Thermally conductive composition, thermally conductive sheet using same, and manufacturing method thereof

Abstract

The present invention provides a thermally conductive composition having high thermal conductivity and low compressive load and plasticity, a thermally conductive sheet using the same, and a method for producing the same. The thermally conductive composition includes a matrix resin (component A) made of a thermosetting resin, a curing catalyst, and thermally conductive particles (component B), and 1500 to 3000 parts by mass of component B is blended for 100 parts by mass of component A. Component B includes the following components B1, B2, B3, and B4, and, relative to the entire component B, it contains 10 to 20 mass% of aluminum nitride (component B1) having a D50 (median diameter) of less than 20 μm, 3 to 9 mass% of aluminum nitride (component B2) having a D50 of 20 μm or more, 50 to 60 mass% of alumina (component B3) having a D50 of 60 to 80 μm, and 11 to 37 mass% of alumina (component B4) having a D50 of less than 60 μm, and the blending ratio (B1) / (B2) of the components B1 and B2 is 1.2 to 3 in mass ratio.

Description

[Technical field]

[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 and a heat sink, a thermally conductive sheet using the same, and a method for producing the same. [Background technology]

[0002] In recent years, the performance of semiconductors such as CPUs has improved remarkably, and the amount of heat generated has also increased. For this reason, heat sinks are attached to electronic components that generate heat, and thermally conductive sheets are used to improve the adhesion between the semiconductor and the heat sink. As devices become smaller, more powerful, and more highly integrated, thermally conductive sheets are required to be soft and have high thermal conductivity. Conventionally, Japanese Patent No. 6246986 and Japanese Patent No. 7039157 have proposed polysiloxane compositions containing large aluminum nitride particles and small aluminum nitride particles or alumina particles. Japanese Patent No. 7082563 and Japanese Patent No. 7205554 have proposed thermally conductive polysiloxane compositions containing aluminum nitride particles. Summary of the Invention

[0003] The present invention relates to a thermally conductive composition comprising a matrix resin (component A) made of a thermosetting resin, a curing catalyst, and thermally conductive particles (component B), The thermally conductive particles (component B) are mixed in an amount of 1500 to 3000 parts by mass per 100 parts by mass of the matrix resin (component A), The thermally conductive particles (component B) include the following components B-1, B-2, B-3, and B-4: The thermally conductive particles (component B) have a content of: 10 to 20 mass% of aluminum nitride (B-1 component) having a D50 (median diameter) of less than 20 μm, 3 to 9 mass% of aluminum nitride (B-2 component) with a D50 (median diameter) of 20 μm or more, 50 to 60 mass% of alumina (B-3 component) having a D50 (median diameter) of 60 to 80 μm, and Contains 11 to 37 mass% of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm, The thermally conductive composition has a blending ratio of the B-1 component to the B-2 component, (B-1) / (B-2), of 1.2 to 3 in terms of mass ratio. [Brief description of the drawings]

[0004] [Figure 1] 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. [Diagram 2] 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. [Diagram 3] FIG. 3 is a scanning electron microscope (SEM) photograph of the rounded AIN of the present invention (B-1, D50=5 μm). [Figure 4] FIG. 4 is a scanning electron microscope (SEM) photograph of the amorphous alumina of the present invention (B-4, D50=4 μm). [Diagram 5] FIG. 5 is a schematic side cross-sectional view of a compression load measuring device used in one embodiment of the present invention. [Figure 6] 6A-B are schematic explanatory views showing a method for measuring the thermal conductivity of a sample in 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 a problem in that increasing the thermal conductivity increases the compressive load and plasticity. In order to solve the above-mentioned problems in the conventional art, the present invention provides a thermally conductive sheet having high thermal conductivity and low compressive load and plasticity, a thermally conductive composition which is the raw material thereof, and a method for producing a thermally conductive sheet using the same.

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

[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 compression load and plasticity, a thermally conductive composition which is a raw material of the thermally conductive sheet, 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 at 50% compression with 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 continuous sheet molding because the thermally conductive composition of the present invention has low plasticity and good moldability.

