Thermally conductive silicone composition and its cured product

Abstract

Provided is a thermally conductive silicone composition that can be compressed to a thickness capable of obtaining sufficient heat dissipation performance even when a process of crushing a material and a heat curing process are simultaneously carried out. 【Solution means】 (A) An organopolysiloxane having an aliphatic unsaturated hydrocarbon group bonded to a silicon atom (B) An organohydrogenpolysiloxane (C) Gallium and / or its alloy having a melting point of -20 to 70 °C (D) A thermally conductive filler having an average particle diameter of 0.1 to 100 μm (E) A platinum group metal catalyst (F-1) An organopolysiloxane in which the molecular chain ends are blocked with hydrolyzable groups and (G) An addition reaction control agent The thermally conductive silicone composition contains: When the value at which the storage elastic modulus G' of the composition is maximum is taken as the curing rate of 100%, the temperature at which the curing rate becomes 10% is 120 °C or higher. The thermally conductive silicone composition is characterized by this.

Description

[Technical Field]

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

[0002] Heat-generating electronic components mounted on printed circuit boards, such as IC packages for CPUs, can experience performance degradation or damage due to temperature increases caused by heat generation during use. Therefore, conventional methods have involved placing a highly thermally conductive sheet or applying thermally conductive grease between the IC package and a heat dissipation member with heat fins to efficiently conduct and dissipate heat generated from the IC package. However, with the increasing performance of electronic components, the amount of heat generated tends to increase, creating a need for the development of materials and components with even greater thermal conductivity than conventional ones.

[0003] Conventional thermal conductive sheets have the advantage of being easy to mount and install, which is beneficial in terms of work and process. Thermal conductive grease, on the other hand, is not affected by the surface irregularities of CPUs, heat dissipation components, etc., and can conform to these irregularities, ensuring close contact between the two without creating gaps, thus having the advantage of low interfacial thermal resistance. However, both thermal conductive sheets and thermal conductive grease are obtained by blending thermal conductive fillers to impart thermal conductivity, but in the case of thermal conductive sheets, the upper limit of their apparent viscosity must be limited to avoid hindering workability and processability in the manufacturing process, and in the case of thermal conductive grease, to avoid problems with workability when applying it to heat-generating electronic components using syringes, etc. Therefore, in both cases, the upper limit of the amount of thermal conductive filler that can be blended is limited, resulting in the disadvantage that sufficient thermal conductivity cannot be obtained.

[0004] Therefore, methods have been proposed to incorporate low-melting-point metals into thermally conductive pastes, and to use granular materials that fix and stabilize liquid metals within a three-phase composite. However, these thermally conductive materials using low-melting-point metals have problems such as contaminating parts other than the coated area, and leaking oily substances after prolonged use. To solve these problems, a method of dispersing gallium and / or gallium alloys in addition-curing silicone has been proposed (Patent Document 1: Japanese Patent Application Publication No. 2013-082816). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-082816 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the process of assembling thermally conductive grease into a package as a heat dissipation material, it is preferable to perform the crushing (pressure or compression) step and the heat curing step simultaneously in order to shorten the process time. However, with conventional addition-curing silicones containing gallium and / or gallium alloys, the curing speed is too fast, making it impossible to compress the applied heat dissipation material to the required thickness, resulting in insufficient heat dissipation performance. The present invention has been made in view of the above problems, and aims to provide a thermally conductive silicone composition that can be compressed to a thickness that provides sufficient heat dissipation performance even when the process of crushing (pressuring or compressing) the material and the heat curing process are carried out simultaneously. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the inventors of the present invention have found that by adding a small amount of a catalyst to a silicone composition containing gallium having a low melting point and / or its alloy and a thermal conductivity filler, a composition in which the gallium and / or its alloy is uniformly dispersed in a particulate state can be easily obtained. Even in the step of assembling the composition into a package, when the steps of crushing the material and the heat curing step are simultaneously carried out, the heat dissipation grease can be compressed to a predetermined thickness, and sufficient heat dissipation performance can be obtained. Thus, the present invention has been completed. That is, the present invention provides a curable organopolysiloxane composition as described below. <1> (A) 100 parts by mass of an organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to silicon atoms and having a kinematic viscosity at 25°C of 10 to 1,000,000 mm 2 / s at the molecular chain ends per molecule, (B) An organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule: an amount such that the number of hydrogen atoms bonded to silicon atoms in this component is 0.5 to 5.0 per alkenyl group in the component (A), (C) One or more selected from the group consisting of gallium and gallium alloys having a melting point of -20 to 70°C: 3,000 to 12,000 parts by mass, (D) A thermal conductivity filler having an average particle size of 0.1 to 100 μm: 10 to 1,000 parts by mass, (E) A platinum group metal catalyst: an amount such that it is 1 to 25 ppm as platinum atoms with respect to the component (A), (F-1) An organopolysiloxane represented by the following general formula (1): 0.1 to 500 parts by mass

