Resin composition, sheet, and metal base substrate

Abstract

The present invention relates to a resin composition, a sheet, and a metal base substrate. The purpose of the present invention is to provide a resin composition and a varnish which contribute to shortening a molding period while improving thermal conductivity and insulation reliability, an inorganic composite sheet thereof, and a metal base substrate. This resin composition is characterized by containing (A) a polyphenylene ether resin, (B) a synthetic rubber, (C) a crosslinking agent, and (D-1) a first inorganic filler, the (D-1) first inorganic filler being boron nitride having an average particle diameter of 10-80 [mu] m.

Description

Technical Field

[0001] The present invention relates to a resin composition, a sheet, and a metal substrate board. Background Art

[0002] In recent years, along with the requirements for miniaturization, high frequency, and high output of electronic devices, in order to achieve high integration of semiconductors, miniaturization of printed wiring boards, etc., the manufacture of printed wiring boards using a lamination method has been actively carried out. High heat dissipation performance is required for these printed wiring boards, and the development of materials with excellent thermal conductivity is underway.

[0003] For example, Patent Document 1 discloses an epoxy resin composition characterized by containing an epoxy resin monomer, a curing agent, and a filler, the above filler including a first filler and a second filler, the first filler including boron nitride particles or aggregates of the above boron nitride particles having a D50 of 20 μm or more and an average aspect ratio of primary particles of 30 or less, and the second filler including boron nitride particles or aggregates of the above boron nitride particles having a D50 of less than 10 μm and an average aspect ratio of 5 or less.

[0004] Patent Document 2 discloses an epoxy resin composition containing an epoxy resin monomer, a curing agent including a novolak resin obtained by novolakizing a biphenol compound, and a mixed filler of α-aluminum oxide and boron nitride.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-165401

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2016-155985 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] As described in Patent Document 1 and Patent Document 2, epoxy resin compositions are usually used for printed wiring boards. This is because epoxy resin compositions are excellent in molding into sheets and B-staging, and also have excellent mechanical properties and heat resistance when made into cured products.

[0011] However, in order to B-stage cure the epoxy resin composition, it is required to perform hot pressing on both sides of the laminate to carry out an addition reaction, but the reaction time is long and the molding cycle is long, which is a problem. In addition, there is also a problem that the inorganic filler in the resin composition may be crushed by pressing and thus cannot exhibit its original thermal conductivity.

[0012] As described above, an object of the present invention is to provide a resin composition, a varnish, an inorganic composite sheet thereof, and a metal substrate that improve thermal conductivity and insulation reliability while contributing to shortening the molding cycle.

[0013] Method for solving the problem

[0014] The present inventors conducted in-depth research to solve the above problems. As a result, it was found that a resin composition containing a polyphenylene ether resin, a crosslinkable resin, and a specific inorganic filler has excellent thermal conductivity and insulation reliability and contributes to shortening the molding cycle.

[0015] That is, the present invention includes the following aspects.

[0016] (1) A resin composition, characterized by comprising (A) a polyphenylene ether resin, (B) a synthetic rubber, (C) a crosslinking agent, and (D-1) a first inorganic filler, wherein the (D-1) first inorganic filler is boron nitride having an average particle size of 10 to 80 μm.

[0017] (2) The resin composition according to (1) above, wherein the (A) polyphenylene ether resin is a terminally modified polyphenylene ether resin containing a substituent having an unsaturated double bond with 2 to 15 carbon atoms in the molecule.

[0018] (3) The resin composition according to (1) or (2) above, wherein the (B) synthetic rubber is at least one selected from the group consisting of 1,2-polybutadiene, 1,4-polybutadiene, styrene-butadiene, maleic acid-modified 1,2-polybutadiene, acrylic acid-modified 1,2-polybutadiene, epoxy-modified 1,2-polybutadiene styrene-conjugated diene block copolymer, hydrogenated styrene-conjugated diene block copolymer, and polyisopropene.

[0019] (4) The resin composition according to any one of (1) to (3) above, wherein the decomposition temperature of the (C) crosslinking agent is 100 to 150 °C.

[0020] (5) The resin composition according to any one of (1) to (4) above, wherein the (C) crosslinking agent is a peroxide type.

[0021] (6) The resin composition according to (5) above, which further comprises (E) a crosslinking aid, and the (E) crosslinking aid is at least one selected from the group consisting of ester acrylate, epoxy acrylate, urethane acrylate, ether acrylate, melamine acrylate, alkyd acrylate, silicone acrylate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, vinyltoluene, ethyl vinylbenzene, styrene, poly-p-methylstyrene, and polyfunctional epoxy.

[0022] (7) The resin composition according to any one of (1) to (6) above further contains alumina and / or aluminum nitride as a second inorganic filler (D-2).

[0023] (8) The resin composition according to any one of (1) to (7) above further contains (F) a silane coupling agent.

[0024] (9) A varnish containing the resin composition according to any one of (1) to (8) above.

