Thermally conductive composition, thermally conductive sheet using same, and production method therefor

Abstract

Provided are: a thermally conductive composition having a high thermal conductivity and a low compressive load and plasticity; a thermally conductive sheet using the thermally conductive composition; and a method for producing the thermally conductive sheet. This thermally conductive composition comprises: a matrix resin (component A) formed of a thermosetting resin; a curing catalyst; and thermally conductive particles (component B), wherein 1500-3000 parts by mass of component B is contained with respect to 100 parts by mass of component A, component B contains component B1, component B2, component B3, and component B4, 10-20 mass % of aluminum nitride having a median diameter (D50) of less than 20 μm (component B1), 3-9 mass % of aluminum nitride having a D50 of at least 20 μm (component B2), 50-60 mass % of alumina having a D50 of 60-80 μm (component B3), and 11-37 mass % of alumina having a D50 of less than 60 μm (component B4) are contained with respect to the entire component B, and the blend ratio (B1) / (B2) of component B1 and component B2 is 1.2-3 in terms of mass ratio.

Description

Thermally conductive composition, thermally conductive sheet using the same, and method for manufacturing the same

[0001] The present invention relates to a thermally conductive composition suitable for being interposed between a heat-generating portion of an electric or electronic component or the like and a heat sink, a thermally conductive sheet using the same, and a method for producing the same.

[0002] In recent years, the performance of semiconductors such as CPUs has improved dramatically, resulting in enormous increases in heat generation. Therefore, heat-generating electronic components are fitted with heat sinks, and thermally conductive sheets are used to improve adhesion between the semiconductor and the heat sink. As devices become smaller, their performance improves, and their integration becomes more advanced, thermally conductive sheets are required to be flexible and have high thermal conductivity. Previously, Japanese Patent Publication Nos. 6246986 and 7039157 proposed polysiloxane compositions containing large-sized aluminum nitride particles and small-sized aluminum nitride particles or alumina particles. Japanese Patent Publication Nos. 7082563 and 7205554 proposed thermally conductive polysiloxane compositions containing aluminum nitride particles.

[0003] The present invention provides a thermally conductive composition comprising a matrix resin (component A) made of a thermosetting resin, a curing catalyst, and thermally conductive particles (component B), wherein 1500 to 3000 parts by mass of the thermally conductive particles (component B) are blended with 100 parts by mass of the matrix resin (component A), and the thermally conductive particles (component B) comprise the following components B-1, B-2, B-3, and B-4, wherein the thermally conductive particles (component B) contain, when the total amount of the thermally conductive particles (component B) is taken as 100% by mass, 10 to 20% by mass of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm, 3 to 9% by mass of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more, 50 to 60% by mass of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm, and The thermally conductive composition contains 11 to 37 mass % of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm, and the blending ratio (B-1) / (B-2) of the B-1 component to the B-2 component is 1.2 to 3 by mass.

[0004] FIG. 1 is a schematic cross-sectional view showing a method of using a thermally conductive sheet according to one embodiment of the present invention. FIG. 2 is a scanning electron microscope (SEM) photograph of spherical alumina (B-3, D50 = 75 μm) according to one embodiment of the present invention. FIG. 3 is a scanning electron microscope (SEM) photograph of rounded alumina (B-1, D50 = 5 μm) according to the present invention. FIG. 4 is a scanning electron microscope (SEM) photograph of amorphous alumina (B-4, D50 = 4 μm) according to the present invention. FIG. 5 is a schematic side cross-sectional view of a compression load measuring device used in one embodiment of the present invention. FIGS. 6A-B are schematic explanatory diagrams showing a method of measuring the thermal conductivity of a sample according to one embodiment of the present invention. Detailed Description of the Invention

[0005] However, conventional thermally conductive compositions and thermally conductive sheets using the same have the problem that increasing the thermal conductivity increases the compressive load and plasticity. In order to solve the above-mentioned conventional problems, the present invention provides a thermally conductive sheet that has high thermal conductivity and low compressive load and plasticity, a thermally conductive composition that is the raw material for the sheet, and a method for manufacturing a thermally conductive sheet using the sheet.

[0006] The thermally conductive composition of the present invention is a thermally conductive composition comprising a matrix resin (component A) made of a thermosetting resin, a curing catalyst, and thermally conductive particles (component B), wherein 1500 to 3000 parts by mass of the thermally conductive particles (component B) are blended with 100 parts by mass of the matrix resin (component A), and the thermally conductive particles (component B) comprise the following components B-1, B-2, B-3, and B-4, wherein the thermally conductive particles (component B) contain, when the total of the thermally conductive particles (component B) is taken as 100% by mass, 10 to 20% by mass of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm, 3 to 9% by mass of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more, 50 to 60% by mass of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm, and The composition contains 11 to 37 mass % of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm, and the blending ratio (B-1) / (B-2) of the B-1 component to the B-2 component is 1.2 to 3 mass %.

[0007] The thermally conductive sheet of the present invention contains the thermally conductive composition described above and is formed into a sheet.

[0008] The method for producing a thermally conductive sheet of the present invention includes the steps of vacuum degassing the thermally conductive composition, rolling it, forming it into a sheet, and then heat-curing it to produce a thermally conductive sheet.