Chemical formula

[0008] Since the heat-conductive silicone composition of the present invention is in a grease state before curing, the workability when applying it on a heat-generating electronic component such as a CPU is good. Further, when pressing the heat dissipation member, it can follow the unevenness on the surfaces of both the heat-generating electronic component and the heat dissipation member, and the two can be adhered without generating a gap therebetween, so that no interfacial thermal resistance occurs. Also, in the process of assembling the heat-conductive silicone composition of the invention into a package, even in a process where the steps of crushing the material and the heat-curing step are carried out simultaneously, the silicone composition can be compressed to a predetermined thickness, and sufficient heat dissipation performance can be obtained. [Embodiments for Carrying Out the Invention]

[0009] Hereinafter, the present invention will be described in more detail.

[0010] [Heat-Conductive Silicone Composition] [(A) Organopolysiloxane] The component (A) of the composition of the present invention is an organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in one molecule and at the molecular chain ends, and is the main agent (base polymer) in the addition reaction-curing type composition of the present invention.

[0011] The kinematic viscosity of the component (A) at 25 °C is in the range of 10 to 1,000,000 mm 2 / s, preferably 50 to 500,000 mm 2 / s. If the kinematic viscosity is less than 10 mm 2 / s, the cured product becomes brittle and is likely to crack. If it is greater than 1,000,000 mm 2 / s, the viscosity of the composition becomes too high and it becomes difficult to handle. In the present invention, the kinematic viscosity is the value at 25 °C measured by an Ostwald viscometer.

[0012] The molecular structure of component (A), the organopolysiloxane, is not limited and can be linear, branched, or partially branched, but is particularly preferred.

[0013] (A) The number of aliphatic unsaturated hydrocarbon groups bonded to the silicon atom in component (A) should be two or more per molecule, preferably 2 to 6, and more preferably 2 to 4. Examples of aliphatic unsaturated hydrocarbon groups include vinyl groups, allyl groups, 1-butenyl groups, and alkenyl groups such as 1-hexenyl groups, but vinyl groups are preferred due to their ease of synthesis and cost. To ensure good flexibility of the resulting cured product, it is preferable that component (A) has this aliphatic unsaturated hydrocarbon group bonded only to the silicon atom at the end of the molecular chain.

[0014] Groups bonded to silicon atoms other than aliphatic unsaturated hydrocarbon groups bonded to silicon atoms include, for example, unsubstituted or substituted monovalent hydrocarbon groups, such as alkyl groups like methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups like cyclopentyl and cyclohexyl groups; aryl groups like phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups like benzyl, 2-phenylethyl, and 2-phenylpropyl groups; and halogenated alkyl groups like chloromethyl, 3,3,3-trifluoropropyl, and 3-chloropropyl groups. From the viewpoint of synthesis and economics, it is preferable that 90% or more of these groups are methyl groups.

[0015] Suitable examples of such organopolysiloxanes include polydimethylsiloxane with dimethylvinylsiloxy groups sealed at both ends of the molecular chain, polydimethylsiloxane with methyldivinylsiloxy groups sealed at both ends of the molecular chain, and dimethylsiloxane-methylphenylsiloxane copolymers with dimethylvinylsiloxy groups sealed at both ends of the molecular chain. The organopolysiloxane of component (A) may be used alone or in combination of two or more types. The amount of component (A) is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, relative to the total thermally conductive silicone composition of the present invention.

[0016] <(B) Organohydrogenpolysiloxane> Component (B) of the present invention composition is an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms (hereinafter referred to as "Si-H groups") in one molecule, and acts as a crosslinking agent for component (A). Specifically, the Si-H groups in component (B) are added to the alkenyl groups in component (A) by a hydrosilylation reaction through the action of the platinum-based catalyst component (E) described below, giving a crosslinked cured product having a three-dimensional network structure with crosslinking bonds.

[0017] The number of Si-H groups in component (B) is 2 or more per molecule, preferably 2 to 30. The molecular structure of component (B) is not particularly limited as long as it satisfies the above requirements, and may be any of the conventionally known structures, such as linear, cyclic, branched, or three-dimensional network (resinous). The number of silicon atoms (or degree of polymerization) in one molecule is usually 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.

[0018] The groups that bond to silicon atoms other than the Si-H group are preferably unsubstituted or substituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and lacking an aliphatic unsaturated bond. Specific examples 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 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine and chlorine. Of these, the methyl group is preferred in terms of ease of synthesis and cost.

