Thermally conductive resin composition, thermally conductive resin sheet, and laminate

Abstract

To provide a thermally conductive resin composition which is excellent in heat resistance and suppresses deterioration of long-term insulation reliability after heat treatment.SOLUTION: A thermally conductive resin composition comprising: a thermosetting resin; a thermosetting agent; and an inorganic filler, wherein the thermosetting agent comprises an imide oligomer, and the inorganic filler comprises boron nitride aggregate particles and silica nanoparticles.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive resin composition, a thermally conductive resin sheet that is a cured product of the thermally conductive resin composition, and a laminate including the thermally conductive resin sheet. [Background technology]

[0002] Power modules have been used in a wide range of fields, including industrial equipment, household electrical appliances, and information terminals. Attempts have been made to use resin sheets as substrates in power modules, and power modules using resin sheets are expected to be used in high-voltage applications, for example. Such resin sheets are generally required to have excellent thermal conductivity, and it is known that heat dissipation can be enhanced by highly loading fillers such as agglomerated particles of boron nitride.

[0003] Patent Document 1 proposes a thermally conductive sheet that uses an inorganic filler (flake boron nitride) with a porosity and average pore diameter within a specific range as a thermally conductive sheet with an excellent balance of heat dissipation and insulation properties. Patent Document 2 proposes an insulating composition that is excellent in insulation, moisture resistance, heat resistance (solder reflow resistance), thermal conductivity, and flexibility and adhesiveness after long-term heating. The insulating composition contains a polyimide resin (A) that is a reaction product of a tetracarboxylic dianhydride and a polyamine compound containing a siloxane diamine, a curing agent (B), and a thermally conductive filler (C), and the thermally conductive filler (C) has a tap density of 0.4 g / cm. 3 More than 2.3g / cm 3 Disclosed is an insulating composition comprising boron nitride (c) having less than [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6634717 [Patent Document 2] Japanese Patent Application Publication No. 2023-119440 Summary of the Invention [Problem to be solved by the invention]

[0005] The manufacturing process for semiconductor packages includes a reflow process, in which resin sheets are exposed to high temperatures of around 200 to 300°C. Therefore, heat resistance that can withstand such high temperatures is required. Poor heat resistance reduces the insulating properties of the resin sheet, resulting in reduced product reliability. Furthermore, resin sheets are also expected to have long-term insulating reliability, such as maintaining their insulating properties even after heat treatment such as the reflow process, even when subjected to temperature cycle loads (repeated temperature changes from low to high).

[0006] As mentioned above, resin sheets with a high fill rate of boron nitride can increase thermal conductivity, but because boron nitride does not mix well with resin, there is concern that when resin sheets containing this material are subjected to external thermal loads, degradation points will occur, causing a deterioration in insulation and reducing the reliability of the power module. Here, thermal load refers to the exposure of resin sheets to high temperatures during the "reflow process" in the semiconductor package manufacturing process mentioned above, as well as temperature cycle loads caused by heat generation and ON / OFF switching from the chip during continuous use after packaging.

[0007] The invention described in Patent Document 1 leaves room for improvement in the heat resistance of the resin sheet. Also, the invention described in Patent Document 2 proposes a means of improving heat resistance by increasing the dispersibility of boron nitride in the composition and incorporating a siloxane structure to impart flexibility, but there is still room for improvement in the long-term insulation reliability after heat treatment. Therefore, an object of the present invention is to provide a thermally conductive resin composition that is excellent in heat resistance and that prevents a decrease in long-term insulation reliability after heat treatment. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result have found that the above-mentioned problems can be solved by a thermally conductive resin composition comprising a thermosetting resin, a thermosetting agent, and an inorganic filler, wherein the thermosetting agent comprises an imide oligomer, and the inorganic filler comprises agglomerated boron nitride particles and silica nanoparticles, thereby completing the present invention. That is, the present invention relates to the following [1] to

[16] .

[0009] [1] A thermally conductive resin composition comprising a thermosetting resin, a thermosetting agent, and an inorganic filler, wherein the thermosetting agent comprises an imide oligomer, and the inorganic filler comprises agglomerated boron nitride particles and silica nanoparticles. [2] The thermally conductive resin composition according to [1] above, wherein the imide oligomer has reactive functional groups at both ends or one end of the molecule that can react with the thermosetting resin, and the reactive functional groups are acid anhydride groups, amine groups, or hydroxyl groups. [3] The thermally conductive resin composition according to [1] or [2] above, wherein the imide oligomer does not have a linear saturated hydrocarbon chain having 16 or more carbon atoms in its skeleton. [4] The thermally conductive resin composition according to any one of the above [1] to [3], wherein the molecular weight of the imide oligomer is 500 to 10,000. [5] The thermally conductive resin composition according to any one of the above [1] to [4], wherein the higher of the softening point and the melting point of the thermosetting resin is 150°C or lower. [6] The thermally conductive resin composition according to any one of the above [1] to [5], wherein the content of the boron nitride agglomerated particles is 65% by volume or more in 100% by volume of the thermally conductive resin composition. [7] The thermally conductive resin composition according to any one of the above [1] to [6], wherein the average particle size of the agglomerated particles of boron nitride is 5 μm or more and 100 μm or less. [8] The thermally conductive resin composition according to any one of the above [1] to [7], wherein the inorganic filler contains an inorganic filler other than agglomerated boron nitride particles and silica nanoparticles. [9] The thermally conductive resin composition according to [8] above, wherein the inorganic filler is at least one selected from the group consisting of alumina, aluminum nitride, magnesium oxide, diamond, and silicon carbide.

[10] The thermally conductive resin composition according to [8] above, wherein the content of the inorganic filler is 5% by volume or more and 40% by volume or less, based on 100% by volume of the thermally conductive resin composition.

[11] The thermally conductive resin composition according to any one of the above [1] to

[10] , wherein the silica nanoparticles have an average particle size of 1 nm or more and 100 nm or less.

[12] The thermally conductive resin composition according to any one of [1] to

[11] above, wherein the content of the silica nanoparticles is 1% by volume or more and 5% by volume or less, based on 100% by volume of the thermally conductive resin composition.

[13] The thermally conductive resin composition according to any one of the above [1] to

[12] , wherein the silica nanoparticles are surface-modified with a surface treatment agent.

[14] The thermally conductive resin composition according to

[13] above, wherein the surface treatment agent is at least one compound having a structure selected from the group consisting of dimethylsilyl, trimethylsilyl, polydimethylsiloxane, aminoalkylsilyl, alkylsilyl, methacrylsilyl, methacrylsilane, methacryl, vinyl, phenyl, phenylamino, phenylaminosilane, and epoxy.

[15] A thermally conductive resin sheet which is a cured product of the thermally conductive resin composition according to any one of the above [1] to

[14] .

