Thermally conductive silicone composition and cured product thereof

Abstract

Provided is a thermally conductive silicone composition which can be compressed to a thickness at which sufficient heat dissipation performance can be obtained even when a step for crushing a material and a heat curing step are performed simultaneously. This thermally conductive silicone composition comprises (A) an organopolysiloxane having an aliphatic unsaturated hydrocarbon group bonded to a silicon atom, (B) an organohydrogenpolysiloxane, (C) gallium and / or an alloy thereof that have a melting point of -20°C 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 having a molecular chain terminal blocked with a hydrolyzable group, and (G) an addition reaction control agent, the thermally conductive silicone composition being characterized in that when a value at which the storage elastic modulus G' of the composition is maximized is defined as a curing rate of 100%, the temperature at which the curing rate is 10% is 120°C or higher.

Description

Thermally conductive silicone composition and its cured product

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

[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 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 without creating gaps between the two, resulting in 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 suppressed to avoid problems with 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 etc. using a syringe, etc. In both cases, the upper limit of the amount of thermal conductive filler that can be blended is limited, resulting in the disadvantage that a sufficient thermal conductivity effect 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).

[0005] Japanese Patent Publication No. 2013-082816

[0006] In the process of assembling a heat-conductive grease into a package as a heat-dissipating 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-dissipating material to a predetermined thickness, resulting in insufficient heat dissipation performance. The present invention has been made in view of the above problem, and aims to provide a heat-conductive silicone composition that can be compressed to a thickness that provides sufficient heat dissipation performance even when the crushing (pressure or compression) step and the heat curing step are performed simultaneously.

[0007] The present inventors, through diligent research to solve the above problems, have found that by blending a small amount of catalyst into a silicone composition containing low-melting-point gallium and / or its alloy and a thermally conductive filler, a composition in which the gallium and / or its alloy is uniformly dispersed in a fine particle state can be easily obtained. Furthermore, even in a process where the material is crushed and the heat curing process is carried out simultaneously when assembling the composition into a package, the heat dissipation grease can be compressed to a predetermined thickness, and sufficient heat dissipation performance can be obtained. This led to the completion of the present invention. That is, the present invention provides the following thermally conductive silicone composition: <1> (A) Kinematic viscosity at 25°C is 10 to 1,000,000 mm 2(A) Organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in 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: in 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 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) 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: in an amount such that it is 1 to 25 ppm of platinum atoms relative to component (A), (F-1) Organopolysiloxane represented by the following general formula (1): 0.1 to 500 parts by mass (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 (A) is independently an alkyl group, an alkenyl group, or an acyl group. Also, a is an integer from 5 to 100, and b is an integer 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: a thermally conductive silicone composition containing 0.1 to 5 parts by mass per 100 parts by mass of component (A), wherein 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. <2> The thermally conductive silicone composition according to <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) the following general formula (2): (In formula (2), R 3is independently an alkyl group having 6 to 16 carbon atoms, R 4 is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, R 5 is independently an alkyl group having 1 to 6 carbon atoms, c is an integer of 1 to 3, d is an integer of 0 to 2, and the sum of c + d is an integer of 1 to 3.), an alkoxysilane compound represented by the formula (1) is contained in an amount of 0.1 to 100 parts by mass with respect to 100 parts by mass of the component (A). The thermally conductive silicone composition according to <1> or <2>. <4> The thermally conductive silicone composition according to any one of <1> to <3>, wherein the component (C) is dispersed in the composition in a particulate form of 1 to 200 μm. <5> A cured product of the thermally conductive silicone composition according to any one of <1> to <4>.

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

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

[0010] [Thermally 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 at the molecular chain terminals, 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. When the kinematic viscosity is less than 10 mm 2 / s, the cured product becomes brittle and is likely to crack. When it is 1,000,000 mm2 If the value is greater than / s, the viscosity of the composition becomes too high, making it difficult to handle. In this invention, the kinematic viscosity is the value obtained at 25°C using 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] The number of aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in component (A) should be two or more per molecule, preferably two to six, and more preferably two to four. Examples of these aliphatic unsaturated hydrocarbon groups include alkenyl groups such as vinyl, allyl, 1-butenyl, and 1-hexenyl groups, but vinyl groups are preferred in terms of ease of synthesis and cost. To ensure good flexibility of the resulting cured product, it is preferable that component (A) has these aliphatic unsaturated hydrocarbon groups bonded only to silicon atoms at the ends 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 are methyl groups.

[0015] Preferable specific examples of such organopolysiloxanes include polydimethylsiloxane blocked at both molecular chain ends with dimethylvinylsiloxy groups, polydimethylsiloxane blocked at both molecular chain ends with methyldivinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymer blocked at both molecular chain ends with dimethylvinylsiloxy groups, and the like. The organopolysiloxane as component (A) may be used alone or in combination of two or more. The blending amount of component (A) is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the whole heat conductive silicone composition of the present invention.

