Thermally conductive addition-curable silicone composition

Abstract

The present invention is a thermally conductive addition-curable silicone composition comprising: (A) an organopolysiloxane having at least one alkynyl group in one molecule and having a kinetic viscosity at 25°C of 60-100,000 mm2 / s; (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and allotropes of carbon; (C) an organohydrogenpolysiloxane having, in one molecule, two or more hydrogen atoms each bonded to a silicon atom; (D) a platinum group metal catalyst; and (E) one or more addition curing reaction control agents selected from the group consisting of acetylene compounds, nitrogen compounds, organophosphorus compounds, oxime compounds, and organochlorine compounds. Thereby provided is a thermally conductive addition-curable silicone composition which provides a cured product having a low storage elastic modulus G' and a high elongation when the composition is heated and cured.

Description

Thermally conductive addition-curable silicone composition

[0001] The present invention relates to a thermally conductive addition-curable silicone composition.

[0002] A common problem with electronic component packages and power modules is the generation of heat during operation and the resulting degradation of performance. Various heat dissipation technologies have been used to solve this problem. In particular, a common technology is to dissipate heat by placing a cooling member near the heat-generating part in close contact with the cooling member and then efficiently removing heat from the cooling member.

[0003] In this case, if there is a gap between the heat-generating part and the cooling member, the air with poor thermal conductivity will get in, reducing heat transfer and preventing the temperature of the heat-generating part from dropping sufficiently. To prevent this air from getting in and improve heat conduction, heat-dissipating materials with good thermal conductivity and conformability to the surface of the part, such as thermal grease and thermal dissipation sheets, are used.

[0004] As a heat countermeasure for actual electronic component packages and power modules, thermal grease that can be compressed thin and has excellent penetration ability into the gap between the heat-generating part and the cooling member is suitable from the viewpoint of heat dissipation performance. Furthermore, addition-curing thermal grease is particularly useful because it can be compressed to the desired thickness and then heat-cured to prevent the heat-generating grease from flowing out (pumping out) due to expansion and contraction caused by the thermal history of repeated heating and cooling of the heat-generating part, thereby improving the reliability of electronic component packages and power modules (for example, Patent Document 1).

[0005] In recent years, with the increasing area and complexity of electronic component packages and power modules, electronic component packages and power modules can sometimes experience very large warpage. For electronic component packages and power modules with large warpage, addition-curable thermal greases that cure softly, i.e., have a low storage modulus G' of the cured product, are often used to accommodate the warpage. On the other hand, addition-curable thermal greases that produce highly elongated cured products are effective for accommodating the expansion and contraction caused by the thermal history of repeated heating and cooling of heat-generating components over long periods of time. Generally, addition-curable thermal greases with a low storage modulus G' of the cured product produce a putty-like cured product, making them less likely to produce highly elongated cured products. Addition-curable thermal greases that produce highly elongated cured products produce cured products with high hardness and strength.

[0006] JP 2016-053140 A

[0007] The present invention has been made in view of the above circumstances, and its object is to provide a thermally conductive addition-curable silicone composition that, when heat-cured, gives a cured product that has a low storage modulus G' and high elongation.

[0008] In order to solve the above problems, the present invention provides a thermally conductive addition-curable silicone composition, comprising: (A) a silicone compound having at least one alkynyl group per molecule and having a kinematic viscosity at 25°C of 60 to 100,000 mm 2 (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes, in an amount that is 10 to 96 mass % based on the total composition; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, in an amount that provides 0.5 to 10 Si—H groups in component (C) relative to the total number of alkynyl groups in component (A); (D) an effective amount of a platinum group metal catalyst; and (E) one or more addition cure reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds, in an amount that is 0.05 to 5 parts by mass based on 100 parts by mass of component (A).

[0009] The thermally conductive addition-curable silicone composition of the present invention, when heat-cured, gives a cured product that has a low storage modulus G' and high elongation.

[0010] The thermally conductive addition-curable silicone composition of the present invention preferably contains, as component (F), an organopolysiloxane represented by the following general formula (1) in an amount of 0.5 to 10 mass % based on the total mass of the silicone composition: (In the formula, R 1 represents a monovalent hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent and does not have an aliphatic unsaturated bond, and each R 1 may be the same or different, and m is an integer of 5 to 100.

