Thermally conductive silicone composition

Abstract

Provided is a thermally conductive silicone composition which contains a low-melting-point metal and which, after curinged, becomes a cured product having excellent adhesion to a substrate and having good thermal conductivity. The thermally conductive silicone composition contains: (A) an organopolysiloxane having at least two aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule, and having a kinematic viscosity of 10 to 1,000,000 mm2 / s at 25 °C; (B) an organohydrogenpolysiloxane; (C) gallium and / or an alloy thereof having a melting point of −20 to 70 °C; (D-1) a thermally conductive filler having an average particle size of 20 to 200 μm; (D-2) a thermally conductive filler having an average particle size of 0.1 to 10 μm; (E) a platinum-group metal catalyst; (F) a reaction control agent; (G) palladium powder; and (H) an organopolysiloxane in which one end of a molecular chain is capped with a hydrolyzable group, and which has a kinematic viscosity of 10 to 10,000 mm2 / s at 25 °C.

Description

Thermally conductive silicone composition

[0001] The present invention relates to a thermally conductive silicone composition and a cured product thereof.

[0002] Heat-generating electronic components mounted on printed wiring boards, for example, IC packages such as CPUs, can suffer performance degradation or damage due to temperature rise caused by heat generated during use, so conventionally, a thermally conductive sheet with good thermal conductivity has been placed between the IC package and a heat dissipation member having heat dissipation fins, or thermally conductive grease has been applied to efficiently conduct and dissipate the heat generated from the IC package, etc. However, as the performance of electronic components, etc. improves, the amount of heat generated therefrom tends to increase, and there is a demand for the development of materials and components with even better thermal conductivity than conventional ones.

[0003] Conventional thermally conductive sheets have the advantage of being easily mounted and attached. Thermally conductive grease, on the other hand, is not affected by the unevenness of the surfaces of CPUs, heat dissipation components, etc., and can conform to the unevenness, adhering them without creating gaps between them, resulting in low interfacial thermal resistance. However, while both thermally conductive sheets and thermally conductive greases are obtained by blending thermally conductive fillers to impart thermal conductivity, the upper limit of the apparent viscosity of thermally conductive sheets must be limited to avoid hindrances to workability and processability during the manufacturing process, and the upper limit of the apparent viscosity of thermally conductive greases must be limited to avoid problems when applying them to heat-generating electronic components using a syringe or other device. In either case, the upper limit of the amount of thermally conductive filler must be limited, resulting in insufficient thermal conductivity.

[0004] Therefore, methods such as incorporating a low-melting-point metal into a thermally conductive paste (Patent Document 1: JP 7-207160 A, Patent Document 2: JP 8-53664 A), and a granular material that acts to fix and stabilize liquid metal in a three-phase composite (Patent Document 3: JP 2002-121292 A) have been proposed. Furthermore, methods such as dispersing gallium or a gallium alloy in curable silicone to solve the problem of oily substances appearing when used over a long period of time (Patent Document 4: JP 2005-112961 A), and methods for increasing the thermal conductivity of thick compositions (Patent Document 5: JP 2010-095730 A) have been proposed. However, with thermally conductive materials using these low-melting-point metals, it is difficult to ensure adhesion of the cured product to electronic components, and there is a problem that the cured product is easily peeled off from the electronic component when external force is applied. Furthermore, a method of suppressing the generation of voids by adding palladium powder has also been proposed, but this was insufficient to solve the problems listed above (Patent Document 6: JP 2022-180701 A).

[0005] Japanese Patent Laid-Open No. 7-207160 Japanese Patent Laid-Open No. 8-53664 Japanese Patent Laid-Open No. 2002-121292 Japanese Patent Laid-Open No. 2005-112961 Japanese Patent Laid-Open No. 2010-095730 Japanese Patent Laid-Open No. 2022-180701

[0006] Therefore, an object of the present invention is to provide a thermally conductive silicone composition that contains a low-melting point metal, which, after curing, will yield a cured product that has excellent adhesion to substrates and good thermal conductivity.

[0007] As a result of extensive research into solving the above problems, the present inventors discovered that by blending low-melting point gallium and / or its alloy, a thermally conductive filler having an average particle size of 20 to 200 μm, and a thermally conductive filler having an average particle size of 0.1 to 10 μm into an addition-curable silicone composition, it is possible to easily obtain a composition in which the gallium and / or its alloy is uniformly dispersed in the form of fine particles, and that when the silicone composition is heat-treated, the cured product has excellent adhesion and is capable of achieving high heat dissipation performance, which led to the completion of the present invention.

[0008] That is, the present invention provides the following curable organopolysiloxane composition and cured product thereof.