[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 made of a thermosetting resin. Examples of the thermosetting resin include silicone resin, epoxy resin, phenol resin, unsaturated polyester resin, melamine resin, acrylic resin, silicone resin, and fluororesin, and silicone resin is 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 resin may be cured using any method such as peroxide, addition, and condensation. As the thermosetting resin, silicone resin is preferred because it has high heat resistance. The matrix resin is preferably formed from at least one selected from an addition-curing silicone polymer, a peroxide-curing silicone polymer, and a condensation-type silicone polymer. In addition, the silicone resin is preferably an addition-curing type because it is not corrosive to the surroundings, there are few by-products released outside the system, and it is reliably cured to a deep portion.

[0012] The matrix resin preferably further contains a silane coupling agent, and more preferably, 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, of the silane coupling agent is added to 100 parts by mass of the matrix resin. The silane coupling agent coats the surface of the thermally conductive particles (component B) (surface treatment), making it easier to fill the matrix resin (component A) (plasticizer function), and also has the effect of preventing the curing catalyst (component C) from being adsorbed to the thermally conductive particles (component B), thereby preventing curing inhibition. When the matrix resin further contains a silane coupling agent, there is an advantage that the storage stability of the thermally conductive composition is excellent.

[0013] The silane coupling agent is, 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 Examples of the silane compound 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) (hereinafter simply referred to as "silane") include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane. The silane compounds can be used alone or in combination of two or more kinds.

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

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

[0016] [ka]

[0017] During the ceremony, Each R 1 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, R 2 is an alkenyl group, k is 0 or a positive integer.

[0018] In the general formula (I), R 1The 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. Specifically, the unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond includes 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. The substituted monovalent hydrocarbon group having no aliphatic unsaturated bond includes groups in which some or all of the hydrogen atoms of the unsubstituted monovalent hydrocarbon group are substituted with halogen atoms such as fluorine, bromine, and chlorine; or cyano groups, for example, halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl; and cyanoethyl groups.

[0019] In the general formula (I), R 2 The alkenyl group is, for example, preferably an alkenyl group having 2 to 6 carbon atoms, particularly preferably 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 used in combination with an organopolysiloxane having at least 3, usually 3 to 30, and preferably about 3 to 20 alkenyl groups, such as vinyl groups and allyl groups, bonded to silicon atoms having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, in one molecule. The molecular structure of the organopolysiloxane used in combination may be any of linear, cyclic, branched, and three-dimensional network molecular structures. The organopolysiloxane used in combination is preferably a linear organopolysiloxane whose main chain is composed of repeated diorganosiloxane units, whose 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 in one 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-terminals (in the middle of the molecular chain). Among them, linear organopolysiloxanes having 1 to 3 alkenyl groups on each of the silicon atoms at both molecular chain terminals, as represented by the following general formula (II), and having a viscosity of 10 to 1,000,000 mPa·s at 25°C, are preferred in terms 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 at both terminals, linear organopolysiloxanes having alkenyl groups bonded to silicon atoms at non-terminals (in the middle of the molecular chain) as substituents in diorganosiloxane units are preferred. This linear organopolysiloxane may contain a small amount of a branched structure (trifunctional siloxane unit) in the molecular chain.

[0023] [ka]

[0024] During the ceremony, Each R 3may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups, at least one of which is an alkenyl group; Each R 4 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, R 5 is an alkenyl group, l and m are each independently 0 or a positive integer.

[0025] In the general formula (II), R 3 The 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 groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; and alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl groups. 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, chlorine, etc.; or a cyano group, etc., 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 the 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 is preferably selected from the group consisting of the above R 1 Specific examples of the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond are the same as those of the substituted or unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond, except that alkenyl groups are not included.

[0027] In general formula (II), R 5 As the alkenyl group of, for example, 2 to 6 carbon atoms, particularly preferably alkenyl groups having 2 to 3 carbon atoms, specifically the R of the formula (I) 2 The same alkenyl groups as those are exemplified, preferably a vinyl group.

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

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

[0030] The organohydrogenpolysiloxane contains an SiH group as described above. In the organohydrogenpolysiloxane, the position of the SiH group is not particularly restricted and may be at the end of the molecular chain or in the non-terminal part (in the middle of the molecular chain) of the molecular chain. Further, as the organic group bonded to a silicon atom other than a hydrogen atom, the R of the general formula (I) 1and the like. Examples of the substituted or unsubstituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds include those shown below.