[0011] In the thermally conductive addition-curable silicone composition of the present invention, component (F) is used to treat the surface of the thermally conductive filler, and plays a role in assisting in achieving high loadings of the filler.

[0012] Furthermore, the thermally conductive addition-curable silicone composition of the present invention preferably contains, as component (G), 0.1 to 10 mass % of an organosilane represented by the following general formula (2) and / or its (partial) hydrolysis condensate, based on the total mass of the silicone composition: ２ ａ Si(OR ３ ) ４－ａ (2) (R ２ are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups having 1 to 20 carbon atoms, and R ３ are independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and a is an integer of 1 to 3.

[0013] In the thermally conductive addition-curable silicone composition of the present invention, component (G) is used to treat the surface of the thermally conductive filler, and plays a role in assisting in achieving high loadings of the filler.

[0014] In the thermally conductive addition-curable silicone composition of the present invention, component (A) is preferably an organopolysiloxane having at least two alkynyl groups per molecule.

[0015] Furthermore, in the thermally conductive addition-curable silicone composition of the present invention, component (A) is preferably an organopolysiloxane having at least two ethynyl groups per molecule.

[0016] When the heat-cured thermally conductive addition-curable silicone composition of the present invention is heated, it gives a cured product that has a low storage modulus G' and high elongation.

[0017] As described above, the thermally conductive addition-curable silicone composition of the present invention, when heat-cured, gives a cured product that has a low storage modulus G' and high elongation. As a result, it can be used favorably in electronic component packages and power modules that are prone to significant warpage, and it can also accommodate expansion and contraction caused by the thermal history of repeated heating and cooling of heat-generating parts over long periods of time.

[0018] As described above, there has been a need for the development of a thermally conductive addition-curable silicone composition that provides a cured product with a low storage modulus G' and high elongation.

[0019] As a result of extensive research into the above-mentioned problems, the present inventors discovered that a thermally conductive addition-curable silicone composition containing the above-mentioned components (A) to (E) can give a cured product that has a low storage modulus G' and high elongation, and thus completed the present invention.

[0020] That is, the present invention provides a thermally conductive addition-curable silicone composition, comprising: (A) a silicone compound having at least one alkynyl group per molecule and having a kinematic viscosity at 25°C of 60 to 100,000 mm 2(B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes, in an amount that is 10 to 96% by mass based on the total composition; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, in an amount that provides 0.5 to 10 Si—H groups in component (C) relative to the total number of alkynyl groups in component (A); (D) an effective amount of a platinum group metal catalyst; and (E) 0.05 to 5 parts by mass of one or more addition cure reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds, based on 100 parts by mass of component (A).

[0021] The present invention will be described in detail below, but the present invention is not limited thereto.

[0022] [Component (A)] Component (A) is a copolymer having at least one, preferably 1 to 100, and more preferably 2 to 50 alkynyl groups per molecule, and a kinematic viscosity at 25°C of 60 to 100,000 mm 2 and organopolysiloxanes in which

[0023] The alkynyl group is preferably a monovalent hydrocarbon group having a carbon-carbon triple bond and having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms. Examples include terminal alkynes such as ethynyl groups and propargyl groups, and internal alkynes having a group other than a hydrogen atom on the carbon atom forming the carbon-carbon triple bond. A terminal alkyne is preferred, and an ethynyl group is more preferred.

[0024] The alkynyl group may be bonded to either a silicon atom at the terminal of the molecular chain or to a silicon atom in the middle of the molecular chain, or to both.

[0025] The organic group other than an alkynyl group bonded to a silicon atom of the organopolysiloxane is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms. Examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, bromine, or chlorine, or with cyano groups, such as chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, and cyanoethyl. Methyl and phenyl groups are particularly preferred.

[0026] The organopolysiloxane has a kinematic viscosity at 25°C of 60 to 100,000 mm 2 / s, preferably 100 to 30,000 mm 2 / s. The kinematic viscosity is 60 mm 2 If the viscosity is less than 100,000 mm / s, the physical properties of the thermally conductive addition-curable silicone composition of the present invention will be reduced, and 2 If the viscosity exceeds 1 / s, the silicone composition will have poor extensibility.

[0027] In the present invention, the kinematic viscosity is a value measured at 25° C. using an Ubbelohde-type Ostwald viscometer (the same applies hereinafter).