[0019] Specific examples of the organohydrogenpolysiloxane component (B) include: dimethylsiloxane-methylhydrogensiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain; methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain; dimethylsiloxane-methylhydrogensiloxane copolymer with one dimethylhydrogensiloxy group and one trimethylsiloxy group sealed at one end of the molecular chain; methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymer with one dimethylhydrogensiloxy group and one trimethylsiloxy group sealed at the other end of the molecular chain; (CH3)2HSiO 1 / 2 Units and (CH3)3SiO 1 / 2 Units and (CH3)HSiO 2 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 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 units, (CH3)2HSiO 1 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 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 units, (CH3)2HSiO 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 Examples include copolymers consisting of units.

[0020] The amount of component (B) is such that the number of Si-H groups in component (B) is 0.5 to 5.0 for each aliphatic unsaturated hydrocarbon group bonded to a silicon atom in component (A), with a range of 0.7 to 3.0 being preferred. If the amount of component (B) is less than the lower limit, the composition cannot be sufficiently networked, and the grease will not harden sufficiently. If it exceeds the upper limit, the resulting thermally conductive silicone composition may become too hard, reducing its reliability, and foaming may occur more easily. (B) The organohydrogenpolysiloxane may be used alone or in combination of two or more types.

[0021] (C) Gallium and / or its alloys 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. Component (C) is added to impart good thermal conductivity to the cured product obtained from the composition of the present invention, and the inclusion of this component is a characteristic feature of the present invention.

[0022] As mentioned above, the melting point of component (C) must be in the range of -20 to 70°C. Although it is physically possible to use components with a melting point below -20°C for use in the present invention, obtaining such components is difficult and therefore uneconomical. Conversely, if the melting point exceeds 70°C, the components will not melt quickly during the composition preparation process, resulting in poor workability. Therefore, as stated above, the appropriate melting point range for component (C) is -20 to 70°C. In particular, components with a melting point in the range of -19 to 50°C are preferable as component (C) because they facilitate the preparation of the composition of the present invention.

[0023] The melting point of metallic gallium is 29.8°C. Representative gallium alloys include, for example, gallium-indium alloys (e.g., Ga-In, mass ratio = 75.4:24.6, melting point = 15.7°C), gallium-tin alloys (mass ratio = 92:8, melting point = 20°C), gallium-tin-zinc alloys (e.g., Ga-Sn-Zn, mass ratio = 82:12:6, melting point = 17°C), and gallium-indium-tin alloys (e.g., Examples include 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).

[0024] This (C) component can be used alone or in combination of two or more types. 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 irregularly shaped particles may be included. The average particle size is preferably 1 to 200 μm, particularly 5 to 150 μm, and more preferably 10 to 100 μm. If the average particle size is too small, the viscosity of the composition becomes too high, resulting in poor spreadability and problems with coating workability. Conversely, if the particle size is too large, the composition becomes non-uniform, making thin-film coating of heat-generating electronic components difficult. The shape, average particle size, and dispersion state within the composition can be maintained until the coating process for heat-generating electronic components if the composition is stored at a low temperature immediately after preparation. The average particle size was calculated by sandwiching the uncured composition between two glass slides and observing it with a digital microscope (for example, a VHX-8000 manufactured by Keyence Corporation). Specifically, 10 particles were randomly selected from the images captured by this measuring instrument, their particle size (or major axis in the case of elliptical particles) was measured, and their average value was calculated.

[0025] The amount of component (C) is 3,000 to 12,000 parts by mass, preferably 4,500 to 12,000 parts by mass, and more preferably 5,500 to 12,000 parts by mass, per 100 parts by mass of component (A). If the amount is less than 3,000 parts by mass, the thermal conductivity will be low, and sufficient heat dissipation performance cannot be obtained if the composition is thick. If the amount is more than 12,000 parts by mass, it will be difficult to obtain a uniform composition, and the viscosity of the composition will be too high, so it may not be possible to obtain a composition that is spreadable and grease-like.

[0026] <(D) Thermally conductive filler> The composition of the present invention must contain, along with component (C), a conventionally known thermal conductive filler (D) that is incorporated into thermal conductive sheets or thermal conductive greases (excluding component (C)).

[0027] The (D) component is not particularly limited as long as it has good thermal conductivity, and conventionally known components can be used. Examples include 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. Furthermore, the (D) component can be used alone or in combination of two or more components. In particular, zinc oxide powder and alumina powder are especially preferred from the standpoint of ease of availability and economic considerations.

[0028] The average particle size of component (D) is 0.1 to 100 μm, preferably in the range of 1 to 20 μm. If the average particle size is too small, the viscosity of the resulting composition will be too high, resulting in poor spreadability. Conversely, if it is too large, it will be difficult to obtain a uniform composition. This average particle size is the volume-based volume-average diameter [MV] measured by laser diffraction-scattering using a Microtrac MT3300EX (manufactured by Nikkiso Co., Ltd.).