[0009] <1> A thermally conductive silicone composition containing the following components (A), (B), (C), (D), (E), (F), (G), and (H): (A) a silicone oil having two or more silicon-bonded aliphatic unsaturated hydrocarbon groups per molecule and having a kinematic viscosity at 25°C of 10 to 1,000,000 mm 2 / s organopolysiloxane: 100 parts by mass; (B) an organohydrogenpolysiloxane consisting of components (B-1) and (B-2): an amount such that {total number of Si—H groups in component (B)} / {number of aliphatic unsaturated hydrocarbon groups in component (A)} is 0.6 to 5.0; (B-1) a linear organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms (Si—H groups) per molecule; (B-2) a cyclic organohydrogenpolysiloxane represented by the following general formula (1): (In formula (1), a is a number from 2 to 8, R 1 are each independently a group selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an epoxy group, an acryloyl group, a methacryloyl group, an ether group, and a trialkoxysilyl group, and R 1 Two or three of the groups represented by R are hydrogen atoms. 2 are each independently selected from an alkyl group having 1 to 6 carbon atoms, an epoxy group, an acryloyl group, a methacryloyl group, an ether group, and a trialkoxysilyl group. (C) gallium and / or its alloys having a melting point of -20 to 70°C: 300 to 20,000 parts by mass per 100 parts by mass of component (A); (D-1) thermally conductive filler having an average particle size of 20 to 200 μm: 10 to 1,000 parts by mass per 100 parts by mass of component (A); (D-2) thermally conductive filler having an average particle size of 0.1 to 10 μm: 10 to 1,000 parts by mass per 100 parts by mass of component (A); (E) platinum group metal catalyst: effective amount; (F) reaction inhibitor: effective amount; (G) palladium powder: 0.00001 to 1.0 part by mass per 100 parts by mass of component (A); (H) organopolysiloxane represented by the following general formula (2): 0.1 to 500 parts by mass per 100 parts by mass of component (A): (In formula (2), R 3 each independently represents an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and no aliphatic unsaturated bond; R 4 are independently an alkyl group, an alkenyl group, or an acyl group. Additionally, b is a number from 5 to 100, and c is a number from 1 to 3.) <2> The thermally conductive silicone composition according to <1>, further comprising (I) 0.1 to 100 parts by mass of an alkoxysilane represented by the following general formula (3) per 100 parts by mass of the component (A): (In formula (3), R 5 are independently alkyl groups having 6 to 16 carbon atoms, and R 6 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, and R 7 are independently an alkyl group having 1 to 6 carbon atoms, d is a number of 1 to 3, e is a number of 0 to 2, and the sum of d+e is a number of 1 to 3.) <3> The thermally conductive silicone composition according to <1> or <2>, further comprising 0.1 to 100 parts by mass of (J) trifluoropropyltrimethoxysilane per 100 parts by mass of component (A). <4> The thermally conductive silicone composition according to any one of <1> to <3>, in which component (C) is dispersed in the composition in the form of particles having a size of 1 to 200 μm. <5> A cured product of the thermally conductive silicone composition according to any one of <1> to <4>.

[0010] Because the thermally conductive silicone composition of the present invention is in a grease-like form before curing, it is easy to apply to heat-generating electronic components such as CPUs, and when a heat dissipation component is pressed against it, it conforms to the irregularities on the surfaces of both components, allowing them to adhere tightly together without creating gaps between them, thereby preventing interfacial thermal resistance. Furthermore, by curing the thermally conductive silicone composition of the present invention through an addition reaction, it is possible to achieve excellent adhesion and high heat dissipation performance. Therefore, the thermally conductive silicone composition of the present invention is useful for efficient heat removal when used, for example, between an IC package such as a CPU and a heat dissipation component having heat dissipation fins.

[0011] [Thermal Conductive Silicone Composition] <(A) Organopolysiloxane> Component (A) of the composition of the present invention is an organopolysiloxane having two or more silicon-bonded aliphatic unsaturated hydrocarbon groups per molecule, and is the main component (base polymer) in the addition reaction cure system of the present invention.

[0012] The kinematic viscosity of component (A) at 25°C is 10 to 1,000,000 mm 2 / s, and is in the range of 50 to 500,000 mm 2 / s range is preferred. 2 If the hardness is less than 1,000,000 mm / s, the cured product will be brittle and prone to cracking. 2 If the kinematic viscosity is greater than 1 / s, the viscosity of the composition will be too high, making it difficult to handle. In the present invention, the kinematic viscosity is the value measured at 25°C using an Ostwald viscometer.

[0013] There are no limitations on the molecular structure of the organopolysiloxane of component (A), and examples include linear, branched, and partially branched linear structures, with linear structures being particularly preferred.

[0014] The number of aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in component (A) should be at least two per molecule, preferably 2 to 10, and more preferably 2 to 5. Examples of these aliphatic unsaturated hydrocarbon groups include alkenyl groups such as vinyl, allyl, 1-butenyl, and 1-hexenyl, with vinyl being preferred from the standpoints of ease of synthesis and cost. These aliphatic unsaturated hydrocarbon groups may be bonded to silicon atoms at either the terminal or intermediate silicon atoms of the molecular chain, but are preferably bonded only to terminal silicon atoms in order to improve the flexibility of the resulting cured product.

[0015] Examples of groups bonded to silicon atoms other than aliphatic unsaturated hydrocarbon groups bonded to silicon atoms include unsubstituted or substituted monovalent hydrocarbon groups, such as alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, 2-phenylethyl, and 2-phenylpropyl; and halogenated alkyl groups such as chloromethyl, 3,3,3-trifluoropropyl, and 3-chloropropyl. From the standpoints of synthesis and economy, it is preferable that 90% or more of these groups be methyl groups.

[0016] Suitable specific examples of such organopolysiloxanes include polydimethylsiloxanes terminally blocked with dimethylvinylsiloxy groups, polydimethylsiloxanes terminally blocked with methyldivinylsiloxy groups, and dimethylsiloxane-methylphenylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups. The organopolysiloxanes of component (A) may be used alone or in combination of two or more different types.

[0017] The content of component (A) in the entire composition of the present invention is preferably 0.1 to 10.0 mass %, and more preferably 1.0 to 8.0 mass %.

[0018] <(B) Organohydrogenpolysiloxane> Component (B) (component (B-1) and component (B-2)) of the composition of the present invention is an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms (hereinafter referred to as "Si—H groups") per molecule, and acts as a crosslinking agent for component (A). That is, the Si—H groups in component (B) undergo an addition reaction via hydrosilylation with the aliphatic unsaturated hydrocarbon groups (e.g., alkenyl groups) in component (A) under the action of a platinum-based catalyst, component (E), described below, to give a crosslinked, cured product having a three-dimensional network structure with crosslinked bonds.