[0028] The molecular structure of the organopolysiloxane is not particularly limited as long as it has the above properties, and examples thereof include a linear structure, a branched structure, and a linear structure having a partially branched or cyclic structure. In particular, an organopolysiloxane having a linear structure in which the main chain is composed of repeating diorganosiloxane units and both molecular chain terminals are blocked with triorganosiloxy groups is preferred. Organopolysiloxanes having a linear structure may also have a partially branched or cyclic structure.

[0029] The blend amount of component (A) is preferably 1.5 to 90 mass %, more preferably 1.7 to 20 mass %, and even more preferably 1.8 to 10 mass %, of the entire thermally conductive silicone composition of the present invention. If it is in this range of 1.5 to 90 mass %, the thermally conductive addition-curable silicone composition of the present invention will have sufficient thermal conductivity, an appropriate increase in viscosity, and excellent workability.

[0030] The organopolysiloxanes may be used singly or in combination of two or more.

[0031] [Component (B)] Component (B) is one or more thermally conductive fillers selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes. Examples include aluminum, silver, copper, metallic silicon, zinc oxide, magnesium oxide, aluminum oxide (alumina), silicon dioxide, cerium oxide, iron oxide, aluminum hydroxide, cerium hydroxide, aluminum nitride, boron nitride, silicon carbide, diamond, graphite, carbon nanotubes, and graphene. These may be used alone or in appropriate combinations of two or more, and are preferably a combination of a large particle component and a small particle component (a combination of components with different average particle sizes).

[0032] The average particle size of the large particle component is preferably in the range of 0.1 to 300 μm, more preferably in the range of 5 to 200 μm, and even more preferably in the range of 10 to 150 μm. The average particle size of the small particle component is preferably in the range of 0.01 μm to 10 μm, and more preferably in the range of 0.1 to 5 μm. Within these ranges, the thermally conductive addition-curable silicone composition of the present invention has an appropriate viscosity, excellent extensibility, and the resulting silicone composition is uniform.

[0033] The ratio of the large particle component to the small particle component is not particularly limited, but is preferably in the range of 9:1 to 1:9 (mass ratio). The shapes of the large particle component and the small particle component are not particularly limited and may be spherical, irregular, acicular, etc.

[0034] The average particle size can be determined, for example, as the volume-based average value (median diameter) in particle size distribution measurement by laser light diffraction method.

[0035] The blending amount of component (B) is 10 to 96 mass % of the entire thermally conductive addition-curable silicone composition of the present invention, preferably 40 to 95.5 mass %, more preferably 70 to 95 mass %, and even more preferably 85 to 93 mass %. If it is more than 96 mass %, the silicone composition will have poor extensibility, and if it is less than 10 mass %, the thermal conductivity will be poor.

[0036] [Component (C)] Component (C) is an organohydrogenpolysiloxane having two or more, preferably 2 to 100, and more preferably 2 to 50 hydrogen atoms bonded to silicon atoms (Si—H groups) per molecule. Any organohydrogenpolysiloxane may be used as long as the Si—H groups in the molecule can undergo an addition reaction with the aliphatic unsaturated hydrocarbon groups in component (A) in the presence of a platinum group metal catalyst to form a crosslinked structure.

[0037] The molecular structure of the organohydrogenpolysiloxane is not particularly limited as long as it has the above properties, and examples thereof include a linear structure, a branched structure, a cyclic structure, and a linear structure partially having a branched or cyclic structure, with linear structures and cyclic structures being preferred.

[0038] The organohydrogenpolysiloxane preferably has a kinematic viscosity at 25°C of 1 to 1,000 mm 2 / s, more preferably 10 to 300 mm 2 / s. The kinematic viscosity is 1 mm 2 / s or more, the physical properties of the thermally conductive addition-curable silicone composition of the present invention are appropriate, and 2 If the viscosity is 1 / s or less, the silicone composition will have sufficient extensibility.