[16] A laminate comprising the thermally conductive resin sheet according to

[15] above, a metal base plate, and a metal plate, the thermally conductive resin sheet and the metal plate being disposed in this order on the metal base plate. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a thermally conductive resin composition that is excellent in heat resistance and that is inhibited from decreasing in long-term insulation reliability after heat treatment. [Brief explanation of the drawings]

[0011] [Figure 1]1 is a schematic cross-sectional view showing a laminate according to one embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing a semiconductor device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0012] [Thermal conductive resin composition] The thermally conductive resin composition of the present invention comprises a thermosetting resin, a thermosetting agent, and an inorganic filler, wherein the thermosetting agent comprises an imide oligomer, and the inorganic filler comprises agglomerated boron nitride particles and silica nanoparticles.

[0013] <Thermosetting resin> The thermally conductive resin composition of the present invention contains a thermosetting resin. The thermosetting resin is not particularly limited, but examples thereof include amino resins such as urea resins and melamine resins, phenolic resins, thermosetting urethane resins, epoxy resins, thermosetting polyimide resins, aminoalkyd resins, and benzoxazine resins. The thermosetting resins used in the thermally conductive resin composition may be used alone or in combination of two or more. Of the above, epoxy resins are preferred as the thermosetting resin.

[0014] Examples of epoxy resins include compounds containing two or more epoxy groups in the molecule. Examples of epoxy resins include styrene skeleton-containing epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, phenol novolac epoxy resins, biphenol epoxy resins, naphthalene epoxy resins, biphenyl epoxy resins, fluorene epoxy resins, phenol aralkyl epoxy resins, naphthol aralkyl epoxy resins, dicyclopentadiene epoxy resins, anthracene epoxy resins, epoxy resins having an adamantane skeleton, epoxy resins having a tricyclodecane skeleton, epoxy resins having a triazine nucleus in the skeleton, and glycidylamine epoxy resins. The epoxy resin may also be a phenoxy resin. The phenoxy resin is, for example, a resin obtained by reacting epihalohydrin with a divalent phenol compound, or a resin obtained by reacting a divalent epoxy compound with a divalent phenol compound. Examples of the phenoxy resin include those having a bisphenol A type skeleton, a bisphenol F type skeleton, a bisphenol A / F mixed type skeleton, a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, a bisphenol TMC skeleton, an adamantane skeleton, or a dicyclopentadiene skeleton. From the viewpoint of improving the flexibility of the thermally conductive resin composition, among the epoxy resins, bisphenol A type epoxy resin or bisphenol F type epoxy resin is preferred.

[0015] From the viewpoint of improving the flexibility and insulating properties of the thermally conductive resin composition, the epoxy resin is preferably a liquid epoxy resin, which means an epoxy resin that is liquid at 25°C. From the viewpoint of improving the flexibility and insulating properties of the thermally conductive resin composition, the thermosetting resin preferably contains a liquid epoxy resin having a viscosity at 25°C of 50,000 m·Pa or less. The viscosity of the liquid epoxy resin is preferably 1000 mPa·s or more and 50000 mPa·s or less, more preferably 1500 mPa·s or more and 20000 mPa·s or less, and even more preferably 2000 mPa·s or more and 10000 mPa·s or less. The viscosity is measured using a Brookfield viscometer at 25°C and 10 rpm.

[0016] From the viewpoint of improving the flexibility and insulating properties of the thermally conductive resin composition, the content of the liquid epoxy resin having a viscosity of 50,000 mPa·s or less at 25°C is preferably 40% by volume or more, more preferably 60% by volume or more, even more preferably 80% by volume or more, and even more preferably 100% by volume, of 100% by volume of the thermosetting resin.

[0017] The softening point and melting point of the thermosetting resin are not particularly limited, but from the viewpoint of ease of production of the thermally conductive resin composition and the thermally conductive resin sheet formed from the composition, the higher of the softening point and the melting point is preferably 150°C or less, more preferably 145°C or less, more preferably 130°C or less, and even more preferably 100°C or less. In this specification, the softening point is a value measured by the softening point test method (ring and ball method) specified in JIS K 7234. The melting point is a value measured as the temperature of the endothermic peak when the temperature is raised at 10°C / min using a differential scanning calorimeter. An example of the differential scanning calorimeter is the EXTEAR DSC6100 (manufactured by SII NanoTechnology Inc.).

[0018] The content of the thermosetting resin is preferably 5% by volume or more, more preferably 10% by volume or more, and preferably 30% by volume or less, more preferably 20% by volume or less, based on 100% by volume of the thermally conductive resin composition. When the content of the thermosetting resin is equal to or greater than these lower limit values, the flexibility of the thermally conductive resin composition is easily improved, and when the content of the thermosetting resin is equal to or less than these upper limit values, a certain amount or more of inorganic filler can be blended, which makes it easier to increase the thermal conductivity. Although the thermally conductive resin composition may contain a solvent, in this specification, 100% by volume of the thermally conductive resin composition means 100% by volume of the total components excluding the solvent. The solvent is removed by processes such as drying and curing when producing a thermally conductive resin sheet from the thermally conductive resin composition.

[0019] <Thermal curing agent> The thermally conductive resin composition of the present invention contains a thermosetting agent. The thermosetting resin can be cured by the thermosetting agent. It is preferable that the thermosetting resin is cured by the thermosetting agent and binds the inorganic filler. In the present invention, the heat curing agent contains an imide oligomer. By containing the imide oligomer, the heat resistance of the thermally conductive resin composition is improved. Therefore, even when exposed to high temperatures during a reflow process or the like, deterioration of the insulating properties can be suppressed.

[0020] The imide oligomer is a compound having an imide skeleton in its main chain, and preferably a compound having an aromatic ring in its skeleton. By having an aromatic ring in its skeleton, the thermally conductive resin composition is less susceptible to thermal decomposition, and heat resistance is likely to be improved. Furthermore, from the viewpoint of improving heat resistance, it is preferable that the imide oligomer does not have a linear saturated hydrocarbon chain having 16 or more carbon atoms in its skeleton.

[0021] The imide oligomer has reactive functional groups at both ends or one end of the molecule that can react with the thermosetting resin, and the reactive functional groups are preferably acid anhydride groups, amino groups, or hydroxyl groups. The amino groups are not particularly limited and may be primary, secondary, or tertiary amino groups. The hydroxyl groups may be phenolic hydroxyl groups or hydroxyl groups other than phenolic hydroxyl groups. Use of an imide oligomer having such reactive functional groups tends to improve the heat resistance of the thermally conductive resin composition. From the viewpoint of heat resistance, the reactive functional groups of the imide oligomer are more preferably acid anhydride groups or phenolic hydroxyl groups.