[0019] (B-1) Component (B-1) is a linear organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (Si—H groups) per molecule. The number of Si—H groups per molecule is two or more, preferably 2 to 30. The molecular structure of component (B-1) is not particularly limited as long as it satisfies the above requirements. The number of silicon atoms (or degree of polymerization) per molecule is typically 3 to 1,000, preferably 5 to 400, more preferably 10 to 300, even more preferably 10 to 100, and particularly preferably 10 to 60.

[0020] The group bonded to a silicon atom other than an Si—H group is preferably an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and having no aliphatic unsaturated bonds. 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 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as fluorine or chlorine. Of these, a methyl group is preferred from the standpoint of ease of synthesis and cost.

[0021] Specific examples of organohydrogenpolysiloxanes of component (B-1) include dimethylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain terminals with dimethylhydrogensiloxy groups, methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers capped at one molecular chain terminal with a dimethylhydrogensiloxy group and one terminal with a trimethylsiloxy group, methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymers capped at one molecular chain terminal with a dimethylhydrogensiloxy group and one terminal with a trimethylsiloxy group, and (CH3)2HSiO 1 / 2 Units and (CH3)3SiO 1 / 2Units and (CH3)HSiO 2 / 2 Units and SiO 4 / 2 a copolymer consisting of (CH3)2HSiO units, 1 / 2 Units and (CH3)3SiO 1 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 a copolymer consisting of (CH3)2HSiO units, 1 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 a copolymer consisting of (CH3)2HSiO units, 1 / 2 Units and SiO 4 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and (C6H5)3SiO 1 / 2 a copolymer consisting of (CH3)2HSiO units, 1 / 2 Units and (CH3)3SiO 1 / 2 Units and (C6H5)2SiO 2 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 and copolymers consisting of units.

[0022] The organohydrogenpolysiloxane of component (B-1) may use either a single compound, or a combination of two or more different compounds.

[0023] (B-2) Component (B-2) is an organohydrogenpolysiloxane represented by the following general formula (1). (In formula (1), a is a number from 2 to 8, R 1 are each independently a group selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an epoxy group, an acryloyl group, a methacryloyl group, an ether group, and a trialkoxysilyl group, and R 1 Two or three of the groups represented by R are hydrogen atoms. 2 are each independently selected from an alkyl group having 1 to 6 carbon atoms, an epoxy group, an acryloyl group, a methacryloyl group, an ether group, and a trialkoxysilyl group.

[0024] Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group.

[0025] R 2 The group represented by the formula: can be, for example, the group shown below.

[0026] Specific examples of the component (B-2) include the following compounds:

[0027] The organohydrogenpolysiloxane of component (B-2) may use either a single compound, or a combination of two or more different compounds.

[0028] The mass ratio of the component (B-1) to the component (B-2) is preferably (B-1):(B-2)=50:50 to 95:5, more preferably 60:40 to 90:10, and particularly preferably 70:30 to 85:15. When the content of the component (B-1) is higher than that of the component (B-2), it becomes easier to adjust the hardness after curing.

[0029] The total amount of organohydrogenpolysiloxane in component (B) is an amount such that the ratio {total number of Si—H groups in component (B)} / {number of aliphatic unsaturated hydrocarbon groups in component (A)} is in the range of 0.6 to 5.0, preferably 1.0 to 3.0. If the amount of component (B) is less than 0.6, sufficient adhesive performance may not be achieved, and adhesion to the substrate may be poor. If the amount exceeds 5.0, the cured product may be too hard, or the shelf life of the composition may be significantly reduced.

[0030] The kinematic viscosity of component (B-1) at 25°C is 85 to 115 mm 2 / s range is preferred, and 90 to 110 mm 2 / s is more preferable. The kinematic viscosity is a value measured using an Ostwald viscometer. The purity of (B-2) is preferably 90% or more, more preferably 95% or more. The purity is a value measured by gas chromatography.

[0031] <(C) Gallium and / or its alloy> The component (C) of the composition of the present invention is gallium and / or an alloy thereof having a melting point of −20 to 70° C. The component (C) is blended to impart good thermal conductivity to a cured product obtained from the composition of the present invention, and the inclusion of this component enhances the thermal conductivity of the present invention.

[0032] As mentioned above, the melting point of component (C) must be in the range of -20 to 70°C. While components below -20°C can be physically used in the present invention, components with melting points below -20°C are difficult to obtain and are therefore economically undesirable. Conversely, components with melting points above 70°C do not melt quickly during the composition preparation process, resulting in poor workability. Therefore, as mentioned above, the melting point of component (C) should be in the range of -20 to 70°C. Components in the range of -19 to 50°C are particularly preferred, as this facilitates the preparation of the composition of the present invention.

[0033] The melting point of metallic gallium is 29.8°C. Representative gallium alloys include, for example, gallium-indium alloys; for example, Ga—In (mass ratio = 75.4:24.6, melting point = 15.7 ° C.), gallium-tin alloys, gallium-tin-zinc alloys; for example, Ga—Sn—Zn (mass ratio = 82:12:6, melting point = 17 ° C.), gallium-indium-tin alloys; for example, Ga—In—Sn (mass ratio = 68.5:21.5:10, melting point = -19 ° C., mass ratio = 62:25:13, melting point = 5.0 ° C., mass ratio = 21.5:16.0:62.5, melting point = 10.7 ° C.), gallium-indium-bismuth-tin alloys; for example, Ga—In—Bi—Sn (mass ratio = 9.4:47.3:24.7:18.6, melting point = 48.0 ° C.), and the like.