[0039] The organic group bonded to the silicon atom of the organohydrogenpolysiloxane may be an unsubstituted or substituted monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon group. It is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms. Examples include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; aralkyl groups such as 2-phenylethyl and 2-phenylpropyl; and groups in which some or all of the hydrogen atoms have been substituted with halogen atoms such as fluorine, bromine, and chlorine, cyano groups, or epoxy ring-containing organic groups (glycidyl or glycidyloxy-substituted alkyl groups), such as chloromethyl, chloropropyl, bromoethyl, trifluoropropyl, cyanoethyl, 2-glycidoxyethyl, 3-glycidoxypropyl, and 4-glycidoxybutyl. Of these, methyl and phenyl groups are preferred.

[0040] The organohydrogenpolysiloxanes may be used singly or in combination of two or more.

[0041] The amount of organohydrogenpolysiloxane in component (C) is an effective amount sufficient to form a cured product from the thermally conductive silicone composition of the present invention, and is an amount such that the ratio of the number of Si—H groups in component (C) to the total number of alkynyl groups in component (A) is 0.5 to 10, preferably 0.7 to 7.5, and more preferably 0.9 to 5.0. If the amount of component (C) is less than 0.5, the addition reaction will not proceed sufficiently, resulting in insufficient crosslinking. If the amount exceeds 10, the crosslinked structure will be non-uniform, which can significantly reduce the shelf life of the composition.

[0042] [Component (D)] Component (D) is a platinum group metal catalyst. It functions to promote the addition reaction of the above-mentioned components. Any conventionally known platinum group metal catalyst used in addition reactions can be used. Examples include platinum-based, palladium-based, and rhodium-based catalysts, with platinum or platinum compounds being preferred, as they are relatively easy to obtain. Specific examples include platinum itself, platinum black, chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds. The platinum group metal catalysts may be used alone or in combination of two or more.

[0043] The amount of component (D) to be blended should be an effective amount as a catalyst, i.e., an effective amount required to promote the addition reaction and cure the thermally conductive addition-curable silicone composition of the present invention. The amount is preferably 0.01 to 10 ppm, more preferably 0.1 to 5 ppm, and even more preferably 0.2 to 3 ppm, calculated as platinum group metal atoms, based on the total mass of the thermally conductive silicone composition of the present invention. A catalyst amount in the range of 0.01 to 10 ppm provides sufficient catalytic effect and is economical. Furthermore, the composition also has sufficient storage stability at 25°C.

[0044] Furthermore, the catalyst of component (D) may be diluted with an organo(poly)siloxane, toluene, or the like to improve dispersibility in the thermally conductive addition-curable silicone composition.

[0045] [Component (E)] Component (E) is one or more addition curing reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. Component (E) is an addition curing reaction inhibitor that suppresses the progress of the hydrosilylation reaction at room temperature and can be added to extend shelf life and pot life. The addition curing reaction inhibitor can be any reaction inhibitor known in the art for use in thermally conductive addition-curable silicone compositions. Examples of such reaction inhibitors include acetylene compounds such as acetylene alcohols (e.g., ethynylmethyldecylcarbinol, 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol), various nitrogen compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, organic phosphorus compounds such as triphenylphosphine, oxime compounds, and organic chloro compounds.

[0046] The amount of component (E) added should be an effective amount as an addition curing reaction inhibitor, i.e., an effective amount necessary to achieve the desired shelf life and pot life. It should be 0.05 to 5 parts by mass, and preferably 0.1 to 2 parts by mass, per 100 parts by mass of component (A). If the amount of addition curing reaction inhibitor is less than 0.05 part by mass, the desired sufficient shelf life and pot life may not be achieved, while if it is more than 5 parts by mass, the curability of the thermally conductive addition-curable silicone composition of the present invention may be reduced.

[0047] The addition cure reaction inhibitor may be diluted with organo(poly)siloxane, toluene, or the like to improve dispersibility in the thermally conductive addition cure silicone composition of the present invention.

[0048] In addition to the above components (A) to (E), the following optional components may also be added to the thermally conductive addition-curable silicone composition of the present invention, if necessary.

[0049] [Component (F)] Component (F) is an organopolysiloxane represented by the following general formula (1): Component (F) is used to treat the surface of the thermally conductive filler and plays a role in assisting in increasing the loading of the filler. (In the formula, R1 represents a monovalent hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent and does not have an aliphatic unsaturated bond, and each R 1 may be the same or different, and m is an integer of 5 to 100.