[0029] The amount of component (D) to be filled is in the range of 10 to 1,000 parts by mass per 100 parts by mass of component (A), preferably in the range of 50 to 500 parts by mass. If the amount of component (D) is less than 10 parts by mass per 100 parts by mass of component (A), the gallium and / or its alloy will not be uniformly dispersed in (A) or in the mixture of component (A) and component (F) described later. If it is more than 1,000 parts by mass, the viscosity of the composition will be high, and it will not be possible to obtain a composition that is spreadable and grease-like.

[0030] <(E) Platinum group metal catalyst> The platinum group metal catalyst component (E) of the composition of the present invention is a component that is added to promote the addition reaction between the aliphatic unsaturated hydrocarbon group bonded to the silicon atom in component (A) and the Si-H in component (B), thereby giving a three-dimensional network-like crosslinked hardened product from the composition of the present invention. However, the platinum group metal catalyst of component (E) does not include the palladium powder of component (H), which will be described later.

[0031] As component (E), any known component used in ordinary hydrosilylation reactions can be used, such as platinum metal (platinum black), chloroplatinic acid, platinum-olefin complex, platinum-alcohol complex, and platinum coordination compound. The amount of component (E) is in the range of 1 to 25 ppm relative to the mass of component (A) as platinum atoms, preferably 2 to 20 ppm, and more preferably 3 to 15 ppm. If the amount of component (E) is less than 1 ppm relative to the mass of component (A) as platinum atoms, the composition will not harden, and if it is more than 25 ppm, the hardening rate will be too fast, causing the silicone composition to harden before it can be fully compressed during the package assembly process, preventing the silicone composition from being compressed to a predetermined thickness and resulting in insufficient heat dissipation performance.

[0032] <(F-1) Surface treatment agent> The composition of the present invention incorporates a polysiloxane represented by the following general formula (1) as a (F-1) surface treatment agent, with the aim of hydrophobizing gallium and / or its alloy of component (C) during composition preparation, improving the wettability of component (C) with the organopolysiloxane of component (A), and uniformly dispersing component (C) as fine particles in the matrix consisting of component (A).

[0033] Furthermore, this (F-1) component also has the effect of improving the wettability of the surface of the thermally conductive filler component (D) mentioned above, thereby improving its uniform dispersion.

[0034] Component (F-1) is an organopolysiloxane represented by the following general formula (1), in which one end of the molecular chain is sealed with a hydrolyzable group, and has a kinematic viscosity of 10 to 10,000 mmHg at 25°C. 2 The value is / s. This kinematic viscosity was measured at 25°C using an Ostwald viscometer. [ka] In formula (1), R 1 R independently represents an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms that does not have an aliphatic unsaturated bond, 2 is independently an alkyl group, an alkenyl group, or an acyl group. Also, a is a number from 5 to 100, and b is a number from 1 to 3.

[0035] In the above general formula (1), R 1This refers to an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10, preferably 1 to 6, carbon atoms and lacking an aliphatic unsaturated bond. Specific examples 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 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine and chlorine. Of these, the methyl group is preferred in terms of ease of synthesis and cost.

[0036] In the above general formula (1), R 2 Examples of alkyl groups include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; alkenyl groups such as vinyl and allyl groups; and acyl groups such as formyl, acetyl, and benzoyl groups. Among these, methyl and ethyl groups are particularly preferred.

[0037] The amount of component (F-1) is in the range of 0.1 to 500 parts by mass per 100 parts by mass of component (A), preferably 1 to 300 parts by mass, and more preferably 10 to 250 parts by mass. If the amount is less than the lower limit, components (C) and (D) will not be sufficiently dispersed and the composition will not be uniform. If it exceeds the upper limit, the amount of component (A) will be relatively small, making the resulting composition difficult to cure, and the thermal conductivity may be significantly reduced due to displacement after the composition is applied to a device such as a CPU.

[0038] <(G) Addition reaction regulator> The addition reaction control agent of component (G) of the composition of the present invention is a component formulated to suppress the hydrosilylation reaction in response to the action of the platinum-based catalyst at room temperature, thereby ensuring the pot life (shelf life, pot life) of the composition of the present invention and preventing interference with coating work on heat-generating electronic components, etc.

[0039] As component (G), any known addition reaction control agent used in typical addition reaction curing silicone compositions can be used, for example, acetylene compounds such as 1-ethynyl-1-cyclohexanol and 3-butyne-1-ol, various nitrogen compounds, organophosphorus compounds, oxime compounds, and organochloro compounds.

[0040] The amount of component (G) to be added varies depending on the amount of component (E) used, and cannot be stated definitively. However, any effective amount that can suppress the progress of the hydrosilylation reaction is sufficient. From the viewpoint of ensuring sufficient pot life and curability of the composition of the present invention, it is preferable to use 0.1 to 5 parts by mass per 100 parts by mass of component (A). In addition, to improve the dispersibility of component (G) in the composition, it may be diluted with an organic solvent such as toluene, xylene, or isopropyl alcohol as needed. Furthermore, component (G) may be used alone or in combination of two or more types.

