermore, from the viewpoint of increasing rigidity, the heat dissipation sheet may be a prepreg in which a thermosetting resin composition of the embodiment is impregnated into a base material such as a woven fabric or nonwoven fabric. Here, a prepreg refers to a composite material in which a resin composition is impregnated into a base material such as a woven fabric or nonwoven fabric. The curing state of the resin composition is stage B.

[0059] A prepreg is prepared, for example, by the following procedure: A nonwoven fabric made of glass fibers, or a woven fabric made of glass threads, and a thermosetting resin composition are prepared. The nonwoven fabric or woven fabric is impregnated with the thermosetting resin composition. The nonwoven fabric or woven fabric impregnated with the thermosetting resin composition is then heated until the thermosetting resin composition reaches the B stage of curing. After that, it is cooled to obtain a prepreg.

[0060] The heat dissipation sheet made from the thermosetting resin composition of the embodiment has been described above. Next, a heat dissipation plate using the thermosetting resin composition of the embodiment will be described.

[0061] [Heat sink] The heat sink of the embodiment comprises a metal plate and a resin layer made of the thermosetting resin composition of the embodiment. The resin layer is laminated on at least one surface of the metal plate.

[0062] From the viewpoint of maintaining the heat dissipation performance of the heat sink and maintaining insulation between the metal plate constituting the heat sink and the substrate, the thickness of the resin layer is preferably 60 μm to 400 μm, and more preferably 120 μm to 200 μm.

[0063] From the viewpoint of efficiently dissipating heat generated from the electronic components mounted on the device, the metal plate is preferably made of a metal with high thermal conductivity. Examples of metals with high thermal conductivity include copper, aluminum, and stainless steel. Among these, copper and aluminum are preferred because they have excellent workability and high thermal conductivity.

[0064] From the viewpoint of processability, the thickness of the metal sheet is 9 μm to 500 μm, and preferably 12 μm to 120 μm.

[0065] A heat sink may be used instead of a metal plate. The heat sink has multiple fins mounted on one side of a base plate. The base plate is made of a metal plate. The thickness of the base plate is 0.3 mm to 50 mm. The fins are made of plates or rods. The height of the fins is 1 mm to 100 mm. The thickness of plate-shaped fins is 0.2 mm to 9 mm, which is thinner than the base plate. Also, the size of plate-shaped fins is smaller than the base plate. For rod-shaped fins, the cross-sectional shape in the direction perpendicular to the longitudinal direction of the fin is, for example, a square or a circle.

[0066] In a heat sink equipped with a resin layer, the resin layer is laminated on the side opposite to the side on which the fins are provided. The heat sink may have the entire surface of the fins covered with the thermosetting resin composition of the embodiment, or only a portion of the surface of the fins may be covered with the thermosetting resin composition of the embodiment.

[0067] The heat sink of the embodiment is manufactured, for example, by the following procedure. A copper foil is prepared as a metal plate. Next, predetermined amounts of epoxy resin, a curing agent, an acrylic copolymer having functional groups in its side chains, boron nitride, a filler, and an organic solvent are added to a container to prepare a thermosetting resin composition (resin composition preparation step). The thermosetting resin composition is applied to the prepared copper foil using a coating device (coating step). Next, the copper foil coated with the thermosetting resin composition is heated until the curing state of the thermosetting resin composition reaches stage B (heating step). After cooling, a heat sink is obtained in which a resin layer made of the thermosetting resin composition is formed on one side of the copper foil. The heating conditions are 100°C to 250°C and 5 seconds to 30 minutes. The heating conditions can be adjusted depending on the thickness of the applied resin composition.

[0068] Examples of organic solvents used when manufacturing the heat dissipation sheet and heat sink of the embodiment include alcohols such as methanol and ethanol; glycols such as ethylene glycol and propylene glycol; glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; glycol dialkyl ethers such as ethylene glycol dimethyl ether and ethylene glycol diethyl ether; alkyl esters such as methyl acetate, ethyl acetate, propyl acetate, and methyl acetoacetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; aliphatic hydrocarbons such as hexane, cyclohexane, and octane; amides such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; and cyclic ethers such as tetrahydrofuran and dioxane.

