Resin composition, sheet, and metal-based substrate

Abstract

To provide a resin composition contributing to shortening the molding cycle while improving thermal conductivity and insulation reliability, and to provide a varnish, an inorganic composite sheet thereof, and a metal-based substrate.SOLUTION: A resin composition comprises (A) a polyphenylene ether resin, (B) a synthetic rubber, (C) a crosslinking agent, and (D-1) a first inorganic filler, where the first inorganic filler (D-1) is boron nitride having an average particle diameter of 10 to 80 μm.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a resin composition, a sheet, and a metal-based substrate.

Background Art

[0002] In recent years, with the demands for miniaturization, high frequency, and high output of electronic devices, in order to achieve high integration of semiconductors and miniaturization of printed wiring boards, the production of printed wiring boards by the build-up method has been actively carried out. These printed wiring boards are required to have high heat dissipation performance, and the development of materials with excellent thermal conductivity has been progressing.

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

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

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described in Patent Documents 1 and 2, generally, an epoxy resin composition is used for printed wiring boards. This is because the epoxy resin composition is excellent in forming into a sheet and B-staging, and also has excellent mechanical properties and heat resistance when cured.

[0007] However, in order to cure the B-stage composed of the epoxy resin composition, it is required to thermally press the laminate from both sides to promote the addition reaction, but the reaction time is long and the molding cycle is long, which is a problem. In addition, there has also been a problem that the inorganic filler in the resin composition may be crushed by pressing and cannot exhibit its original thermal conductivity.

[0008] From the above, an object of the present invention is to provide a resin composition, a varnish, its inorganic composite sheet, and a metal base substrate that contribute to shortening the molding cycle while improving thermal conductivity and insulation reliability.

Means for Solving the Problems

[0009] The inventors of the present invention conducted intensive studies 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 is excellent in thermal conductivity and insulation reliability and contributes to shortening the molding cycle.

[0010] That is, the present invention includes the following aspects. (1) (A) A polyphenylene ether resin, (B) a synthetic rubber, (C) a crosslinking agent, and (D-1) a first inorganic filler, The resin composition, wherein the (D-1) first inorganic filler is boron nitride having an average particle diameter of 10 to 80 μm. (2) The resin composition according to (1) above, 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 the above (1) or (2), 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 polyisopropylene. (4) The resin composition according to any one of the above (1) to (3), wherein the decomposition temperature of the (C) crosslinking agent is 100 to 150 °C. (5) The resin composition according to any one of the above (1) to (4), wherein the (C) crosslinking agent is a peroxide type. (6) Further, it contains (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, vinyl toluene, ethyl vinyl benzene, styrene, polyp-methylstyrene, and polyfunctional epoxy. The resin composition according to the above (5). (7) Further, as the (D-2) second inorganic filler, it contains alumina and / or aluminum nitride. The resin composition according to any one of the above (1) to (6). (8) Further, it contains (F) a silane coupling agent. The resin composition according to any one of the above (1) to (7). (9) A varnish containing the resin composition according to any one of the above (1) to (8). (10) An inorganic composite sheet formed by applying the varnish according to the above (9) to a carrier material and forming a varnish layer with a thickness of 100 to 200 μm in an uncured state. (11) An inorganic composite sheet having an uncured varnish layer formed by applying the varnish according to the above (9) to a carrier material, wherein the inorganic composite sheet is formed by laminating two sheets to a thickness of 100 to 200 μm. (12) A metal-based substrate formed by laminating and molding the inorganic composite sheet described in (10) or (11) above. (13) In the inorganic composite sheet layer (excluding the carrier material) of the cross-section of the metal-based substrate, among the (D-1) first inorganic fillers, boron nitride with an average particle diameter of 30 to 70 μm is observed in 70% or more of the inorganic composite sheet layer. The metal-based substrate described in (12) above.