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

[0032] [ka]

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

[0034] <Curing catalyst (C component)> As the curing catalyst of the component C, a catalyst used in a hydrosilylation reaction can be used. Examples of the curing catalyst include platinum black, platinum (II) chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin or vinylsiloxane, a complex of platinum and a vinyldisiloxane, a platinum-based catalyst such as platinum bisacetoacetate, a palladium-based catalyst, and a rhodium-based catalyst. Although a two-component curing silicone polymer usually contains a platinum-based metal catalyst, even if the thermally conductive composition of the present invention contains a two-component curing silicone polymer, an additional platinum-based metal catalyst is preferably added to the thermally conductive composition of the present invention. The platinum-based metal catalyst is added in order to control the curing speed 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, relative to 100 parts by mass of the matrix resin (component A).

[0036] <Thermal conductive particles (component B)> The thermally conductive particles (component B) include the following components B-1, B-2, B-3, and B-4: The thermally conductive particles (component B) have a content of: 10 to 20 mass% of aluminum nitride (B-1 component) having a D50 (median diameter) of less than 20 μm, 3 to 9 mass% of aluminum nitride (B-2 component) with a D50 (median diameter) of 20 μm or more, 50 to 60 mass% of alumina (B-3 component) having a D50 (median diameter) of 60 to 80 μm, and It contains 11 to 37 mass % of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm. When the total amount of the thermally conductive particles (component B) is 100 mass %, preferably 10 to 18 mass% of 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) with 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 It contains 15 to 35 mass % of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm. The thermally conductive particles (component B) are more preferably, 10 to 16 mass% of aluminum nitride (B-1 component) having a D50 (median diameter) of less than 20 μm, 4 to 8 mass% of aluminum nitride (B-2 component) with D50 (median diameter) of 20 μm or more, 51 to 58 mass% of alumina (B-3 component) having a D50 (median diameter) of 60 to 80 μm, and It contains 20 to 33 mass % of alumina (B-4 component) with a D50 (median diameter) of less than 60 μm.

[0037] In the present invention, the thermally conductive particles (B component) are used in combination with a plurality of types of thermally conductive inorganic particles having different average particle sizes. This is because the thermally conductive inorganic particles having a small particle size are filled between the larger particles, and the particles can be filled in a state close to close packing, and the thermal conductivity of the cured product of the thermally conductive composition is increased. This is also because the cured product of the thermally conductive composition has low plasticity and is a thermally conductive composition with good moldability. This is also because the cured product of the thermally conductive composition can be molded into a heat dissipation sheet: TIM (Thermal Interface Material), which has a low compression load and is easier to handle than putty-like materials.

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

[0039] The thermally conductive particles (component B) are blended in an amount of 1500 to 3000 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 1700 to 2800 parts by mass, and more preferably 2000 to 2500 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, B-2, and B-4 components are preferably round or irregularly pulverized particles. Round or irregularly pulverized particles are easily available and are therefore preferred. In the following, the irregularly pulverized particles are also simply referred to 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 (B component), the ratio of the total mass of alumina to the total mass of aluminum nitride is preferably 4 to 5.5, more preferably 4.1 to 5.3. This is because the manufacturing cost of the thermally conductive composition can be reduced by increasing the total mass of alumina. Fig. 2 shows a scanning electron microscope (SEM) photograph of the spherical alumina (B-3, D50=75 μm) used in the present invention, Fig. 3 shows a scanning electron microscope (SEM) photograph of the rounded AIN (B-1, D50=5 μm) used in the present invention, and Fig. 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 other components as necessary. 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 contain organic or inorganic pigments for coloring and color matching. The thermally conductive composition may contain the silane coupling agent.

[0043] <Thermal conductive composition (compound)> The thermally conductive composition of the present invention can be cured by heating or the like. The thermal conductivity of the cured product of the thermally 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 has an instantaneous load value of preferably 1000N or less, more preferably 950N or less, and even more preferably 900N or less when compressed by 50% with 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 crushed, and when interposed between a heat generating part and a heat sink, the physical load on the heat generating part can be reduced. In addition, the cured product of the thermally conductive composition has a steady load value of preferably 1000N or less, more preferably 950N or less, and even more preferably 900N or less when compressed by 50% with 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 crushed, and when interposed between a heat generating part and a heat sink, the physical load on the heat generating part can be reduced.