[0009] By using the above composition, the present invention can provide a thermally conductive sheet having high thermal conductivity and low compressive load and plasticity, a thermally conductive composition as a raw material thereof, and a method for producing the thermally conductive sheet. Specifically, the plasticity of the thermally conductive composition before curing and after degassing is preferably 60 or less, the instantaneous load value of the cured product of the thermally conductive composition when compressed 50% to a diameter of 28.6 mm and a thickness of 2 mm is preferably 1000 N or less, and the preferred thermal conductivity is 7 W / m·K or more. Furthermore, the method for producing the thermally conductive sheet of the present invention allows for continuous sheet molding due to the low plasticity and good moldability of the thermally conductive composition of the present invention.

[0010] The present invention is a thermally conductive composition comprising a matrix resin (component A), a curing catalyst (component C), and thermally conductive particles (component B).

[0011] <Matrix Resin (Component A)> The matrix resin is a thermosetting resin. Examples of the thermosetting resin include silicone resin, epoxy resin, phenolic resin, unsaturated polyester resin, melamine resin, acrylic resin, silicone resin, and fluororesin, with silicone resin being preferred. Examples of the thermosetting resin include rubber, elastomer, gel, putty, and grease. Specific examples of the thermosetting resin include silicone rubber, silicone gel, acrylic rubber, and fluororubber. Silicone resins may be cured using any method, such as peroxide, addition, or condensation. Silicone resins are preferred as the thermosetting resin due to their high heat resistance. The matrix resin is preferably formed from at least one selected from addition-curable silicone polymers, peroxide-curable silicone polymers, and condensation-curable silicone polymers. Furthermore, the silicone resin is preferably an addition-curable type due to its lack of corrosiveness to the surrounding area, its low release of by-products outside the system, and its reliable deep curing.

[0012] The matrix resin preferably further contains a silane coupling agent. Specifically, the silane coupling agent is preferably added in an amount of 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, per 100 parts by mass of the matrix resin. The silane coupling agent coats the surfaces of the thermally conductive particles (component B) (surface treatment), making them easier to fill into the matrix resin (component A) (plasticizer function), and also prevents the curing catalyst (component C) from being adsorbed onto the thermally conductive particles (component B), preventing curing inhibition. The inclusion of a silane coupling agent in the matrix resin has the advantage of providing excellent storage stability to the thermally conductive composition.

[0013] The silane coupling agent may be, for example, a compound represented by the formula R(CH3) a Si(OR') 4-a (R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a partial hydrolyzate thereof. a Si(OR') 4-a(R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) Examples of silane compounds (hereinafter simply referred to as "silane") represented by the formula (R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane. These silane compounds can be used alone or in combination.

[0014] The matrix resin preferably contains a base polymer component (component A1) and a crosslinking component (A2). (1) Base Polymer Component (Component A1) The base polymer component is, for example, an organopolysiloxane containing two or more silicon-bonded alkenyl groups per molecule. The organopolysiloxane is the main component (base polymer component) in the matrix resin of the present invention. This organopolysiloxane contains two or more silicon-bonded alkenyl groups per molecule, such as vinyl groups or allyl groups, each having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms. From the viewpoint of workability and curability, the viscosity of the organopolysiloxane is preferably 10 to 1,000,000 mPa·s, particularly 100 to 100,000 mPa·s, at 25°C.

[0015] Specifically, an organopolysiloxane represented by the following general formula (I) containing alkenyl groups bonded to silicon atoms at both ends of the molecular chain per molecule can be used. This organopolysiloxane is a linear organopolysiloxane whose side chains are blocked with alkyl groups. From the viewpoint of workability, curability, and the like, an organopolysiloxane with a viscosity of 10 to 1,000,000 mPa·s at 25°C is desirable. Note that this linear organopolysiloxane may also contain a small amount of branched structures (trifunctional siloxane units) in the molecular chain.

[0016]

[0017] In the formula, each R 1 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, R 2 is an alkenyl group, and k is 0 or a positive integer.

[0018] In general formula (I), R 1 The unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond is preferably, for example, a hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples of the unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl. Examples of the substituted monovalent hydrocarbon group having no aliphatic unsaturated bond include groups in which some or all of the hydrogen atoms of the unsubstituted monovalent hydrocarbon group have been substituted with halogen atoms such as fluorine, bromine, or chlorine; or with cyano groups, such as halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl; and cyanoethyl groups.

[0019] In general formula (I), R 2The alkenyl group is preferably an alkenyl group having 2 to 6 carbon atoms, particularly 2 to 3. Specific examples of the alkenyl group include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a hexenyl group, and a cyclohexenyl group, and the vinyl group is preferred.

[0020] In general formula (I), k is 0 or a positive integer, preferably 0 or a positive integer satisfying 0≦k≦10,000, more preferably 5≦k≦2,000, and even more preferably 10≦k≦1,200.

[0021] The organopolysiloxane of component A1 may be an organopolysiloxane having three or more, typically 3 to 30, and preferably about 3 to 20, alkenyl groups having 2 to 8, particularly 2 to 6, carbon atoms bonded to silicon atoms per molecule, such as vinyl groups or allyl groups. The molecular structure of the organopolysiloxane used in combination may be linear, cyclic, branched, or three-dimensional network. The organopolysiloxane used in combination is preferably a linear organopolysiloxane whose main chain is composed of repeating diorganosiloxane units, both molecular chain terminals are blocked with triorganosiloxy groups, and whose viscosity at 25°C is 10 to 1,000,000 mPa·s, particularly 100 to 100,000 mPa·s.