[0034] This component (C) can be used alone or in combination of two or more. The liquid or solid fine particles of gallium and / or its alloy present in the uncured composition of the present invention are generally spherical, although irregular particles may also be present. The average particle size is typically 1 to 200 μm, preferably 5 to 150 μm, and more preferably 10 to 100 μm. If the average particle size is too small, the viscosity of the composition will be too high, resulting in poor extensibility and poor coating workability. Conversely, if the average particle size is too large, the composition will be non-uniform, making it difficult to apply a thin film to heat-generating electronic components, etc. As described above, the shape, average particle size, and dispersion state within the composition can be maintained until the coating process onto heat-generating electronic components, etc., because the composition is quickly stored at low temperatures after preparation. The average particle size was calculated by sandwiching the uncured composition between two glass slides and observing it with a VHX-8000 (manufactured by Keyence Corporation). That is, 10 particles were randomly selected from the image taken by this measuring device, the particle size of each was measured, and the average value of these was calculated.

[0035] The blending amount of this component (C) is 300 to 20,000 parts by mass, particularly preferably 2,000 to 15,000 parts by mass, and even more preferably 3,000 to 12,000 parts by mass, per 100 parts by mass of the component (A). If the blending amount is less than 300 parts by mass, the thermal conductivity will be low, and if the composition is thick, sufficient heat dissipation performance will not be obtained. If the blending amount is more than 20,000 parts by mass, it will be difficult to obtain a homogeneous composition, and the viscosity of the composition will be too high, which may prevent the composition from being obtained as a spreadable grease-like composition.

[0036] <(D) Thermally conductive filler> In addition to the component (C), the composition of the present invention must also contain a thermally conductive filler (D) (excluding component (C)) that is conventionally incorporated into known thermally conductive sheets or thermally conductive greases.

[0037] This component (D) (component (D-1) and component (D-2)) is not particularly limited as long as it has good thermal conductivity, and any conventionally known component can be used, such as aluminum powder, zinc oxide powder, alumina powder, boron nitride powder, aluminum nitride powder, silicon nitride powder, copper powder, diamond powder, nickel powder, zinc powder, stainless steel powder, and carbon powder. This component (D) can be used either alone or in combination of two or more. From the standpoints of availability and economy, zinc oxide powder and alumina powder are particularly preferred.

[0038] Component (D-1) has the effect of improving the adhesion of the cured product, and the average particle size of component (D-1) is 20 to 200 μm, preferably 30 to 170 μm, more preferably 50 to 160 μm, and particularly preferably 105 to 150 μm. An average particle size of 20 to 200 μm allows for a uniform composition to be obtained, and the resulting cured product can maintain stable adhesion. This average particle size is the volume-based mean diameter [MV] measured using a Microtrac MT3300EX (manufactured by Nikkiso Co., Ltd.).

[0039] The blending amount of component (D-1) is in the range of 10 to 1,000 parts by mass, preferably 20 to 500 parts by mass, and more preferably 30 to 300 parts by mass, per 100 parts by mass of component (A). If the blending amount of component (D-1) is less than 10 parts by mass per 100 parts by mass of component (A), the component will not disperse uniformly in the mixture, and when the resulting composition is cured, sufficient adhesion to the substrate may not be ensured. If the blending amount is more than 1,000 parts by mass, the viscosity of the composition will increase, and it may not be possible to obtain a composition that is extensible and grease-like.

[0040] Component (D-2) has the effect of maintaining the composition in a uniform state, and the average particle size of component (D-2) is 0.1 to 10 μm, preferably 0.2 to 5 μm, and particularly preferably 0.5 to 2.5 μm. An average particle size of 0.1 to 10 μm allows for the production of a uniform, extensible grease-like composition. This average particle size is the volume-based mean diameter [MV] measured using a Microtrac MT3300EX (manufactured by Nikkiso Co., Ltd.).

[0041] The amount of component (D-2) blended is preferably in the range of 10 to 1,000 parts by mass, more preferably 50 to 500 parts by mass, and particularly preferably 70 to 300 parts by mass, per 100 parts by mass of component (A). If the amount of component (D-2) blended is less than 10 parts by mass per 100 parts by mass of component (A), it becomes difficult to uniformly disperse gallium and / or its alloy in component (A) or in a mixture of component (A) and component (H), which will be described later. If the amount is more than 1,000 parts by mass, the viscosity of the composition increases, and it may not be possible to obtain a composition that is in the form of an extensible grease.

[0042] The mass ratio of component (D-1) to component (D-2) is preferably (D-1):(D-2)=50:50 to 10:90, more preferably 45:55 to 15:85, and particularly preferably 40:60 to 20:80. When the content of component (D-2) is higher than that of component (D-1), a suitable grease composition can be obtained.

[0043] <(E) Platinum Group Metal Catalyst> The platinum group metal catalyst of component (E) of the composition of the present invention is a component incorporated to promote the addition reaction between the silicon-bonded aliphatic unsaturated hydrocarbon groups in component (A) and the Si-H in component (B), thereby providing a crosslinked, cured product in a three-dimensional network state from the composition of the present invention. However, the platinum group metal catalyst of component (E) does not include palladium powder of component (G), which will be described later.

[0044] Any of the known compounds used in ordinary hydrosilylation reactions can be used as component (E), including, for example, platinum metal (platinum black), chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, platinum coordination compounds, etc. The amount of component (E) added is not particularly limited, as long as it is an effective amount necessary to cure the composition of the present invention, but typically, for example, it is preferably about 0.1 to 500 ppm, and more preferably 1 to 200 ppm, of platinum atoms relative to the mass of component (A).