Advantages of the Invention

[0011] By using a polyphenylene ether resin, a synthetic rubber, and a specific inorganic filler, the resin composition of the present invention is excellent in thermal conductivity and insulation reliability, and can contribute to the improvement of the molding cycle.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a detailed description will be given of an embodiment of the present invention. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within a range that does not inhibit the effects of the present invention. It can be done.

[0013] <Resin Composition> The resin composition of the present embodiment contains (A) a polyphenylene ether resin, (B) a synthetic rubber, (C) a cross-linking agent, and (D-1) a first inorganic filler, and the (D-1) first inorganic filler is boron nitride having an average particle diameter of 10 to 80 μm.

[0014] [(A) Polyphenylene Ether Resin] The polyphenylene ether resin used in the present invention can be obtained, for example, by homopolycondensation using a compound having a phenolic hydroxyl group alone or by copolymerization using two or more of such compounds. When a polyphenylene ether resin is used, it is possible to suppress an increase in the fluidity of the resin composition, and since the resulting cured product exhibits low dielectric properties, the insulation reliability can be improved.

[0015] 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.

[0016] 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-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.

[0017] In addition, the polyphenylene ether resin used in the present invention may be commercially available in the form of an alloy polymer with polystyrene or the like. Such alloy polymers can also be used. Examples of the alloy polymer include an alloy polymer of poly(2,6-dimethyl-1,4-phenylene) ether and polystyrene, and an alloy polymer of poly(2,6-dimethyl-1,4-phenylene) ether and a styrene-butadiene copolymer.

[0018] Among the polyphenylene ether resins used in the present invention, a resin having 1 to 4 methyl groups bonded to the carbon atoms of the phenylene skeleton per phenylene skeleton is preferable. Further, the polyphenylene ether resin preferably has a weight average molecular weight of 500 or more and 5000 or less, more preferably 500 or more and 2000 or less, and even more preferably 1000 or more and 2000 or less. The weight average molecular weight is measured using gel permeation chromatography (GPC) and is a value in terms of polystyrene.

[0019] The blending amount of the polyphenylene ether resin in the resin composition of the present invention is not particularly limited, but from the viewpoint of good cured product properties, when the total solid content of the resin composition is 100 mass, it is preferably 25 wt% or less, and preferably 13 to 15 wt%. When it is within the above range, the peel strength of the obtained inorganic composite sheet is excellent and preferable.

[0020] 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.

[0021] The substituent having an unsaturated double bond having 2 to 15 carbon atoms in the molecule is not particularly limited in structure, and examples thereof include the following formula.

[0022]

Chemical formula

[0023] In formula (1), Y represents a hydrocarbon group having 1 to 13 carbon atoms, an arylene group, or a carbonyl group. Each R1 independently represents a hydrogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 13 carbon atoms (for example, a linear hydrocarbon group, a cyclic hydrocarbon group), an aryl group, an alkoxy group, an allyloxy group, an amino group, or a hydroxyl group.

[0024] The terminal-modified polyphenylene ether of the present embodiment preferably has an average number (terminal substitution number) of substituents having an unsaturated double bond having 2 to 15 carbon atoms in the molecule at the molecular terminal per molecule of the terminal-modified polyphenylene ether of 1.5 to 3, more preferably 1.7 to 2.7, and even more preferably 1.8 to 2.5. When within the above range, crosslinking points are sufficiently formed, the resulting cured product has excellent heat resistance, and also suppresses excessive progress of the reaction, and is preferable because it is excellent in storage stability and fluidity maintenance of the resin composition.

[0025] The terminal substitution number of the terminal-modified polyphenylene ether includes a numerical value representing the average value of the number of substituents per molecule of all the terminal-modified polyphenylene ethers present in 1 mol of the terminal-modified polyphenylene ether. This terminal substitution number can be measured, for example, by measuring the number of hydroxyl groups remaining in the obtained terminal-modified polyphenylene ether and calculating the decrease from the number of hydroxyl groups of the polyphenylene ether before terminal modification. It is calculated by the decrease from the number of hydroxyl groups of the polyphenylene ether before terminal modification. The method for measuring the number of hydroxyl groups remaining in the terminal-modified polyphenylene ether can be determined by adding a quaternary ammonium salt (tetraethylammonium hydroxide) that associates with the hydroxyl group to a solution of the terminal-modified polyphenylene ether and measuring the UV absorbance of the mixed solution.