[0022] In organopolysiloxanes containing two or more alkenyl groups bonded to silicon atoms per molecule, the alkenyl groups may be bonded to any part of the molecule. For example, they may be bonded to silicon atoms at the molecular chain terminals or non-terminal locations (in the middle of the molecular chain). Among these, linear organopolysiloxanes represented by the following general formula (II), in which one to three alkenyl groups are bonded to silicon atoms at both molecular chain terminals, and which have a viscosity at 25°C of 10 to 1,000,000 mPa·s are preferred from the viewpoints of workability and curability. However, when the number of alkenyl groups bonded to silicon atoms at the molecular chain terminals of this linear organopolysiloxane is one or two in total, linear organopolysiloxanes in which the alkenyl groups bonded to non-terminal locations (in the middle of the molecular chain) are used as substituents in, for example, diorganosiloxane units are preferred. This linear organopolysiloxane may contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain.

[0023]

[0024] In the formula, each R 3 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups, at least one of which is an alkenyl group; 4 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, R 5 is an alkenyl group, and l and m are each independently 0 or a positive integer.

[0025] In general formula (II), R 3The unsubstituted or substituted monovalent hydrocarbon group is preferably, for example, a hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples of the unsubstituted monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl. Examples of the substituted monovalent hydrocarbon group include groups in which some or all of the hydrogen atoms of the unsubstituted monovalent hydrocarbon group have been substituted with halogen atoms such as fluorine, bromine, or chlorine; or a cyano group, such as halogen-substituted alkyl groups such as a chloromethyl group, a chloropropyl group, a bromoethyl group, or a trifluoropropyl group; and a cyanoethyl group.

[0026] In general formula (II), R 4 As the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, a hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, is preferred. 4 The unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond includes the above-mentioned R 1 Specific examples of the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond are the same as those of the group 1, except that alkenyl groups are not included.

[0027] In general formula (II), R 5 The alkenyl group in the formula (I) is preferably an alkenyl group having 2 to 6 carbon atoms, particularly preferably an alkenyl group having 2 to 3 carbon atoms. 2 Examples of the alkenyl group include the same as those of the alkenyl group in the above, and a vinyl group is preferred.

[0028] In general formula (II), l and m are each independently 0 or a positive integer, preferably 0 or a positive integer that satisfies 0 < l + m ≦ 10,000, preferably 5 ≦ l + m ≦ 2,000, more preferably 10 ≦ l + m ≦ 1,200, and preferably an integer that satisfies 0 < l / (l + m) ≦ 0.2, more preferably 0.0011 ≦ l / (l + m) ≦ 0.1.

[0029] (2) Crosslinking Component (Component A2) The crosslinking component of Component A2 of the present invention is, for example, an organohydrogenpolysiloxane. This organohydrogenpolysiloxane functions as a crosslinking agent. A cured product is formed by addition reaction (hydrosilylation) between SiH groups in this organohydrogenpolysiloxane and alkenyl groups in the organopolysiloxane of Component A1. Any organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (i.e., SiH groups) per molecule can be used as the crosslinking component (Component A2). The molecular structure of this organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure. Furthermore, organohydrogenpolysiloxanes having a number of silicon atoms per molecule (i.e., degree of polymerization) of 2 to 1,000, particularly about 2 to 300, are preferably used as the crosslinking component (Component A2).

[0030] The organohydrogenpolysiloxane contains SiH groups as described above. In the organohydrogenpolysiloxane, the position of the SiH groups is not particularly limited, and they may be at the terminals of the molecular chain or at non-terminal locations (in the middle of the molecular chain). Furthermore, examples of organic groups bonded to silicon atoms other than hydrogen atoms include R in the general formula (I). 1 and unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, similar to those shown above.

[0031] An example of the organohydrogenpolysiloxane of component A2 is one represented by the following formula (III).

[0032]

[0033] In the above formula, each R 6may be the same or different and are each an alkyl group, a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, an alkoxy group, or a hydrogen atom, provided that at least two of them are hydrogen atoms. L is an integer of 0 to 1,000, preferably an integer of 0 to 300, and M is an integer of 1 to 200.

[0034] <Curing Catalyst (Component C)> Catalysts used in hydrosilylation reactions can be used as the curing catalyst for Component C. Examples of the curing catalyst include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins or vinylsiloxanes, complexes of platinum with vinyldisiloxanes, platinum-based catalysts such as platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. Two-component curing silicone polymers typically contain a platinum-based metal catalyst. However, even when the thermally conductive composition of the present invention contains a two-component curing silicone polymer, it is preferable to add an additional platinum-based metal catalyst to the thermally conductive composition of the present invention. The platinum-based metal catalyst is added to control the curing rate of the thermally conductive composition.

[0035] The curing catalyst is contained in the thermally conductive composition in an amount of, for example, 0.01 to 1000 parts by mass, preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 50 parts by mass, per 100 parts by mass of the matrix resin (component A).

[0036] <Thermal conductive particles (component B)> The thermal conductive particles (component B) comprise the following components B-1, B-2, B-3, and B-4, and when the total amount of the thermal conductive particles (component B) is taken as 100% by mass, the thermal conductive particles (component B) comprise: 10 to 20% by mass of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm; 3 to 9% by mass of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more; 50 to 60% by mass of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm; and 11 to 37% by mass of alumina (component B-4) having a D50 (median diameter) of less than 60 μm. When the total amount of the thermally conductive particles (component B) is taken as 100% by mass, the thermally conductive particles (component B) preferably contain 10 to 18% by mass of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm, 3.5 to 8.5% by mass of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more, 50 to 58% by mass of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm, and 15 to 35% by mass of alumina (component B-4) having a D50 (median diameter) of less than 60 μm. When the total amount of the thermally conductive particles (component B) is taken as 100% by mass, the thermally conductive particles (component B) more preferably contain 10 to 16% by mass of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm, 4 to 8% by mass of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more, 51 to 58% by mass of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm, and 20 to 33% by mass of alumina (component B-4) having a D50 (median diameter) of less than 60 μm.