[0050] In the above formula (1), R １ is a monovalent hydrocarbon group having 1 to 10 carbon atoms which may have a substituent, is preferably a monovalent saturated aliphatic hydrocarbon group which may have a substituent, or a monovalent aromatic hydrocarbon group which may have a substituent, and is more preferably a monovalent saturated aliphatic hydrocarbon group which may have a substituent.

[0051] Specific examples of the monovalent saturated aliphatic hydrocarbon group which may have a substituent include linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl, branched alkyl groups such as isopropyl, isobutyl, tert-butyl, isopentyl, and neopentyl, cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl, and halogen-substituted alkyl groups such as chloromethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, and bromopropyl. The number of carbon atoms is preferably 1 to 10, more preferably 1 to 8, and even more preferably 1 to 6.

[0052] Specific examples of the monovalent aromatic hydrocarbon group which may have a substituent include aryl groups such as a phenyl group or a tolyl group, aralkyl groups such as a benzyl group or a 2-phenylethyl group, and halogen-substituted aryl groups such as an α,α,α-trifluorotolyl group or a chlorobenzyl group. The number of carbon atoms in the monovalent aromatic hydrocarbon group is preferably 6 to 10, more preferably 6 to 8, and even more preferably 6.

[0053] In the above formula (1), R １Among these, methyl, ethyl, 3,3,3-trifluoropropyl and phenyl groups are preferred, methyl, ethyl and phenyl groups are more preferred, and methyl group is particularly preferred.

[0054] In the above formula (1), m is an integer between 5 and 100, preferably between 5 and 80, and more preferably between 10 and 60. When the value of m is 5 or greater, oil bleeding from the silicone composition is suppressed, and pumping-out resistance is improved. Furthermore, when the value of m is 100 or less, sufficient wettability with the filler is achieved, the viscosity of the thermally conductive silicone composition of the present invention is appropriate, and application workability is improved.

[0055] The blend amount of component (F) is preferably 0.5 to 10% by mass, and more preferably 1.0 to 8.0% by mass, based on the total mass of the thermally conductive silicone composition of the present invention. A blend amount of 0.5 to 10% by mass allows the silicone composition to have an appropriate viscosity range.

[0056] The component (F) may be used alone or in combination of two or more.

[0057] [Component (G)] The component (G) is an organosilane represented by the following general formula (2) and / or its (partial) hydrolysis condensate (partial hydrolysis condensate, hydrolysis condensate): ２ ａ Si(OR ３ ) ４－ａ (2) (R ２ are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups having 1 to 20 carbon atoms, and R ３ are independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and a is an integer of 1 to 3.

[0058] Component (G) is used to treat the surface of the thermally conductive filler, and plays a role in assisting in increasing the loading of the filler.

[0059] In the above formula (2), R ２Examples of the alkyl group include alkyl groups, cycloalkyl groups, and alkenyl groups, and specific examples thereof include alkyl groups such as methyl group, ethyl group, propyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, and octadecyl group; cycloalkyl groups such as cyclopentyl group and cyclohexyl group; alkenyl groups such as vinyl group and allyl group; aryl groups such as phenyl group and tolyl group; aralkyl groups such as 2-phenylethyl group and 2-methyl-2-phenylethyl group; and halogenated hydrocarbon groups such as 3,3,3-trifluoropropyl group, 2-(perfluorobutyl)ethyl group, 2-(perfluorooctyl)ethyl group, and p-chlorophenyl group.

[0060] In the above formula (2), a is 1, 2 or 3, with 1 being particularly preferred.

[0061] In the above formula (2), R ３ The alkyl group may be a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0062] The blend amount of component (G) is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5.0% by mass, of the entire thermally conductive silicone composition of the present invention. A blend amount of 0.1 to 10% by mass allows the thermally conductive silicone composition to have an appropriate viscosity range.

[0063] The component (G) may be used alone or in combination of two or more.

[0064] [Other Components] The thermally conductive addition-curable silicone composition of the present invention may contain a non-reactive organo(poly)siloxane, such as methylpolysiloxane, to adjust the strength and viscosity of the silicone composition. Furthermore, the thermally conductive addition-curable silicone composition of the present invention may contain a hydrolyzable organopolysiloxane, various modified silicones, or a hydrolyzable organosilane to impart adhesive properties to the silicone composition. Furthermore, a solvent may be added to adjust the viscosity of the silicone composition. Furthermore, a conventionally known antioxidant, such as 2,6-di-tert-butyl-4-methylphenol, may be added as needed to prevent deterioration of the silicone composition. Furthermore, dyes, pigments, flame retardants, anti-settling agents, thixotropy improvers, and the like may be added as needed.