[0045] The plasticity of the thermally conductive composition after defoaming before curing is preferably 60 or less, more preferably 10 to 60, even more preferably 20 to 55, and particularly preferably 30 to 50. A thermally conductive composition with such low plasticity has good moldability. The plasticity can be determined by dividing the thickness (t) of a sample after compressing the sample between two metal plates at a constant load (100N) for a constant time (15 seconds) at a measurement temperature of 25°C using a Wallace plastometer according to JIS K 6300-3, ISO 2007:1991 by the thickness (t0) of the sample before compression (t0). The smaller the P0, the more flexible the composition is. Since the thermally conductive composition is molded into a sheet after defoaming, the plasticity before curing and after defoaming 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 a step 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, leaving it for about 5 to 10 minutes, and degassing it. The rolling can be performed by roll rolling, press working, etc., but roll rolling is preferred because it allows 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 become a thermally conductive sheet with high electrical insulation when cured.

[0049] The volume resistivity (JIS K6249) of the thermally conductive composition is 10 10 ~10 14 It is preferable that the electrical resistance of the thermally conductive composition is Ω·cm, whereby when the thermally conductive composition is cured, a thermally conductive sheet having high electrical insulation properties can be obtained.

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

[0051] The following description will be given with reference to the drawings. In the following drawings, the same reference numerals indicate the same objects. FIG. 1 is a schematic cross-sectional view of a heat dissipation structure 30 incorporating a heat conductive sheet according to an embodiment of the present invention. The heat conductive sheet 31b dissipates heat generated by an electronic component 33 such as a semiconductor element, and 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 heat conductive sheet 31a is sandwiched between the heat spreader 32 and a heat sink 35. The heat 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 a rectangular plate shape, and has a main surface 32a facing the electronic component 33 and a side wall 32b erected along the outer periphery of the main surface 32a. The heat spreader 32 has a thermally conductive sheet 31b provided on a main surface 32a surrounded by side walls 32b, and a heat sink 35 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), The thermally conductive particles (component B) are mixed in an amount of 1500 to 3000 parts by mass per 100 parts by mass of the matrix resin (component A), The thermally conductive particles (component B) include the following components B-1, B-2, B-3, and B-4: The thermally conductive particles (component B) have a content of: 10 to 20 mass% of aluminum nitride (B-1 component) having a D50 (median diameter) of less than 20 μm, 3 to 9 mass% of aluminum nitride (B-2 component) with a D50 (median diameter) of 20 μm or more, 50 to 60 mass% of alumina (B-3 component) having a D50 (median diameter) of 60 to 80 μm, and Contains 11 to 37 mass% of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm, A thermally conductive composition in which the blending ratio of the B-1 component to the B-2 component, (B-1) / (B-2), is 1.2 to 3 in terms of mass ratio.

[0054] [Item 2] The thermally conductive composition according to Item 1, wherein a cured product of the thermally conductive composition has a thermal conductivity of 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 at 50% compression of a diameter of 28.6 mm and a thickness of 2 mm of 1000 N or less, preferably 950 N or less, and more preferably 900 N or less, when 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 thermally conductive composition has a plasticity after defoaming before curing of 60 or less, preferably 10 to 60, more preferably 20 to 55, and further preferably 30 to 50.

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

[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 represented by the formula R(CH3) a Si(OR') 4-a Item 8. The thermally conductive composition according to item 7, wherein the silane compound is represented by the formula (I): (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, and is 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 (component B) is 100 mass%, preferably 10 to 18 mass% of 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) with 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 It contains 15 to 35 mass % of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm. The thermally conductive particles (component B) are more preferably, 10 to 16 mass% of aluminum nitride (B-1 component) having a D50 (median diameter) of less than 20 μm, 4 to 8 mass% of aluminum nitride (B-2 component) with D50 (median diameter) of 20 μm or more, 51 to 58 mass% of alumina (B-3 component) having a D50 (median diameter) of 60 to 80 μm, and 9. The thermally conductive composition according to any one of items 1 to 8, comprising 20 to 33 mass % of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm.