[0026] [(B) Synthetic Rubber] 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 polyisopropylene. From the viewpoints of electrical properties and heat resistance, styrene-butadiene and epoxy-modified 1,2-polybutadiene are particularly preferred. Blending a synthetic rubber is preferable because the flexibility of the resulting resin composition and the adhesion to metal are improved.

[0027] [(C) Crosslinking agent] The crosslinking agent used in the present invention is not particularly limited, but more preferably has a decomposition temperature of 100 to 150 °C. Examples of the crosslinking agent include sulfur-based, peroxide-based, quinoid-based, and bismaleimide-based crosslinking agents. In this specification, the "decomposition temperature" refers to the 10-hour half-life temperature.

[0028] Examples of the sulfur-based crosslinking agent include sulfur, tetramethylthiuram disulfide, 2-(morpholinodithio)benzothiazole, and morpholine disulfide.

[0029] Examples of the peroxide-based crosslinking agent include dicumyl peroxide, tert-butyl cumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexine-3, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, and α,α'-bis(tert-butylperoxy-m-isopropyl)benzene.

[0030] Examples of the quinoid-based crosslinking agent include p-quinone dioxime, p,p'-dibenzoylquinone dioxide, and p-nitrosobenzene.

[0031] Examples of the bismaleimide-based compounds include 4,4'-bismaleimidodiphenylamine and N,N'-m-phenylenebismaleimide. Note that when a peroxide-based crosslinking agent is used, the bismaleimide-based crosslinking agent can also be used as a crosslinking aid, which will be described later.

[0032] The crosslinking agent is preferably a peroxide-based one, more preferably dicumyl peroxide. It is preferable that the crosslinking agent is peroxide-based because the reaction does not proceed at the temperature for removing the solvent when producing a sheet from the varnish.

[0033] The mixing ratios of the above-mentioned (A) polyphenylene ether resin, (B) synthetic rubber, and (C) crosslinking agent are not particularly limited. For example, when the total mass of the three components is 100, it is preferably in the range of (A):(B):(C) = 30:25:60 to 50:5:45. Being within the above range is preferable because it is excellent in electrical properties and heat resistance.

[0034] [Inorganic filler] ≪(D-1) First inorganic filler≫ (Boron nitride) The boron nitride of this 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 inorganic composite sheet described later is formed, the thermal conductivity in the thickness direction is improved, which is preferable.

[0035] The average particle size of the boron nitride is preferably 10 μm or more and 80 μm or less, more preferably 30 μm or more and 70 μm or less. Being within the above range is preferable because the thermal conductivity of the resulting cured product is improved. In the present invention, the "average particle size" of the first inorganic filler refers to the particle size of aggregated or massive secondary particles.

[0036] For the boron nitride of this embodiment, commercially available products can be used, such as HP-40MF, HP40-J2 (manufactured by Mizushima Alloy Iron Co., Ltd.), PTX60 (manufactured by Momentive), Agglomerates50 (manufactured by 3M), etc. Preferred are HP-40MF and HP40-J2 (manufactured by Mizushima Alloy Iron Co., Ltd.) which are fired without internal voids and made into aggregates.

[0037] The boron nitride of this embodiment can also be produced by a known method. For example, the method described in JP-A-2019-073409 can be used.

[0038] In the resin composition of this embodiment, the content of boron nitride 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.

[0039] ≪(D-2) Second inorganic filler≫ The resin composition of the present invention may contain a second inorganic filler, and examples of the second inorganic filler include alumina and / or aluminum nitride. Alumina and / or aluminum nitride is preferable because it has excellent thermal conductivity.