[0025] (10) An inorganic composite sheet formed by coating the varnish according to (9) above on a carrier material and forming a thickness of 100 to 200 μm in a state where the varnish layer is not cured.

[0026] (11) An inorganic composite sheet having an uncured varnish layer formed by coating the varnish according to (9) above on a carrier material, wherein two sheets of the inorganic composite sheet are laminated to form a thickness of 100 to 200 μm.

[0027] (12) A metal base substrate formed by laminating and molding the inorganic composite sheet according to (10) or (11) above.

[0028] (13) The metal base substrate according to (12) above, wherein in the inorganic composite sheet layer (excluding the carrier material) of the cross-section of the metal base substrate, boron nitride having an average particle size of 30 to 70 μm in the above (D-1) first inorganic filler is observed in the inorganic composite sheet layer at 70% or more.

[0029] Advantages of the Invention

[0030] The resin composition of the present invention uses a polyphenylene ether resin, a synthetic rubber, and a specific inorganic filler, and has excellent thermal conductivity and insulation reliability, and can contribute to the improvement of the molding cycle. Detailed Embodiments

[0031] Hereinafter, an embodiment of the present invention will be described in detail. The present invention is not limited to the following embodiments, and appropriate changes can be made within the scope that does not prevent the effects of the present invention.

[0032] [<Resin Composition>]

[0033] The resin composition of the present embodiment contains (A) a polyphenylene ether resin, (B) a synthetic rubber, (C) a crosslinking agent, and (D-1) a first inorganic filler, and the above (D-1) first inorganic filler is boron nitride having an average particle size of 10 to 80 μm.

[0034] [(A) Polyphenylene Ether Resin]

[0035] The polyphenylene ether resin used in the present invention can be obtained, for example, by homopolycondensation of a compound having a phenolic hydroxyl group alone or by copolymerization of two or more such compounds. When using the polyphenylene ether resin, it is possible to suppress the increase in the fluidity of the resin composition, and in addition, the obtained cured product exhibits low dielectric properties, so that the insulation reliability can be improved.

[0036] Examples of the compound having a phenolic hydroxyl group include 2,6-dimethylphenol, 2,6-diethylphenol, 2,6-dipropylphenol, 2-methyl-6-ethylphenol, 2-methyl-6-propylphenol, 2-ethyl-6-propylphenol, m-cresol, 2,3-dimethylphenol, 2,3-dipropylphenol, 2-methyl-3-ethylphenol, 2-methyl-3-propylphenol, 2-ethyl-3-methylphenol, 2-ethyl-3-propylphenol, 2-propyl-3-methylphenol, 2-propyl-3-ethylphenol, 2,3,6-trimethylphenol, 2,3,6-triethylphenol, 2,3,6-tripropylphenol, 2,6-dimethyl-3-ethylphenol, 2,6-dimethyl-3-propylphenol, and the like.

[0037] Specific examples of the polyphenylene ether resin obtained by homopolycondensation or copolymerization of the compound having a phenolic hydroxyl group include poly(2,6-dimethyl-1,4-phenylene) ether, poly(2,6-diethyl-1,4-phenylene) ether, poly(2,6-dipropyl-1,4-phenylene) ether, poly(2-methyl-6-ethyl-1,4-phenylene) ether, poly(2-methyl-6-propyl-1,4-phenylene) ether, poly(2-ethyl-6-propyl-1,4-phenylene) ether, 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer, 2,6-diethylphenol / 2,3,6-trimethylphenol copolymer, 2,6-dipropylphenol / 2,3,6-trimethylphenol copolymer, a graft copolymer obtained by graft-polymerizing styrene onto poly(2,6-dimethyl-1,4-phenylene) ether, and a graft copolymer obtained by graft-polymerizing styrene onto 2,6-dimethylphenol / 2,3,6-trimethylphenol copolymer.

[0038] In addition, the polyphenylene ether resin used in the present invention is sometimes commercially available in the form of an alloyed polymer with polystyrene or the like. Such an alloyed polymer can also be used. Examples of the alloyed polymer include an alloyed polymer of poly(2,6-dimethyl-1,4-phenylene) ether and polystyrene, an alloyed polymer of poly(2,6-dimethyl-1,4-phenylene) ether and a styrene-butadiene copolymer, and the like.

[0039] Among the polyphenylene ether resins used in the present invention, a resin in which each phenylene skeleton has 1 to 4 methyl groups bonded to the carbon atoms of the phenylene skeleton is preferred. In addition, the weight-average molecular weight of the polyphenylene ether resin is preferably 500 or more and 5000 or less, more preferably 500 or more and 2000 or less, and still more preferably 1000 or more and 2000 or less. The weight-average molecular weight is a value obtained by measuring using gel permeation chromatography (GPC) and converting to polystyrene equivalent.

[0040] The blending amount of the polyphenylene ether resin in the resin composition of the present invention is not particularly limited. From the aspect of good cured product properties, when the total solid content of the resin composition is 100 parts by mass, it is preferably 25 wt% or less, and preferably 13 to 15 wt%. If it is within the above range, the peel strength of the obtained inorganic composite sheet is excellent, and thus it is preferred.