[0041] <Other ingredients> In addition to the essential components listed above, the curable organopolysiloxane composition of the present invention may optionally contain the following components. <(H) Palladium powder> The silica supported with palladium powder having an average particle size of 1 to 100 nm in the composition of the present invention is an optional component that is added to absorb hydrogen generated in the system and suppress voids.

[0042] The average particle size of the palladium powder of component (H) is preferably 1 to 100 nm, and more preferably 1 to 70 nm, from the viewpoint of handling during compounding and hydrogen adsorption efficiency. The average particle size is the volume-based cumulative average diameter measured by FFT-power spectroscopy using NanoTrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.).

[0043] The amount of component (H) is preferably 0.00001 to 1.0 parts by mass, and more preferably in the range of 0.0005 to 0.1 parts by mass, per 100 parts by mass of component (A), in terms of palladium atoms, from the viewpoint of void suppression effect and heat conduction path formation.

[0044] Any type of silica can be used to support the palladium powder, including fumed silica, wet silica, crystalline silica, and fused silica. There are no particular restrictions on the method of compounding component (H), and component (H) may be added and dispersed in the composition as is. Alternatively, a paste-like mixture obtained by uniformly dispersing component (H) in organopolysiloxane or the like using a device such as a three-roll mill may be added to the composition. The average particle size of the carrier (e.g., crystalline silica) is the volume-based cumulative average diameter measured by laser diffraction / scattering using Microtrac MT3300EX (manufactured by Nikkiso Co., Ltd.). Component (H) may be used alone or in combination of two or more types.

[0045] <(F-2) Alkoxysilane> Furthermore, the composition of the present invention may further contain the following alkoxysilanes as component (F-2). (F-2) General formula (2) below: [ka] (In formula (2), R 3 R is an alkyl group having 9 to 16 carbon atoms, 4 R is an independent unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, 5(Each is an alkyl group having 1 to 6 carbon atoms, c is an integer from 1 to 3, d is an integer from 0 to 2, and the sum of c + d is an integer from 1 to 3.)

[0046] In the above general formula (2), R 3 Examples of such groups include nonyl groups, decyl groups, dodecyl groups, and tetradecyl groups. If the number of carbon atoms is less than 9, the wettability of components (C) and (D) above is not sufficiently improved, and if the number of carbon atoms exceeds 16, the organosilane of component (F-2) solidifies at room temperature, making it inconvenient to handle and reducing the low-temperature properties of the resulting composition.

[0047] Also, R in the general formula (2) above 4 Examples of such groups include alkyl groups such as methyl, ethyl, propyl, hexyl, and octyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl groups; and halogenated hydrocarbon groups such as 3,3,3-trifluoropropyl, 2-(nonafluorobutyl)ethyl, 2-(heptadecafluorooctyl)ethyl, and p-chlorophenyl groups. Among these, methyl and ethyl groups are particularly preferred.

[0048] Also, R in the general formula (2) above 5 Examples of alkyl groups include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups. Among these, methyl and ethyl groups are particularly preferred.

[0049] The following are some suitable examples of this (F-2) component. [ka]

[0050] Furthermore, this (F-2) component can be used alone or in combination of two or more types. In addition, the amount added is preferably in the range of 0.1 parts by mass or more per 100 parts by mass of component (A), as this makes it easier to achieve the desired viscosity of the composition. If the amount is greater than 100 parts by mass, the wetter effect will not increase, which is uneconomical. Therefore, the amount is preferably in the range of 0.1 to 100 parts by mass, and more preferably 1 to 50 parts by mass, per 100 parts by mass of component (A).

[0051] <Optional components other than those listed above> In addition to the components (A) to (H) described above, the composition of the present invention may optionally contain conventionally known antioxidants such as 2,6-di-t-butyl-4-methylphenol. Furthermore, adhesive aids, mold release agents, dyes, pigments, flame retardants, settling inhibitors, and / or thixotropic enhancers may be added as needed. It is preferable to add 0.0001 to 0.1% by mass of the above optional components to the total composition.

[0052] <Viscosity of the composition> In terms of workability, the silicone composition of the present invention preferably has a viscosity in the range of 10 to 1,000 Pa·s, and more preferably 30 to 400 Pa·s, as measured at 25°C. This viscosity was measured at 25°C using a spiral viscometer PC-ITL (manufactured by Malcolm Corporation).