[0040] (Alumina) In this embodiment, "alumina" is aluminum oxide, and it may be various transition aluminas such as γ, δ, θ, κ, etc., or may contain alumina hydrate in the transition alumina, but in terms of better stability, it is basically preferably in the α crystal form.

[0041] The shape of the alumina is preferably spherical or polyhedral, and more preferably polyhedral with 14 or more faces. By having 14 or more faces, the interplanar distance between particles becomes closer compared to polyhedra with less than 14 faces, making it easier to obtain excellent thermal conductivity, which is preferable.

[0042] The shape of alumina can be confirmed by a scanning electron microscope (SEM). Using a JCM7000 manufactured by JEOL, observe the images obtained from multiple SEM images from any field of view of the sample. Then, for the observation results of 50 randomly selected alumina particles, the shape of 60% or more of the particles can be determined as the shape possessed by the sample based on the number.

[0043] In this embodiment, the average particle size of alumina is preferably 25 μm or more and 45 μm or less. When the average particle size is 25 μm or more, it is preferable to suppress the increase in viscosity when made into a varnish. When the average particle size is 45 μm or less, it is preferable because of excellent processability of the sheet.

[0044] In this specification, the "average particle size" is defined as the value calculated as the volume-based median diameter D50 from the volume-based cumulative particle size distribution measured by a laser diffraction / scattering particle size distribution measuring device. 。

[0045] In the resin composition of this embodiment, the content of alumina may be 30 to 80 parts by mass, or may be 40 to 70 parts by mass, per 100 parts by mass of the total solid content of the resin composition. The suitable content of alumina can be set according to the content of boron nitride described later.

[0046] For the alumina in this embodiment, commercially available alumina particles may be used, or alumina particles produced by the methods described in JP-A-2016-028993 and WO 2021 / 070729 may also be used.

[0047] Examples of commercially available alumina particles include DAW45 (manufactured by Denka), CB-A20S, CB-AS30S, CB-P15 (manufactured by Resonaak), AZ series (manufactured by Nippon Steel & Sumikin Materials & Chemicals), AH40-S (manufactured by DIC), and AO-502 (manufactured by Admatechs). From the perspective of fluidity, CB-A20S, CB-A30S, CB-P15 (manufactured by Resonaak), AO-502 (manufactured by Admatechs) are good, and from the perspective of thermal conductivity, AH40-S (manufactured by DIC) is good, but it is not limited to these.

[0048] Note that these alumina particles may be used alone or in combination of a plurality. However, it is preferable to use them in combination of a plurality. When used in combination of a plurality, it is preferable that the polyhedral alumina particles contain 50% by mass or more, more preferably 60% by mass or more, in all the alumina. By being within the above range, the resulting inorganic composite sheet and the metal base substrate have particularly excellent thermal conductivity, which is preferable.

[0049] (aluminum nitride) As the aluminum nitride, known and commonly used ones are used. However, it is preferably granular with an average particle diameter 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.), but are not limited thereto.

[0050] In the resin composition of the present 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, per 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.

[0051] Within the above range, the contents of (D-1) the first inorganic filler and (D-2) the second inorganic filler may be in any combination. However, the mass ratio of (D-1) the first inorganic filler to (D-2) the second inorganic filler is preferably 50:50 to 5:95, more preferably 45:55 to 10:90, and particularly preferably 40:60 to 15:85. Being within the above range is preferable because both the thermal conductivity and the insulation reliability can be achieved at an excellent level.

[0052] By combining (D-1) the first inorganic filler and (D-2) the second inorganic filler, a conventionally excellent thermal conductivity can be obtained, so that the filling amount in the resin composition can be reduced. Further, by reducing the filling amount, the breakdown voltage of the resin composition increases, and furthermore, the variation in the breakdown voltage is suppressed, and the electrical characteristics can be stabilized. From the viewpoint of the properties obtained, it is particularly preferable that (D-1) is the first inorganic filler alone.