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

[0063] [Item 11] The thermally conductive composition according to any one of Items 1 to 10, wherein the blending 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, and more preferably 2000 to 2500 parts by mass.

[0064] [Item 12] The thermally conductive composition according to any one of Items 1 to 11, wherein 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.

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

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

[0067] [Item 15] The thermally conductive composition according to any one of Items 1 to 14, wherein the base polymer component is an organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule, preferably an organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule, the alkenyl groups being 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 of the silicon atoms at both molecular chain terminals.

[0068] [ka]

[0069] During the ceremony, Each R 1 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, R 2 is an alkenyl group, k is 0 or a positive integer.

[0070] [ka]

[0071] During the ceremony, 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; Each R 4 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, R 5 is an alkenyl group, l and m are each independently 0 or a positive integer.

[0072] [Item 16] The thermally conductive composition according to any one of Items 1 to 15, wherein 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). [ka]

[0073] In the above formula, Each R 6 may be the same or different and are an alkyl group, a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, an alkoxy group, or a hydrogen atom, and at least two of them are hydrogen atoms. L is an integer from 0 to 1,000, preferably an integer from 0 to 300, M is an integer from 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 a vinylsiloxane, a complex of platinum with a vinyldisiloxane, a platinum-based catalyst such as platinum bisacetoacetate, a palladium-based catalyst, or a rhodium-based catalyst.

[0075] [Item 18] The thermally conductive composition is preferably an addition reaction type silicone composition (uncured composition), and more preferably a compound having the following composition: (Component A) Matrix resin The matrix resin includes the following (A1) and (A2). (A1) Base polymer component: a linear organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in each molecule. (A2) Crosslinking component: An organohydrogenpolysiloxane containing at least two SH groups per molecule, in an amount of less than 1 mole per mole of silicon-bonded alkenyl groups in the above-mentioned component A1. In addition to the components (A1) and (A2), the composition may contain an organopolysiloxane having no reactive groups, such as unreacted silicone oil, for example, dimethylpolysiloxane. The total of the base polymer component (A1), the crosslinking component (A2), the unreacted silicone oil and the silane coupling agent is 100 parts by mass. The curing catalyst (B component) and the thermally conductive particles (C component) are as described in item 1. (C) Platinum-based metal catalyst: Amount of 0.01 to 1000 ppm by mass relative to the matrix resin (component A) (D) Other additives: Silane coupling agents, hardening 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 thermally conductive sheet has a thickness 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 it.

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

[0081] <50% compression load value> The method for measuring the compression load was 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, and 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 by the load cell 6. The maximum load value when the thickness is compressed by 50% ("50% compression load value (instantaneous)") and the load value after maintaining the compression for one minute, "50% compression load value (steady state)", are recorded. Measurement conditions Sample: Cylindrical (diameter 28.6 mm, thickness 2 mm) Compression ratio: 50% Aluminum plate size: circular (diameter 28.6 mm) (compression surface) Compression speed: 5mm / min Compression method: TRIGGER method (the point where a load of 2N is detected is the measurement start position) Measuring device: Aiko Engineering, MODEL-1310NW (load cell 200kgf)

[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 Figure 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 to generate a constant amount of heat, and analyzes the thermal characteristics from the temperature rise of the sensor 12. The sensor 12 has a tip 14 with a diameter of 7 mm, and as shown in Figure 6B, has a double spiral electrode structure, with an applied current electrode 15 and a resistance value electrode (temperature measurement electrode) 16 arranged at the bottom. The thermal conductivity was calculated using the following formula (Equation 1).

[0083]

number

[0084] <Plasticity> The plasticity was measured in accordance with JIS K 6300-3, ISO 2007:1991 using a Wallace plastometer. The thickness (t) of the thermally conductive composition was compressed between two metal plates at a constant load (100N) for a constant time (15 seconds) at a measurement temperature of 23°C, and the value was divided by the thickness (t0) of the thermally conductive composition before compression to obtain the plasticity (P0=t / t0×100). The larger the P0, the more flexible the composition is. The plasticity before curing and after defoaming is the plasticity of the thermally conductive composition after defoaming the thermally conductive composition (compound) for 5 minutes under reduced pressure of -0.1 Pa.