[0037] In the present invention, the thermally conductive particles (component B) are made of a combination of multiple types of thermally conductive inorganic particles with different average particle sizes. This allows the smaller particles to be embedded between the larger particles, resulting in a nearly close-packed structure, enhancing the thermal conductivity of the cured thermally conductive composition. This also results in a cured thermally conductive composition with low plasticity and excellent moldability. Furthermore, this allows the cured thermally conductive composition to be molded into a thermal interface material (TIM), which has a low compressive load and is easier to handle than putty-like materials.

[0038] The blending ratio (B-1) / (B-2) of the B-1 component to the B-2 component is 1.2 to 3 by mass, preferably 1.3 to 2.9, and more preferably 1.3 to 2.8, because the use of such a blending ratio makes it possible to obtain a cured product of the thermally conductive composition that has high thermal conductivity and low compressive load and plasticity.

[0039] The thermally conductive particles (component B) are blended in an amount of 1,500 to 3,000 parts by mass per 100 parts by mass of the matrix resin (component A). The blending amount of the thermally conductive particles (component B) per 100 parts by mass of the matrix resin (component A) is preferably 1,700 to 2,800 parts by mass, and more preferably 2,000 to 2,500 parts by mass. This blending ratio is because a cured product of the thermally conductive composition having high thermal conductivity and low compressive load and plasticity can be obtained.

[0040] The B-1 component, B-2 component, and B-4 component are preferably rounded or irregularly pulverized particles. Rounded or irregularly pulverized particles are easily available and are therefore preferred. Hereinafter, "irregularly pulverized" will also be referred to simply as "irregular." The B-3 component is preferably spherical. By making the B-3 component spherical, it becomes easier to compound the thermally conductive composition.

[0041] In the thermally conductive particles (component B), the ratio of the total mass of alumina to the total mass of aluminum nitride is preferably 4 to 5.5, and more preferably 4.1 to 5.3. This is because increasing the total mass of alumina reduces the production cost of the thermally conductive composition. Figure 2 shows a scanning electron microscope (SEM) photograph of the spherical alumina (B-3, D50 = 75 μm) used in the present invention, Figure 3 shows a scanning electron microscope (SEM) photograph of the rounded alumina (B-1, D50 = 5 μm) used in the present invention, and Figure 4 shows a scanning electron microscope (SEM) photograph of the amorphous alumina (B-4, D50 = 4 μm).

[0042] <Other Additives> The thermally conductive composition of the present invention may contain components other than those described above, as needed. For example, the thermally conductive composition may contain heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardant assistants, and curing retarders. The thermally conductive composition may also contain organic or inorganic pigments for coloring or color matching. The thermally conductive composition may also contain the silane coupling agent described above.

[0043] <Thermal Conductive Composition (Compound)> The thermal conductive composition of the present invention can be cured by heating or the like. The thermal conductivity of the cured product of the thermal conductive composition is preferably 7 W / m K or more, more preferably 7 to 15 W / m K, and even more preferably 7 to 14 W / m K. A cured product having such a thermal conductivity is suitable as a heat-dissipating sheet: TIM (Thermal Interface Material).

[0044] The cured product of the thermally conductive composition preferably has an instantaneous load value of 1000 N or less, more preferably 950 N or less, and even more preferably 900 N or less, when compressed 50% to a diameter of 28.6 mm and a thickness of 2 mm, as measured in accordance with ASTM D575-91:2012. This makes the cured product more easily crushable, thereby reducing the physical load on the heat-generating part when interposed between the heat-generating part and the heat-dissipating part. Furthermore, the cured product of the thermally conductive composition preferably has a steady load value of 1000 N or less, more preferably 950 N or less, and even more preferably 900 N or less, when compressed 50% to a diameter of 28.6 mm and a thickness of 2 mm, as measured in accordance with ASTM D575-91:2012. This makes the cured product more easily crushable, thereby reducing the physical load on the heat-generating part when interposed between the heat-generating part and the heat-dissipating part.

[0045] The plasticity of the thermally conductive composition after degassing before curing is preferably 60 or less, more preferably 10 to 60, even more preferably 20 to 55, and particularly preferably 30 to 50. Thermally conductive compositions with such low plasticity exhibit good moldability. The plasticity can be determined in accordance with JIS K 6300-3 and ISO 2007:1991 using a Wallace plastometer at a measurement temperature of 25°C. The sample is compressed between two metal plates at a constant load (100 N) for a fixed time (15 seconds). The plasticity (P = t / t × 100) is calculated by dividing the thickness (t) of the sample by the thickness (t) of the sample before compression. A smaller P indicates greater flexibility. Because the thermally conductive composition is degassed before sheet formation, the plasticity before curing and after degassing is important.

[0046] The thermally conductive composition of the present invention, when formed into a sheet, is highly versatile and suitable as a TIM. The thickness of the sheet containing the thermally conductive composition (i.e., the thermally conductive sheet) is preferably in the range of 0.2 to 10 mm.

[0047] The method for producing a thermally conductive sheet of the present invention includes the steps of vacuum-degassing the thermally conductive composition, rolling it, forming it into a sheet, and then heat-curing it to obtain a thermally conductive sheet. The vacuum degassing can be performed by reducing the pressure of the thermally conductive composition to -0.08 to -0.1 Pa and leaving it for about 5 to 10 minutes to degas it. The rolling can be performed by roll-rolling, press-forming, or the like, but roll-rolling is preferred because it allows for continuous production.