[0053] [(E) Crosslinking aid] In the present embodiment, when a peroxide-based crosslinking agent is used as the (C) crosslinking agent, it is preferable to further add a crosslinking aid from the viewpoint of promoting an efficient crosslinking reaction. Examples of the crosslinking aid include at least one selected from the group consisting of ester acrylate, epoxy acrylate, urethane acrylate, ether acrylate, melamine acrylate, alkyd acrylate, silicon acrylate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, vinyltoluene, ethyl vinylbenzene, styrene, polyparamethylstyrene, and polyfunctional epoxy. From the viewpoints of electrical characteristics and heat resistance, triallyl isocyanurate is particularly preferable.

[0054] The blending amount of the (E) crosslinking aid is preferably 0.5 to 5 wt% when the entire resin composition (excluding the inorganic filler) is 100. Within the above range, the crosslinking reaction can proceed efficiently.

[0055] [(F) Silane coupling agent] Examples of the silane coupling agent include epoxy silane.

[0056] <Varnish> The resin composition of the present invention can be suitably used for varnish. As the method for preparing the varnish, a known method can be used, and the resin composition can be dissolved (diluted) in an organic solvent to obtain a varnish.

[0057] As the solvent, for example, polar solvents such as methyl ethyl ketone, methoxypropanol, N,N-dimethylformamide, and dimethyl sulfoxide can be used. The solvent may be only one kind, or two or more kinds may be used in combination.

[0058] The amount of the solvent used is not particularly limited, and can be appropriately determined in consideration of, for example, sheet processability. Specifically, it is preferable to adjust so that the viscosity of the obtained varnish becomes 3000 mPa·s to 15000 mPa·s. When the viscosity is 3000 mPa·s or more, it is preferable because appearance defects due to repulsion during coating are suppressed. When the viscosity is 15000 mPa·s or less, it is preferable because appearance defects due to streaks during coating are suppressed.

[0059] 〔Other components〕 The varnish can contain other components as long as the object of the present invention is not impaired. For example, a dispersant and the like can be mentioned.

[0060] The dispersant is not particularly limited as long as it is a dispersant used for paints. For example, Disperbyk-110, 111, 180, 161, BYK-W996, W9010, W903, etc. can be mentioned. 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 within the above range.

[0061] <Inorganic composite sheet> The varnish is suitably used for an inorganic composite sheet. The inorganic composite sheet is obtained by applying the above-mentioned varnish to a carrier material and heating and drying it. Note that the inorganic composite sheet is formed in a semi-cured state on the surface of the carrier material. That is, the heating and drying means B-stage formation, and by heating the varnish applied to the carrier material, a part of the cross-linking reaction in the varnish is carried out. Therefore, the inorganic composite sheet of the present embodiment has the property of curing after being once melted by heating and pressing in laminated molding.

[0062] The method of applying the varnish is not particularly limited and can be carried out by known methods. For example , methods such as comma coating, die coating, lip coating, gravure coating, etc. can be mentioned. As a method of forming an inorganic composite sheet with a predetermined thickness, a comma coating method of passing an object to be coated between gaps , a die coating method of applying a varnish with a regulated flow rate from a nozzle, etc. are preferable .

[0063] The thickness of the inorganic composite sheet formed on the carrier material is preferably 100 to 200 μm. When the thickness is 200 μm or less, the thermal resistance becomes small, which is preferable. The closer the thickness is to 20 0 μm, the generation of microvoids during sheet formation can be suppressed, and the breakdown voltage becomes large, which is preferable. When two inorganic composite sheets are laminated and used, it is preferable to adjust the thickness per sheet so that the thickness after lamination pressing is 100 to 200 μm. The resin composition of the present invention can be made thinner compared to conventional ones, and since the carrier material can be easily peeled off, it is possible to obtain an inorganic composite sheet with a thickness of 100 to 200 μm even in the case of two-layer laminated press formation.