[0053] [Preparation of the composition of the present invention] The thermally conductive silicone composition of the invention, (i) A step of kneading the above (A), (C), (D), and (F-1), and if present, the above (F-2) component and the above (H) component at a temperature in the range of 20 to 120°C and above the melting point of the above (C) component to obtain a homogeneous mixture (i); (ii) stopping the kneading of mixture (i) and cooling the temperature of mixture (i) to below the melting point of component (C) to obtain mixture (ii); and (iii) Adding component (B), component (E), and component (G), and optionally other components, to mixture (ii) and kneading at a temperature below the melting point of component (C) to obtain a homogeneous mixture (iii). It can be obtained by a manufacturing method having, but is not limited to, the method described herein.

[0054] In step (i) above, the silica supporting the liquid gallium and / or alloy of component (C), the thermally conductive filler of component (D), and the palladium powder of component (H) is uniformly dispersed in a mixed solution of component (A) and either (F-1) or (F-2), or two or more of them.

[0055] In step (ii), the cooling or defrosting operation is preferably carried out quickly. In step (ii), component (C), which is uniformly dispersed in a matrix consisting of component (A) and a mixture of either (F-1) and (F-2) or two or more thereof, maintains its average particle size and the aforementioned dispersion state.

[0056] It is preferable to complete step (iii) as quickly as possible. At the end of step (iii), there is no substantial change in the dispersion state of the fine particles of component (C). After the completion of step (iii), the generated composition should be placed in a container and promptly stored in a freezer, refrigerator, or the like at a temperature of approximately -30 to -10°C, preferably -25 to -15°C. It is also preferable to use a vehicle equipped with refrigeration equipment for transportation. By storing and transporting the composition at low temperatures in this way, the composition and dispersion state of the present invention can be stably maintained, even during long-term storage.

[0057] The composition of the present invention, manufactured in this manner, is characterized in that, when the storage modulus G' of the thermally conductive silicone composition is measured using a viscoelasticity measuring device capable of measuring shear elasticity, with a program set to increase the temperature from 25°C to 125°C at 10°C / min, from 125°C to 145°C at 2°C / min, from 145°C to 150°C at 0.5°C / min, and then maintain at 150°C for 7,200 seconds, the value at which the storage modulus G' is maximum is defined as the curing rate of 100%, and the temperature at which the curing rate becomes 10% is 120°C or higher. Examples of viscoelasticity measuring devices capable of measuring shear elasticity include the viscoelasticity measuring device (ARES-G2: manufactured by TA Instruments Co., Ltd.). The composition of the present invention, which has a curing rate of 10% at a temperature of 120°C or higher, can be compressed to a predetermined thickness even when pressurization (compression) and curing are carried out simultaneously, as described below. The predetermined thickness depends on the pressurizing pressure, but as a guideline for a thickness that can obtain sufficient heat dissipation performance, for example, when pressurized at a pressure of 0.50 MPa, it is preferably 30.0 μm or less, more preferably 25.0 μm or less.

[0058] The composition of the present invention can be cured by holding it at a temperature of 80 to 180°C for about 30 to 240 minutes. The composition of the present invention may also be cured under pressure. The pressure during curing is not particularly limited, but 0.10 to 1.5 MPa is good, and 0.40 to 0.80 MPa is more preferable. Post-curing may also be performed after curing. The composition of the present invention can compress and cure an uncured material simultaneously, with the pressure being within the range described above. The curing temperature is preferably 100 to 170°C, and more preferably 120 to 170°C. Furthermore, the curing time is preferably 30 to 180 minutes, and more preferably 50 to 120 minutes. The cured product of the composition of the present invention can be used as a thermally conductive cured product for forming a thermally conductive layer by interposing it between a heat-generating electronic component and a heat-dissipating member. [Examples]

[0059] The present invention will be further described below with reference to examples, but the present invention is not limited thereto. The components (A) to (H) used in the following examples and comparative examples are shown below. Viscosity was measured using a spiral viscometer PC-ITL (manufactured by Malcolm Corporation), and kinematic viscosity was measured at 25°C using an Ostwald viscometer (manufactured by Shibata Scientific Co., Ltd.). The vinyl number was measured using the Hanus method in accordance with JIS K 0070, and the value was calculated from the obtained iodine number.

