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

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

[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.

[0002] When a device equipped with many electronic components such as IC chips and transistors is operated, the components generate a large amount of heat. If the heat is not dissipated sufficiently, the performance of the electronic components will be impaired due to the heat, causing the device to malfunction. To efficiently dissipate the heat, the circuit board on which the electronic components are mounted is equipped with a metal heat sink with high thermal conductivity, sandwiched between an insulating heat dissipation sheet.

[0003] Patent Documents 1 and 2 disclose a heat-dissipating sheet having insulating properties and a thermally conductive resin composition that constitutes this heat-dissipating sheet.

[0004] JP 2017-25186 A JP 2014-193965 A

[0005] The heat dissipation sheets described in Patent Documents 1 and 2 have excellent heat dissipation properties, but are prone to dielectric breakdown when high voltages are applied. For this reason, it is difficult to use such heat dissipation sheets as heat dissipation sheets with long-term voltage resistance characteristics for use with power semiconductors installed in electric vehicles, for example. Long-term voltage resistance characteristics refer to the ability to resist dielectric breakdown even when a constant voltage is applied for a long period of time. This characteristic is evaluated, for example, under conditions of 150°C, 1 kV, and 10 years.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a heat dissipation sheet and a heat dissipation plate having excellent heat dissipation properties and long-term voltage resistance characteristics, a thermosetting resin composition constituting them, a method for manufacturing a heat dissipation sheet, and a method for manufacturing a heat dissipation plate.

[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 a 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 fraction of the boron nitride is 55 vol% or more and 70 vol% or less relative to 100 vol% of the thermosetting resin composition, and the volume fraction of the filler is 0.3 vol% or more and 2.0 vol% or less relative to 100 vol% of the thermosetting resin composition.

[0008] [2] The filler may be 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.

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

[0010] [4] The boron nitride may be composed of at least one type selected from the group consisting of boron nitride having a scale shape and agglomerated boron nitride in which a plurality of boron nitrides are aggregated.

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

[0012] [6] The heat dissipation sheet according to the present invention is composed of a resin layer, and the resin layer is composed of the thermosetting resin composition according to any one of [1] to [5].

[0013] [7] The resin layer may be in a semi-cured state.

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

[0015] [9] The cured state of the resin layer may be semi-cured.

[0016]

[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], an application 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]

[11] A 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], an application 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.

[0018] According to the present invention, it is possible to provide a heat dissipation sheet and a heat dissipation plate having excellent heat dissipation properties and long-term voltage resistance characteristics, a thermosetting resin composition constituting these, a method for manufacturing a heat dissipation sheet, and a method for manufacturing a heat dissipation plate.

[0019] Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail. The following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it 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 includes an epoxy resin, a curing agent, an acrylic copolymer having a functional group on a side chain, boron nitride, and a filler.

[0022] (Epoxy Resin) From the viewpoint of improving long-term voltage resistance characteristics after curing, the epoxy resin contained in the thermosetting resin composition of the embodiment preferably has two or more epoxy groups in one molecule and has 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.

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

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

[0025] From the viewpoint of improving the long-term voltage resistance characteristics after curing and increasing the thermal conductivity, the content of the epoxy resin is preferably 14 parts by weight or more and 23 parts by weight or less, and more preferably 14 parts by weight or more and 21 parts by weight or less, relative to 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] (Curing Agent) The curing agent cures the epoxy resin. Examples of the curing agent include diaminodiphenylmethane (DDM), diaminodiphenylsulfone (DDS), diaminodiphenylether (DDE), hexamethylenediamine, dicyandiamide, and phenol novolac epoxy resin. From the viewpoint of ease of control of the curing reaction, the curing agent is preferably dicyandiamide or diaminodiphenylsulfone. Furthermore, two or more types of curing agents may be used in combination.

[0027] The content of the curing agent is preferably 5 parts by weight or more and 40 parts by weight or less per 100 parts by weight of the epoxy resin, from the viewpoint of improving the long-term voltage resistance characteristics after curing and improving the heat resistance.