[0064] As the carrier material, it is preferable to use a polymer film or a metal sheet. As the polymer film, polyolefins such as polyethylene, polypropylene, polyvinyl chloride, etc., polyesters such as polyethylene terephthalate, polycarbonate, acetyl cellulose , tetrafluoroethylene, etc. can be mentioned. As the metal sheet, examples of the metal sheet include metal foils such as copper foil, aluminum foil, nickel foil, etc. can be given. Furthermore, as the carrier material, release paper, etc. can be mentioned.

[0065] <Metal-based substrate> ​​​The inorganic composite sheet of the present invention can be laminated and suitably used as a metal-based substrate. Specifically, two or more of the inorganic composite sheets obtained above are laminated to a desired thickness, and then metal foil is disposed on the outermost layer on one or both sides thereof to form a laminate, and this laminate is integrally laminated by heating and pressing such as press molding. Here, as the metal foil, a single, alloy, or composite metal foil such as copper, aluminum, brass, nickel, etc. can be used. As the conditions for heating and pressing the laminate, it may be appropriately adjusted under the conditions where the varnish is cured and then heated and pressed. However, if the pressure of pressing is too low, bubbles may remain inside the obtained metal-based substrate, and the electrical characteristics may deteriorate. Therefore, it is preferable to press under conditions that satisfy the moldability. For example, a metal-based substrate can be obtained by integrally molding by heating and pressing at a heating temperature of 100 to 200 ° C and a pressure of 0.98 to 4.9 MPa for 10 minutes to 2 hours.

Example

[0066] Hereinafter, the present invention will be described in more detail based on examples, but this description does not limit the present invention.

[0067] 〔Preparation of filler〕 In this embodiment, a combination of a plurality of fillers was used. The blending of each filler is shown in Table 1.

[0068] The fillers used are as follows. HP40MF100 (agglomerated boron nitride, JFE Minerals Co., Ltd.) HP40MFJ2 (agglomerated boron nitride, JFE Minerals Co., Ltd.) AH-40S (polyhedral alumina, DIC Corporation)

[0069] [Production Example 1] 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, and then filled into a graphite crucible. In an arc furnace, under an argon atmosphere, heating was carried out at 2200 °C for 5 hours to synthesize boron carbide. The synthesized boron carbide mass was pulverized in a ball mill for 40 minutes, sieved using a sieve to a particle size of 75 μm or less, and further washed with an aqueous nitric acid solution to remove impurities such as iron content, and then filtered and dried to produce boron carbide powder with an average particle size of 33 μm.

[0070] After filling the boron carbide powder into a boron nitride crucible, using a resistance heating furnace, under a nitrogen gas atmosphere, heating was carried out at 2000 °C and 9 atmospheres (0.8 MPa) for 10 hours to obtain boron carbonitride.

[0071] 100 parts by mass of the boron carbonitride and 200 parts by mass of boric acid were mixed using a Henschel mixer, and then filled into a boron nitride crucible. Using a resistance heating furnace under a pressure condition of 0.3 MPa, under a nitrogen gas atmosphere, the heating rate from room temperature to 1000 °C was 10 °C / min, and the heating rate from 1000 °C was 2 °C / min. The temperature was raised to a holding temperature of 2000 °C, and heating was carried out at the holding temperature of 2000 °C for a holding time of 10 hours to synthesize massive boron nitride in which primary particles were aggregated into a massive shape.

[0072] The synthesized massive boron nitride was pulverized in a mortar for 10 minutes, and then classified using a nylon sieve with a mesh size of 95 μm using a sieve. By pulverizing and classifying the fired product, boron nitride powder composed of massive boron nitride in which primary particles were aggregated into a massive shape was obtained.