[0041] The polyphenylene ether resin of the present invention is more preferably a terminally modified polyphenylene ether resin terminally modified with a substituent having an unsaturated double bond having 2 to 15 carbon atoms in the molecule.

[0042] The structure of the substituent having an unsaturated double bond having 2 to 15 carbon atoms in the molecule is not particularly limited, and examples thereof include the following formula.

[0043] [Chemical formula 1]

[0044]

[0045] In formula (1), Y represents a hydrocarbon group having 1 to 13 carbon atoms, an arylene group or a carbonyl group. R1 each independently represents a hydrogen atom, a hydroxyl group or a hydrocarbon group having 1 to 13 carbon atoms (e.g., a linear hydrocarbon group, a cyclic hydrocarbon group), an aryl group, an alkoxy group, an allyloxy group, an amino group, a hydroxyl group.

[0046] The average number of substituents having an unsaturated double bond having 2 to 15 carbon atoms in the molecule (terminal substitution number) at the molecular terminal of each molecule of the terminally modified polyphenylene ether of the present embodiment is preferably 1.5 to 3, more preferably 1.7 to 2.7, and still more preferably 1.8 to 2.5. When it is within the above range, crosslinking points are sufficiently formed, the heat resistance of the obtained cured product is excellent, and in addition, the excessive progress of the reaction is suppressed, and the storage stability and fluidity maintenance of the resin composition are excellent, and thus it is preferred.

[0047] It should be noted that the number of terminal substituents of the end-modified polyphenylene ether can be exemplified by a numerical value representing the average number of substituents per molecule of all the end-modified polyphenylene ethers present in 1 mole of the end-modified polyphenylene ether. The number of terminal substituents can be measured, for example, as follows: Measure the number of hydroxyl groups remaining in the obtained end-modified polyphenylene ether, calculate the reduction amount compared to the number of hydroxyl groups of the polyphenylene ether before end-modification, and thereby conduct the measurement. It is calculated from the reduction amount of the number of hydroxyl groups of the polyphenylene ether before end-modification. The method for measuring the number of hydroxyl groups remaining in the end-modified polyphenylene ether can be obtained by adding a quaternary ammonium salt (tetraethylammonium hydroxide) associated with the hydroxyl group to a solution of the end-modified polyphenylene ether and measuring the UV absorbance of the mixed solution.

[0048] [(B) Synthetic rubber]

[0049] The crosslinkable resin used in the present invention is not particularly limited. For example, it is preferably at least one selected from the group consisting of 1,2-polybutadiene, 1,4-polybutadiene, styrene-butadiene, maleic acid-modified 1,2-polybutadiene, acrylic acid-modified 1,2-polybutadiene, epoxy-modified 1,2-polybutadiene, styrene-conjugated diene block copolymer, hydrogenated styrene-conjugated diene block copolymer, and polyisopropene. From the viewpoints of electrical properties and heat resistance, styrene-butadiene and epoxy-modified 1,2-polybutadiene are particularly preferred. By incorporating the synthetic rubber, the flexibility and the adhesion to metal of the obtained resin composition are improved, and thus it is preferred.

[0050] [(C) Crosslinking agent]

[0051] The crosslinking agent used in the present invention is not particularly limited, and the decomposition temperature is more preferably 100 to 150 °C. As the crosslinking agent, sulfur-based, peroxide-based, quinone-based, and bismaleimide-based can be exemplified. It should be noted that in this specification, the "decomposition temperature" represents the 10-hour half-life temperature.

[0052] As the above sulfur-based, sulfur, tetramethylthiuram disulfide, 2-(morpholinodithio)benzothiazole, dithiomorpholine, etc. can be exemplified.

[0053] As the above peroxide-based, dicumyl peroxide, tert-butylcumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexene-3, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, α,α'-bis(tert-butylperoxy-m-isopropyl)benzene, etc. can be exemplified.

[0054] As the above quinone type, p-benzoquinone dioxime, p,p'-dibenzoylquinone dioxide, p-nitrosobenzene, etc. can be exemplified.

[0055] Examples of the bismaleimide-based compounds include 4,4'-bismaleimide diphenylamine and N,N'-m-phenylene bismaleimide. It should be noted that when a peroxide-based crosslinking agent is used, the bismaleimide-based crosslinking agent can also be used as a crosslinking aid described later.

[0056] As the crosslinking agent, a peroxide-based one is preferred, and dicumyl peroxide is more preferred. When it is a peroxide-based crosslinking agent, no reaction occurs at the temperature for removing the solvent when producing the sheet from the varnish, so it is preferred.

[0057] The mixing ratios of the above (A) polyphenylene ether resin, (B) synthetic rubber, and (C) crosslinking agent are not particularly limited. For example, when the total mass of the above three components is set to 100, the range of (A):(B):(C) = 30:25:45 to 50:5:45 is preferred. By being within the above range, excellent electrical properties and heat resistance are obtained, so it is preferred.