[0022] The molecular weight of the imide oligomer is preferably 500 to 10,000. When the molecular weight is within this range, the heat resistance of the thermally conductive resin composition is likely to be improved. The molecular weight of the imide oligomer is more preferably 700 to 7,000, and even more preferably 900 to 5,000. The molecular weight of the imide oligomer is preferably 500 or more, more preferably 700 or more, and even more preferably 900 or more, and is preferably 10,000 or less, more preferably 7,000 or less, and even more preferably 5,000 or less. The molecular weight is a number average molecular weight measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent. Examples of columns used for measuring the number average molecular weight calculated as a polystyrene equivalent by GPC include JAIGEL-2H-A (manufactured by Japan Analytical Industry Co., Ltd.). Specifically, the measurement can be performed using tetrahydrofuran as a solvent at room temperature and a flow rate of 1 mL / min. The solvent is not particularly limited as long as it dissolves the sample to be measured, and the flow rate can be selected according to the column and device.

[0023] Examples of the imide oligomer include an imide oligomer having a segment derived from an acid dianhydride represented by the following formula (1) and a segment derived from a polyamine compound. In this case, the segment derived from the acid dianhydride represented by formula (1) is preferably present at the end of the main chain, and more preferably at both ends of the main chain. Examples of the polyamine compound include aromatic diamine compounds, aliphatic diamine compounds, and aliphatic triamine compounds.

[0024] [ka] In formula (1), A is an acid dianhydride residue, which is a tetravalent group represented by the following formula (3-1) or (3-2).

[0025] [ka] In formulas (3-1) and (3-2), * represents a bonding position, and in formula (3-1), Z represents a bond, an oxygen atom, a carbonyl group, a sulfur atom, a sulfonyl group, a linear or branched divalent hydrocarbon group which may have an oxygen atom at the bonding position, or a divalent group having an aromatic ring which may have an oxygen atom at the bonding position. The hydrogen atoms of the aromatic ring in formulas (3-1) and (3-2) may be substituted.

[0026] The polyamine compound may be an aromatic polyamine compound or an aliphatic polyamine compound, and among these, an aromatic polyamine compound is preferred. By using an imide oligomer having a segment derived from an aromatic polyamine compound, it becomes easier to obtain a thermally conductive resin composition having excellent heat resistance.

[0027] Examples of the aromatic polyamine compound include aromatic diamine compounds and aromatic triamine compounds, and the aromatic diamine compound represented by the following formula (2) is preferred. [ka] In formula (2), B is an aromatic diamine residue, and is a divalent group represented by the following formula (4-1) or (4-2): 1 ~R 4 are each independently a hydrogen atom or a monovalent hydrocarbon group.

[0028] [ka] In formula (4-1) and formula (4-2), * represents a bonding position, and in formula (4-1), Y represents a bond, an oxygen atom, a carbonyl group, a sulfur atom, a sulfonyl group, a linear or branched divalent hydrocarbon group which may have an oxygen atom at the bonding position, or a divalent group having an aromatic ring which may have an oxygen atom at the bonding position. In formula (4-1) and formula (4-2), some or all of the hydrogen atoms of the phenylene group may be substituted with a hydroxyl group or a monovalent hydrocarbon group.

[0029] Examples of the aliphatic polyamine compound include an aliphatic diamine compound, an aliphatic triamine compound, etc. Commercially available aliphatic diamine compounds and aliphatic triamine compounds include Versamine 551 and Versamine 552 manufactured by BASF, and Priamine 1071, Priamine 1073, Priamine 1074, and Priamine 1075 manufactured by Croda.

[0030] Specifically, the imide oligomer is preferably an imide oligomer represented by the following formula (5-1), (5-2), (5-3), (5-4), or (5-5). [ka]

[0031] In formulas (5-1) to (5-5), A represents an acid dianhydride residue and may be the same as in formula (1). In formulas (5-1) to (5-5), A may be the same or different. In formulas (5-1) to (5-5), B represents an aliphatic diamine residue or an aromatic diamine residue, or an aliphatic triamine residue or an aromatic triamine residue. In formulas (5-3) and (5-4), B may be the same or different. When B represents an aliphatic diamine residue or an aliphatic triamine residue, the number of carbon atoms is, for example, 4 to 60. When B represents an aromatic diamine residue or an aromatic triamine residue, the number of carbon atoms is, for example, 6 to 60. When B represents an aromatic diamine residue, the group may be as described in formula (2). In formula (5-2), X is a hydrogen atom, a halogen atom, or an optionally substituted monovalent hydrocarbon group, and in formula (5-4), W is a hydrogen atom, a halogen atom, or an optionally substituted monovalent hydrocarbon group. In formulas (5-3) and (5-4), n is the number of repeating units. Note that n is not particularly limited, but is, for example, 1 to 20, and preferably 1 to 10.

[0032] An example of a method for producing an imide oligomer having an acid anhydride group as a reactive functional group is a method of reacting an acid dianhydride represented by the above formula (1) with a polyamine compound such as the above-mentioned aromatic diamine compound, aliphatic diamine compound, or aliphatic triamine compound.

[0033] A specific example of a method for reacting the acid dianhydride represented by the above formula (1) with a polyamine compound is shown below. First, a polyamine compound is dissolved in a solvent (e.g., N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc.) in which the resulting amic acid oligomer is soluble. The acid dianhydride represented by formula (1) is then added to the resulting solution and reacted to obtain an amic acid oligomer solution. The amic acid oligomer is then recovered by removing the solvent from the resulting amic acid oligomer solution by heating or reducing the pressure, or by reprecipitation in a poor solvent such as water, methanol, or hexane. The amic acid oligomer is then heated at about 200°C or higher for at least one hour to promote the imidization reaction. By adjusting the molar ratio of the acid dianhydride represented by formula (1) to the polyamine and the imidization conditions, an imide oligomer having the desired number-average molecular weight and acid anhydride groups at both ends as reactive functional groups can be obtained.

[0034] The imide oligomer may have a segment derived from the acid dianhydride represented by the above formula (1) and a segment derived from the phenolic hydroxyl group-containing monoamine represented by the following formula (5). Furthermore, the imide oligomer may have a segment derived from the acid dianhydride represented by the above formula (1), a segment derived from the above polyamine compound, and a segment derived from a phenolic hydroxyl group-containing monoamine represented by the following formula (5): In this case, it is preferable that the main chain has a segment derived from a phenolic hydroxyl group-containing monoamine represented by the following formula (5) at its terminal, and more preferably at both terminals of the main chain.

[0035] [ka] In formula (5), Ar is an optionally substituted divalent aromatic group, and R 5 and R 6 are each independently a hydrogen atom or a monovalent hydrocarbon group.