[0028] The equivalent weight of the curing agent is 0.3 equivalents or more and 0.8 equivalents or less relative to 1 equivalent of the epoxy group contained in the epoxy resin, and from the viewpoints of improving the long-term voltage resistance characteristic and improving the heat resistance, it is preferably 0.3 equivalents or more and 0.6 equivalents or less.

[0029] (Acrylic Copolymer Having a Functional Group in the Side Chain) Examples of the acrylic copolymer having a functional group in the side chain include an acrylic acid ester copolymer having a functional group in the side chain and a (meth)acrylic acid ester copolymer having a functional group in the side chain.

[0030] The acrylic acid ester copolymer having a functional group in the side chain and the (meth)acrylic acid ester copolymer having a functional group in the side chain may be composed of a single monomer or two or more monomers. Examples of the 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, and cyano group-containing monomers.

[0031] Examples of the acrylic acid ester monomer include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; alkyl (meth)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 (meth)acrylates such as hydroxyethyl (meth)acrylate; N,N-dimethylaminoalkyl acrylates such as N,N-dimethylaminomethyl acrylate; N,N-dimethylaminoalkyl (meth)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 (meth)acrylate.

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

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

[0034] An example of the amide group-containing monomer is acrylamide.

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

[0036] An example of the cyano group-containing monomer is acrylonitrile.

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

[0038] The content of the acrylic copolymer having a functional group in the side chain is 10 parts by weight or more and 40 parts by weight or less, and preferably 10 parts by weight or more and 30 parts by weight or less, relative to 100 parts by weight of the epoxy resin, from the viewpoint of improving the long-term voltage resistance characteristics after curing.

[0039] The acrylic copolymer having a functional group in a side chain has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, and an epoxy group. The functional group is preferably a carboxyl group from the viewpoint of improving long-term voltage resistance characteristics after curing. The acrylic copolymer having a functional group in a side chain may have two or more functional groups.

[0040] When the functional group is, for example, a carboxyl group, the acid value is 3 KOHmg / g or more and 20 KOHmg / g or less, and preferably 10 KOHmg / g or more and 20 KOHmg / g or less, from the viewpoint of improving the long-term voltage resistance characteristics after curing. The acid value is measured by titration using 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 Oil Seal Co., Ltd.), Nipol (registered trademark, manufactured by Zeon Corporation), Vamac (registered trademark, manufactured by DuPont), Leocoat (manufactured by Toray Coatex Co., Ltd.), and Parachron (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. The average particle size (D50) of scaly boron nitride is preferably 7.0 μm or more and 15 μm or less from the viewpoint of improving dispersibility. The average particle size (D50) of agglomerated boron nitride is preferably 10 μm or more and 40 μm or less from the viewpoint of improving dispersibility.

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

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

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

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

[0047] From the viewpoint of maintaining a high breakdown voltage, the volume ratio of the filler is preferably 0.3 vol% or more and 2.0 vol% or less, and more preferably 0.5 vol% or more and 1.5 vol% or less, relative to 100 vol% of the thermosetting resin composition.

[0048] The filler has insulating properties and 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. From the viewpoint of improving the long-term voltage resistance characteristics after curing, the filler is preferably silica, which has a low dielectric constant. The filler may be composed of two or more fillers.

[0049] The filler has a spherical shape, which prevents the electric field from concentrating on the filler when a voltage is applied to the cured thermosetting resin composition, making the cured thermosetting resin composition less susceptible to dielectric breakdown.

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

[0051] As described above, the thermosetting resin composition of the embodiment can be obtained by mixing the above-mentioned materials. 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, which is composed of the thermosetting resin composition of the embodiment.

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

[0054] The heat dissipation sheet of the embodiment is produced, for example, by the following procedure. A thermosetting resin composition is prepared by adding predetermined amounts of an 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 an application device (application step). The film coated with the thermosetting resin composition is then 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 depending on the thickness of the applied thermosetting resin composition. The film is peeled off from the obtained heat dissipation sheet when in use. Here, the semi-cured state refers to a state in which the curing reaction of the thermosetting resin composition has progressed partially. The semi-cured state is also referred to as the B-stage.