[0048] The thermally conductive composition preferably has a breakdown voltage (JIS K6249) of 7 to 16 kV / mm, which allows the thermally conductive composition to be cured to form a thermally conductive sheet with high electrical insulation.

[0049] The volume resistivity (JIS K6249) of the thermally conductive composition is 10 10 ~10 14 It is preferable that the electrical resistance is Ω·cm, which allows the thermally conductive composition to be cured to form a thermally conductive sheet with high electrical insulation.

[0050] An example of the thermally conductive composition of the present invention is preferably an addition reaction type silicone composition (uncured composition), and more preferably a compound with the following composition: (Component A) Matrix Resin The matrix resin contains the following (A1) and (A2): (A1) Base Polymer Component: A linear organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule; (A2) Crosslinking Component: An organohydrogenpolysiloxane containing at least two SH groups per molecule, in an amount less than 1 mole per mole of silicon-bonded alkenyl groups in Component A1. An organopolysiloxane having no reactive groups other than Components (A1) and (A2), such as unreacted silicone oil, may also be included, such as dimethylpolysiloxane. The total amount of Base Polymer Component (A1), Crosslinking Component (A2), unreacted silicone oil, and silane coupling agent is 100 parts by mass. The curing catalyst (Component B) and thermally conductive particles (Component C) are as described above. (C) Platinum-based metal catalyst: 0.01 to 1000 ppm by mass relative to the matrix resin (component A). (D) Other additives: silane coupling agents, cure retarders, colorants, etc. may be included in any amounts.

[0051] The following description will be made with reference to the drawings. In the following drawings, the same reference numerals indicate the same components. FIG. 1 is a schematic cross-sectional view of a heat dissipation structure 30 incorporating a thermally conductive sheet according to one embodiment of the present invention. The thermally conductive sheet 31b dissipates heat generated by an electronic component 33, such as a semiconductor device. The thermally conductive sheet 31b is fixed to a main surface 32a of the heat spreader 32 facing the electronic component 33, and is sandwiched between the electronic component 33 and the heat spreader 32. The thermally conductive sheet 31a is sandwiched between the heat spreader 32 and a heat sink 35. The thermally conductive sheets 31a and 31b, together with the heat spreader 32, constitute a heat dissipation member that dissipates heat from the electronic component 33. The heat spreader 32 is formed, for example, in the shape of a rectangular plate, and has a main surface 32a facing the electronic component 33 and a sidewall 32b extending along the outer periphery of the main surface 32a. The heat spreader 32 has a main surface 32a surrounded by side walls 32b, on which a thermally conductive sheet 31b is provided, and a heat sink 35 is provided on another surface 32c opposite to the main surface 32a, via the thermally conductive sheet 31a. The electronic component 33 is, for example, a semiconductor element such as a BGA, and is mounted on a wiring board 34.

[0052] The present invention includes the following aspects.

[0053] [Item 1] A thermally conductive composition comprising a matrix resin (component A) made of a thermosetting resin, a curing catalyst, and thermally conductive particles (component B), wherein 1500 to 3000 parts by mass of the thermally conductive particles (component B) are blended with 100 parts by mass of the matrix resin (component A), and the thermally conductive particles (component B) comprise the following components B-1, B-2, B-3, and B-4, wherein the thermally conductive particles (component B) comprise, when the total of the thermally conductive particles (component B) is taken as 100% by mass, 10 to 20% by mass of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm, 3 to 9% by mass of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more, 50 to 60% by mass of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm, and A thermally conductive composition comprising 11 to 37 mass% of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm, and a blending ratio (B-1) / (B-2) of the B-1 component to the B-2 component of 1.2 to 3 by mass.

[0054] [Item 2] The thermally conductive composition according to Item 1, wherein the thermal conductivity of a cured product of the thermally conductive composition is 7 W / m K or more, preferably 7 to 15 W / m K, and more preferably 7 to 15 W / m K.

[0055] [Item 3] The thermally conductive composition according to Item 1 or 2, wherein the cured product of the thermally conductive composition has an instantaneous load value of 1000 N or less, preferably 950 N or less, and more preferably 900 N or less, when compressed by 50% to a diameter of 28.6 mm and a thickness of 2 mm, as measured in accordance with ASTM D575-91:2012.

[0056] [Item 4] The thermally conductive composition according to any one of Items 1 to 3, wherein the plasticity of the thermally conductive composition after degassing before curing is 60 or less, preferably 10 to 60, more preferably 20 to 55, and even more preferably 30 to 50.

[0057] [Item 5] The thermosetting resin is preferably selected from silicone resin, epoxy resin, phenolic resin, unsaturated polyester resin, melamine resin, acrylic resin, silicone resin, and fluororesin, and more preferably silicone resin. The thermally conductive composition according to any one of Items 1 to 4.

[0058] [Item 6] The thermally conductive composition according to any one of Items 1 to 5, wherein the matrix resin is at least one selected from an addition-curable silicone polymer, a peroxide-curable silicone polymer, and a condensation-curable silicone polymer.

[0059] [Item 7] The thermally conductive composition according to any one of Items 1 to 6, wherein the matrix resin preferably further contains a silane coupling agent, and more preferably contains 0.1 to 10 parts by mass of the silane coupling agent per 100 parts by mass of the matrix resin.