[0085] (Examples 1 to 6, Comparative Examples 1 to 7) 1.Material composition (1) Matrix resin (component A) A two-part room temperature addition curing silicone polymer (silicone component) containing commercially available polyorganosiloxane was used. One part (liquid A) contains a base polymer component (polyorganosiloxane, component A1 of component A) and a platinum group metal catalyst, while the other part (liquid B) contains a base polymer component (polyorganosiloxane, component A1 of component A) and a crosslinking agent component (component A2 of component A), organohydrogenpolysiloxane. The ratio of liquid A to liquid B is A:B = 100:100 by mass. This two-part room temperature addition curing silicone polymer is addition cured by mixing at room temperature to become a silicone resin.

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

[0087] (3) Curing catalyst (C component) 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 so that the polyorganosiloxane was sufficiently cured.

[0088] (4) Silane coupling agents 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 under reduced pressure of -0.1 Pa for 5 minutes.

[0090] 3.Sheet forming process The thermally conductive composition was sandwiched between release-treated polyethylene terephthalate (PET) films, rolled into a sheet of 2.0 mm thickness using a constant speed roll, and cured by heating in this state at 100°C for 10 minutes to obtain a thermally conductive sheet (thermally conductive silicone rubber sheet). When molding was possible under the above conditions, it was judged as "possible", and when it was not possible, it was judged as "NG".

[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-part 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] [Table 1]

[0093] [Table 2]

[0094] From Tables 1 and 2 we can see the following: (1) In comparison with Comparative Examples 1 to 6, the thermal conductivity of the thermally conductive sheets in Examples 1 to 5 is high, and the compressive load and the plasticity before curing and after degassing are low. (2) Compared with Comparative Example 1 (only component B-1), the load value of the thermal conductive sheet in Examples 1 and 2 is reduced by combining two types of aluminum nitride (component B-1 and component B-2) with different particle sizes. (3) In Examples 1, 3, 4, and 5, even if the (B-2) component having a large particle size is variously changed, there is no effect on the load value of the thermally conductive sheet. (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 sheet is high or it is impossible to mix it into the thermally conductive composition. (5) In Comparative Example 5 (wherein the content of the (B-3) component is below the specified range) and Comparative Example 6 (wherein the content of the (B-1) component is below the specified range), the thermal conductivity and the 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 a heat dissipation sheet to be interposed between a heat generating portion of an electric or electronic part and a heat sink. [Explanation of symbols]

[0096] 1. Compression load measuring device 2 Sample stage 3,5 Aluminum plate 4. Thermally conductive sheet sample 6 Load Cells 11 Thermal conductivity measuring device 12 Sensors 13a, 13b Thermally conductive sheet sample 14 Sensor tip 15 Electrode for applied current 16 Resistance electrode (temperature measurement electrode) 30 Heat dissipation structure 31a, 31b Thermally conductive sheet 32 Heat spreader 32b Heat spreader sidewall 33 Electronic Components 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), 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 thermally conductive particles (component B) include the following components B-1, B-2, B-3, and B-4: The thermally conductive particles (component B) have a content of: 10 to 20 mass% of aluminum nitride (B-1 component) having a D50 (median diameter) of less than 20 μm, 3 to 9 mass% of aluminum nitride (B-2 component) having a D50 (median diameter) of 20 μm or more, 50 to 60 mass% of alumina (B-3 component) having a D50 (median diameter) of 60 to 80 μm, and Contains 11 to 37 mass% of alumina (B-4 component) having a D50 (median diameter) of less than 60 μm, A thermally conductive composition in which the blending ratio (B-1) / (B-2) of the B-1 component and the B-2 component is 1.2 to 3 in mass ratio.

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

4. 2. The thermally conductive composition according to claim 1, wherein the thermally conductive composition has a plasticity of 60 or less after degassing before curing.

5. 2. The thermally conductive composition according to claim 1, wherein the matrix resin is at least one selected from the group consisting of an addition-curable silicone polymer, a peroxide-curable silicone polymer, and a condensation-curable silicone polymer.

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

7. 2. The thermally conductive composition according to claim 1, wherein the B-1, B-2, and B-4 components are round 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 thermally conductive sheet has a thickness 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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