[0055] The thickness of the film used to prepare the heat dissipation sheet of the embodiment is 25 μm or more and 100 μm or less. The thickness of the film is determined depending on the thickness of the resin layer. Examples of the material for the film include polyethylene, polypropylene, polyimide, polyamide, polyethylene naphthalate, and polyethylene terephthalate.

[0056] To facilitate peeling of the film, the surface of the film may be subjected to a release treatment, such as a silicone-based treatment or a fluorine-based treatment.

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

[0058] In order to enhance rigidity, the heat dissipation sheet may be a prepreg in which a substrate such as a woven fabric or a nonwoven fabric is impregnated with the thermosetting resin composition of the embodiment. Here, the prepreg refers to a composite material in which a substrate such as a woven fabric or a nonwoven fabric is impregnated with the resin composition. The cured state of the resin composition is in the B-stage.

[0059] A prepreg is produced, for example, by the following procedure: A nonwoven fabric made of glass fibers or a woven fabric made by weaving glass yarns 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 a B-stage cured state. The prepreg is then cooled to obtain a prepreg.

[0060] The heat dissipation sheet made of 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 Dissipation Plate] The heat dissipation plate of the embodiment includes 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] The thickness of the resin layer is from 60 μm to 400 μm, preferably from 120 μm to 200 μm, from the viewpoint of maintaining the heat dissipation properties of the heat sink and maintaining insulation between the metal plate constituting the heat sink and the substrate.

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

[0064] From the viewpoint of workability, the thickness of the metal plate is 9 μm or more and 500 μm or less, and preferably 12 μm or more and 120 μm or less.

[0065] A heat sink may be used instead of the metal plate. The heat sink has a plurality of fins attached to one surface of a base plate. The base plate is made of a metal plate. The thickness of the base plate is 0.3 mm or more and 50 mm or less. The fins are made of plates or rods. The height of the fins is 1 mm or more and 100 mm or less. The thickness of the plate-shaped fins is 0.2 mm or more and 9 mm or less, which is thinner than the base plate. The size of the plate-shaped fins is also smaller than the base plate. The cross-sectional shape of the rod-shaped fins in a direction perpendicular to the longitudinal direction of the fins is, for example, square or circular.

[0066] The heat sink having a resin layer has a resin layer laminated on the surface opposite to the surface on which the fins are provided. Note that the entire surface of the fins of the heat sink may be 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 fabricated, for example, by the following procedure. Copper foil is prepared as a metal plate. Next, a predetermined amount 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 an application device (application step). Next, the copper foil coated with the thermosetting resin composition is heated until the thermosetting resin composition reaches a B-stage cured state (heating step). After cooling, a heat sink is obtained in which a resin layer composed 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 producing the heat dissipation sheets and heat dissipation plates of the embodiments 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] The coating device used to produce the heat dissipation sheet and heat dissipation plate of the embodiment can be a known coater. Examples of coaters include a die coater and a comma coater. The heat dissipation plate using the thermosetting resin composition of the embodiment has been described above.

[0070] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples in any way.

[0071] The following were used as components contained in the resin compositions in the examples and comparative examples: (Epoxy Resins) (1) JER152: Multifunctional 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] (Curing agent) Seikacure S: diaminodiphenylsulfone, amine value 62 g / eq, manufactured by Wakayama Seika Co., Ltd.

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

[0074] (Acrylic copolymers having functional groups on the side chains) (1) 1HY-2002M: acrylic copolymer having carboxyl groups on the side chains, weight average molecular weight of about 280,000, acid value of 20 KOH mg / g, manufactured by Taisei Fine Chemical Co., Ltd. (2) SG-600TEA: acrylic copolymer having hydroxyl groups on the side chains, weight average molecular weight of about 1,200,000, hydroxyl value of 5 KOH mg / g, manufactured by Nagase ChemteX Corporation (3) SG-P3: acrylic copolymer having epoxy groups on the side chains, weight average molecular weight of about 1,200,000, epoxy value of 0.21 eq / kg, manufactured by Nagase ChemteX Corporation.