[0045] <(F) Reaction Inhibitor> The reaction inhibitor of component (F) of the composition of the present invention is an optional component that inhibits the hydrosilylation reaction caused by the action of the platinum-based catalyst at room temperature, thereby ensuring the usable life (shelf life, pot life) of the composition of the present invention and preventing any interference with the coating operation of heat-generating electronic components, etc.

[0046] Any of the known addition reaction inhibitors used in ordinary addition reaction curable silicone compositions can be used as component (F), including, for example, acetylene compounds such as 1-ethynyl-1-cyclohexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.

[0047] The amount of component (F) to be added can be determined appropriately based on the amount of component (E) used, and should be an effective amount that adequately suppresses the progress of the hydrosilylation reaction. To ensure sufficient pot life and curability of the composition of the present invention, the amount is typically about 0.1 to 5 parts by mass, preferably 0.2 to 3 parts by mass, and more preferably about 0.3 to 2 parts by mass, per 100 parts by mass of component (A). To improve dispersibility in the composition, component (F) can be diluted with an organic solvent such as toluene, xylene, or isopropyl alcohol, as necessary. Component (F) may be used alone or in combination of two or more types.

[0048] <(G) Palladium Powder> The component (G) of the composition of the present invention is palladium powder, which is blended to absorb hydrogen generated in the system and suppress voids.

[0049] The average particle size of the palladium powder of component (G) is preferably 1 to 100 nm, more preferably 2 to 70 nm, and even more preferably 3 to 50 nm, from the viewpoints of ease of handling during blending and hydrogen adsorption efficiency. The average particle size is a cumulative average diameter on a volume basis measured using a Nanotrac UPA-EX150 manufactured by Nikkiso Co., Ltd.

[0050] The blending amount of component (G) is 0.00001 to 1.0 part by mass, preferably 0.0005 to 0.1 part by mass, and particularly preferably 0.001 to 0.15 part by mass, per 100 parts by mass of component (A) from the viewpoints of void suppression effect and formation of heat conduction paths.

[0051] The method for incorporating component (G) is not particularly limited, and component (G) may be added and dispersed in the composition as is. Alternatively, component (G) may be supported on a carrier, such as silica, including fumed silica, wet silica, crystalline silica, and fused silica, and then incorporated. Alternatively, component (G) may be dispersed in a solvent and then added to the composition. Furthermore, component (G) may be uniformly dispersed in an organopolysiloxane or the like using a device such as a three-roll mill, and the resulting paste-like mixture may be added to the composition. The average particle size of the carrier (e.g., crystalline silica) is the cumulative average diameter measured on a volume basis using a Microtrac MT3300EX (manufactured by Nikkiso Co., Ltd.). Component (G) may be used alone or in combination of two or more types.

[0052] <(H) Surface Treatment Agent> The composition of the present invention contains an organopolysiloxane represented by the following general formula (2) as a surface treatment agent (H) for the purposes of hydrophobizing the gallium and / or alloy thereof, component (C), during preparation of the composition, improving the wettability of component (C) with the organopolysiloxane, component (A), and dispersing component (C) as fine particles uniformly within the matrix composed of component (A).

[0053] Similarly, component (H) also improves the wettability of the surface of the thermally conductive filler (D) and improves its uniform dispersion.

[0054] Component (H) is an organopolysiloxane represented by the following general formula (2), in which one end of the molecular chain is blocked with a hydrolyzable group and the kinematic viscosity at 25°C is 10 to 10,000 mm 2 The kinematic viscosity is preferably a value measured at 25°C using an Ostwald viscometer. (In formula (2), R 3each independently represents an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and no aliphatic unsaturated bond; R 4 are independently an alkyl group, an alkenyl group, or an acyl group; b is a number from 5 to 100, and c is a number from 1 to 3.

[0055] R in the above general formula (2) 3 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10, preferably 1 to 6, carbon atoms and containing no aliphatic unsaturated bonds. Specific examples thereof 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 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine or chlorine. Of these, a methyl group is preferred in terms of ease of synthesis and cost.

[0056] R in the above general formula (2) 4 Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; alkenyl groups such as vinyl and allyl; and acyl groups such as formyl, acetyl, and benzoyl. Of these, methyl and ethyl groups are particularly preferred.

[0057] In the general formula (2), b is a number from 5 to 100, preferably from 10 to 80, and more preferably from 20 to 60. In addition, in the general formula (2), c is a number from 1 to 3, preferably 2 or 3, and particularly preferably 3.

[0058] The blending amount of component (H) is in the range of 0.1 to 500 parts by mass, preferably 1 to 300 parts by mass, and more preferably 10 to 250 parts by mass, per 100 parts by mass of component (A). If the blending amount is less than 0.1 part by mass, components (C) and (D) will not disperse sufficiently to form a homogeneous composition, while if the blending amount exceeds 500 parts by mass, the amount of component (A) will be relatively small, making it difficult to cure the resulting composition, and misalignment may occur after the composition is applied to a device such as a CPU, resulting in a significant decrease in thermal conductivity.

[0059] <Other Components> In addition to the essential components described above, the thermally conductive silicone composition of the present invention may also contain the following components, if necessary.

[0060] The composition of the present invention may further contain, as component (I), an alkoxysilane represented by the following general formula (3). (In formula (3), R 5 are independently alkyl groups having 6 to 16 carbon atoms, and R 6 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, and R 7 are independently alkyl groups having 1 to 6 carbon atoms, d is a number from 1 to 3, e is a number from 0 to 2, and the sum of d and e is a number from 1 to 3.