[0069] A known coater can be used as the coating apparatus when manufacturing the heat dissipation sheet and the heat dissipation plate of the embodiment. Examples of coaters include die coaters and comma coaters. The heat sink using the thermosetting resin composition of the embodiment has been described above. [Examples]

[0070] The present invention will be further described in detail by the following examples. The present invention is not limited in any way by the following examples.

[0071] The following components were used as the resin compositions in the examples and comparative examples. (Epoxy resin) (1) JER152: Polyfunctional epoxy resin, epoxy equivalent 177 g / eq, manufactured by Mitsubishi Chemical Corporation. (2) JER828: Bisphenol A type epoxy resin, epoxy equivalent 190 g / eq, manufactured by Mitsubishi Chemical Corporation.

[0072] (Hardening agent) Seika Cure S: Diaminodiphenylsulfone, amine value 62g / eq, manufactured by Wakayama Seika Co., Ltd.

[0073] (Curing accelerator) BF3-MEA: Boron trifluoride monoethylamine, manufactured by Stella Chemifa.

[0074] (Acrylic copolymer having functional groups in its side chains) (1) 1HY-2002M: Acrylic copolymer having carboxyl groups in the side chain, weight-average molecular weight approximately 280,000, acid value 20KOH mg / g, manufactured by Taisei Fine Chemical Co., Ltd. (2) SG-600TEA: Acrylic copolymer having hydroxyl groups in the side chain, weight-average molecular weight approximately 1.2 million, hydroxyl value 5KOH mg / g, manufactured by Nagase ChemteX Corporation. (3) SG-P3: Acrylic copolymer with epoxy groups in the side chains, weight-average molecular weight approximately 1.2 million, epoxy value 0.21 eq / kg, manufactured by Nagase ChemteX Corporation.

[0075] (Boron nitride) (1) DF-10N: Aggregated boron nitride, average particle size (D50) 15 μm, manufactured by Tokuyama Corporation. (2) HP-40MF100: Aggregated boron nitride, average particle size (D50) 40 μm, manufactured by Mizushima Iron Alloy Co., Ltd. (3) S-03: Boron nitride with a flaky shape, average particle size (D50) 7 μm, manufactured by Tokuyama Corporation.

[0076] (Filler) (1) S0-C2: Spherical silica, average particle size (D50) 0.5 μm, manufactured by Admatex Corporation. (2) YC100C-LHH: Spherical silica, average particle size (D50) 0.1 μm, manufactured by Admatex Co., Ltd. (3) S0-C5: Spherical silica, average particle size (D50) 1.5 μm, manufactured by Admatex Co., Ltd. (4) FB-3SDC: Spherical silica, average particle size (D50) 3.0 μm, manufactured by Denka Co., Ltd. (5) FB-7SDC: Spherical silica, average particle size (D50) 5.0 μm, manufactured by Denka Co., Ltd. (6) FB-105FD: Spherical silica, average particle size (D50) 11.0 μm, manufactured by Denka Co., Ltd. (7) AO-502: Spherical alumina, average particle size (D50) 0.2 μm, manufactured by Admatex Co., Ltd. (8) Nano BN: Spherical boron nitride, average particle size (D50) 0.5 μm, manufactured by Denka Co., Ltd.

[0077] In the examples and comparative examples, each evaluation method and measurement method was carried out by the following methods.

[0078] <Long-term withstand voltage characteristics> (1) Sample preparation procedure (1-1) Fabrication of a heat dissipation sheet A thermosetting resin composition, which will form the resin layer, was applied to the release-treated surface of a 50 μm thick release PET (polyethylene terephthalate) film (manufactured by Unitika, TR) to a thickness of 180 μm after drying. Next, the thermosetting resin composition was heated at 120°C for 10 minutes until it reached a semi-cured state (Stage B). After cooling, a heat dissipation sheet was obtained.