[0060] [Item 8] The silane coupling agent is a compound represented by the formula R(CH3) a Si(OR') 4-aItem 8. The thermally conductive composition according to Item 7, wherein the silane compound is a silane compound represented by the formula (I) (wherein R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a partial hydrolyzate thereof, preferably methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, or octadecyltriethoxysilane.

[0061] [Item 9] When the total of the thermally conductive particles (B component) is 100 mass%, preferably, aluminum nitride (B-1 component) having a D50 (median diameter) of less than 20 μm, 3.5 to 8.5 mass% of aluminum nitride (B-2 component) having a D50 (median diameter) of 20 μm or more, 50 to 58 mass% of alumina (B-3 component) having a D50 (median diameter) of 60 to 80 μm, and 15 to 35 mass% of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm. Item 9. The thermally conductive particles (component B), when the total amount of the thermally conductive particles (component B) is 100 mass%, more preferably contain 10 to 16 mass% of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm, 4 to 8 mass% of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more, 51 to 58 mass% of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm, and 20 to 33 mass% of alumina (component B-4) having a D50 (median diameter) of less than 60 μm. The thermally conductive composition according to any one of Items 1 to 8.

[0062] [Item 10] The blending ratio (B-1) / (B-2) of the B-1 component and the B-2 component is preferably 1.3 to 2.9, more preferably 1.3 to 2.8, in mass ratio. The thermally conductive composition according to any one of items 1 to 9.

[0063] [Item 11] The amount of the thermally conductive particles (component B) per 100 parts by mass of the matrix resin (component A) is preferably 1700 to 2800 parts by mass, more preferably 2000 to 2500 parts by mass. The thermally conductive composition according to any one of items 1 to 10.

[0064] [Item 12] The B-1 component, the B-2 component, and the B-4 component are rounded or irregularly pulverized particles, and the B-3 component is spherical. The thermally conductive composition according to any one of Items 1 to 11.

[0065] [Item 13] In the thermally conductive particles (component B), the ratio of alumina total mass / aluminum nitride total mass is preferably 4 to 5.5, more preferably 4.1 to 5.3. The thermally conductive composition according to any one of items 1 to 12.

[0066] [Item 14] The thermally conductive composition according to any one of Items 1 to 13, wherein the matrix resin comprises a base polymer component (A1 component) and a crosslinking component (A2).

[0067] [Item 15] The base polymer component is an organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule, preferably an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, the alkenyl groups being preferably vinyl groups, allyl groups, or the like, having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, and more preferably an organopolysiloxane represented by general formula (I) containing alkenyl groups bonded to silicon atoms at both molecular chain terminals in one molecule, or a linear organopolysiloxane represented by general formula (II) having 1 to 3 alkenyl groups on each silicon atom at both molecular chain terminals.

[0068]

[0069] In the formula, each R 1 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, R 2 is an alkenyl group, and k is 0 or a positive integer.

[0070]

[0071] In the formula, each R 3 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups, at least one of which is an alkenyl group; 4 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, R 5 is an alkenyl group, and l and m are each independently 0 or a positive integer.

[0072] [Item 16] The crosslinking component is an organohydrogenpolysiloxane, preferably an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) in one molecule, and more preferably an organohydrogenpolysiloxane represented by general formula (III):

[0073] In the above formula, each R 6 may be the same or different and are each an alkyl group, a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, an alkoxy group, or a hydrogen atom, provided that at least two of them are hydrogen atoms. L is an integer of 0 to 1,000, preferably an integer of 0 to 300, and M is an integer of 1 to 200.

[0074] [Item 17] The thermally conductive composition according to any one of Items 1 to 16, wherein the curing catalyst is a catalyst used in a hydrosilylation reaction, and is preferably a platinum group metal catalyst such as platinum black, platinic chloride, chloroplatinic acid, a reaction product of chloroplatinic acid with a monohydric alcohol, a complex of chloroplatinic acid with an olefin or vinylsiloxane, a complex of platinum with vinyldisiloxane, platinum bisacetoacetate, or the like, a palladium catalyst, or a rhodium catalyst.

[0075] [Item 18] The thermally conductive composition is preferably an addition reaction type silicone composition (uncured composition), and more preferably a compound with the following composition: (Component A) Matrix Resin The matrix resin contains the following (A1) and (A2): (A1) Base Polymer Component: A linear organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule; (A2) Crosslinking Component: An organohydrogenpolysiloxane containing at least two SH groups per molecule, in an amount less than 1 mole per mole of silicon-bonded alkenyl groups in Component A1; An organopolysiloxane having no reactive groups other than Components (A1) and (A2), such as unreacted silicone oil, e.g., dimethylpolysiloxane, may also be included. The total amount of Base Polymer Component (A1), Crosslinking Component (A2), unreacted silicone oil, and silane coupling agent is 100 parts by mass. The (Component B) curing catalyst and (Component C) thermally conductive particles are as described in Item 1. (C) Platinum-based metal catalyst: 0.01 to 1000 ppm by mass relative to the matrix resin (component A). (D) Other additives: silane coupling agents, cure retarders, colorants, etc. may be included in any amounts.

[0076] [Item 19] A thermally conductive sheet comprising the thermally conductive composition according to any one of items 1 to 18 and formed into a sheet.

[0077] [Item 20] The thermally conductive sheet according to Item 19, wherein the thickness of the thermally conductive sheet is in the range of 0.2 to 10 mm.

[0078] [Item 21] A method for producing a thermally conductive sheet, comprising the steps of vacuum degassing the thermally conductive composition according to any one of items 1 to 18, rolling it, forming it into a sheet, and then heat-curing it to produce a thermally conductive sheet.