[0061] R in the above general formula (3) 5 Examples of the alkyl group include hexyl, octyl, nonyl, decyl, dodecyl, tetradecyl, etc. If the number of carbon atoms is less than 6, the improvement in the wettability of components (C) and (D) is insufficient, and if it exceeds 16, the organosilane of component (I) solidifies at room temperature, making it difficult to handle and potentially reducing the low-temperature properties of the resulting composition.

[0062] In addition, R in the above general formula (3) 6Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, hexyl, and octyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl; and halogenated hydrocarbon groups such as 3,3,3-trifluoropropyl, 2-(nonafluorobutyl)ethyl, 2-(heptadecafluorooctyl)ethyl, and p-chlorophenyl. Of these, methyl and ethyl groups are particularly preferred.

[0063] In addition, R in the above general formula (3) 7 Examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, etc. Among these, methyl and ethyl groups are particularly preferred.

[0064] In the general formula (3), d is preferably a number from 1 to 3, more preferably 1 or 2, and particularly preferably 1. In the general formula (3), e is preferably a number from 0 to 2, more preferably 0 or 1, and particularly preferably 0. In the general formula (3), d+e is preferably a number from 1 to 3, more preferably 1 or 2, and particularly preferably 1.

[0065] Specific examples of suitable components (I) include the following:

[0066] Component (I) can be used singly or in combination of two or more. The viscosity of the composition is likely to fall within the desired range if the amount is 0.1 part by mass or more per 100 parts by mass of component (A). However, if the amount is more than 100 parts by mass, the wetter effect is not enhanced and this is uneconomical. Therefore, the amount is preferably 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass, and particularly preferably 5 to 30 parts by mass per 100 parts by mass of component (A).

[0067] The composition of the present invention may further contain trifluoropropyltrimethoxysilane as component (J) in some cases. The amount of trifluoropropyltrimethoxysilane added is preferably 0.1 parts by mass or more per 100 parts by mass of component (A), as this tends to bring the viscosity of the composition into the desired range. However, an amount greater than 100 parts by mass is uneconomical because the wetter effect is not enhanced. Therefore, the amount is preferably 0.1 to 100 parts by mass, more preferably 0.3 to 50 parts by mass, and particularly preferably 0.5 to 30 parts by mass. The components (H), (I), and (J) may be used alone or in combination.

[0068] <Optional Components Other Than the Above> In addition to the components (A) to (J) described above, the composition of the present invention may contain, as needed, a conventionally known antioxidant such as 2,6-di-t-butyl-4-methylphenol. Furthermore, adhesion promoters, release agents, dyes, pigments, flame retardants, anti-settling agents, and / or thixotropy improvers may also be blended as needed. When optional components are added, the content of the optional components in the composition of the present invention is preferably 0.01 to 5.0% by mass, more preferably 0.1 to 3.0% by mass.

[0069] The thermally conductive silicone composition of the present invention can be stored at low temperatures for long periods of time as a one-part additive type by mixing the above components (A) through (J) and other optional components.

[0070] [Method for Producing Thermally Conductive Silicone Composition] The thermally conductive silicone composition of the present invention can be produced by mixing the above-mentioned components. There are no particular restrictions on the order in which the components are added, but the composition can be produced by mixing components (A) to (H) and, if necessary, other components. For example, the thermally conductive silicone composition of the present invention can be produced by separately preparing composition (I) containing components (A), (C), (D), (G), and (H), and composition (II) containing components (B), (E), and (F), and then mixing these two compositions.

[0071] The components of the thermally conductive silicone composition of the present invention may be mixed at room temperature or heated, and the mixing temperature is preferably 25 to 200° C., and more preferably 50 to 180° C. Furthermore, degassing may be carried out during heating or mixing at 25° C.

[0072] [Physical Properties of Thermally Conductive Silicone Composition] The thermally conductive silicone composition of the present invention preferably has a viscosity measured at 25°C in the range of 10 to 1,000 Pa·s, and more preferably in the range of 30 to 400 Pa·s. If the viscosity measured at 25°C is 10 Pa·s or higher, the particle size of the low-melting point metal is maintained and uniform dispersion is possible, and if it is 1,000 Pa·s or lower, extensibility can be ensured and work efficiency will not decrease. Note that this viscosity is a value measured at 25°C using a spiral viscometer PC-ITL (manufactured by Malcom Co., Ltd.).

[0073] The thermally conductive silicone composition of the present invention preferably has a thermal conductivity at 25° C. of at least 2.0 W / m·K before the composition is cured.

[0074] The thermally conductive silicone composition of the present invention is characterized in that the silicone composition is sandwiched between a silicon substrate measuring 10 mm × 10 mm × 1 mm thick and a nickel substrate measuring 20 mm × 20 mm × 1 mm thick, and cured by heating at 150°C for 60 minutes while applying a pressure of 20 psi. The cured product is then subjected to a pull test using a bond tester, and the fracture surface of the cured product exhibits cohesive failure.

[0075] The thermally conductive silicone composition of the present invention is sandwiched between two nickel substrates, each 10 mm in diameter and 1 mm in thickness, and then heated at 150°C for 60 minutes while applying a pressure of 50 psi to cure the composition. The thickness of the cured product of the composition is preferably 20 to 200 μm, more preferably 30 to 170 μm, even more preferably 50 to 160 μm, and particularly preferably 105 to 150 μm. If the thickness is 20 μm or more, the adhesiveness of the cured product of the composition to the member is maintained, and the fracture surface in a pull test shows cohesive failure. If the thickness exceeds 200 μm, the cured product of the composition may be too thick, resulting in reduced thermal performance.