[0058] It should be noted that when the following (E) crosslinking aid is contained, if (A):(B):(C):(E) = 41.7:3:0.3:55 to 65:28:2:5, excellent electrical properties and heat resistance are obtained, so it is preferred.

[0059] [Inorganic filler]

[0060] [[<(D-1) First inorganic filler>]]

[0061] (Boron nitride)

[0062] The boron nitride of the present embodiment is aggregated boron nitride or massive boron nitride in which flaky boron nitride is randomly oriented. By using aggregated boron nitride or massive boron nitride, the orientation of boron nitride in the plane direction is suppressed, and when the following inorganic composite sheet is produced, the thermal conductivity in the thickness direction is improved, so it is preferred.

[0063] The average particle size of the above boron nitride is preferably 10 μm or more and 80 μm or less, and more preferably 30 μm or more and 70 μm or less. When within the above range, the thermal conductivity of the obtained cured product is improved, so it is preferred. It should be noted that in the present invention, the "average particle size" in the first inorganic filler refers to the particle size of aggregated or massive secondary particles.

[0064] The boron nitride of the present embodiment can use commercially available boron nitride, and examples include HP-40MF, HP40-J2 (manufactured by Mizushima Alloys Co., Ltd.), PTX60 (manufactured by Momentive), Agglomerates50 (manufactured by 3M), etc. HP-40MF and HP40-J2 (manufactured by Mizushima Alloys Co., Ltd.) which are sintered without internal voids to form aggregates are preferred.

[0065] The boron nitride of the present embodiment can also be produced by a known method. For example, the method described in Japanese Patent Application Laid-Open No. 2019-073409 can be used.

[0066] The content of the boron nitride in the resin composition of the present embodiment may be 60 to 85 parts by mass, preferably 65 to 80 parts by mass, per 100 parts by mass of the total solid content of the resin composition.

[0067] <<(D-2) Second Inorganic Filler>>

[0068] The resin composition of the present invention may contain a second inorganic filler. As the above-mentioned second inorganic filler, alumina and / or aluminum nitride can be cited. If it is alumina and / or aluminum nitride, the thermal conductivity is excellent, so it is preferred.

[0069] (Alumina)

[0070] In the present embodiment, "alumina" is alumina, and it can be various crystalline forms of transition alumina such as γ, δ, θ, κ, etc., or it can also contain alumina hydrate in the transition alumina. From the aspect of more excellent stability, it is preferably substantially α-crystalline form.

[0071] The shape of the above-mentioned alumina is preferably spherical or polyhedral, and particularly preferably polyhedral with 14 or more faces. By having 14 or more faces, the inter-planar distance between particles becomes closer compared to polyhedra with less than 14 faces, and thus it is easy to obtain excellent thermal conductivity, so it is preferred.

[0072] The shape of alumina can be confirmed by a scanning electron microscope (SEM). Using JCM7000 manufactured by JEOL Ltd., observe the image obtained from multiple SEM images from an arbitrary field of view of the sample. Then, for the observation results of 50 randomly selected alumina particles, the shape of the particles that account for 60% or more on a number basis can be judged as the shape of the sample.

[0073] The average particle diameter of the alumina in the present embodiment is preferably 25 μm or more and 45 μm or less. When the average particle diameter is 25 μm or more, the increase in viscosity is suppressed when making varnish, so it is preferred. When the average particle diameter is 45 μm or less, the processability of the sheet is excellent, so it is preferred.

[0074] In this specification, the "average particle diameter" is a value calculated as the volume-based median particle diameter D50 in the volume-based cumulative particle size distribution measured by a laser diffraction / scattering particle size distribution measuring device.

[0075] The content of alumina in the resin composition of this embodiment may be 30 to 80 parts by mass, or may be 40 to 70 parts by mass, in 100 parts by mass of the total solid content of the resin composition. The appropriate content of alumina can be set according to the content of boron nitride described later.

[0076] For the alumina of this embodiment, commercially available alumina particles can be used, or alumina particles manufactured by the methods described in Japanese Unexamined Patent Application Publication No. 2016-028993 and International Publication No. 2021 / 070729 can be used.

[0077] Examples of commercially available alumina particles include DAW45 (manufactured by Denka Co., Ltd.), CB-A20S, CB-AS30S, CB-P15 (manufactured by Risen Noko Co., Ltd.), AZ series (manufactured by NIPPON STEEL Chemical&Material Co., Ltd.), AH40-S (manufactured by DIC Corporation), AO-502 (manufactured by Admatechs Corporation). From the viewpoint of fluidity, it can be CB-A20S, CB-A30S, CB-P15 (manufactured by Risen Noko Co., Ltd.), AO-502 (manufactured by Admatechs Corporation). From the viewpoint of thermal conductivity, it can be AH40-S (manufactured by DIC Corporation), but it is not limited to these.