[0036] Examples of methods for producing an imide oligomer having a hydroxyl group as a reactive functional group include the following methods. That is, examples of the method include a method of reacting the acid dianhydride represented by the above formula (1) with the phenolic hydroxyl group-containing monoamine represented by the above formula (5), and a method of reacting the acid dianhydride represented by the above formula (1) with the above polyamine compound, and then further reacting with the phenolic hydroxyl group-containing monoamine represented by the above formula (5).

[0037] A specific example of a method for reacting the acid dianhydride represented by the above formula (1) with the phenolic hydroxyl group-containing monoamine represented by the above formula (5) is shown below. First, the phenolic hydroxyl group-containing monoamine represented by formula (5) is dissolved in a solvent (e.g., N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc.) in which the resulting amic acid oligomer is soluble. The dianhydride represented by formula (1) is then added to the resulting solution and reacted to obtain an amic acid oligomer solution. The amic acid oligomer is then recovered by removing the solvent from the resulting amic acid oligomer solution by heating or reducing the pressure, or by reprecipitation in a poor solvent such as water, methanol, or hexane. The amic acid oligomer is then further heated at about 200°C or higher for at least 1 hour to allow the imidization reaction to proceed. By adjusting the molar ratio of the dianhydride represented by formula (1) to the phenolic hydroxyl group-containing monoamine represented by formula (5) and the imidization conditions, an imide oligomer having a desired number-average molecular weight and phenolic hydroxyl groups at both ends as reactive functional groups can be obtained.

[0038] A specific example of a method in which the acid dianhydride represented by the above formula (1) is reacted with a polyamine compound, and then the resulting mixture is further reacted with a phenolic hydroxyl group-containing monoamine represented by the above formula (5) is shown below. First, a polyamine compound is dissolved in a solvent (e.g., N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc.) in which the amic acid oligomer obtained by the reaction is soluble. The acid dianhydride represented by the above formula (1) is added to the resulting solution and reacted to obtain a solution of amic acid oligomer (A) having acid anhydride groups at both ends. The solvent is then removed from the resulting amic acid oligomer (A) solution by heating or reducing the pressure, or the amic acid oligomer (A) is recovered by reprecipitation in a poor solvent such as water, methanol, or hexane, and the amic acid oligomer (A) is then further heated at about 200°C or higher for at least 1 hour to allow the imidization reaction to proceed. The resulting imide oligomer having acid anhydride groups as reactive functional groups at both ends is dissolved in a solvent (e.g., N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc.) and the phenolic hydroxyl-containing monoamine represented by formula (5) is added and reacted to obtain a solution of amic acid oligomer (B). The solvent is removed from the resulting amic acid oligomer (B) solution by heating or reducing pressure, or the amic acid oligomer (B) is recovered by reprecipitation in a poor solvent such as water, methanol, or hexane, and the solution is then heated at about 200°C or higher for at least 1 hour to allow the imidization reaction to proceed. By adjusting the molar ratio of the acid dianhydride represented by formula (1), the polyamine compound, and the phenolic hydroxyl-containing monoamine represented by formula (5), as well as the imidization conditions, an imide oligomer having a desired number-average molecular weight and having hydroxyl groups as reactive functional groups at both ends can be obtained.

[0039] The method for producing an imide oligomer having an amine group as a reactive functional group is not particularly limited, and examples thereof include a method in which an imide oligomer having an acid anhydride group at a terminal is obtained by the above-mentioned method and the imide oligomer is reacted with a polyamine compound (e.g., an aromatic diamine compound). Another example is a method in which, when producing an imide oligomer by the above-mentioned method, the acid anhydride and the polyamine compound are adjusted to an appropriate molar ratio.

[0040] The heat curing agent contained in the thermally conductive resin composition of the present invention may include a heat curing agent other than an imide oligomer. Examples of heat curing agents other than an imide oligomer include phenol compounds (phenolic heat curing agents), acid anhydrides, cyanate ester compounds, and carbodiimide compounds. When a heat curing agent other than an imide oligomer is used, one type may be used alone, or two or more types may be used. The content of the imide oligomer in 100% by volume of the heat curing agent is preferably 50% by volume or more, more preferably 80% by volume or more, and even more preferably 100% by volume.

[0041] Examples of the phenol compound include novolac type phenol, biphenol type phenol, naphthalene type phenol, dicyclopentadiene type phenol, aralkyl type phenol, and dicyclopentadiene type phenol.

[0042] Examples of acid anhydrides include styrene / maleic anhydride copolymer, benzophenone tetracarboxylic anhydride, pyromellitic anhydride, trimellitic anhydride, 4,4'-oxydiphthalic anhydride, phenylethynylphthalic anhydride, glycerol bis(anhydrotrimellitate) monoacetate, ethylene glycol bis(anhydrotrimellitate), methyl tetrahydrophthalic anhydride, methyl hexahydrophthalic anhydride, and trialkyl tetrahydrophthalic anhydride.

[0043] Examples of the cyanate ester compound include novolac-type cyanate resins and bisphenol-type cyanate resins. Examples of the bisphenol-type cyanate resins include bisphenol A-type cyanate resins, bisphenol E-type cyanate resins, and tetramethylbisphenol F-type cyanate resins.

[0044] The carbodiimide compound includes a resin having one or more carbodiimide groups (-N=C=N-) in the molecule.

[0045] The content of the heat curing agent in the thermally conductive resin composition is not particularly limited, but is preferably 1 vol% or more, more preferably 5 vol% or more, even more preferably 10 vol% or more, even more preferably 15 vol% or more, and preferably 30 vol% or less, more preferably 25 vol% or less, based on 100 vol% of the thermally conductive resin composition.

[0046] <Curing accelerator> The thermally conductive resin composition may further contain a curing accelerator. The use of a curing accelerator increases the curing rate, allowing the thermosetting resin to be cured quickly and the crosslinked structure in the thermally conductive resin composition to be uniform. In addition, the number of unreacted functional groups is reduced, resulting in a higher crosslink density. The curing accelerator is not particularly limited, and conventionally known curing accelerators can be used. Specific examples include anionic curing accelerators such as imidazole compounds, cationic curing accelerators such as amine compounds, curing accelerators other than anionic and cationic curing accelerators such as phosphorus compounds and organometallic compounds, and radical curing accelerators such as peroxides. The curing accelerator may be used alone or in combination of two or more kinds.

[0047] Examples of the imidazole compound include 2-undecylimidazole, 2-heptadecylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1,2-dimethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, and 1-cyanoethyl-2-phenylimidazolium trimethylimidazole. Examples thereof include melitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-dihydroxymethylimidazole.

[0048] Examples of the amine compound include diethylamine, triethylamine, diethylenetetramine, triethylenetetramine, and 4,4-dimethylaminopyridine. Examples of the phosphorus compound include triphenylphosphine compounds.