[0073] [Production Example 2] Synthesis was carried out under the same conditions as in Production Example 1, except that the pulverization during the synthesis of boron carbide was carried out for 1 hour, and boron carbide with an average particle size of 20 μm (carbon content 19.9%) was synthesized as a raw material.

[0074] (Average particle diameter D50) The value calculated as the volume-based median diameter D50 shall be used from the volume-based cumulative particle size distribution measured by a laser diffraction / scattering type particle size distribution measuring device.

[0075]

Table 1

[0076] 〔Preparation of Resin〕 The resin was prepared according to Table 2.

[0077] The materials used are as follows. Polyphenylene ether (NORYL SA9000, number average molecular weight 1900: manufactured by SABIC) Epoxy (the following three components were mixed and used in a formulation of a:b:c = 11:6:3) a: Epiklon 850 (manufactured by DIC Corporation, bisphenol A type epoxy resin) b: NC-3000 (manufactured by Nippon Kayaku Co., Ltd., phenol biphenyl aralkyl epoxy resin) c: VG-3101 (manufactured by Printec Co., Ltd., trifunctional epoxy resin) Styrene-butadiene copolymer (SBS: manufactured by Asahi Kasei Corporation) 1,4-Polybutadiene (PB: manufactured by Nippon Soda Co., Ltd.) Triallyl isocyanurate (TAIC: manufactured by Mitsubishi Chemical Corporation) Dicumyl peroxide (Perk Mill D, decomposition temperature 116.4°C: manufactured by NOF Corporation) 1,1-Di((t-butylperoxy)cyclohexyl)propane (Perhexa C, decomposition temperature 90.7°C: manufactured by NOF Corporation)

[0078]

Table 2

[0079] 〔Examples 1 to 8, Comparative Example 1〕 Using the adjusted filler and resin, a resin composition was obtained according to Table 3. Further, an inorganic composite sheet and a metal-based substrate were produced and evaluated according to the following methods.

[0080] (Fabrication of Metal-Based Substrate) The obtained resin composition was kneaded in a planetary mixer, and a varnish with a viscosity adjusted to 3000 mPa·s was obtained by adding a predetermined amount of solvent (toluene). Next, this varnish was applied to a polyethylene terephthalate (PET) film with a thickness of 75 μm and dried by heating at 130°C for 8 minutes to form an inorganic composite sheet with a thickness of 150 μm in a B-stage state on one side of the carrier material.

[0081] One obtained inorganic composite sheet was stacked, 18-μm copper foil was placed on the coated sheet and a 1-mm aluminum plate, and heat and pressure molding was carried out at a heating temperature of 175°C and a pressure of 2.94 MPa for 30 minutes in a vacuum to fabricate a metal-based substrate. In the comparative example using epoxy, since it could not be fabricated under the above conditions, the heating temperature was changed to 175°C and the pressure was changed to 2.94 MPa for 90 minutes, and heat and pressure molding was carried out.

[0082] 〔Example 9〕 (Fabrication of Laminated Inorganic Composite Sheet) The resin composition obtained according to Table 3 was kneaded in a planetary mixer, and a varnish with a viscosity adjusted to 3000 mPa·s was obtained by adding a predetermined amount of solvent (toluene). Next, this varnish was applied to a polyethylene terephthalate (PET) film with a thickness of 75 μm and dried by heating at 130°C for 8 minutes to form an inorganic composite sheet with a thickness of 100 μm in a B-stage state on one side of the carrier material.

[0083] Two obtained inorganic composite sheets were stacked, 18-μm copper foil was placed on both sides, and heat and pressure molding was carried out at a heating temperature of 175°C and a pressure of 2.94 MPa for 30 minutes in a vacuum to fabricate a metal-based substrate.

[0084] In the conventional inorganic composite sheet, it was impossible to peel off the carrier material and handle it alone, and it was difficult to form a thin-film inorganic composite sheet. Therefore, when it was used by laminating and pressing, it became thick, and it was impossible to obtain an inorganic composite sheet like the present embodiment.