[0078] It should be noted that these alumina particles can be used alone or in combination of multiple kinds, and it is preferably used in combination of multiple kinds. When using multiple kinds in combination, the polyhedral alumina particles preferably contain 50% by mass or more, more preferably 60% by mass or more, in all the alumina. By being within the above range, the obtained inorganic composite sheet and metal substrate have particularly excellent thermal conductivity, so it is preferred.

[0079] (aluminum nitride)

[0080] As the above-mentioned aluminum nitride, well-known and commonly used aluminum nitride can be used, and preferably granular with an average particle size of 0.5 to 100 μm. Examples of commercially available aluminum nitride include FAN-f05-A1, FAN-f30-A1, FAN-f50-A1, FAN-f80-A1 (manufactured by Furukawa Electric Co., Ltd.), etc., but it is not limited to these.

[0081] In the resin composition of this embodiment, (D-1) a first inorganic filler and (D-2) a second inorganic filler can be used in combination. When used in combination, the total content of (D-1) the first inorganic filler and (D-2) the second inorganic filler is preferably 60 to 85 parts by mass, more preferably 65 to 80 parts by mass, in 100 parts by mass of the total solid content of the resin composition. By being within the above range, an increase in the viscosity of the resin composition or its varnish can be suppressed, and a uniform coating film can be formed.

[0082] If within the above range, the contents of (D-1) the first inorganic filler and (D-2) the second inorganic filler can be any combination, and the mass ratio of (D-1) the first inorganic filler to (D-2) the second inorganic filler can be 50:50 to 95:5, more preferably 55:45 to 90:10, and particularly preferably 60:40 to 85:15. If within the above range, both thermal conductivity and insulation reliability can be achieved at an excellent level, so it is preferred.

[0083] By combining (D-1) the first inorganic filler and (D-2) the second inorganic filler, a thermal conductivity more excellent than before can be obtained, so the filling amount in the resin composition can be reduced. In addition, by reducing the filling amount, the breakdown voltage of the resin composition becomes higher, and furthermore, the deviation of the breakdown voltage is suppressed, and the electrical characteristics can be stabilized. It should be noted that from the viewpoint of the obtained characteristics, (D-1) the first inorganic filler alone is particularly preferred.

[0084] [(E) Crosslinking aid]

[0085] In the present embodiment, when a peroxide-based is used as (C) the crosslinking agent, from the viewpoint of performing an effective crosslinking reaction, it is preferred to further add a crosslinking aid. As the above crosslinking aid, for example, at least one selected from the group consisting of ester acrylate, epoxy acrylate, urethane acrylate, ether acrylate, melamine acrylate, alkyd acrylate, silicone acrylate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, vinyltoluene, ethyl vinylbenzene, styrene, poly-p-methylstyrene, and polyfunctional epoxy is preferably used, and triallyl isocyanurate is particularly preferred from the viewpoints of electrical characteristics and heat resistance.

[0086] When the entire resin composition (excluding inorganic fillers) is set to 100, the compounding amount of (E) the crosslinking aid is preferably 25 to 50 wt%. By being within the above range, the crosslinking reaction can be efficiently carried out.

[0087] [(F) Silane coupling agent]

[0088] Examples of the silane coupling agent include epoxy silane.

[0089] <Varnish>

[0090] The resin composition of the present invention can be suitably used for varnish. As the preparation method of the above varnish, a known method can be used, and the above resin composition can be dissolved (diluted) in an organic solvent to prepare a varnish.

[0091] As the above-mentioned solvent, polar solvents such as methyl ethyl ketone, methoxypropanol, N,N-dimethylformamide, dimethyl sulfoxide, etc. can be used. The above-mentioned solvent can be only one kind, or two or more kinds can be used in combination.

[0092] The amount of the above-mentioned solvent used is not particularly limited, and can be appropriately determined in consideration of, for example, sheet processability. Specifically, it is preferably prepared in such a way that the viscosity of the obtained varnish becomes 1500 mPa·s to 15000 mPa·s. When the viscosity is 1500 mPa·s or more, the appearance defects caused by repulsion during coating are suppressed, so it is preferred. When the viscosity is 15000 mPa·s or less, the appearance defects caused by stripe unevenness during coating are suppressed, so it is preferred.

[0093] [Other components]

[0094] The above-mentioned varnish can contain other components within the range that does not impair the object of the present invention. For example, a dispersant, etc. can be cited.

[0095] As the above-mentioned dispersant, as long as it is a dispersant used in the coating field, there is no particular limitation. For example, Disperbyk-110, 111, 180, 161, BYK-W996, W9010, W903, etc. can be cited. By using a dispersant, not only the dispersibility of the inorganic filler can be improved, but also the viscosity of the varnish can be adjusted to the above range.

[0096] [Inorganic composite sheet]

[0097] The above-mentioned varnish is suitable for use in an inorganic composite sheet. The inorganic composite sheet is formed by coating the above-mentioned varnish on a carrier material and heating and drying it.