[0049] Examples of the organometallic compound include zinc naphthenate, cobalt naphthenate, tin octoate, cobalt octoate, bisacetylacetonate cobalt(II), and trisacetylacetonate cobalt(III). The peroxides include dicumyl peroxide and Perhexyl 25B.

[0050] <Inorganic filler> The inorganic filler contained in the thermally conductive resin composition of the present invention contains agglomerated boron nitride particles and silica nanoparticles.

[0051] (Boron nitride agglomerated particles) The thermally conductive resin composition of the present invention contains agglomerated particles of boron nitride, which increases the thermal conductivity and improves the heat dissipation properties. Boron nitride agglomerated particles are agglomerated particles formed by agglomerating primary particles. Whether or not boron nitride agglomerated particles are agglomerated particles can generally be determined by, for example, cross-sectional observation using a scanning electron microscope (SEM). Note that boron nitride agglomerated particles may maintain the agglomerated particle shape or may be deformed, collapsed, crushed, etc., when subjected to various processes such as press molding. However, even if the boron nitride agglomerated particles are deformed, collapsed, crushed, etc., when subjected to processes such as press molding after being mixed with a thermosetting resin, they are generally not oriented and exist in a certain degree of aggregation. Therefore, for example, by observing the cross section described above, it is suggested that they are boron nitride agglomerated particles, and whether or not they are agglomerated particles can be determined thereby.

[0052] From the viewpoint of effectively enhancing the insulating properties and thermal conductivity, the boron nitride agglomerated particles incorporated into the thermally conductive resin composition preferably have an average particle size of 5 μm or more, more preferably 10 μm or more, and preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. The average particle size of agglomerated particles can be measured by laser diffraction / scattering. The average particle size is calculated by taking the particle size (d50) of the agglomerated particles when the cumulative volume is 50%.

[0053] The method for producing the boron nitride agglomerated particles is not particularly limited, and they can be produced by known methods. For example, they can be obtained by agglomerating (granulating) pre-prepared primary particles, and specific examples include spray drying and fluidized bed granulation. Spray drying (also called spray drying) can be classified into two-fluid nozzle methods, disk methods (also called rotary methods), and ultrasonic nozzle methods depending on the spray method, and any of these methods can be used. Furthermore, the method for producing agglomerated particles of boron nitride does not necessarily require a granulation step. For example, agglomerated particles may be formed by spontaneous aggregation of primary particles of boron nitride as crystals of boron nitride crystallized by a known method grow. Examples of boron nitride agglomerated particles include "PTX60" manufactured by Momentive Corporation and "HP-40 MF100" manufactured by JFE Mineral Co., Ltd.

[0054] From the viewpoint of improving thermal conductivity, the content of the boron nitride agglomerated particles is preferably 65% ​​by volume or more, more preferably 70% by volume or more, and preferably 90% by volume or less, more preferably 80% by volume or less, based on 100% by volume of the thermal conductive resin composition. When the content of the boron nitride agglomerated particles is equal to or greater than these lower limits, the thermal conductivity of the thermally conductive resin composition and the thermally conductive resin sheet formed from the composition is improved, and when the content of the boron nitride agglomerated particles is equal to or less than these upper limits, the adhesion of the thermally conductive resin sheet to a metal plate or the like is improved.

[0055] (silica nanoparticles) The thermally conductive resin composition of the present invention contains silica nanoparticles, which improves the long-term insulation reliability after heat treatment. More specifically, the inclusion of silica particles can suppress deterioration of insulation properties even when the thermally conductive resin composition or a thermally conductive resin sheet formed from the composition is subjected to a temperature cycle load (repeated temperature increases and decreases) after being exposed to high temperatures in a reflow process or the like. Although the reason for this is not clear, it is presumed that the inclusion of silica nanoparticles in the thermally conductive resin composition prevents the concentration of electric charges, thereby improving the long-term insulation reliability.

[0056] The average particle size of the silica nanoparticles is 200 nm or less, preferably 100 nm or less, more preferably 70 nm or less, even more preferably 50 nm or less, even more preferably 20 nm or less, and even more preferably 10 nm or less. When the average particle size of the silica nanoparticles is below these lower limits, the long-term insulation reliability is likely to be improved. Although the lower limit of the average particle size is not particularly limited, the average particle size of the silica nanoparticles is preferably 1 nm or more. The average particle size of silica nanoparticles can be measured by laser diffraction / scattering. The average particle size is calculated by taking the particle size (d50) of silica nanoparticles when the cumulative volume is 50%. If aggregated particles are present, it is recommended to disintegrate the particles before measuring by laser diffraction / scattering. One example of disintegration is ultrasonic treatment of silica nanoparticles in water.

[0057] From the viewpoint of long-term insulation reliability of the thermally conductive resin composition, the silica nanoparticles are preferably surface-modified with a surface treatment agent. The surface treatment agent is preferably at least one compound having a structure selected from the group consisting of dimethylsilyl, trimethylsilyl, polydimethylsiloxane, aminoalkylsilyl, alkylsilyl, methacrylsilyl, methacrylsilane, methacryl, vinyl, phenyl, phenylamino, phenylaminosilane, and epoxy. Among them, surface treatment agents having a dimethylsilyl, trimethylsilyl, phenyl, polydimethylsiloxane, methacrylsilyl, or methacrylsilane structure are preferred, and surface treatment agents having a dimethylsilyl or methacrylsilyl structure are more preferred. Examples of surface treatment agents having a polydimethylsiloxane structure include silicone oil. Examples of surface treatment agents having a methacrylsilane structure include silane coupling agents having a methacryl group.

[0058] The content of silica nanoparticles is preferably 1% by volume or more, more preferably 1.5% by volume or more, even more preferably 2% by volume or more, and preferably 5% by volume or less, more preferably 4% by volume or less, even more preferably 3% by volume or less, based on 100% by volume of the thermally conductive resin composition. When the content of silica nanoparticles in the thermally conductive resin composition is equal to or greater than the above-mentioned lower limit, the long-term insulation reliability is likely to be improved.When the content of silica nanoparticles is equal to or less than the above-mentioned upper limit, the generation of voids is likely to be suppressed in a thermally conductive resin sheet formed from the thermally conductive resin composition.

[0059] The inorganic filler may contain an inorganic filler other than the boron nitride agglomerated particles and silica nanoparticles, and the inorganic filler is preferably at least one selected from the group consisting of alumina, aluminum nitride, magnesium oxide, diamond, and silicon carbide. When the inorganic filler is contained, the content is preferably 5% by volume or more and 40% by volume or less in 100% by volume of the thermally conductive resin composition.