[0085] (Thermal conductivity) The inorganic composite sheets were laminated and hot-pressed at a heating temperature of 175 °C and a pressure of 2.94 MPa for 90 minutes in a vacuum to obtain a sheet cured product with a thickness of 1 mm. The thermal diffusivity and specific heat of the sheet cured product at 25 °C were measured using a thermal conductivity measuring device (LFA467 HyperFlash, manufactured by NETZSCH). Next, the density of this heat dissipation member was measured by the Archimedes method. The thermal conductivity of this heat dissipation member was estimated from the product of the obtained thermal diffusivity, specific heat, and density.

[0086] (Evaluation of 90-degree peel strength (peeling strength)) Based on JIS C 6481, the peeling strength of the copper foil of the obtained metal base substrate was measured. As the peel strength measuring device, "Autograph" manufactured by Shimadzu Corporation was used. The peeling strength of the copper foil was measured for 20 test samples. The average value of the measured values of the peeling strength of the copper foil in 20 test samples was taken as the 90-degree peel strength.

[0087] (Evaluation of dielectric breakdown strength) The copper foil on the obtained metal base substrate was etched to pattern the copper foil into a circle with a diameter of 2.5 cm to obtain test samples. Using a withstand voltage tester (YST-243AT-100, manufactured by Yamayo Testing Instruments 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 dividing the dielectric breakdown voltage by the thickness of the test sample.

[0088] (Area ratio) The cross-section of the obtained metal-based 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 SEM to obtain SEM images and elemental mapping images. In the elemental mapping analysis, the distribution of nitrogen was analyzed.

[0089] From the obtained TEM image and elemental mapping image, (D-1) the first inorganic filler was identified, and the area ratio of the (D-1) first inorganic filler with an average particle diameter of 30 to 70 μm was calculated.

[0090]

Table 3

[0091] In any of the resin compositions of the examples, compared with the resin compositions of the comparative examples, curing proceeded at a low pressure in a short time, so that the molding cycle could be significantly shortened.

Claims

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

2. 2. The resin composition according to claim 1, wherein the polyphenylene ether resin (A) 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 synthetic rubber (B) is at least one selected from the group consisting of 1,2-polybutadiene, 1,4-polybutadiene, styrene butadiene, malein-modified 1,2-polybutadiene, acrylic-modified 1,2-polybutadiene, epoxy-modified 1,2-polybutadiene, styrene-conjugated diene block copolymer, hydrogenated styrene-conjugated diene block copolymer, and polyisopropylene.

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

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

6. The resin composition according to claim 5, further comprising a crosslinking aid (E), the crosslinking aid (E) being at least one selected from the group consisting of ester acrylate, epoxy acrylate, urethane acrylate, ether acrylate, melamine acrylate, alkyd acrylate, silicon acrylate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, vinyl toluene, ethyl vinyl benzene, styrene, polyparamethylstyrene, and polyfunctional epoxy.

7. The resin composition according to claim 1, further comprising alumina and / or aluminum nitride as a second inorganic filler (D-2).

8. The resin composition according to claim 1 or 6, further comprising (F) a silane coupling agent.

9. A varnish comprising the resin composition according to claim 1.

10. 10. An inorganic composite sheet comprising a carrier material coated with the varnish according to claim 9 and a varnish layer formed in an uncured state to a thickness of 100 to 200 μm.

11. An inorganic composite sheet having an uncured varnish layer formed by applying the varnish according to claim 9 to a carrier material, the inorganic composite sheet being formed by laminating two inorganic composite sheets to a thickness of 100 to 200 μm.

12. A metal base substrate obtained by laminating and molding the inorganic composite sheet according to claim 10 or 11.

13. In the inorganic composite sheet layer (excluding the carrier material) of the cross section of the metal base substrate, the (D-1) first inorganic filler is observed to have an average particle size of 30 to 70 μm in 70% or more of the inorganic composite sheet layer.

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