[0079] (1-2) Preparation of samples for measurement The release PET film was peeled off the heat dissipation sheet prepared in (1-1), and the heat dissipation sheet was laminated between a 35 μm thick rolled copper foil (manufactured by JX Nippon Oil & Metals, BHY) and a 1 mm thick aluminum plate (manufactured by Showa Denko, A1100). The sheet was then heated and pressurized at 185°C, 10 MPa, and 180 minutes. After that, it was heated in a 160°C oven for 5 hours and cooled to room temperature. Next, the rolled copper foil was etched into a circular shape with a diameter of 20 mm, washed with water, and dried to obtain a sample for measurement. The rolled copper foil was laminated onto the heat dissipation sheet so that the rough surface of the rolled copper foil was in contact with the heat dissipation sheet.

[0080] (2)Measurement method The measurement samples prepared in (1-2) were immersed in oil at 150°C, and a DC 10kV voltage was applied between the aluminum plate and the rolled copper foil. The time from application of the voltage until dielectric breakdown occurred was measured. Four tests were performed for each sample, and the shortest time was defined as the insulation retention time.

[0081] The evaluation criteria were as follows: Excellent: Insulation retention time is 100 hours or more. Good: Insulation retention time is 50 hours or more, but less than 100 hours. Poor: Insulation retention time is less than 50 hours. The measurement samples that were able to maintain insulation for more than 100 hours under the above test conditions possess long-term withstand voltage characteristics sufficient to maintain insulation under conditions of 150°C, 1kV, and 10 years.

[0082] <Thermal conductivity> (1) Sample preparation procedure (1-1) Fabrication of a heat dissipation sheet A thermosetting resin composition was applied to the release surface of a 50 μm thick release PET (polyethylene terephthalate) film (manufactured by Unitika, TR) so that the thickness after drying was 180 μm. Next, the thermosetting resin composition was heated at 120°C for 10 minutes until it reached a semi-cured state (Stage B). After cooling, a heat dissipation sheet composed of the resin layer was obtained. A total of two heat dissipation sheets were prepared using the same method.

[0083] (1-2) Preparation of samples for measurement The two heat dissipation sheets prepared in (1-1) were laminated so that their resin layers were in contact with each other, and then heated and pressurized at 185°C, 10 MPa, and for 180 minutes. After that, the release PET film was peeled off to obtain a sample for measurement.

[0084] (2)Measurement method The thermal conductivity was calculated by measuring the thermal diffusivity (α), specific heat (Cp), and density (ρ) of the sample and substituting them into the following formula. Thermal conductivity [W / (m·K)]=α[mm 2 / s] × Cp[J / kg·K] × ρ[g / cm 3 ] α[mm 2 / s]: Thermal diffusion coefficient Cp[J / g·K]: Specific heat ρ[g / cm 3 ]:density

[0085] (2-1) Measurement of thermal diffusivity (α) The thermal diffusivity (α) was determined using the laser flash method. One side of the sample was heated by irradiating it with pulsed light, and the temperature change on the other side was measured. The measurements were performed using a NETZSCH LFA447 under conditions of 25°C. The half-time method was used for analysis.

[0086] (2-2) Measurement of specific heat (Cp) The specific heat Cp (J / g·K) was measured using differential scanning calorimetry (DSC). Specific heat measurements were performed using a TA Instruments Q200 device under conditions of a heating rate of 10°C / min and a temperature range of -30°C to 50°C. Based on the data obtained from the measurements, the specific heat was calculated according to the method specified in JIS K7123.

[0087] (2-3) Measurement of density (ρ) The density (ρ) was measured using the immersion method with a Shimadzu AUX220, SMK-401.