[0060] (A) Ingredients: Dimethylpolysiloxane with both ends sealed with dimethylvinylsilyl groups, having the following kinematic viscosity at 25°C; (A-1) Kinematic viscosity: 100mm 2 / s, vinyl value: 0.0400 mol / 100g (A-2) Kinematic viscosity: 600mm 2 / s, vinyl value: 0.0150 mol / 100g (A-3) Kinematic viscosity: 30,000mm 2 / s, vinyl value: 0.0036 mol / 100g

[0061] (B) Ingredients: (B-1) An organohydrogenpolysiloxane represented by the following structural formula, having a SiH content of 0.0015 mol / g [ka] (The order of the siloxane units in parentheses in the formula is undefined.) (B-2) Organohydrogenpolysiloxane represented by the following structural formula, with a SiH content of 0.0055 mol / g [ka] (The order of the siloxane units in parentheses in the formula is undefined.) (B-3) Organohydrogenpolysiloxane represented by the following structural formula, having a SiH content of 0.0013 mol / g [ka]

[0062] (C) Ingredients: (C-1) Metallic gallium (melting point = 29.8°C) (C-2) Ga-In alloy (mass ratio = 75.4:24.6, melting point = 15.7℃) (C-3) Ga-In-Sn alloy (mass ratio = 68.5:21.5:10, melting point = -19℃) (C-4)Ga-In-Sn alloy (mass ratio = 62:25:13, melting point = 5.0℃) (c-5) Metallic Indium (Melting point = 156.2℃) <For comparison>

[0063] (D) Ingredients: (D-1) Alumina powder (average particle size: 5.2 μm) (D-2) Zinc oxide powder (average particle size: 1.0 μm)

[0064] (E) Ingredients: (E-1) Dimethylpolysiloxane complex of platinum-divinyltetramethyldisiloxane (with both ends sealed with dimethylvinylsilyl groups, kinematic viscosity: 600 mmHg) 2 / s) solution (platinum atom content: 1% by mass)

[0065] (F) component: (F-1) Kinematic viscosity represented by the following structural formula: 32 mm 2 / s one-terminus trimethoxysilyl group sealed dimethylpolysiloxane [ka] (F-2) Structural formula C 10 H 21 Organosilanes represented by Si(OCH3)3 In the procedure for preparing the composition, "(F) component" refers to the combined (F-1) and (F-2) used in each example described in Table 1 or Table 2.

[0066] (G) Ingredients: (G-1)1-ethynyl-1-cyclohexanol

[0067] (H) Component: (H-1) 1.0% by mass of palladium-supported crystalline silica (average particle size of palladium powder: 2 nm, average particle size of crystalline silica: 5 μm)

[0068] [Examples 1-6, Comparative Examples 1-7] <Preparation of Composition> Each component was collected in the compositional ratios listed in Tables 1 and 2, and the compositions were prepared as follows. In a 250 ml internal volume conditioning mixer (manufactured by Thinky Co., Ltd., product name: Awatori Rentaro), components (A), (C), (D), (F), and (H) were added, and the mixture was heated to 70°C and kneaded for 5 minutes while maintaining that temperature. Then, the kneading was stopped and the mixture was cooled to 25°C. Next, components (B), (E), and (G) were added to a mixture of components (A), (C), (D), (F), and (H), and kneaded at 25°C until homogeneous to prepare each composition.

[0069] <Viscosity Measurement> The absolute viscosity of the compositions was measured using a Malcolm Corporation PC-1TL (10 rpm) at 25°C.

[0070] <Measurement of kinematic viscosity> Kinematic viscosity was measured using an Ostwald viscometer (manufactured by Shibata Scientific Co., Ltd.) at 25°C.

[0071] <Measurement of thermal conductivity> Each of the compositions obtained above was poured into a 3cm thick mold, covered with kitchen wrap, and measured using a Model QTM-500 manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0072] <(C) Particle size measurement> 0.1 g of each composition obtained above was sandwiched between two glass slides, and 10 particles were randomly selected from the images taken with a VHX-8000 digital microscope manufactured by Keyence Corporation. The particle size (or major axis in the case of elliptical particles) of each particle was measured, and the average value was calculated.

[0073] <Measurement of Storage Modulus> A silicone composition was applied to a thickness of 2 mm between two cross-hatch plates with a diameter of 2.5 cm. A program was created to heat the coated plates from 25°C to 125°C at a rate of 10°C / min, from 125°C to 145°C at a rate of 2°C / min, and from 145°C to 150°C at a rate of 0.5°C / min, and then maintain the temperature at 150°C for 7,200 seconds. The storage modulus G' was measured, and the value at which the storage modulus G' was maximized was defined as 100% curing rate, and the temperature at which the curing rate reached 10% was read. A viscoelasticity measuring device (ARES-G2: manufactured by TA Instruments Co., Ltd.) was used for the measurements.

[0074] <Measurement of thermal resistance> Each of the compositions obtained above was sandwiched between 15mm x 15mm x 1mm thick Ni plates, heated on a hot plate heated to 150°C for 5 minutes while applying a pressure of 0.50 MPa with a weight, and after removing the weight, it was heat-cured at 150°C for 60 minutes without pressure to prepare test specimens for thermal resistance measurement, and the thermal resistance was measured using a thermal resistance meter (NETZSCH model: LFA447).

[0075] <Measuring material thickness> The material thickness was measured using a test specimen prepared for thermal resistance measurement. The material thickness was calculated by first measuring the thickness of the Ni plate with a microgauge and subtracting this from the total thickness of the test specimen.