[0079] [Item 22] The method for producing a thermally conductive sheet according to Item 21, wherein the vacuum degassing is performed by reducing the pressure of the thermally conductive composition to −0.08 to −0.1 Pa, leaving it for about 5 to 10 minutes, and degassing.

[0080] [Examples] The present invention will be explained below using examples, but is not limited to these examples. Various parameters were measured by the methods described below.

[0081] <50% Compression Load Value> The compression load was measured in accordance with ASTM D575-91:2012. FIG. 5 is a schematic side cross-sectional view of a compression load measuring device used in one embodiment of the present invention. This compression load measuring device 1 includes a sample stage 2 and a load cell 6. A thermally conductive sheet sample 4 is sandwiched between aluminum plates 3 and 5, attached as shown in FIG. 5, and compressed to a specified thickness using the load cell 6. The maximum load value when compressed to 50% of the thickness ("50% Compression Load Value (Instantaneous)") and the load value after maintaining that compression for one minute ("50% Compression Load Value (Steady State)") are recorded. Measurement conditions Sample: Cylindrical (diameter 28.6 mm, thickness 2 mm) Compression rate: 50% Aluminum plate size: Circular (diameter 28.6 mm) (compression surface) Compression speed: 5 mm / min Compression method: TRIGGER method (method in which the point at which a load of 2 N is detected is the measurement start position) Measuring device: Aiko Engineering, MODEL-1310NW (load cell 200 kgf)

[0082] <Thermal Conductivity> The thermal conductivity of the thermally conductive sheet was measured using a hot disk (compliant with ISO 22007-2:2008). As shown in FIG. 6A, this thermal conductivity measuring device 11 sandwiches a polyimide film sensor 12 between two thermally conductive sheet samples 13a and 13b, applies a constant power to the sensor 12, and generates a constant amount of heat, analyzing the thermal characteristics from the temperature rise of the sensor 12. The sensor 12 has a 7 mm diameter tip 14 and, as shown in FIG. 6B, has a double spiral electrode structure, with an applied current electrode 15 and a resistance value electrode (temperature measurement electrode) 16 located at the bottom. The thermal conductivity was calculated using the following equation (Equation 1):

[0083]

[0084] <Plasticity> Plasticity was measured in accordance with JIS K 6300-3, ISO 2007:1991 using a Wallace plastometer. The thermally conductive composition was compressed between two metal plates at a measurement temperature of 23°C under a constant load (100 N) for a constant time (15 seconds). The thickness (t) of the thermally conductive composition after compression was divided by the thickness (t) of the thermally conductive composition before compression, and the result was calculated as plasticity (P0 = t / t0 × 100). A larger P0 indicates greater flexibility. The prepared pre-cure post-degassing plasticity is the plasticity of the thermally conductive composition after degassing for 5 minutes under a reduced pressure of -0.1 Pa.

[0085] (Examples 1 to 6, Comparative Examples 1 to 7) 1. Material Components (1) Matrix Resin (Component A) A commercially available two-component room temperature addition-curing silicone polymer (silicone component) containing polyorganosiloxane was used. One component (Component A) contains a base polymer component (polyorganosiloxane, Component A1 of Component A) and a platinum group metal catalyst, while the other component (Component B) contains a base polymer component (polyorganosiloxane, Component A1 of Component A) and a crosslinker component (Component A2 of Component A), an organohydrogenpolysiloxane. The ratio of Components A and B was A:B = 100:100 by mass. This two-component room temperature addition-curing silicone polymer undergoes addition curing by mixing at room temperature to form a silicone resin.

[0086] (2) Thermally conductive particles (components B-1 to B-4) The thermally conductive particles listed in Table 1 were used. The average particle size is the D50 (median diameter) of the cumulative particle size distribution on a volume basis, measured by laser diffraction light scattering. An example of the measuring device used is the LA-950S2 laser diffraction / scattering particle distribution measuring device manufactured by Horiba, Ltd. Additionally, AlN in the table is an abbreviation for aluminum nitride.・B-1: Rounded aluminum nitride (D50 = 5 μm) ・B-1: Irregular aluminum nitride (D50 = 15 μm) ・B-2: Rounded aluminum nitride (D50 = 20 μm) ・B-2: Rounded aluminum nitride (D50 = 30 μm) ・B-2: Rounded aluminum nitride (D50 = 70 μm) ・B-2: Rounded aluminum nitride (D50 = 100 μm) ・B-3: Spherical alumina (D50 = 75 μm) ・B-4: Irregular alumina (D50 = 0.3 μm) ・B-4: Irregular alumina (D50 = 0.7 μm) ・B-4: Irregular alumina (D50 = 4.0 μm) ・B-4: Irregular alumina (D50 = 2.2 μm)

[0087] (3) Curing catalyst (component C) A platinum-vinyldisiloxane complex (platinum group metal catalyst) was used as the curing catalyst (component C). As described above, the two-component curing silicone polymer (silicone component) contains a platinum group metal catalyst. When preparing the thermally conductive composition of each example, an additional platinum group metal catalyst was added to the thermally conductive composition to ensure that the polyorganosiloxane was sufficiently cured.

[0088] (4) Silane Coupling Agent Decyltrimethoxysilane was used as the silane coupling agent.

[0089] 2. Thermally conductive composition (compound) The amounts of each material shown in Table 1 were weighed out and placed in a mixer to prepare a thermally conductive composition. This thermally conductive composition was degassed at a reduced pressure of -0.1 Pa for 5 minutes.