[0060] <Other ingredients> In addition to the above components, the thermally conductive resin composition according to the present invention may contain additives such as a coupling agent such as a silane coupling agent, a dispersant, a flame retardant, an antioxidant, a tackifier, a plasticizer, a thixotropy-imparting agent, and a colorant, as well as a solvent.

[0061] <Thermal conductive resin sheet> The thermally conductive resin sheet of the present invention is a cured product of the above-described thermally conductive resin composition. The thermally conductive resin composition can be cured by heating at a temperature equal to or higher than the curing temperature of the thermosetting resin. The cured product may be partially cured or completely cured. The amount of each component in 100% by volume of the thermally conductive resin sheet is the same as the amount of each component in 100% by volume of the thermally conductive resin composition.

[0062] The thickness of the thermally conductive resin sheet of the present invention is not particularly limited, but is preferably 180 μm or less. A thickness of 180 μm or less can reduce the thermal resistance of the thermally conductive resin sheet, improving heat dissipation. The thickness of the thermally conductive resin sheet is preferably 180 μm or less, more preferably 150 μm or less, and is preferably 80 μm or more, more preferably 100 μm or more.

[0063] The method for producing the thermally conductive resin sheet of the present invention is not particularly limited, but may include a method in which the thermally conductive resin composition described above is applied to a substrate such as a release PET film, dried, and cured. The drying conditions are, for example, a drying temperature of 60 to 100°C, preferably 70 to 90°C. The thermally conductive resin sheet of the present invention can be cured by heating at a temperature equal to or higher than the curing temperature of the thermosetting resin to form a thermally conductive resin sheet. Curing is preferably performed by heating under pressure. The thermally conductive resin sheet can constitute a part of the laminate shown below.

[0064] [Laminate] As shown in FIG. 1, the laminate of the present invention comprises a thermally conductive resin sheet 10 of the present invention, a metal base plate 11, and a metal plate 12, and is a laminate 13 having the thermally conductive resin sheet 10 and the metal plate 12 on the metal base plate 11 in this order.

[0065] The laminate of the present invention may be produced by press molding. Specifically, the laminate may be produced by stacking a metal base plate, a thermally conductive resin sheet, and a metal plate in this order and press molding the stack. The press molding completely cures the thermally conductive resin sheet, allowing the metal base plate and the metal plate to be bonded with a certain level of adhesive strength or greater. The press molding may be carried out at a temperature of, for example, 150° C. or higher and 250° C. or lower, preferably 180° C. or higher and 210° C. or lower, and at a pressure of, for example, 8 MPa or higher and 25 MPa or lower. The pressing time is not particularly limited, but is, for example, from 10 minutes to 240 minutes, preferably from 30 minutes to 200 minutes. The pressing may be performed under normal pressure or may be performed using a vacuum press. The laminate of the metal base plate, the thermally conductive resin sheet, and the metal plate may be pressed under a reduced pressure environment, specifically, for example, under an environment of 10 kPa or less, preferably 3 kPa or less, more preferably 1.5 kPa or less.

[0066] Since the metal base plate 11 and the metal plate 12 each function as a thermal conductor, their thermal conductivity is preferably 10 W / m·K or higher. Materials used for these include metals such as aluminum, copper, gold, and silver, as well as graphite sheets. From the viewpoint of more effectively increasing thermal conductivity, aluminum, copper, or gold is preferred, and aluminum or copper is more preferred. The thickness of the metal base plate 11 is preferably 0.1 to 5 mm, and the thickness of the metal plate 12 is preferably 10 to 2000 μm, more preferably 10 to 900 μm. The metal plate may be a plate such as a copper plate or a foil such as a copper foil.

[0067] The laminate 13 is preferably used as a circuit board. When used as a circuit board, the metal plate 12 in the laminate 13 may have a circuit pattern. The circuit pattern may be appropriately patterned depending on the elements to be mounted on the circuit board. The circuit pattern is not particularly limited, but may be formed by etching or the like. In the circuit board, the metal base plate 11 is used as a heat sink or the like.

[0068] [Semiconductor Devices] The present invention also provides a semiconductor device having the above-described laminate. Specifically, as shown in Fig. 2, the semiconductor device 15 includes a laminate 13 having a thermally conductive resin sheet 10, a metal base plate 11, and a metal plate 12, and a semiconductor element 14 provided on the metal plate 12 of the laminate 13. The metal plate 12 may be patterned by etching or the like to have a circuit pattern.

[0069] Although two semiconductor elements 14 are shown in FIG. 2 , the number of semiconductor elements 14 is not limited and may be any number equal to or greater than one. Furthermore, other electronic components (not shown), such as transistors, may be mounted on the metal plate 12 in addition to the semiconductor elements 14. Each semiconductor element 14 is connected to the metal plate 12 via a connecting conductive portion 16 formed on the metal plate 12. The connecting conductive portion 16 is preferably formed of solder. Furthermore, a sealing resin 19 is provided on the surface of the laminate 13 facing the metal plate 12. At least the semiconductor elements 14 are sealed with the sealing resin 19, and, if necessary, the metal plate 12 may also be sealed with the sealing resin 19 together with the semiconductor elements 14. Although the semiconductor elements 14 are not particularly limited, it is preferable that at least one of them is a power element (i.e., a power semiconductor element), and thus the semiconductor device 15 is preferably a power module. A power module is used, for example, in an inverter or the like. Furthermore, the power module is used in industrial equipment such as elevators and uninterruptible power supplies (UPS), but its use is not particularly limited.

[0070] Leads 20 are connected to the metal plate 12. The leads 20 extend, for example, from the sealing resin 19 to the outside and connect the metal plate 12 to an external device or the like. Wires 17 may also be connected to the semiconductor element 14. The wires 17 may connect the semiconductor element 14 to another semiconductor element 14, the metal plate 12, the leads 20, or the like, as shown in FIG. 2 . The semiconductor element 14 generates heat when power is supplied via the leads 20 or the like to operate it, but the heat generated by the semiconductor element 14 is transmitted to the metal base plate 11 via the thermally conductive resin sheet 10 and dissipated from the metal base plate 11. The metal base plate 11 may be connected to a heat sink consisting of heat dissipation fins or the like as needed.

[0071] The semiconductor device 15 may be manufactured through a reflow process. Specifically, in the manufacturing method of the semiconductor device 15, first, a laminate 13 is prepared, and a connection conductive portion 16 is formed on the metal plate 12 of the laminate 13 by solder printing or the like, and a semiconductor element 14 is mounted on the connection conductive portion 16. The laminate 13 with the semiconductor element 14 mounted thereon is then passed through a reflow furnace and heated therein, and the semiconductor element 14 is connected to the metal plate 12 by the connection conductive portion 16. The temperature in the reflow furnace is not particularly limited, but is, for example, about 200 to 300°C. In the manufacturing method of the semiconductor device 15, after the reflow process, a sealing resin 19 may be laminated on the laminate 13 to seal the semiconductor element 14. Furthermore, before sealing with the sealing resin 19, wires 17, leads 20, etc. may be attached as appropriate. Although the above describes a mode in which the semiconductor element 14 is connected to the metal plate 12 by a reflow process, the present invention is not limited to such a mode, and for example, the laminate 13 (i.e., the circuit board) may be connected to another board (not shown) by a reflow process.