[0076] <(D) Particle size measurement> The average particle size of the thermally conductive filler is the volume-based cumulative average diameter measured using a Microtrac MT3300EX manufactured by Nikkiso Co., Ltd.

[0077] <(H) Component Particle Size Measurement> The average particle size of the palladium powder is the volume-based cumulative average diameter measured using a NanoTrac UPA-EX150 manufactured by Nikkiso Co., Ltd. The average particle size of the crystalline silica carrier is also the volume-based cumulative average diameter measured using a MicroTrac MT3300EX manufactured by Nikkiso Co., Ltd.

[0078] [Table 1]

[0079] [Table 2]

[0080] From the results in Tables 1 and 2, the thermally conductive silicone compositions of Examples 1 to 6 that satisfy the requirements of the present invention can yield a uniform grease-like composition, in which component (C), which is a thermally conductive filler, is uniformly dispersed in a fine particle state, and the material thickness can be compressed to a desired thickness. The resulting cured product can achieve high heat dissipation performance. On the other hand, in Comparative Example 1, where the amount of catalyst was small, the material did not harden. In Comparative Example 2, where the amount of catalyst was large, in Comparative Example 3, where the H / Vi ratio was too high, and in Comparative Example 5, where the amount of component (C), a thermally conductive filler, was small, the hardening was too fast, preventing the material from being compressed to the desired thickness, resulting in poor heat dissipation performance. Furthermore, in Comparative Example 6, where the content of component (C) was too high, and in Comparative Example 7, where the melting point of component (C) was too high, a uniform, grease-like composition could not be obtained. [Industrial applicability]

[0081] The thermally conductive silicone composition of the present invention has good thermal conductivity, and by adjusting the curing speed, the compression and heat curing processes of the material can be carried out simultaneously during the package assembly process, thereby enabling high efficiency in the assembly process. Furthermore, by using it between an IC package such as a CPU and a heat dissipation member having heat dissipation fins, it is possible to efficiently remove heat.

Claims

1. (A) Kinematic viscosity at 25°C is 10 to 1,000,000 mm² 2 Organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to a silicon atom of / s at the end of the molecular chain in one molecule: 100 parts by mass, (B) Organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule: an amount such that the number of hydrogen atoms bonded to silicon atoms in component (A) is 0.5 to 5.0 per alkenyl group in the component. (C) One or more substances selected from the group consisting of gallium and gallium alloys, having a melting point of -20 to 70°C: 3,000 to 12,000 parts by mass, (D) Thermally conductive filler with an average particle size of 0.1 to 100 μm: 10 to 1,000 parts by mass, (E) Platinum group metal catalyst: an amount such that the platinum atom content is 1 to 25 ppm relative to the component (A), (F-1) Organopolysiloxane represented by the following general formula (1): 0.1 to 500 parts by mass 【Chemistry 1】 (In formula (1), R 1 R independently represents an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms that does not have an aliphatic unsaturated bond, 2 (These are independently alkyl groups, alkenyl groups, or acyl groups. Also, a is a number from 5 to 100, and b is a number from 1 to 3.) and (G) One or more addition reaction control agents selected from the group consisting of acetylene compounds, nitrogen compounds, organophosphorus compounds, oxime compounds and organochloro compounds: 0.1 to 5 parts by mass per 100 parts by mass of component (A) A thermally conductive silicone composition containing, A thermally conductive silicone composition characterized in that, when measuring the storage modulus G' of the thermally conductive silicone composition using a viscoelasticity measuring device capable of measuring shear elasticity, and programming the temperature to be raised from 25°C to 125°C at 10°C / min, from 125°C to 145°C at 2°C / min, from 145°C to 150°C at 0.5°C / min, and then maintained at 150°C for 7,200 seconds, the value at which the storage modulus G' is maximized is defined as the curing rate of 100%, and the temperature at which the curing rate becomes 10% is 120°C or higher.

2. Furthermore, the thermally conductive silicone composition according to claim 1, further comprising (H) silica supported with palladium powder having an average particle size of 1 to 100 nm, in an amount of 0.00001 to 1.0 parts by mass per 100 parts by mass of component (A) as palladium atoms.

3. Furthermore, (F-2) General formula (2) below: 【Chemistry 2】 (In formula (2), R 3 R is an alkyl group having 6 to 16 carbon atoms, 4 R is an independent unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, 5 (Each is an alkyl group having 1 to 6 carbon atoms, c is an integer from 1 to 3, d is an integer from 0 to 2, and the sum of c + d is an integer from 1 to 3.) The thermally conductive silicone composition according to claim 1, comprising 0.1 to 100 parts by mass of an alkoxysilane compound represented by (A) per 100 parts by mass 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 parts measuring 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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