[0098] It should be noted that the above-mentioned inorganic composite sheet is formed in a semi-cured state on the surface of the carrier material. That is, the above-mentioned heating and drying means performing B-stage curing. By heating the varnish coated on the carrier material, a part of the cross-linking reaction in the varnish proceeds. Therefore, the inorganic composite sheet of the present embodiment has the property of being temporarily melted and then cured by heat pressing during lamination molding.

[0099] The coating method of the varnish is not particularly limited and can be implemented by a known method. For example, comma coating, die coating, die lip coating, gravure coating, etc. can be cited. As a method for forming an inorganic composite sheet with a specified thickness, a comma coating method in which the object to be coated passes through a gap, a die coating method in which the varnish with adjusted flow rate is coated from a nozzle, etc. are preferred.

[0100] The thickness of the above-mentioned inorganic composite sheet formed on the carrier material is preferably 100 to 200 μm. If the thickness is 200 μm or less, the thermal resistance becomes smaller, so it is preferred. The closer the thickness is to 200 μm, the more the generation of micropores during sheet formation can be suppressed, and the dielectric breakdown voltage increases, so it is preferred. When two inorganic composite sheets are laminated and used, it is preferred to adjust the thickness of each sheet so that the thickness after lamination and pressing becomes 100 to 200 μm. The resin composition of the present invention can be made thinner compared with conventional resin compositions, and the carrier material can be easily peeled off. Therefore, even if it is formed by laminating and pressing two sheets, an inorganic composite sheet with a thickness of 100 to 200 μm can be obtained.

[0101] As the above-mentioned carrier material, a polymer film or a metal sheet is preferably used. As the above-mentioned polymer film, polyolefins such as polyethylene, polypropylene, and polyvinyl chloride, polyesters such as polyethylene terephthalate, polycarbonate, acetyl cellulose, tetrafluoroethylene, etc. can be cited. As the above-mentioned metal sheet, metal foils such as copper foil, aluminum foil, and nickel foil can be exemplified. Furthermore, as the carrier material, release paper etc. can be cited.

[0102] <Metal substrate board>

[0103] The inorganic composite sheet of the present invention can be suitably laminated and formed and used as a metal substrate board. Specifically, two or more of the above-mentioned obtained inorganic composite sheets are laminated to form a desired thickness. Then, metal foil is disposed on the outermost layer on one side or both sides thereof to form a laminate, and the laminate is laminated and integrated by heating and pressing such as press molding to obtain. Here, as the metal foil, copper, aluminum, brass, nickel, etc. alone can be used, or alloy or composite metal foil can also be used. As the conditions for heating and pressing the laminate, it is only necessary to appropriately adjust and heat and press under the conditions for curing the varnish. However, if the pressure during pressing is too low, air bubbles will remain inside the obtained metal substrate board, and sometimes the electrical properties will deteriorate. Therefore, it is preferred to perform pressing under conditions that satisfy the formability. For example, it is possible to heat and press and mold for 10 minutes to 2 hours under the conditions of a heating temperature of 100 to 200 °C and a pressure of 0.98 to 4.9 MPa to integrally form and obtain a metal substrate board.

[0104] Examples

[0105] Hereinafter, the present invention will be further described in detail based on examples, but this description does not limit the present invention.

[0106] [Preparation of filler]

[0107] In this embodiment, a material using a combination of multiple fillers is used. The blending of each filler is shown in Table 1.

[0108] The fillers used are as follows.

[0109] HP40MF100 (Agglomerated boron nitride, JFE MINERAL COMPANY, LTD.)

[0110] HP40MFJ2 (Agglomerated boron nitride, JFE MINERAL COMPANY)

[0111] AH-40S (Polyhedral alumina, DIC CORPORATION)

[0112] [Production Example 1]

[0113] 100 parts by mass of orthoboric acid (manufactured by Shin Nippon Chemical Co., Ltd.) and 35 parts by mass of acetylene black (HS100, manufactured by Denka Co., Ltd.) were mixed using a Henschel mixer, filled into a graphite crucible, and heated in an argon atmosphere at 2200 °C for 5 hours in an electric arc furnace to synthesize boron carbide. The synthesized boron carbide block was pulverized with a ball mill for 40 minutes, sieved through a sieve to a particle size of 75 μm or less, further washed with an aqueous nitric acid solution to remove impurities such as iron, and then filtered and dried to produce boron carbide powder with an average particle size of 33 μm.

[0114] After filling the above boron carbide powder into a boron nitride crucible, it was heated using a resistance heating furnace in a nitrogen atmosphere at 2000 °C and 9 atmospheres (0.8 MPa) for 10 hours to obtain boron carbonitride.

[0115] 100 parts by mass of the above boron carbonitride and 200 parts by mass of boric acid were mixed using a Henschel mixer, filled into a boron nitride crucible, and using a resistance heating furnace, under a pressure condition of 0.3 MPa, in a nitrogen atmosphere, the heating rate from room temperature to 1000 °C was set to 10 °C / minute, the heating rate from 1000 °C was set to 2 °C / minute, and it was heated to a holding temperature of 2000 °C and held at this holding temperature of 2000 °C for 10 hours to synthesize agglomerated block boron nitride in which primary particles are aggregated into a block.