[0072] Furthermore, when manufacturing a laminate comprising a thermally conductive resin sheet, a metal base plate, and a metal plate, the thermally conductive resin sheet can be placed between the metal base plate and the metal plate, and heated and pressurized by press molding to bond the metal base plate and the metal plate via the thermally conductive resin sheet, thereby manufacturing the laminate. [Example]

[0073] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0074] The components used in the examples and comparative examples are as follows. <Thermosetting resin> Epoxy resin 1: Bisphenol A epoxy resin, "YD-127" manufactured by Nippon Steel Chemical & Material Co., Ltd., liquid, viscosity (25°C) 10,000 mPa·s Epoxy resin 2: Bisphenol A epoxy resin, Mitsubishi Chemical Corporation "jer825", liquid (25°C), 4000-7000 mPa·s Epoxy resin 3: Bisphenol A epoxy resin, Mitsubishi Chemical Corporation "JER630", liquid (25°C), 500-1000 mPa·s

[0075] <Thermal curing agents, curing accelerators> ·Thermal curing agent 1··imide oligomer (IMO-1), synthesized as described below. ·Thermal curing agent 2··imide oligomer (IMO-2), synthesized as described below. Heat curing agent 3: Cyanate ester compound "BA3000S" manufactured by Lonza Co., Ltd. Curing accelerator: 2-phenyl-4-methylimidazole, Shikoku Chemicals Corporation "2P4MZ-PW"

[0076] <Synthesis of Curing Agent 1 (IMO-1)> 104 parts by weight of 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (Tokyo Chemical Industry Co., Ltd.) was dissolved in 300 parts by weight of N-methylpyrrolidone (Fujifilm Wako Pure Chemical Industries, Ltd., "NMP"). To the resulting solution was added 28 parts by weight of dimer diamine Priamine 1074 (Croda) diluted with 100 parts by weight of N-methylpyrrolidone, and the mixture was stirred at 25°C for 2 hours to react, yielding an amic acid oligomer solution. After removing N-methylpyrrolidone from the resulting amic acid oligomer solution under reduced pressure, the mixture was heated at 300°C for 2 hours to yield imide oligomer composition B (imidization rate 93%). The obtained imide oligomer composition B was subjected to 1H-NMR, GPC, and FT-IR analyses. As a result, it was confirmed that imide oligomer composition B contained an imide oligomer having a structure represented by the above formula (5-1) or (5-3) (A is a 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride residue, and B is a dimer diamine residue). In addition, the number average molecular weight of imide oligomer composition B was 2200.

[0077] <Synthesis of Curing Agent 2 (IMO-2)> 20 parts by weight of 1,3-bis(3-aminophenoxy)benzene APB-N (Mitsui Fine Chemicals, Inc.) was dissolved in 200 parts by weight of N-methylpyrrolidone (Wako Pure Chemical Industries, Ltd.). 20 parts by weight of 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (Tokyo Chemical Industry Co., Ltd.) was added to the resulting solution, and the mixture was stirred at 25°C for 2 hours to react, yielding an amic acid oligomer solution. After removing the N-methylpyrrolidone from the resulting amic acid oligomer solution under reduced pressure, the mixture was heated at 300°C for 2 hours to yield the imide oligomer IMO-2 (imidization rate 97%). The imide oligomer had acid anhydride groups at both ends, no linear saturated hydrocarbon chain with 16 or more carbon atoms in its backbone, and a number-average molecular weight of 1310.

[0078] <Dispersant> Carboxylic acid ester dispersant: Kusumoto Chemicals "HIPLAAD ED-216"

[0079] <Inorganic filler> Boron nitride agglomerated particles, JFE Mineral "HP-40 MF100", average particle size 40 μm Silica nanoparticles 1: Nippon Aerosil Co., Ltd. "RY300", average particle size 100 nm, polydimethylsiloxane surface modification Silica nanoparticles 2: Nippon Aerosil "RX300", average particle size 100 nm, trimethylsilyl surface modified Silica nanoparticles 3: Nippon Aerosil "R976S", average particle size 100 nm, dimethylsilyl surface modified Silica nanoparticles 4: Admatechs "Y50SM-AH2", average particle size 50 nm, surface modified with methacrylsilane Silica nanoparticles 5 "YA010C-SP3" manufactured by Admatechs Co., Ltd., average particle size 10 nm, phenyl surface modification Silica nanoparticles 6: Admatechs "Y10SM-AH1", average particle size 10 nm, surface modified with methacrylsilane

[0080] [Examples 1 to 23, Comparative Examples 1 and 2] (Preparation of laminate) The epoxy resin, heat curing agent, curing accelerator, dispersant, boron nitride agglomerated particles, and silica nanoparticles were mixed to obtain a thermally conductive resin composition containing each component in the amounts shown in Tables 1 and 2. The thermally conductive resin composition was coated onto a release PET sheet (50 μm thick) using a 350 mm wide doctor blade to a desired thickness. The coated sheet was cut to a size of 300 mm x 500 mm, placed on a metal rack, and dried in an oven at 80°C for 20 minutes to obtain a sheet-like thermally conductive resin composition A (130 μm thick) formed on the release PET sheet. The oven used was a Yamato Scientific DKM600. Two sheets of the dried thermally conductive resin composition A were laminated together with the release PET sheets still attached, and the release PET sheets were then peeled off to produce a sheet of thermally conductive resin composition C. A 0.5 mm thick copper plate was then laminated on one side of the sheet of thermally conductive resin composition C, and a 2.0 mm thick copper plate was then laminated on the second side. A laminate was then produced by vacuum pressing at a temperature of 195°C, a pressure of 20 MPa, and for 80 minutes. This laminate was a copper plate, a thermally conductive resin sheet (a cured product of the thermally conductive resin composition), and a copper plate laminated in this order.

