Thermally conductive silicone gel components

Abstract

DEPCT65 The thermal conductive silicone gel components of this invention consist of the following A to F: (A) (B) Organopolysiloxanes with two alkynyl groups per molecule; (B) Organohydrogen polysiloxanes with Two Si-H groups per molecule; (C) organohydrogen polysiloxanes with three or more Si-H groups per molecule. (D) At least one compound selected from the group consisting of D1 and D2: (D1) Organopolysiloxanes with one alkynyl group per molecule and (D2) organohydrogen polysiloxanes. Containing one Si-H group per molecule; (E) platinum catalyst; and (F) heat conducting filler. 100 to 600% by volume compared to 100% by volume of the total volume of A to E. Components A through F will maintain their shape with this configuration; the thermally conductive silicone gel component can reduce heat. The oily consistency even though the product is a gel-like consistency. -----------------------------------------------------------

Description

Thermally conductive silicone gel composition

[0001] The present invention relates to a thermally conductive silicone gel composition suitable for placement between a heat-generating portion of an electric or electronic component and a heat sink.

[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 equipped with heat sinks, and thermally conductive silicone gels are used to improve adhesion between the semiconductor and the heat sink. Conventional thermally conductive silicone gel cured products have been achieved by biasing the ratio of alkenyl groups to Si-H groups in the composition, leaving unreacted portions. However, when a gel cured product is produced by biasing the ratio of alkenyl groups to Si-H groups, unreacted oil from the raw material remains in the cured product, causing oil bleeding. Patent Document 1 proposes a heat dissipation material containing an organopolysiloxane having one or more alkenyl groups bonded to silicon atoms per molecule, an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, a platinum-based catalyst, and a thermally conductive filler. Patent Document 2 proposes a thermally conductive silicone rubber molded product obtained by curing and molding a composition containing an organopolysiloxane containing an alkenyl group per molecule, a thermally conductive filler, an organohydrogenpolysiloxane having an average of one to three hydrogen atoms directly bonded to silicon atoms per molecule, and a platinum-based curing catalyst. Patent Document 3 proposes a heat dissipation material obtained by curing an addition reaction-curable silicone gel composition containing an organopolysiloxane having an average of 0.1 to 2 alkenyl groups bonded to silicon atoms per molecule, an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, a platinum-based catalyst, and a thermally conductive filler.

[0003] JP 2008-184549 A JP 2008-160126 A Japanese Patent No. 4993611 A

[0004] However, conventional thermally conductive silicone gel compositions still suffer from the problem of excessive oil bleeding.

[0005] In order to solve the above-mentioned problems of the prior art, the present invention provides a thermally conductive silicone gel composition that is a gel-like cured product yet exhibits low oil bleeding.

[0006] The thermally conductive silicone gel composition of the present invention is characterized by being obtained by curing components containing the following A to F: A: an organopolysiloxane having two alkenyl groups per molecule; B: an organohydrogenpolysiloxane having two Si—H groups per molecule; C: an organohydrogenpolysiloxane having three or more Si—H groups per molecule; D: at least one compound selected from D1 and D2 below; D1: an organopolysiloxane having one alkenyl group per molecule; D2: an organohydrogenpolysiloxane having one Si—H group per molecule; E: a platinum catalyst; F: a thermally conductive filler in an amount of 100 to 600 vol%, when the total amount of A to E above is 100 vol%.

[0007] The thermally conductive silicone gel composition of the present invention is obtained by curing components including A to F described above, and yet is a gel-like cured product that exhibits low oil bleeding.

[0008] 1A and 1B are explanatory diagrams showing a method for measuring the thermal conductivity of a sample in one embodiment of the present invention.