[0075] (Boron nitride) (1) DF-10N: agglomerated boron nitride, average particle size (D50) 15 μm, manufactured by Tokuyama Corporation; (2) HP-40MF100: agglomerated boron nitride, average particle size (D50) 40 μm, manufactured by Mizushima Ferroalloy Co., Ltd.; (3) S-03: boron nitride having a scale 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 Admatechs Co., Ltd. (2) YC100C-LHH: spherical silica, average particle size (D50) 0.1 μm, manufactured by Admatechs Co., Ltd. (3) S0-C5: spherical silica, average particle size (D50) 1.5 μm, manufactured by Admatechs 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 Admatechs 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, the evaluation and measurement methods were as follows.

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

[0079] (1-2) Preparation of Measurement Sample The release PET film was peeled off from 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 Mining & Metals Corporation, BHY) and a 1 mm thick aluminum plate (manufactured by Showa Denko K.K., A1100), and heated and pressed at 185 ° C, 10 MPa, and 180 minutes. It was then heated in an oven at 160 ° C 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 measurement sample. The rolled copper foil was laminated on 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 sample prepared in (1-2) was immersed in oil at 150°C, and a DC voltage of 10 kV was applied between the aluminum plate and the rolled copper foil, and the time from application to dielectric breakdown was measured. The test was performed four times for each sample, and the shortest time was taken as the insulation retention time.

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

[0082] <Thermal Conductivity> (1) Sample Preparation Procedure (1-1) Preparation of Heat Dissipation Sheet A thermosetting resin composition was applied to the release-treated surface of a 50 μm-thick release PET (polyethylene terephthalate) film (TR, manufactured by Unitika Ltd.) so that the thickness after drying would be 180 μm. Next, the thermosetting resin composition was heated at 120°C for 10 minutes until it reached a semi-cured state (B stage). After cooling, a heat dissipation sheet composed of a resin layer was obtained. A total of two heat dissipation sheets were prepared in the same manner.

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

[0084] (2) Measurement Method The thermal conductivity was calculated by measuring the thermal diffusion coefficient (α), specific heat (Cp), and density (ρ) of the measurement 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 diffusion coefficient (α) The thermal diffusion coefficient (α) was measured using a laser flash method, in which one side of the measurement sample was heated by irradiating it with pulsed light, and the temperature change on the other side was measured. The measurement was carried out at 25°C using an LFA447 manufactured by NETZSCH. The half-time method was used as the analysis method.

[0086] (2-2) Measurement of Specific Heat (Cp) Specific heat Cp (J / g K) was measured by differential scanning calorimetry (DSC). Specific heat measurement was performed using a TA Instruments Q200 device at a heating rate of 10°C / min over a temperature range of -30°C to 50°C. Based on the data obtained from the measurement, the specific heat was calculated according to JIS K7123.

[0087] (2-3) Measurement of Density (ρ) The density (ρ) was measured by the liquid immersion method using AUX220, SMK-401 manufactured by Shimadzu Corporation.

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

[0089] <Breakdown Voltage> (1) Measurement Sample The measurement sample prepared in <Long-term voltage resistance characteristics> was used.

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

[0091] Example 1 90 parts by weight of JER152 and 10 parts by weight of JER828 were added to a container, bringing the total weight of the epoxy resin to 100 parts by weight. To this, 26.85 parts by weight of Seikacure 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 volume 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] (Example 2) to (Example 21), (Comparative Example 1) to (Comparative Example 18) As shown in Tables 1 to 6, thermosetting resin compositions were obtained by changing the type and content of each component in the same manner as in Example 1. The unit of content in the tables is "parts by weight" unless otherwise specified.

[0093] Table 1 shows the evaluation results of the long-term voltage resistance characteristics, thermal conductivity, and breakdown voltage of the heat dissipation sheet when the volume fraction (volume %) of the filler in the thermosetting resin composition was changed. As shown in Examples 1 to 5, the long-term voltage resistance characteristics showed good evaluation results when the volume fraction (volume %) of the filler was 0.3 volume % or more and 2.0 volume % or less. The thermal conductivity and breakdown voltage also showed good evaluation results.

[0094]

[0095] Table 2 shows the evaluation results of the long-term voltage resistance, thermal conductivity, and breakdown voltage of the heat dissipation sheet when the type of boron nitride and the amount of filler were changed. As shown in Examples 6 to 8, the long-term voltage resistance showed good evaluation results when the thermosetting resin composition contained a filler, regardless of the type of boron nitride. The thermal conductivity and breakdown voltage also showed good evaluation results.