[0076] The thermally conductive silicone composition of the present invention preferably has a storage modulus after curing of 20 to 200 kPa, and more preferably 40 to 150 kPa. A storage modulus of 20 kPa or more maintains the strength of the material and allows it to maintain adhesion to the component, while a storage modulus of 200 kPa or less maintains the flexibility of the material and allows it to conform to warping of the component.

[0077] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these. Components (A) to (J) used in the following examples and comparative examples are shown below. The kinematic viscosity is a value measured using an Ostwald viscometer (manufactured by Shibata Scientific Co., Ltd.). The viscosity is a value measured using a spiral viscometer PC-ITL (manufactured by Malcom Co., Ltd.) (rotation speed: 10 rpm). The average particle size is the volume-based volume mean diameter [MV] measured using a Microtrac MT3300EX (manufactured by Nikkiso Co., Ltd.).

[0078] Component (A) A-1: ​​A copolymer having both ends capped with dimethylvinylsilyl groups and a kinematic viscosity of 100 mm at 25°C. 2 A-2: Dimethylpolysiloxane having a kinematic viscosity of 30,000 mm at 25°C (vinyl value: 0.04 mol / 100 g) and a vinyl value of 0.04 mol / 100 g. A-3: Dimethylpolysiloxane having a kinematic viscosity of 30,000 mm at 25°C (vinyl value: 0.04 mol / 100 g). 2 / s dimethylpolysiloxane (vinyl value: 0.0038 mol / 100 g)

[0079] Component (B-1) B-1-1: A copolymer having 16 silicon-bonded hydrogen atoms in the side chain and a kinematic viscosity (25°C) of 113 mm 2 / s organohydrogenpolysiloxane represented by the following formula (H value: 0.00547 mol / g)

[0080] Component (B-2) B-2-1: Organohydrogenpolysiloxane with a purity of 96% represented by the following formula (H value: 0.0085 mol / g)

[0081] (C) Component C-1: Metallic gallium (melting point = 29.8 ° C) C-2: Ga-In-Sn alloy (mass ratio = 62:25:13, melting point = 5.0 ° C)

[0082] Component (D-1) D-1-1: Zinc oxide powder (average particle size: 15.0 μm) (for comparative example) D-1-2: Zinc oxide powder (average particle size: 20.0 μm) D-1-3: Zinc oxide powder (average particle size: 30.0 μm) D-1-4: Zinc oxide powder (average particle size: 70.0 μm) D-1-5: Alumina powder (average particle size: 120.0 μm) D-1-6: Alumina powder (average particle size: 150.0 μm) D-1-7: Alumina powder (average particle size: 220 μm) (for comparative example)

[0083] Component (D-2) D-2-1: Zinc oxide powder (average particle size: 1.0 μm)

[0084] Component (E) E-1: Dimethylpolysiloxane of platinum-divinyltetramethyldisiloxane complex (both ends of which are blocked with dimethylvinylsilyl groups, kinematic viscosity: 600 mm 2 / s) solution (platinum atom content: 1% by mass)

[0085] Component (F) F-1: 1-ethynyl-1-cyclohexanol

[0086] Component (G) G-1: Palladium powder (average particle size: 5 nm)

[0087] Component (H) H-1: kinematic viscosity of 32 mm represented by the following structural formula 2 / s dimethylpolysiloxane terminated at one end with a trimethoxysilyl group

[0088] (I) Component I-1: Structural formula C 10 H 21 Alkoxysilane represented by Si(OCH3)3

[0089] Component (J) J-1: Trifluoropropyltrimethoxysilane

[0090] The silicone compositions of Examples 1 to 10 and Comparative Examples 1 to 6 were obtained by mixing the above components (A) to (H) as follows: Components (A), (C), (D), (G), and (H) were placed in a 300 ml mixer (manufactured by Primix Corporation) and mixed at room temperature (15 to 30°C) for 20 minutes. Next, components (B), (E), and (F) were each added to the mixer and mixed at room temperature for 5 minutes each.

[0091] The properties of the resulting compositions were evaluated by the following methods, and the results are shown in Tables 1 and 2.

[0092] Measurement of particle size of component (C): 0.1 g of each composition obtained above was sandwiched between two glass slides, and from the image taken with a VHX-8000 manufactured by Keyence Corporation, 10 particles were randomly selected, the particle size of each was measured, and the average value was calculated.

[0093] Thermal Conductivity The thermal conductivity (W / m·K) of the composition before curing at 25° C. was measured using a thermal property measuring device TPS-2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0094] Storage Modulus The storage modulus of each silicone composition was measured at 150°C using an ARES-G2 manufactured by TA Instruments Co., Ltd. Each silicone composition was sandwiched between two parallel plates with a diameter of 2.5 cm, and the thickness of the silicone composition was 2 mm. The temperature increase program was to increase the temperature to 125°C at 10°C / min, and then increase the temperature from 125°C to 150°C at 2°C / min, and then hold the temperature at 150°C for 2 hours, at which point the storage modulus (kPa) was confirmed.