[0116] The synthesized block boron nitride was crushed in a mortar for 10 minutes and then sieved using a nylon sieve with a sieve hole of 95 μm. By crushing and classifying the fired product, boron nitride powder composed of agglomerated block boron nitride in which primary particles are aggregated into a block was obtained.

[0117] [Production Example 2]

[0118] The pulverization during boron carbide synthesis was 1 hour, and boron carbide with an average particle size of 20 μm (carbon content 19.9%) was synthesized as a raw material. Otherwise, it was synthesized under the same conditions as in Production Example 1.

[0119] (Average particle size D50)

[0120] The value calculated as the volume-based median particle diameter D50 based on the volume-based cumulative particle size distribution measured by a laser diffraction / scattering type particle size distribution measuring device.

[0121] [Table 1]

[0122]

[0123] [Preparation of Resin]

[0124] The resin was prepared according to Table 2.

[0125] The materials used are as described below.

[0126] [Polyphenylene Oxide Resin]

[0127] Polyphenylene oxide (NORYL SA9000, number average molecular weight 1900, manufactured by SABIC)

[0128] [Epoxy Resin (the following three components are mixed and used in a ratio of a:b:c = 11:6:3)]

[0129] a: 850 (manufactured by DIC Corporation, bisphenol A type epoxy resin)

[0130] b: NC-3000 (manufactured by Nippon Kayaku Co., Ltd., phenol biphenyl aralkyl epoxy resin)

[0131] c: VG-3101 (manufactured by Printec Co., Ltd., trifunctional epoxy resin)

[0132] [Table 2]

[0133] Resin A Resin B Resin C Resin D Resin E Resin F PPE 50 40 60 50 50 Epoxy 97 SBS 10 10 10 10 PB 10 TAIC 38 48 28 38 38 PERCUMYLD 2 2 2 2 PERHEXA C 2 2E4MZ 3 Total amount 100 100 100 100 100 100

[0134] [Examples 1 to 9, Comparative Example 1]

[0135] Using the prepared filler and resin, they were compounded according to Table 3 to obtain a resin composition. Furthermore, an inorganic composite sheet and a metal substrate were produced and evaluated according to the following method.

[0136] (Production of Metal Substrate)

[0137] The obtained resin composition was kneaded with a planetary mixer and a specified amount of solvent (toluene) was added thereto to obtain a varnish having a viscosity adjusted to 3000 mPa·s. Then, this varnish was coated on a film made of polyethylene terephthalate (PET) with a thickness of 75 μm and heated and dried at 130°C for 8 minutes, whereby an inorganic composite sheet in a B-stage state was formed on one side of the carrier material with a thickness of 150 μm.

[0138] Overlap one sheet of the obtained inorganic composite sheet, place a 18-μm copper foil on the coated sheet and a 1-mm aluminum plate, and heat and press them at a heating temperature of 175 °C and a pressing pressure of 2.94 MPa in a vacuum for 30 minutes to fabricate a metal base substrate. It should be noted that in the comparative example using epoxy, it was impossible to fabricate under the above conditions. Therefore, the heating and pressing time was changed to 90 minutes at a heating temperature of 175 °C and a pressing pressure of 2.94 MPa for heating and pressing forming.

[0139] [Example 10]

[0140] (Fabrication of laminated inorganic composite sheet)

[0141] The resin composition obtained according to Table 3 was kneaded with a planetary mixer and a specified amount of a solvent (toluene) was added thereto to obtain a varnish having a viscosity adjusted to 3000 mPa·s. Then, this varnish was coated on a 75-μm-thick polyethylene terephthalate (PET) film and dried by heating at 130 °C for 8 minutes, whereby an inorganic composite sheet in a B-stage state with a thickness of 100 μm was formed on one side of the carrier material.

[0142] Overlap two sheets of the obtained inorganic composite sheet, place 18-μm copper foils on both sides, and heat and press them at a heating temperature of 175 °C and a pressing pressure of 2.94 MPa in a vacuum for 30 minutes to fabricate a metal base substrate.

[0143] In the conventional inorganic composite sheet, it was impossible to peel off the carrier material for separate treatment, and it was also difficult to form a thin-film inorganic composite sheet. Therefore, when laminated and pressed for use, it became thick and it was impossible to obtain the inorganic composite sheet as in the present embodiment.

[0144] (Thermal conductivity)

[0145] Layering the inorganic composite sheets, heat and press them at a heating temperature of 175 °C and a pressing pressure of 2.94 MPa in a vacuum for 90 minutes to obtain a sheet solidified product with a thickness of 1 mm. The thermal diffusivity and specific heat of the above sheet solidified product at 25 °C were measured using a thermal conductivity measuring device (LFA467 HyperFlash, manufactured by NETZSCH). Then, the density of the heat dissipation member was measured by the Archimedes method. Based on the product of the obtained thermal diffusivity, specific heat, and density, the thermal conductivity of the heat dissipation component was estimated.