[0009] The present invention uses as a molecular weight modifier at least one compound selected from organopolysiloxanes having one alkenyl group per molecule and organohydrogenpolysiloxanes having one Si—H group per molecule, thereby achieving a low-oil-bleed, heat-dissipating silicone gel that gels even when cured to minimize unreacted alkenyl groups and Si—H groups, and that produces a silicone gel cured product with minimal oil bleed. Oil bleed from the cured product can cause contamination of surrounding components, potentially resulting in component malfunctions. Therefore, a low-oil-bleed, heat-dissipating silicone gel can eliminate these problems.

[0010] More specifically, it is a thermally conductive silicone gel composition obtained by curing components containing the following A to F: A: an organopolysiloxane having two alkenyl groups per molecule; B: an organohydrogenpolysiloxane having two Si—H groups per molecule; C: an organohydrogenpolysiloxane having three or more Si—H groups per molecule; D: at least one compound selected from D1 and D2 below; D1: an organopolysiloxane having one alkenyl group per molecule; D2: an organohydrogenpolysiloxane having one Si—H group per molecule; E: a platinum catalyst; F: 100 to 600 vol % of the thermally conductive filler, when the total amount of A to E is 100 vol %.

[0011] Adding component D can reduce the molecular weight of the silicone gel after the curing reaction. Component D has only one reactive site, so if two components D react with a polymer with two reactive groups, for example, the molecule will not be able to increase its molecular weight any further. Furthermore, if the molecular weight becomes too large, the cured product will become too hard, so component D is added to reduce the hardness of the cured product. While conventional technology prevents the molecular weight from becoming too large by leaving unreacted portions of the raw material, this invention uses component D to adjust the molecular weight.

[0012] The thermally conductive silicone gel composition of the present invention preferably has an Asker C hardness of 60 or less, more preferably 40 or less, and even more preferably 10 to 25. If the hardness is too low, the strength of the heat dissipation material decreases, making it difficult to handle. If the hardness is too high, the sheet adhesion decreases, resulting in reduced heat dissipation performance. In addition, if the hardness is too high, excessive stress is applied to surrounding components when compressing the heat dissipation material, making the components more susceptible to deformation. Furthermore, when a molded product of the thermally conductive silicone gel composition of the present invention is sandwiched between polytetrafluoroethylene (PTFE) filter paper, compressed to a thickness of 1.8 mm, and left in an 80°C atmosphere for 24 hours, the oil bleed rate is preferably 0.5 wt% or less, more preferably 0.45 wt% or less. If the hardness is higher than 0.5 wt%, oil bleed from the composition is likely to occur during use.

[0013] The amounts of components A to D are preferably as follows, assuming component A is 100 parts by weight: B: 1 to 300 parts by weight; C: 0.1 to 20 parts by weight; and D: 0.1 to 50 parts by weight. However, the ratio of Si-H groups to alkenyl groups in all components A to D, Si-H groups / alkenyl groups, is preferably 0.5 to 2.0, and more preferably 0.7 to 1.5. If the ratio is lower or higher than this, unreacted oil from the raw materials will remain in the cured product, causing oil bleeding.

[0014] Each component will be described below. (1) Component A Component A of the present invention is an organopolysiloxane having two alkenyl groups per molecule, and is the main component (base polymer component) in the silicone gel composition of the present invention. This organopolysiloxane has two silicon-bonded alkenyl groups per molecule, such as vinyl or allyl groups, each having 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms. This organopolysiloxane may be linear, or may contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain. The alkenyl groups are preferably located at both ends of the molecular chain. The viscosity is 10 to 100,000 mm at 25°C. 2 / s, especially 100 to 10,000 mm 2 / s is desirable from the viewpoint of workability, curing property, etc. The viscosity is given in the manufacturer's catalog, etc., but it is a kinematic viscosity at 25°C measured with an Ubbelohde viscometer.

[0015] The substituents other than alkenyl groups in component A are the same or different unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds, and for example, those having 1 to 10 carbon atoms, and particularly 1 to 6 carbon atoms, are preferred.Specific examples 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 groups in which some or all of the hydrogen atoms of these groups 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.