[0016] <(B) Organohydrogenpolysiloxane> Component (B) of the composition of the present invention 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) above. That is, the Si-H groups in this component (B) are added by a hydrosilylation reaction to the alkenyl groups in component (A) by the action of the platinum-based catalyst of component (E) described later, to give a crosslinked cured product having a three-dimensional network structure with crosslinking bonds.

[0017] The number of Si-H groups in component (B) is two or more in one molecule, and 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 ones, such as linear, cyclic, branched, three-dimensional network (resinous), etc. 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, still 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 / 2A 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 composed of units, etc.

[0020] The blending amount of component (B) is such that the number of Si-H groups in component (B) is 0.5 to 5.0 with respect to one aliphatic unsaturated hydrocarbon group bonded to a silicon atom in component (A), and a range of 0.7 to 3.0 is preferable. If the blending amount of component (B) is less than the above lower limit, the composition cannot be sufficiently crosslinked, so the grease cannot be sufficiently cured. If it exceeds the above upper limit, the resulting thermally conductive silicone composition may become too hard and its reliability may deteriorate, and foaming may easily occur. The organohydrogenpolysiloxane of component (B) may be used alone or in combination of two or more.

[0021] <(C) Gallium and / or its alloy> The component (C) of the composition of the present invention is gallium and / or its alloy having a melting point of -20 to 70°C. This component (C) is a component blended to impart good thermal conductivity to the cured product obtained from the composition of the present invention, and the blending of this component is a 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 economically undesirable. Conversely, if the melting point exceeds 70°C, it 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; for example, 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; for example, Ga-Sn-Zn (mass ratio = 82:12:6, melting point = 17°C), and gallium-indium-tin alloys; for example 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 shape of the liquid or solid fine particles of gallium and / or its alloy present in the uncured composition of the present invention is generally spherical, but irregular shapes may be included. The average particle size is usually 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 it is too large, the composition becomes non-uniform, making it difficult to apply a thin film to heat-generating electronic components, etc. The shape, average particle size, and dispersion state in the composition can be maintained until the coating process for heat-generating electronic components, etc., if the composition is stored at a low temperature immediately after preparation. The average particle size was calculated by sandwiching the composition before curing between two glass slides and observing it with a digital microscope (for example, a VHX-8000 manufactured by Keyence Corporation). Specifically, ten 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, together with component (C) above, (D) a thermally conductive filler (excluding component (C)) that is conventionally known to be incorporated into thermally conductive sheets or thermally conductive greases.

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

[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 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 of component (E) in 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 contain the palladium powder of component (H) 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 is formulated with 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) described 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 mm at 25°C. 2 The value is / s. This kinematic viscosity was measured at 25°C using an Ostwald viscometer. 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 Control Agent> The addition reaction control agent of component (G) of the composition of the present invention is a component that is formulated to suppress the hydrosilylation reaction in 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) used varies depending on the amount of component (E) used and cannot be stated definitively, but it should be an effective amount that can suppress the progress of the hydrosilylation reaction. 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 used diluted with an organic solvent such as toluene, xylene, or isopropyl alcohol as needed. Component (G) may be used alone or in combination of two or more types.

[0041] <Other Components> In addition to the essential components listed above, the following components may be added to the thermally conductive silicone composition of the present invention as needed. <(H) Palladium Powder> Silica supported with palladium powder having an average particle size of 1 to 100 nm, which is component (H) of 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 a 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> The composition of the present invention may also further contain the following alkoxysilane as component (F-2): (F-2) General formula (2) below: (In formula (2), R 3 R is an alkyl group having 9 to 16 carbon atoms, 4 R is an 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) 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] Furthermore, R in the above general formula (2) 4Examples of these 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] Furthermore, R in the above general formula (2) 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.

[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 does not increase and it 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 mentioned 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 viscosity of the silicone composition of the present invention is preferably in the range of 10 to 1,000 Pa·s, and more preferably 30 to 400 Pa·s, when 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 can be obtained by a manufacturing method comprising: (i) kneading the above (A), (C), (D), and (F-1), and if present, the above (F-2) and the above (H) at a temperature in the range of 20 to 120°C and above the melting point of the above (C) 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 the above (C) to obtain mixture (ii); and (iii) adding the above (B), the above (E), and the above (G), and optionally other components, to mixture (ii) and kneading at a temperature below the melting point of the above (C) to obtain a homogeneous mixture (iii).

[0054] In step (i) above, the silica supporting the liquid gallium and / or alloy thereof 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 thereof.