[0065] [Step of Preparing the Thermally Conductive Addition-Curable Silicone Composition] The method for producing the thermally conductive addition-curable silicone composition of the present invention will now be described. The method for producing the thermally conductive addition-curable silicone composition of the present invention is not particularly limited, but the thermally conductive addition-curable silicone composition is prepared by mixing the above-mentioned components (A) to (E), and, if necessary, also component (F), component (G), and / or other components.

[0066] Specifically, the above-mentioned components (A) to (E), and optionally, component (F), component (G), and / or other components, are mixed at 25°C for typically 3 minutes to 24 hours, preferably 5 minutes to 12 hours, and more preferably 10 minutes to 6 hours, using a mixer such as Trimix, Twinmix, or Planetary Mixer (all registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultramix (registered trademark of mixers manufactured by Mizuho Industries Co., Ltd.), or Hibismix (registered trademark of mixers manufactured by Primix Corporation). Degassing may be performed during mixing, and the mixture may be mixed while heating at a temperature in the range of 40 to 200°C.

[0067] In the present invention, it is preferable to first mix components (A) and (B) at a temperature of 50 to 200°C, and then mix components (C), (D), and (E) at 25°C, in order to ensure that the thermally conductive addition-curable silicone composition exhibits good thermal conductivity and an appropriate viscosity.

[0068] The thermally conductive addition-curable silicone composition of the present invention preferably has a viscosity measured at 25°C of 10 to 1,000 Pa·s, more preferably 20 to 700 Pa·s, and even more preferably 40 to 500 Pa·s. If the viscosity is in the range of 10 to 1,000 Pa·s, the thermally conductive addition-curable silicone composition of the present invention will easily retain its shape, the thermally conductive filler will be uniform throughout the silicone composition, and the composition will be easy to discharge and apply, resulting in excellent workability. The above viscosity can be obtained by adjusting the blending amounts of the various components described above.

[0069] In the present invention, the viscosity is the absolute viscosity of the thermally conductive addition-curable silicone composition measured at 25°C using a Malcolm viscometer (Type PC-1T) (Rotor A, 10 rpm, shear rate 6 [1 / s]).

[0070] Furthermore, the thermally conductive addition-curable silicone composition of the present invention typically has a thermal conductivity of 0.5 to 100 W / m K, but preferably has a thermal conductivity of 2.5 W / m K or greater in order to exhibit excellent heat dissipation performance when mounted in an electronic component package or power module.

[0071] In the present invention, the thermal conductivity is a value measured by wrapping each thermally conductive addition-curable silicone composition in kitchen wrap and measuring the thermal conductivity using a TPS-2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0072] The curing conditions for heat curing the thermally conductive addition-curable silicone composition of the present invention are not particularly limited, but are typically 80 to 200°C, preferably 100 to 180°C, for 15 minutes to 4 hours, preferably 30 minutes to 2 hours.

[0073] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0074] First, the following components were prepared for use in preparing the thermally conductive addition-curable silicone composition of the present invention: The kinematic viscosity is the value measured at 25°C using an Ubbelohde-Ostwald viscometer.

[0075] [Component (A)] A-1: ​​A copolymer having a kinematic viscosity of 850 mm at 25°C and a polymer end capped with dimethylethynyl groups. 2 / s dimethylpolysiloxane (ethynyl group amount = 0.00013 mol / g) A-2: Both ends are blocked with dimethylethynyl groups, and the kinematic viscosity at 25 ° C is 4,000 mm 2 / s dimethylpolysiloxane (ethynyl group amount = 0.000067 mol / g) A-3: Both ends are blocked with dimethylethynyl groups, and the kinematic viscosity at 25 ° C is 16,000 mm 2 a-4: Dimethylpolysiloxane having a kinematic viscosity of 1,000 mm at 25°C, and a dimethylvinylsilyl group-blocked copolymer of 1,000 mm at 25°C. 2 a-5: Dimethylpolysiloxane having a kinematic viscosity of 5,000 mm at 25°C (vinyl group amount = 0.00010 mol / g) 2 / s dimethylpolysiloxane (vinyl group amount = 0.000064 mol / g)