[0016] The alkenyl group in component A preferably has 2 to 6 carbon atoms, and particularly preferably 2 to 3 carbon atoms. Specific examples include vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl groups, with vinyl being preferred.

[0017] (2) Component B Component B of the present invention is an organohydrogenpolysiloxane having two Si—H groups per molecule, preferably a linear molecular structure, with the Si—H groups preferably located at both ends of the molecular chain. The number of silicon atoms per molecule (i.e., degree of polymerization) can be from 2 to 1,000, and preferably from 2 to 300.

[0018] (3) Component C Component C of the present invention is an organohydrogenpolysiloxane having three or more Si—H groups per molecule, and the molecular structure may be linear or may contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain.

[0019] Examples of the organohydrogenpolysiloxane of component C include those having the following structure:

[0020]

[0021] In the above formula, R 6are the same or different and are hydrogen, an alkyl group, a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, or an alkoxy group, and at least three are hydrogen. L is an integer of 0 to 1,000, particularly an integer of 0 to 300, and M is an integer of 1 to 200.

[0022] (4) Component D The component D of the present invention is at least one compound selected from the following compounds D1 and D2.

[0023] (5) Component D1 This component of the present invention is an organopolysiloxane having one alkenyl group per molecule. It has one silicon-bonded alkenyl group per molecule, such as a vinyl group or an allyl group, having 2 to 8 carbon atoms, especially 2 to 6, as an addition-reactive group, and the remaining silicon atoms are blocked with monovalent hydrocarbon groups. The molecular structure may be linear, or it may contain a small amount of branched structure (trifunctional siloxane units) in the molecular chain. The viscosity at 25°C is 10 to 100,000 mm. 2 / s, especially 100 to 10,000 mm 2 / s is desirable from the viewpoint of workability and curability. Component D1 has only one reactive group, so the molecular weight of the cured product can be kept low. This allows for a soft cured product with as little unreacted residue as possible.

[0024] (6) Component D2 Component D2 of the present invention is an organohydrogenpolysiloxane having one Si—H group per molecule. It has one Si—H group per molecule as an addition-reactive reactive group, and the remaining silicon atoms are blocked with monovalent hydrocarbon groups. The molecular structure may be linear, or it may contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain. Its viscosity at 25°C is 10 to 100,000 mm 2 / s, especially 100 to 10,000 mm 2 / s is desirable from the viewpoint of workability and curability. Component D2 has only one reactive group, so the molecular weight of the cured product can be kept low. This allows for a soft cured product with as little unreacted residue as possible.

[0025] The monovalent hydrocarbon group in components D1 and D2 is preferably, for example, one having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples 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 groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, bromine, or chlorine, or with a cyano group, such as a halogen-substituted alkyl group such as a chloromethyl group, a chloropropyl group, a bromoethyl group, or a trifluoropropyl group; and a cyanoethyl group.

[0026] (7) Catalyst Component (Component E) Component E is a catalyst component that accelerates the curing of the composition. Catalysts used in hydrosilylation reactions can be used as Component E. Examples include platinum black, chloroplatinic acid, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins or vinylsiloxanes, platinum-based catalysts such as platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. The amount of Component E to be added may be any amount necessary for curing, and can be adjusted appropriately depending on the desired curing rate, etc. It is preferable to add 0.01 to 1,000 ppm by weight of metal atoms to the alkenyl group-containing component in the composition.

[0027] (8) The thermally conductive particles of the F component are preferably inorganic particles such as alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silica other than hydrophilic fumed silica. These inorganic particles may be added alone or in combination. The thermally conductive particles may be in various shapes, such as spherical, scaly, or polyhedral. The specific surface area of ​​the thermally conductive particles should be 0.06 to 15 m. 2 / g is preferred. The specific surface area is a BET specific surface area, and the measurement method is in accordance with JIS R1626. When using the average particle size, the range of 0.1 to 100 μm is preferred. The particle size is measured by measuring the D50 (median diameter) of the cumulative particle size distribution on a volume basis using a laser diffraction light scattering method. An example of an instrument for this measurement is the LA-950S2 laser diffraction / scattering particle distribution analyzer manufactured by Horiba, Ltd.