[0088] The evaluation criteria were as follows: Good: 6W / (m·K) or higher. Poor: Less than 6W / (m·K).

[0089] <Dielectric Breakdown Voltage> (1) Sample for measurement The measurement samples used were those prepared using the <long-term withstand voltage characteristics> method.

[0090] (2) Evaluation method The test sample was immersed in oil at 25°C, and the voltage was increased at intervals of 1kV / 0.5sec. The voltage at which dielectric breakdown occurred was measured. The test was performed five times, and the average value was calculated. The evaluation criteria were as follows: Good: Voltage 9kV or higher, Poor: Voltage is less than 9kV.

[0091] (Example 1) 90 parts by weight of JER152 and 10 parts by weight of JER828 were added to a container to make a total of 100 parts by weight of epoxy resin. To this, 26.85 parts by weight of Seika Cure S, 0.3 parts by weight of BF3-MEA, 15 parts by weight of 1HY-2002M, 338.0 parts by weight of DF-10N (55% by volume relative to 100% by volume of the thermosetting resin composition), 1.8 parts by weight of S0-C2 (0.4% by weight relative to 100% by weight of the thermosetting resin composition), and 200 parts by weight of methyl ethyl ketone as an organic solvent were added. These were then stirred at room temperature to obtain a thermosetting resin composition.

[0092] (Examples 2) to (Examples 21), (Comparative Example 1) to (Comparative Example 18) As shown in Tables 1 to 6, thermosetting resin compositions were obtained by preparing them in the same manner as in Example 1, but with variations in the type and content of each component. Unless otherwise specified, the units of content in the tables are "parts by weight".

[0093] Table 1 shows the evaluation results of the long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage of the heat dissipation sheet when the volume percentage (vol%) of the filler in the thermosetting resin composition is varied. As shown in Examples 1 to 5, the long-term withstand voltage characteristics showed good results when the volume percentage (vol%) of the filler was between 0.3 vol% and 2.0 vol%. In addition, the thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0094] [Table 1]

[0095] Table 2 shows the evaluation results of the long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage of the heat dissipation sheet when the type of boron nitride and the amount of filler are varied. As shown in Examples 6 to 8, the long-term withstand voltage characteristics showed good results regardless of the type of boron nitride, due to the inclusion of filler in the thermosetting resin composition. In addition, the thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0096] [Table 2]

[0097] Tables 3A and 3B show the evaluation results of the long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage of the heat dissipation sheet when the amount of boron nitride and filler are varied. As shown in Examples 9 to 11, the long-term withstand voltage characteristics were good when the volume percentage (vol%) of boron nitride was 55 vol% to 70 vol% and the thermosetting resin composition contained filler. In addition, the thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0098] [Table 3A]

[0099] [Table 3B]

[0100] Table 4 shows the evaluation results for the long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage of the heat dissipation sheet when the filler shape is spherical. As shown in Examples 12 and 13, the long-term withstand voltage characteristics showed good results due to the inclusion of spherical fillers in the thermosetting resin composition. In addition, the thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0101] [Table 4]

[0102] Table 5 shows the evaluation results of the long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage of the heat dissipation sheet when the average particle size (D50) of the filler is changed. As shown in Examples 14 to 17, the long-term withstand voltage characteristics showed good evaluation results when the average particle size (D50) of the filler contained in the thermosetting resin composition was between 0.5 μm and 5.0 μm. In addition, the thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0103] [Table 5]

[0104] Table 6 shows the evaluation results of the long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage of the heat dissipation sheet, differing depending on the presence or absence of epoxy resin, the presence or absence of curing accelerator, and the functional groups of the acrylic copolymer. Table 6 also shows the evaluation results of the long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage of the heat dissipation sheet when nano-BN (boron nitride) is used as the filler.