[0076] [Component (B)] B-1: Spherical aluminum powder with an average particle size of 12 μm B-2: Spherical aluminum powder with an average particle size of 9 μm B-3: Irregular-shaped zinc oxide powder with an average particle size of 0.4 μm

[0077] [Component (C)] C-1: Methylhydrogendimethylpolysiloxane represented by the following formula (3) (Si—H content=0.00127 mol / g) C-2: Methylhydrogendimethylpolysiloxane represented by the following formula (4) (Si—H amount=0.00126 mol / g) C-3: Methylhydrogendimethylpolysiloxane represented by the following formula (5) (Si—H amount=0.00190 mol / g)

[0078] [Component (D)] D-1: A solution of platinum-divinyltetramethyldisiloxane complex dissolved in the same dimethylpolysiloxane as in A-4 (platinum atom content: 1% by mass)

[0079] [Component (E)] E-1: 1-ethynyl-1-cyclohexanol represented by the following formula (6):

[0080] [Component (F)] F-1: a dimethylpolysiloxane having one end blocked with a trimethoxysilyl group, represented by the following formula (7):

[0081] [Component (G)] G-1: Organosilane represented by the following formula (8):

[0082] Examples 1 to 5, Comparative Examples 1 to 7 Preparation of Thermally Conductive Addition-Curable Silicone Compositions Thermally conductive addition-curable silicone compositions were prepared by blending the above components (A) to (G) in the amounts shown in Tables 1 and 2 by the method shown below. In Tables 1 and 2, SiH / SiE is the ratio of the total number of SiH groups in component (C) to the total number of ethynyl groups in component (A), and SiH / SiVi is the ratio of the total number of SiH groups in component (C) to the total number of vinyl groups in component (A).

[0083] Components (A) and (B) were added to a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.), and then component (F) or (G) was added. When component (F) was added, mixing was carried out for 1 hour at 170°C, and when component (G) was added, mixing was carried out for 1 hour at 70°C. After mixing, the mixture was cooled to 40°C or below, and then components (C), (D), and (E) were added and mixed until uniform, thereby preparing a thermally conductive addition-curable silicone composition.

[0084] The viscosity, thermal conductivity, storage modulus G', and elongation at break of each of the thermally conductive addition-curable silicone compositions obtained above were measured according to the methods described below. The results are shown in Tables 1 and 2.

[0085] [Viscosity] The absolute viscosity of each thermally conductive addition-curable silicone composition was measured at 25°C using a Malcolm viscometer (Type PC-1T) (Rotor A, 10 rpm, shear rate 6 [1 / s]). [Thermal Conductivity] Each thermally conductive addition-curable silicone composition was wrapped in kitchen wrap, and the thermal conductivity was measured using a TPS-2500S (manufactured by Kyoto Electronics Manufacturing Co., Ltd.). [Storage Modulus G'] Each thermally conductive addition-curable silicone composition was applied to a thickness of 2 mm between two parallel plates with a diameter of 2.5 cm. A program was created to raise the temperature of the applied plates from 25°C to 150°C at a rate of 5°C / min, and then maintain them at 150°C for 7,200 seconds, and the storage modulus G' was read 5,100 seconds after the start of the test. A viscoelasticity measuring device (ARES-G2: manufactured by TA Instruments) was used for the measurements. [Elongation at Break] Each thermally conductive addition-curable silicone composition was heated at 150°C for 60 minutes to cure and produce a 2 mm thick sheet, which was then cut into a No. 2 dumbbell shape in accordance with JIS K6251 and the elongation at break was measured.

[0086]

[0087]

[0088] The evaluation results in Tables 1 and 2 show that the thermally conductive addition-curable silicone compositions of Examples 1 to 5, which satisfy the requirements of the present invention, have a low storage modulus G' when heat-cured and give highly elongated cured products. On the other hand, the thermally conductive addition-curable silicone compositions of Comparative Examples 1 to 7, which were prepared using component (a-4) or (a-5) as component (A), had a low storage modulus G' when heat-cured, but the cured products were putty-like and the elongation at break could not be measured.