[0095] Pull test: Each silicone composition was sandwiched between a 10 mm x 10 mm silicon substrate and a 20 mm x 20 mm nickel substrate, and heat-cured at 150°C for 60 minutes while being pressurized with a 20 psi clip. Thereafter, the composition was pulled in a 90° direction relative to the silicon substrate surface using a Dage series-4000PXY (manufactured by Dage Deutchland GmbH), and the fracture surface and adhesive strength were confirmed. The state of the fracture surface was visually inspected for the silicone composition adhering to the silicon substrate surface and the nickel substrate surface, and evaluated as follows: Silicone composition adhered to both the silicon substrate surface and the nickel substrate surface (cohesive failure): ◯ Silicone composition adhered to either the silicon substrate surface or the nickel substrate surface (interfacial peeling): ×

[0096] Thickness of silicone composition (cured product) after curing Two nickel substrates, each 10 mm in diameter and 1 mm thick, were prepared, and the thickness of each was measured using a micrometer (MDC-25MX, manufactured by Mitutoyo Corporation). The silicone composition was sandwiched between the two nickel substrates, and cured by heating at 150°C for 60 minutes while applying a pressure of 50 psi. The thicknesses of the nickel substrates and the cured product of the silicone composition were then measured using the micrometer, and the thickness of the nickel substrate was subtracted from the measured thickness to calculate the thickness of the cured product of the silicone composition.

[0097]

[0098]

[0099] The results in Tables 1 and 2 demonstrate that the thermally conductive silicone compositions of Examples 1 to 10, which satisfied the requirements of the present invention, were capable of producing silicone compositions containing a liquid metal that had high thermal conductivity yet low viscosity, and that had a low elastic modulus yet excellent adhesion to substrates after heat curing.

[0100] On the other hand, in Comparative Example 1, the amount of component (C) was too large, resulting in a significant increase in viscosity and resulting in a lump-like consistency instead of a paste.

[0101] In Comparative Example 2, the amount of component (C) was too small, so sufficient thermal conductivity could not be maintained.

[0102] In Comparative Example 3, the particle size of component (D-1) was as small as 15 μm, and therefore the fracture surface after the pull test showed interfacial peeling, and sufficient adhesion could not be maintained.

[0103] In Comparative Example 4, the particle size of component (D-1) was as large as 221 μm, and the thickness of the cured product was therefore too large.

[0104] In Comparative Example 5, the ratio of {total number of Si—H groups in component (B)} / {number of Si—Vi groups in component (A)} was 5.5, which was too high, and therefore the elastic modulus was too high.

[0105] In Comparative Example 6, the ratio of {the total number of Si—H groups in component (B)} / {the number of Si—Vi groups in component (A)} was 0.5, which was too high, resulting in an excessively low elastic modulus, resulting in interfacial peeling in the pull test, and a significant decrease in adhesion.

[0106] The results of the above examples demonstrate that the thermally conductive silicone composition of the present invention can provide a thermally conductive silicone composition that has high thermal conductivity yet low viscosity, and that has a low elastic modulus yet exhibits excellent adhesion to substrates after heat curing.

Claims

1. A thermally conductive silicone composition containing the following components (A), (B), (C), (D), (E), (F), (G), and (H): (A) a silicone oil having two or more silicon-bonded aliphatic unsaturated hydrocarbon groups per molecule and having a kinematic viscosity at 25°C of 10 to 1,000,000 mm 2 / s organopolysiloxane: 100 parts by mass; (B) an organohydrogenpolysiloxane consisting of components (B-1) and (B-2): an amount such that {total number of Si—H groups in component (B)} / {number of aliphatic unsaturated hydrocarbon groups in component (A)} is 0.6 to 5.0; (B-1) a linear organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms (Si—H groups) per molecule; (B-2) a cyclic organohydrogenpolysiloxane represented by the following general formula (1): (In formula (1), a is a number from 2 to 8, R 1 are each independently a group selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an epoxy group, an acryloyl group, a methacryloyl group, an ether group, and a trialkoxysilyl group, and R 1 Two or three of the groups represented by R are hydrogen atoms. 2 are each independently selected from an alkyl group having 1 to 6 carbon atoms, an epoxy group, an acryloyl group, a methacryloyl group, an ether group, and a trialkoxysilyl group. (C) gallium and / or its alloys having a melting point of -20 to 70°C: 300 to 20,000 parts by mass per 100 parts by mass of component (A); (D-1) thermally conductive filler having an average particle size of 20 to 200 μm: 10 to 1,000 parts by mass per 100 parts by mass of component (A); (D-2) thermally conductive filler having an average particle size of 0.1 to 10 μm: 10 to 1,000 parts by mass per 100 parts by mass of component (A); (E) platinum group metal catalyst: effective amount; (F) reaction inhibitor: effective amount; (G) palladium powder: 0.00001 to 1.0 part by mass per 100 parts by mass of component (A); (H) organopolysiloxane represented by the following general formula (2): 0.1 to 500 parts by mass per 100 parts by mass of component (A): (In formula (2), R 3 each independently represents an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and no aliphatic unsaturated bond; R 4 are independently an alkyl group, an alkenyl group, or an acyl group; b is a number from 5 to 100, and c is a number from 1 to 3.

2. The thermally conductive silicone composition according to claim 1, further comprising (I) an alkoxysilane represented by the following general formula (3) in an amount of 0.1 to 100 parts by mass per 100 parts by mass of component (A): (In formula (3), R 5 are independently alkyl groups having 6 to 16 carbon atoms, and R 6 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, and R 7 are independently alkyl groups having 1 to 6 carbon atoms, d is a number from 1 to 3, e is a number from 0 to 2, and the sum of d and e is a number from 1 to 3.

3. The thermally conductive silicone composition according to claim 1, further comprising (J) trifluoropropyltrimethoxysilane in an amount of 0.1 to 100 parts by weight per 100 parts by weight of component (A).

4. The thermally conductive silicone composition according to claim 1, wherein component (C) is dispersed in the composition in the form of particles of 1 to 200 μm.

5. A cured product of the thermally conductive silicone composition according to any one of claims 1 to 4.

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