[0090] 3. Sheet molding The thermally conductive composition was sandwiched between release-treated polyethylene terephthalate (PET) films, rolled using a constant speed roll, and molded into a sheet with a thickness of 2.0 mm. This was then heated and cured at 100°C for 10 minutes to obtain a thermally conductive sheet (thermally conductive silicone rubber sheet). The moldability was judged as "possible" if molding was possible under the above conditions, and "NG" if not.

[0091] The conditions and results of the examples are shown in Table 1, and the conditions and results of the comparative examples are shown in Table 2. In Tables 1 and 2, the amount of each material is shown in parts by mass when the matrix resin (component A, two-component room-temperature curing silicone polymer) is taken as 100 parts by mass (100 g). The specific gravities of the matrix resin (component A), silane coupling agent, and platinum group metal catalyst are all 0.98, the specific gravities of alumina (components B-3 and B-4) are 3.98, and the specific gravities of aluminum nitride (components B-1 and B-2) are 3.32.

[0092]

[0093]

[0094] Tables 1 and 2 reveal the following: (1) The thermal conductivity of the thermally conductive sheets in Examples 1 to 5 is higher than that of Comparative Examples 1 to 6, and the compressive load and pre-curing and post-degassing plasticity are lower. (2) Compared to Comparative Example 1 (B-1 component only), the load value of the thermally conductive sheets in Examples 1 and 2 is lower due to the combination of two types of aluminum nitride (B-1 component, B-2 component) with different particle sizes. (3) In Examples 1, 3, 4, and 5, even if the (B-2) component with a larger particle size is varied, the load value of the thermally conductive sheets is not affected. (4) As shown in Comparative Examples 1, 3, and 4, when either the (B-1) component or the (B-2) component is not included or when two types of the (B-2) component are included, the load value of the thermally conductive sheets is high or they cannot be mixed into the thermally conductive composition. (5) In Comparative Example 5 (where the content of component (B-3) is below the specified range) and Comparative Example 6 (where the content of component (B-1) is below the specified range), the thermal conductivity and load value of the thermally conductive sheet are both low.

[0095] The thermally conductive composition and thermally conductive sheet of the present invention are suitable as a thermal interface material (TIM) that is placed between a heat-generating portion of an electric or electronic part and a heat sink.

[0096] REFERENCE SIGNS LIST 1 Compression load measuring device 2 Sample stage 3, 5 Aluminum plate 4 Thermally conductive sheet sample 6 Load cell 11 Thermal conductivity measuring device 12 Sensor 13a, 13b Thermally conductive sheet sample 14 Sensor tip 15 Applied current electrode 16 Resistance value electrode (temperature measurement electrode) 30 Heat dissipation structure 31a, 31b Thermally conductive sheet 32 ​​Heat spreader 32b Heat spreader side wall 33 Electronic component 34 Wiring board 35 Heat sink

Claims

1. A thermally conductive composition comprising a matrix resin (component A) made of a thermosetting resin, a curing catalyst, and thermally conductive particles (component B), wherein 1,500 to 3,000 parts by mass of the thermally conductive particles (component B) are blended with 100 parts by mass of the matrix resin (component A), and the thermally conductive particles (component B) comprise the following components B-1, B-2, B-3, and B-4, wherein the thermally conductive particles (component B) comprise, when the total of the thermally conductive particles (component B) is taken as 100% by mass, 10 to 20% by mass of aluminum nitride (component B-1) having a D50 (median diameter) of less than 20 μm, 3 to 9% by mass of aluminum nitride (component B-2) having a D50 (median diameter) of 20 μm or more, 50 to 60% by mass of alumina (component B-3) having a D50 (median diameter) of 60 to 80 μm, and A thermally conductive composition comprising 11 to 37 mass% of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm, and a blending ratio (B-1) / (B-2) of the B-1 component to the B-2 component being 1.2 to 3 by mass.

2. The thermally conductive composition according to claim 1, wherein the thermal conductivity of the cured product of the thermally conductive composition is 7 W / m·K or more.

3. The thermally conductive composition according to claim 1 or 2, wherein the cured product of the thermally conductive composition has an instantaneous load value of 1000 N or less when compressed 50% to a diameter of 28.6 mm and a thickness of 2 mm, as measured in accordance with ASTM D575-91:2012.

4. The thermally conductive composition according to any one of claims 1 to 3, wherein the thermally conductive composition has a plasticity of 60 or less after degassing before curing.

5. A thermally conductive composition according to any one of claims 1 to 4, wherein the matrix resin is at least one selected from the group consisting of addition-curing silicone polymers, peroxide-curing silicone polymers, and condensation-curing silicone polymers.

6. The thermally conductive composition according to any one of claims 1 to 5, further comprising 0.1 to 10 parts by mass of a silane coupling agent per 100 parts by mass of the matrix resin.

7. A thermally conductive composition according to any one of claims 1 to 6, wherein the B-1, B-2, and B-4 components are rounded or irregularly pulverized particles, and the B-3 component is spherical.

8. A thermally conductive sheet comprising the thermally conductive composition according to any one of claims 1 to 7 and formed into a sheet.

9. The thermally conductive sheet according to claim 8, wherein the thickness of the thermally conductive sheet is in the range of 0.2 to 10 mm.

10. A method for producing a thermally conductive sheet, comprising the steps of vacuum degassing the thermally conductive composition according to any one of claims 1 to 7, rolling it, forming it into a sheet, and then heat curing it to produce a thermally conductive sheet.

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