[0105] As shown in Example 18, the long-term withstand voltage characteristics showed good evaluation results regardless of the presence or absence of a curing accelerator. Furthermore, the thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0106] Furthermore, as shown in Examples 19 to 21, when the functional group of the side chain of the acrylic copolymer was a carboxyl group, a hydroxyl group, or an epoxy group, the long-term withstand voltage characteristics showed good evaluation results. In addition, the thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0107] Furthermore, as shown in Example 19, using nano-BN (boron nitride) as a filler also yielded good evaluation results for long-term withstand voltage characteristics. Thermal conductivity and dielectric breakdown voltage also showed good evaluation results.

[0108] Furthermore, comparing Example 1 with Comparative Example 18 in Table 1, for example, the inclusion of epoxy resin in the thermosetting resin composition resulted in favorable evaluation results for the long-term withstand voltage characteristics and thermal conductivity of Example 1. The dielectric breakdown voltage also showed favorable evaluation results.

[0109] [Table 6]

[0110] As shown in Tables 1 to 6, the heat dissipation sheets of Examples 1 to 21 exhibited excellent long-term withstand voltage characteristics, thermal conductivity, and dielectric breakdown voltage.

[0111] Based on the above results, the heat dissipation sheets and heat dissipation plates made from the thermosetting resin compositions of the embodiments exhibit excellent heat dissipation and long-term withstand voltage characteristics.

[0112] This invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent meaning of the invention are considered to be within the scope of this invention.

[0113] This application is based on Japanese Patent Application No. 2021-171904, filed on 20 October 2021. The entire specification, claims, and drawings of Japanese Patent Application No. 2021-171904 are incorporated herein by reference.

Claims

1. A thermosetting resin composition comprising an epoxy resin, a curing agent, an acrylic copolymer having functional groups in its side chains, boron nitride, and a filler, The average particle size (D50) of the boron nitride is 7.0 μm or more and 60 μm or less. The average particle size (D50) of the filler is 0.5 μm or more and 5.0 μm or less. The volume percentage of the boron nitride is 55% to 70% by volume relative to 100% by volume of the thermosetting resin composition. A thermosetting resin composition in which the volume percentage of the filler is 0.3% by volume or more and 2.0% by volume or less based on 100% by volume of the thermosetting resin composition.

2. The thermosetting resin composition according to claim 1, wherein the filler is composed of at least one selected from the group consisting of silica, alumina, boron nitride, magnesium oxide, aluminum hydroxide, magnesium hydroxide, zinc oxide, silicon nitride, silicon carbide, gallium nitride, and talc.

3. The thermosetting resin composition according to claim 1, wherein the shape of the filler is spherical.

4. The thermosetting resin composition according to claim 1, wherein the boron nitride is composed of at least one selected from the group consisting of boron nitride having a flaky shape and aggregated boron nitride in which a plurality of boron nitrides are aggregated.

5. The thermosetting resin composition according to claim 1, wherein the functional group has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, and an epoxy group.

6. A heat dissipation sheet comprising a resin layer, wherein the resin layer is composed of a thermosetting resin composition according to any one of claims 1 to 5.

7. The heat dissipation sheet according to claim 6, wherein the cured state of the resin layer is a semi-cured state.

8. A heat sink comprising a metal plate and a resin layer made of a thermosetting resin composition according to any one of claims 1 to 5, wherein the resin layer is laminated on at least one surface of the metal plate.

9. The heat sink according to claim 8, wherein the curing state of the resin layer is a semi-cured state.

10. A resin composition preparation step for preparing a thermosetting resin composition according to any one of claims 1 to 5, A coating step of applying the thermosetting resin composition to the film, A method for manufacturing a heat dissipation sheet, comprising a heating step of heating the film to which the thermosetting resin composition has been applied.

11. A resin composition preparation step for preparing a thermosetting resin composition according to any one of claims 1 to 5, A coating step of applying the thermosetting resin composition to a metal plate, A method for manufacturing a heat sink, comprising a heating step of heating the metal plate to which the thermosetting resin composition has been applied.

Images