[0096]

[0097] Tables 3A and 3B show the evaluation results of the long-term voltage resistance, thermal conductivity, and breakdown voltage of the heat dissipation sheet when the amount of boron nitride and the amount of filler were changed. As shown in Examples 9 to 11, the long-term voltage resistance showed good evaluation results when the volume fraction (volume %) of boron nitride was 55% or more and 70% or less, and a filler was included in the thermosetting resin composition. The thermal conductivity and breakdown voltage also showed good evaluation results.

[0098]

[0099]

[0100] Table 4 shows the evaluation results of the long-term voltage resistance, thermal conductivity, and breakdown voltage of the heat dissipation sheet when the filler shape was spherical. As shown in Examples 12 and 13, the long-term voltage resistance showed good evaluation results when the thermosetting resin composition contained spherical fillers. The thermal conductivity and breakdown voltage also showed good evaluation results.

[0101]

[0102] Table 5 shows the evaluation results of the long-term voltage resistance characteristics, thermal conductivity, and breakdown voltage of the heat dissipation sheet when the average particle diameter (D50) of the filler was changed. As shown in Examples 14 to 17, the long-term voltage resistance characteristics showed good evaluation results when the average particle diameter (D50) of the filler contained in the thermosetting resin composition was 0.5 μm or more and 5.0 μm or less. The thermal conductivity and breakdown voltage also showed good evaluation results.

[0103]

[0104] Table 6 shows the evaluation results of the long-term voltage resistance, thermal conductivity, and breakdown voltage of heat dissipation sheets with and without epoxy resin, with and without curing accelerator, and with different functional groups in the acrylic copolymer. Table 6 also shows the evaluation results of the long-term voltage resistance, thermal conductivity, and breakdown voltage of heat dissipation sheets when nano BN (boron nitride) is used as a filler.

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

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

[0107] Furthermore, as shown in Example 19, the use of nano-BN (boron nitride) as a filler also showed good evaluation results for the long-term voltage resistance characteristics. In addition, good evaluation results were also shown for the thermal conductivity and the dielectric breakdown voltage.

[0108] Furthermore, for example, comparing Example 1 and Comparative Example 18 in Table 1, by including an epoxy resin in the thermosetting resin composition, Example 1 showed good evaluation results for the long-term voltage resistance characteristics and thermal conductivity.Furthermore, the dielectric breakdown voltage also showed good evaluation results.

[0109]

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

[0111] From the above results, the heat dissipation sheets and heat dissipation plates made from the thermosetting resin compositions of the embodiments have excellent heat dissipation properties and long-term voltage resistance characteristics.

[0112] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to illustrate the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

[0113] This application is based on Japanese Patent Application No. 2021-171904, filed on October 20, 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 a functional group on a side chain, 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 ratio of the boron nitride is 55 volume% or more and 70 volume% or less with respect to 100 volume% of the thermosetting resin composition, A thermosetting resin composition, wherein a volume ratio of the filler is 0.3 volume % or more and 2.0 volume % or less relative to 100 volume % of the thermosetting resin composition.

2. 2. The thermosetting resin composition according to claim 1, wherein the filler is 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 filler has a spherical shape.

4. 2. The thermosetting resin composition according to claim 1, wherein the boron nitride is at least one selected from the group consisting of scaly boron nitride and agglomerated 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, the resin layer being composed of the thermosetting resin composition according to any one of claims 1 to 5.

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

8. A heat sink comprising: a metal plate; and a resin layer formed from the thermosetting resin composition according to claim 1 , the resin layer being laminated on at least one surface of the metal plate.

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

10. A resin composition preparation step of preparing the thermosetting resin composition according to any one of claims 1 to 5; a coating step of coating the thermosetting resin composition on a film; and a heating step of heating the film to which the thermosetting resin composition is applied.

11. A resin composition preparation step of preparing the thermosetting resin composition according to any one of claims 1 to 5; A coating step of coating the thermosetting resin composition on a metal plate; and a heating step of heating the metal plate to which the thermosetting resin composition has been applied.

Images