[0028] The thermally conductive particles may be a combination of at least two inorganic particles with different average particle sizes. In this way, the thermally conductive inorganic particles with smaller particle sizes are embedded between the larger particles, allowing for a close-packed state and improving thermal conductivity. The at least two inorganic particles with different average particle sizes are preferably a combination of particles with an average particle size of 10 μm or less and particles with an average particle size of more than 10 μm.

[0029] The thermally conductive particles used in the present invention may be surface-treated in part or in whole with a silane coupling agent. The silane coupling agent may be mixed with the thermally conductive particles in advance for pretreatment, or may be added when mixing the matrix resin and thermally conductive particles (integral blending method). In the case of the integral blending method, it is preferable to add 0.01 to 10 parts by weight of the silane coupling agent per 100 parts by weight of the thermally conductive particles. The surface treatment makes it easier for the thermally conductive filler to be filled into the matrix resin and makes it less likely for the platinum catalyst to be adsorbed onto the thermally conductive filler, thereby reducing the occurrence of curing inhibition.

[0030] The thermally conductive particles are a Si(OR') 4-a(R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, preferably R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a partial hydrolyzate thereof, or a silane coupling agent such as an alkoxysilane compound having 1 to 20 carbon atoms, or an alkoxy group-containing silicone. Examples of the alkoxysilane compounds (hereinafter simply referred to as "silanes") 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. Alkoxysilanes and single-terminated silanol siloxanes may also be used as surface treatment agents. The term "surface treatment" as used herein includes not only covalent bonding but also adsorption.

[0031] The composition of the present invention may contain other components as needed. For example, heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardants, and flame retardant assistants may be added. Organic or inorganic particle pigments may also be added for the purpose of coloring and toning.

[0032] The present invention will be described below using examples, but is not limited to these examples. Various parameters were measured by the following methods.

[0033] <Oil-Bleeding Rate> The oil-bleeding rate of a thermally conductive silicone gel composition was measured by sandwiching a molded product 25 mm wide, 25 mm long, and 3.0 mm thick between PTFE filter paper, compressing it to a thickness of 1.8 mm, and leaving it in an 80°C atmosphere for 24 hours. The oil adsorbed by the PTFE filter paper was taken as bleed oil and calculated using the following formula: Oil-Bleeding Rate = (Paper Weight After Test - Filter Paper Weight Before Test) ÷ Silicone Gel Weight Before Test × 100 <Hardness> Measurement was performed using an Asker Rubber Hardness Tester Type C in accordance with JIS K 7312. <Thermal Conductivity> The thermal conductivity of the thermally conductive silicone gel sheet was measured using a hot disc (in accordance with ISO / CD 22007-2). As shown in Figure 1A, this thermal conductivity measuring device 1 sandwiches a polyimide film sensor 2 between two samples 3a and 3b, applies a constant power to the sensor 2, generates a constant amount of heat, and analyzes the thermal characteristics from the temperature rise of the sensor 2. The sensor 2 has a tip 4 with a diameter of 7 mm, and as shown in Figure 1B, has a double spiral electrode structure with an applied current electrode 5 and a resistance value electrode (temperature measurement electrode) 6 located at the bottom. The thermal conductivity is calculated using the following formula (Equation 1). <Viscosity> The viscosity is described in the manufacturer's catalogue, etc., and is a kinematic viscosity at 25°C measured using an Ubbelohde viscometer.