[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 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 composition 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 that increases 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 maintains 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 reaches 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, in which the temperature at which the curing rate reaches 10% is 120°C or higher, can be compressed to a predetermined thickness even when pressurization (compression) and curing are performed 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, and 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 preferred, and 0.40 to 0.80 MPa is more preferred. Post-curing may also be performed after curing. The composition of the present invention can be compressed and cured simultaneously with the uncured material, and the pressure used during this process may be 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 to form a thermally conductive layer by interposing it between a heat-generating electronic component and a heat-dissipating member.

[0059] The present invention will be further described below with reference to examples, but the present invention is not limited thereto. Components (A) to (H) used in the following examples and comparative examples are shown below. The viscosity was measured using a spiral viscometer PC-ITL (manufactured by Malcolm Corporation), and the 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) Components: Dimethylpolysiloxane with both ends sealed with dimethylvinylsilyl groups, having the following kinematic viscosity at 25°C; (A-1) Kinematic viscosity: 100 mm 2 / s, vinyl value: 0.0400 mol / 100g (A-2) kinematic viscosity: 600 mm 2 / s, vinyl value: 0.0150 mol / 100g (A-3) kinematic viscosity: 30,000 mm² 2 / s, vinyl value: 0.0036 mol / 100g

[0061] (B) Component: (B-1) Organohydrogenpolysiloxane represented by the following structural formula, having an SiH content of 0.0015 mol / g (In the formula, the order of the siloxane units in parentheses is undefined.) (B-2) Organohydrogenpolysiloxane represented by the following structural formula, having an SiH content of 0.0055 mol / g (In the formula, the order of the siloxane units in parentheses is undefined.) (B-3) Organohydrogenpolysiloxane represented by the following structural formula, having an SiH content of 0.0013 mol / g

[0062] (C) Components: (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) (C-3) Ga-In-Sn alloy (mass ratio = 68.5:21.5:10, melting point = -19°C) (C-4) Ga-In-Sn alloy (mass ratio = 62:25:13, melting point = 5.0°C) (C-5) Metallic indium (melting point = 156.2°C) <For comparison>

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

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

[0065] (F) Component: (F-1) Kinematic viscosity represented by the following structural formula: 32 mm² 2 / s one-terminus trimethoxysilyl group-blocked dimethylpolysiloxane (F-2) Structural formula C 10 H 21 An organosilane 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) Ingredient: (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 Compositions> Each component was taken in the composition ratios shown in Tables 1 and 2, and the compositions were prepared as follows. Components (A), (C), (D), (F), and (H) were added to a 250 ml internal volume conditioning mixer (manufactured by Thinky Co., Ltd., product name: Awatori Rentaro), and the mixture was heated to 70°C and kneaded for 5 minutes while maintaining the temperature. Then, the kneading was stopped and the mixture was cooled to 25°C. Next, components (B), (E), and (G) were added to the mixture of components (A), (C), (D), (F), and (H), and the mixture was kneaded at 25°C until uniform to prepare each composition.

[0069] <Viscosity Measurement> The absolute viscosity of the composition was measured using a Malcolm Co., Ltd. PC-1TL (10 rpm) measuring device, all 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 3 cm 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 of Component> 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 an ellipse) 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 maximum 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 measurement.

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

[0075] <Measurement of Material Thickness> The material thickness was measured using a test specimen prepared for measuring thermal resistance. The material thickness was calculated by first measuring the thickness of the Ni plate with a microgauge and subtracting it 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) 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 the volume-based cumulative average diameter measured using a MicroTrac MT3300EX manufactured by Nikkiso Co., Ltd.

[0078]

[0079]

[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 yield a uniform grease-like composition, the thermally conductive filler component (C) is uniformly dispersed in a fine particle state, and the material thickness can be compressed to the 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 Si-H / Si-Vi ratio was too high, and in Comparative Example 5, where the amount of the thermally conductive filler component (C) was small, hardening occurred too quickly, preventing the material from being compressed to the predetermined thickness, resulting in low 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.

[0081] The thermally conductive silicone composition of the present invention has good thermal conductivity, and by adjusting the curing rate, 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 (A) Organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in 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: in 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 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) 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: in an amount such that it is 1 to 25 ppm of platinum atoms relative to component (A), (F-1) Organopolysiloxane represented by the following general formula (1): 0.1 to 500 parts by mass (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 (A) 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.) 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: a thermally conductive silicone composition containing 0.1 to 5 parts by mass per 100 parts by mass of component (A), wherein 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.

2. 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: (In formula (2), R 3 R is an alkyl group having 6 to 16 carbon atoms, 4 R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, 5 The thermally conductive silicone composition according to claim 1, comprising 0.1 to 100 parts by mass of an alkoxysilane compound represented by (c) (where c is an alkyl group having 1 to 6 carbon atoms independently, 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) 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.

Images