[0146] (Evaluation of 90-degree peel strength (peel strength))

[0147] According to JIS C6481, the peel strength of the copper foil on the obtained metal substrate was measured. As the peel strength measuring device, "Autograph" manufactured by Shimadzu Corporation was used. The peel strength of the copper foil was measured for 20 test samples. The average value of the measured values of the peel strength of the copper foil in the 20 test samples was taken as the 90-degree peel strength.

[0148] (Evaluation of dielectric breakdown strength)

[0149] The copper foil in the obtained metal substrate was etched to pattern the copper foil into a circle with a diameter of 2.5 cm, obtaining test samples. Using a withstand voltage tester (YST-243AT-100, manufactured by Yamayo Tester Co., Ltd.), an alternating voltage was applied at a temperature of 25 °C so that the voltage increased at a rate of 0.5 kV / second in the through-layer direction. The voltage at which a current of 10 mA flowed through the test sample was taken as the dielectric breakdown voltage. The dielectric breakdown strength was calculated by normalizing the dielectric breakdown voltage by dividing it by the thickness of the test sample.

[0150] (Area ratio)

[0151] The cross-section of the obtained metal substrate was observed with a scanning electron microscope (SEM, JSM-IT100, manufactured by JEOL Ltd.), and elemental mapping analysis was performed by energy dispersive X-ray spectroscopy (EDX) attached to the above SEM to obtain an SEM image and an elemental mapping image. In the elemental mapping analysis, the distribution of nitrogen was analyzed.

[0152] Based on the obtained SEM image and elemental mapping image, the (D-1) first inorganic filler was identified, and the area ratio of the (D-1) first inorganic filler with an average particle size of 30 to 70 μm was calculated. Specifically, based on the area and average particle size of the identified (D-1) first inorganic filler, the area of the (D-1) first inorganic filler with an average particle size of 30 to 70 μm was obtained and calculated with the entire measurement field of view as the denominator. The above area ratio is preferably 50 area% or more, more preferably 65 area% or more, and particularly preferably 70 area% or more.

[0153] [Table 3]

[0154]

[0155] *Example 10 is a two-layer laminated metal substrate

[0156] Compared with the resin composition of the comparative example, any resin composition of the examples was cured at low pressure and in a short time, so the molding cycle time could be significantly shortened.

Claims

1. A resin composition, characterized in that The invention comprises (A) a polyphenylene ether resin, (B) a synthetic rubber, (C) a crosslinking agent and (D-1) a first inorganic filler, wherein the first inorganic filler (D-1) is boron nitride having an average particle size of 10 to 80 μm.

2. The resin composition according to claim 1, wherein The (A) polyphenylene ether resin is a terminal-modified polyphenylene ether resin containing a substituent having an unsaturated double bond having 2 to 15 carbon atoms in the molecule.

3. The resin composition according to claim 1, wherein The (B) synthetic rubber is at least one selected from the group consisting of 1,2-polybutadiene, 1,4-polybutadiene, styrene butadiene, maleic acid-modified 1,2-polybutadiene, acrylic acid-modified 1,2-polybutadiene, epoxy-modified 1,2-polybutadiene, styrene conjugated diene block copolymers, hydrogenated styrene conjugated diene block copolymers and polyisocyanate.

4. The resin composition according to claim 1, wherein The decomposition temperature of the (C) cross-linking agent is 100-150°C.

5. The resin composition according to claim 4, wherein The (C) cross-linking agent is a peroxide-based agent.

6. The resin composition according to claim 5, further comprising (E) a crosslinking aid, wherein the (E) crosslinking aid is at least one selected from the group consisting of ester acrylates, epoxy acrylates, urethane acrylates, ether acrylates, melamine acrylates, alkyd acrylates, silicone acrylates, triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, vinyltoluene, ethylvinylbenzene, styrene, poly(p-methylstyrene) and multifunctional epoxies. 7 . The resin composition according to claim 1 , further comprising aluminum oxide and / or aluminum nitride as (D-2) a second inorganic filler. 8 . The resin composition according to claim 1 , further comprising (F) a silane coupling agent. 9 . A varnish comprising the resin composition according to claim 1 . 10 . An inorganic composite sheet, which is obtained by applying the varnish according to claim 9 onto a carrier material, and forming the varnish layer to have a thickness of 100 to 200 μm in an uncured state.

11. An inorganic composite sheet comprising an uncured varnish layer formed by applying the varnish according to claim 9 onto a carrier material, wherein: The inorganic composite sheet is formed by laminating two sheets to have a thickness of 100 to 200 μm. 12 . A metal base substrate, which is formed by laminating the inorganic composite sheet according to claim 10 or 11.

13. The metal base substrate according to claim 12, wherein: In the inorganic composite sheet layer of the cross section of the metal base substrate, boron nitride with an average particle size of 30 to 70 μm in the (D-1) first inorganic filler accounts for more than 70% of the inorganic composite sheet layer, and the inorganic composite sheet layer does not include a carrier material.

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