[0034] (Examples 1 to 4, Comparative Example 1) 1. Raw material components (1) Component A having a kinematic viscosity of 350 mm 2 (1) As component B, an organohydrogenpolysiloxane having two Si—H groups per molecule was used: a product of KCC under the trade name "HP12". (2) As component C, an organohydrogenpolysiloxane having three or more Si—H groups per molecule was used: a product of Elkem Silicones under the trade name "BS FLD 626V30H2.5". (3) As component D1, an organohydrogenpolysiloxane having a kinematic viscosity of 100 mm was used: a product of KCC under the trade name "BS FLD 626V30H2.5". (4) As component D2, an organohydrogenpolysiloxane having a kinematic viscosity of 100 mm was used: a product of KCC under the trade name "HP12". 2 Organopolysiloxane having one vinyl group per molecule and a kinematic viscosity of 1 mm / s: Gelest Co., Ltd., product name "MCR-V21" was used as component D2. 2An organohydrogenpolysiloxane having a viscosity of 1 / s and one Si-H group per molecule, manufactured by Gelest, under the trade name "SIT8721.0," was used. (6) The platinum catalyst for component E, manufactured by Dow-Toray Industries, was "SRX212." (7) Ethynylcyclohexanol was used as the cure retarder. (8) The thermally conductive filler for component F was used as shown in Table 1. The alumina for component F, having an average particle size of 2.1 μm, was surface-treated with 1.1 parts by weight of decyltrimethoxysilane per 100 parts by weight of alumina. 2. Mixing, Molding, and Curing Method: Components A to F were mixed, sandwiched between PET films, and rolled to a thickness of 3.0 mm to form a sheet, which was then cured at 100°C for 10 minutes. The cured sheet obtained in this manner was evaluated.

[0035]

[0036] From the above results, it was confirmed that Examples 1 to 4 were thermally conductive silicone gel compositions with low oil bleeding, even though they were gel-like cured products.

[0037] The thermally conductive silicone gel composition of the present invention is suitable for use between a heat-generating portion of an electric or electronic part and a heat sink.

[0038] REFERENCE SIGNS LIST 1 Thermal conductivity measuring device 2 Sensor 3a, 3b Sample 4 Sensor tip 5 Applied current electrode 6 Resistance value electrode (temperature measurement electrode)

Claims

Updated 21 / 07 / 2569.

1. The thermally conductive silicone gel composition, assembled with components A to F below, was constructed by curing the components. Component A: 100 parts by weight; A. Organopolysiloxane with two alkynyl groups in one molecule; B. Organohydrogen polysiloxane with two Si-H groups in one molecule: 1 to 300 parts by weight; the molecular structure of component B is linear, and Si-H is present at both ends of the molecular chain; C. Organohydrogen polysiloxane with three or more Si-H groups in one molecule: 0.1 to 20. D. At least one compound selected from D1 and D2 below: 0.1 to 50 parts by weight. D1. Organopolysiloxane containing one alkynyl group per molecule. D2. Organohydrogen polysiloxane containing one Si-H group per molecule. E. Platinum catalyst: the amount required for stabilization. F. Thermally conductive filler is 100 to 600% by volume when the total volume of A to E is 100% by volume, where the ratio of Si-H to alkynyl groups in all components A to D is Si-H / alkinyl groups = 0.5 to 2.