[0081] (Breakdown voltage, initial and after heat treatment at 300°C) In the obtained laminate, a copper plate having a thickness of 0.5 mm was etched to form a circular pattern having a diameter of 2 cm, and the patterned copper foil was cut into a 4 cm square at the center to obtain a laminate sample. Using a voltage resistance tester ("MODEL 7473" manufactured by ETECH Electronics), 200 V was applied across the laminate sample in Fluorinert, and after holding for 5 seconds, an AC voltage was applied using a step-up method in which the voltage was increased by 200 V and held for 5 seconds in the same manner. The voltage at which a current of 10 mA flowed through the laminate sample was taken as the initial breakdown voltage A1 (breakdown voltage before reflow). The insulation properties were evaluated based on the measured initial breakdown voltage A1 according to the following criteria. Note that the lower the alphabetical order, the better the insulation properties. A: 60kV / mm or more B: 50kV / mm or more and less than 60kV / mm C: 40kV / mm or more and less than 50kV / mm D: 30kV / mm or more and less than 40kV / mm E: Less than 30 kV / mm

[0082] A 4 cm square laminate sample was obtained in the same manner as in the initial insulation evaluation. The obtained laminate sample was placed on the hot plate surface with the 2 mm thick copper plate side facing outward, and the hot plate temperature was adjusted so that the surface temperature of the thermally conductive resin sheet of the laminate sample reached 300°C. The laminate sample was then heat-treated in this state for 5 minutes. The dielectric breakdown voltage of the laminate sample heat-treated at 300°C was measured in the same manner as in the evaluation of the initial dielectric breakdown voltage. The insulation after the 300°C treatment was evaluated based on the above-mentioned evaluation criteria using the measured dielectric breakdown voltage A2 (dielectric breakdown voltage after reflow) after the 300°C heat treatment. The breakdown voltage reduction rate was calculated from the initial breakdown voltage (A1) and the breakdown voltage after treatment at 300°C (A2), and evaluated according to the following criteria. Note that the lower the alphabetical order, the better the breakdown voltage reduction rate. Breakdown voltage reduction rate (%) = [(A1-A2) / A1] x 100 A: 10% or less B: More than 10% and less than 20% C: More than 20% and less than 30% D: More than 30%

[0083] (Long-term insulation reliability evaluation (heat cycle characteristics)) A laminate sample heat-treated at 300° C. and used in measuring the breakdown voltage (A2) was prepared in the same manner. The laminate sample was subjected to a thermal cycle test using a bath-type thermal shock tester (TSB-51) manufactured by ESPEC Corporation, in which one cycle consisted of holding the sample at -40°C, then heating it to 150°C, holding it at 150°C, and then cooling it to -40°C. The dielectric breakdown voltage of each laminate sample after 500 cycles and after 1000 cycles was measured and evaluated according to the following criteria. A: 50kV / mm or more B: 25kV / mm or more and less than 50kV / mm C: Less than 25 kV / mm

[0084] [Table 1]

[0085] JPEG2026028563000008.jpg229127

[0086] The results of each example show that the thermally conductive resin sheets formed from the thermally conductive resin composition of the present invention, which contains a thermosetting resin, an imide oligomer as a thermosetting agent, and boron nitride agglomerated particles and silica nanoparticles as inorganic fillers, exhibited excellent heat resistance, with a low rate of decrease in breakdown voltage when heat-treated at 300° C. Furthermore, the thermally conductive resin sheets of the examples also exhibited excellent long-term insulation reliability, as shown by the results of a thermal cycle test. In contrast, the thermally conductive resin sheet of Comparative Example 1 did not contain imide oligomer, and had a high rate of decrease in breakdown voltage and poor heat resistance. Furthermore, the thermally conductive sheet of Comparative Example 1 also had poor long-term insulation reliability. The thermally conductive resin sheet of Comparative Example 2 did not contain nanosilica particles, and also had poor long-term insulation reliability. [Explanation of symbols]

[0087] 10. Thermally conductive resin sheet 11 Metal base plate 12 metal plate 13 Laminate 14 Semiconductor elements 15 Semiconductor devices 16 Conductive connection part 17 wires 19 Sealing resin 20 Lead

Claims

1. The composition includes a thermosetting resin, a thermosetting agent, and an inorganic filler, the thermal curing agent comprises an imide oligomer; The thermally conductive resin composition, wherein the inorganic filler comprises agglomerated boron nitride particles and silica nanoparticles.

2. 2. The thermally conductive resin composition according to claim 1, wherein the imide oligomer has reactive functional groups at both ends or one end of the molecule that can react with the thermosetting resin, and the reactive functional groups are acid anhydride groups, amine groups, or hydroxyl groups.

3. The thermally conductive resin composition according to claim 1 or 2, wherein the imide oligomer does not have a linear saturated hydrocarbon chain having 16 or more carbon atoms in its skeleton.

4. 3. The thermally conductive resin composition according to claim 1, wherein the imide oligomer has a molecular weight of 500 to 10,000.

5. 3. The thermally conductive resin composition according to claim 1, wherein the higher of the softening point and the melting point of the thermosetting resin is 150°C or lower.

6. 3. The thermally conductive resin composition according to claim 1, wherein the content of the boron nitride agglomerated particles is 65% by volume or more based on 100% by volume of the thermally conductive resin composition.

7. 3. The thermally conductive resin composition according to claim 1, wherein the boron nitride agglomerated particles have an average particle size of 5 μm or more and 100 μm or less.

8. The thermally conductive resin composition according to claim 1 or 2, wherein the inorganic filler comprises an inorganic filler other than agglomerated boron nitride particles and silica nanoparticles.

9. 9. The thermally conductive resin composition according to claim 8, wherein the inorganic filler is at least one selected from the group consisting of alumina, aluminum nitride, magnesium oxide, diamond, and silicon carbide.

10. 9. The thermally conductive resin composition according to claim 8, wherein the content of the inorganic filler is 5% by volume or more and 40% by volume or less, based on 100% by volume of the thermally conductive resin composition.

11. The thermally conductive resin composition according to claim 1 or 2, wherein the silica nanoparticles have an average particle size of 1 nm or more and 100 nm or less.

12. 3. The thermally conductive resin composition according to claim 1, wherein the content of the silica nanoparticles is 1% by volume or more and 5% by volume or less, based on 100% by volume of the thermally conductive resin composition.

13. The thermally conductive resin composition according to claim 1 or 2, wherein the silica nanoparticles are surface-modified with a surface treatment agent.

14. 14. The thermally conductive resin composition according to claim 13, wherein the surface treatment agent is at least one compound having a structure selected from the group consisting of dimethylsilyl, trimethylsilyl, polydimethylsiloxane, aminoalkylsilyl, alkylsilyl, methacrylsilyl, methacrylsilane, methacryl, vinyl, phenyl, phenylamino, phenylaminosilane, and epoxy.

15. A thermally conductive resin sheet which is a cured product of the thermally conductive resin composition according to claim 1 or 2.

16. A laminate comprising: the thermally conductive resin sheet according to claim 15; a metal base plate; and a metal plate, the thermally conductive resin sheet and the metal plate being disposed on the metal base plate in this order.

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