[0089] Therefore, when heat-cured, the thermally conductive addition-curable silicone composition of the present invention gives a cured product that has a low storage modulus G' and high elongation. As a result, it can be used favorably in electronic component packages and power modules that are prone to significant warpage, and it can also accommodate the expansion and contraction that occurs with the thermal history of repeated heating and cooling of heat-generating components over long periods of time.

[0090] This specification encompasses the following aspects: [1]: A thermally conductive addition-curable silicone composition, comprising: (A) a silicone compound having at least one alkynyl group per molecule and a kinematic viscosity at 25°C of 60 to 100,000 mm 2 (B) at least one thermally conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and carbon allotropes, in an amount that is 10 to 96% by mass based on the total composition; (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, in an amount that provides 0.5 to 10 Si—H groups in component (C) relative to the total number of alkynyl groups in component (A); (D) an effective amount of a platinum group metal catalyst; and (E) one or more addition cure reaction inhibitors selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds, in an amount that is 0.05 to 5 parts by mass based on 100 parts by mass of component (A). [2]: Furthermore, (F) an organopolysiloxane represented by the following general formula (1): an amount of 0.5 to 10% by mass based on the total mass of the composition, (In the formula, R 1 represents a monovalent hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent and does not have an aliphatic unsaturated bond, and each R 1 may be the same or different, and m is an integer of 5 to 100. [3]: The thermally conductive addition-curable silicone composition according to [1], further comprising: (G) an organosilane and / or a (partial) hydrolysis condensate thereof represented by the following general formula (2): in an amount of 0.1 to 10 mass % based on the total mass of the composition; ２ ａ Si(OR ３ ) ４－ａ (2) (R ２ are independently unsubstituted or halogen-substituted monovalent hydrocarbon groups having 1 to 20 carbon atoms, and R ３are independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and a is an integer of 1 to 3. [4]: ​​The thermally conductive addition-curable silicone composition according to [1] or [2], characterized in that component (A) is an organopolysiloxane having at least two alkynyl groups per molecule. [5]: The thermally conductive addition-curable silicone composition according to any one of [1] to [4], characterized in that component (A) is an organopolysiloxane having at least two ethynyl groups per molecule.

[0091] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A heat-conductive addition-curing silicone composition, comprising: (A) an organopolysiloxane having at least one alkynyl group in one molecule and a kinematic viscosity at 25 °C of 60 to 100,000 mm 2 / s; (B) at least one heat-conductive filler selected from the group consisting of metals, metal oxides, metal hydroxides, metal nitrides, metal carbides, and allotropes of carbon, in an amount of 10 to 96% by mass based on the total composition; (C) an organohydrogenpolysiloxane having hydrogen atoms bonded to two or more silicon atoms in one molecule, in an amount such that the number of Si-H groups in component (C) is 0.5 to 10 relative to the total number of alkynyl groups in component (A); (D) a platinum group metal catalyst, in an effective amount; and (E) one or more addition-curing reaction control agents selected from the group consisting of acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds, in an amount of 0.05 to 5 parts by mass per 100 parts by mass of component (A). The heat-conductive addition-curing silicone composition is characterized by containing the above components.

2. Further, (F) an organopolysiloxane represented by the following general formula (1): in an amount of 0.5 to 10% by mass based on the whole composition, (wherein R 1 represents a monovalent hydrocarbon group having 1 to 10 carbon atoms, which may have a substituent and represents a monovalent hydrocarbon group having no aliphatic unsaturated bond, and each R 1 may be the same or different. m is an integer of 5 to 100.) The thermally conductive addition-curing silicone composition according to claim 1, characterized by containing the same.

3. Further, (G) an organosilane represented by the following general formula (2) and / or its (partial) hydrolysis condensate: in an amount of 0.1 to 10% by mass based on the whole composition, R ２ ａ Si(OR ３ ) ４－ａ (2) (R ２ is independently an unsubstituted or halogen-substituted monovalent hydrocarbon group having 1 to 20 carbon atoms, R ３ is independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and a is an integer of 1 to 3.) The thermally conductive addition-curable silicone composition according to claim 1, characterized by containing the same.

4. The thermally conductive addition-curing silicone composition according to claim 1, wherein component (A) is an organopolysiloxane having at least two alkynyl groups in one molecule.

5. The thermally conductive addition-curing silicone composition according to claim 1, wherein component (A) is an organopolysiloxane having at least two ethynyl groups in one molecule.

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