0. The thermally conductive particles of component F include incorporation of inorganic particles with an average particle diameter of 10 micrometers or less, and inorganic particles with an average particle diameter greater than 10 micrometers, and a thermally conductive silicone gel composition characterized by an oil leakage rate of 0.5% by weight or less when a molded product with a width of 25 mm, a length of 25 mm, and a thickness of 3.0 mm is sandwiched between polytetrafluoroethylene (PTFE) filter paper, compressed to a thickness of 1.8 mm, and left for a period of time. 24 hours in an 80°C atmosphere. DEPCT651. Thermally conductive silicone gel composition consisting of the following components A through F: A. Organopolysiloxane with two alkynyl groups per molecule; B. Organohydrogen polysiloxane with two Si-H groups per molecule; C. Organohydrogen polysiloxane with three or more Si-H groups per molecule; D. At least one compound selected from groups D1 and D2: D1. Organopolysiloxane with one alkynyl group per molecule and D2. Organohydrogen polysiloxane with one Si-H group per molecule; E.The platinum catalyst in the amount required for curing; and F. thermal conductive filler in the amount of 100 to 600% by volume compared to 100% by volume of the total volume of A to E, where components A to F are cured, where the thermally conductive silicone gel composition consists of 1 to 300 parts by weight of component B, 0.1 to 20 parts by weight of component C, and 0.1 to 50 parts by weight of component D compared to 100 parts by weight of component A, where the ratio of Si-H groups to alkyl groups (Si-H / Alkyl groups) The alkylinity (alkylinyl) in all components A to D is 0.5 to 2.0, and the oil leakage rate of the thermally conductive silicone gel composition is 0.5% by weight or less, which is measured in such a manner that the thermally conductive silicone gel composition is formed into a molded product with a width of 25 mm, a length of 25 mm, and a thickness of 3.0 mm, and then the molded product is sandwiched between polytetrafluoroethylene (PTFE) filter paper, compressed to a thickness of 1.8 mm and left for 24 hours in an atmosphere of 80 degrees Celsius.Thermally conductive silicone gel composition pursuant to Reputation 1 where the hardness of the thermally conductive silicone gel composition is 60 or less, measured by the ASKER rubber hardness tester, type C, according to JISK73123. Thermally conductive silicone gel composition pursuant to Reputation 1 or 2 where the alkynyl groups of component A are present at both ends of the organopolysiloxane molecular chain. Thermally conductive silicone gel composition pursuant to any one of Reputations 1 to 3 where the organopolysiloxane of component A has a kinematic viscosity value. 10 to 100,000 square millimeters per second at 25 degrees Celsius.

5. The silicone gel composition conducts heat according to one of the claims 1 to 4 where the molecular structure of component B is linear.

6. The silicone gel composition conducts heat according to one of the claims 1 to 5 where the Si-H groups of component B are present at both ends of the molecular chain.

7. The silicone gel composition conducts heat according to one of the claims 1 to 6 where the average number of polymerization levels of component B is 2 to 1000. 8.A thermally conductive silicone gel component according to one of the claims 1 through 7, where the organohydrogen polysiloxane of component C is represented by the following chemical formula 1: [Chemical Formula 1](Chemical Formula), where R6 is the same or different and represents hydrogen, alkyl group, phenyl group, epoxy group, acryloyyl group, methacryloyl group or alkoxy group and at least three R6 are hydrogen and L represents an integer 0 through 1000 and M represents an integer 1 through 2009. A thermally conductive silicone gel component according to one of the claims 1 through 7.

10. The silicone gel composition is thermally conductive according to one of the claims 1 through 9, whereby the thermally conductive particles of component F are inorganic particles of at least one of the following materials selected from alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide and other silicas besides hydrophilic fume silica.

12. Thermally conductive silicone gel compositions pursuant to one of Reputations 1 through 10 where the thermally conductive particles of component F are combined with inorganic particles with an average particle size of 10 µm or less and inorganic particles with an average particle size greater than 10 µm.

13. Thermally conductive silicone gel compositions pursuant to one of Reputations 1 through 11 where the thermally conductive particles of component F are surface treated with at least one silane coupling agent selected from alkoxysilane compounds denoted by RaSi(OR')4-a (where R represents replaced or unreplaced organic groups with 1 to 20 carbon atoms, R' represents alkyl groups with 1 to 4 carbon atoms and is 0 or 1), some hydrolysates of alkoxysilane compounds and silicones containing alkoxy groups.

14. Thermally conductive silicone gel compositions pursuant to Reputation 12 where at least one silane coupling agent is added in an amount of 0.01 to 10 parts by weight relative to 100 parts by weight of the thermally conductive particles of component F for surface treatment.