Thermally conductive silicone grease composition and method for producing same

Abstract

A thermally conductive silicone grease composition 10 comprises: a first thermally conductive silicone grease; a second thermally conductive silicone grease; and connection portions thereof. The first thermally conductive silicone grease 7a, 7b contains a curing reaction catalyst but do not contain a crosslinking agent. The second thermally conductive silicone grease 8a, 8b does not contain a curing reaction catalyst but contains a crosslinking agent. The first and second thermally conductive silicone greases are each, at at least one surface opposing the other, connected to the other with a connection portion therebetween. Connection portions 9a, 9b, 9c are cured, but portions other than the connection portions are uncured.

Description

Thermally conductive silicone grease composition and method for producing same

[0001] The present invention relates to a thermally conductive silicone grease composition in which first and second thermally conductive silicone greases are joined via a bond formed by curing, and to a method for producing the same.

[0002] In recent years, the performance of semiconductors such as CPUs has improved dramatically, resulting in a huge increase in the amount of heat generated. Heat sinks are therefore attached to heat-generating electronic components, and thermally conductive grease is used to improve adhesion between the heat sink and heat-generating components such as semiconductors. As devices become smaller, more powerful, and more highly integrated, thermally conductive greases are required to have high thermal conductivity as well as drop resistance.

[0003] Japanese Patent Application Laid-Open No. 2020-104078 proposes filling two syringes with one-component and two-component thermally conductive grease, with the discharge port serving as a mixing section, and discharging the mixed one-component and two-component thermally conductive grease. The present inventor also proposed in Japanese Patent Application Laid-Open No. 6674590 a thermally conductive sheet in which a cured sheet and an uncured sheet are laminated in the plane direction.

[0004] The present invention provides a thermally conductive silicone grease composition comprising a first thermally conductive silicone grease, a second thermally conductive silicone grease, and a joint therebetween, wherein the first thermally conductive silicone grease contains a curing reaction catalyst but does not contain a crosslinking agent, the second thermally conductive silicone grease does not contain a curing reaction catalyst but does contain a crosslinking agent, the first and second thermally conductive silicone greases are joined via the joint on at least one opposing surface, the joint is cured, and the first and second thermally conductive silicone greases are in an uncured state apart from the joint.

[0005] FIG. 1A is a schematic plan view of a state in which first and second thermally conductive silicone greases according to one embodiment of the present invention are applied alternately in the form of cylinders from their respective dispensers, and FIG. 1B is a schematic plan view of the resulting product after compression molding. FIG. 2A is a schematic plan view of a state in which first and second thermally conductive silicone greases according to another embodiment of the present invention are applied alternately in the form of dots from their respective dispensers, and FIG. 2B is a schematic plan view of the resulting product after compression molding. FIG. 3 is a schematic cross-sectional view showing a method of using a thermally conductive sheet according to one embodiment of the present invention. FIGS. 4A-B are schematic explanatory diagrams showing a method of measuring the thermal conductivity of a sample according to one embodiment of the present invention. FIGS. 5A-D are schematic explanatory diagrams illustrating a drop test used in one embodiment of the present invention. FIG. 6 is a 5000x magnification photograph of amorphous alumina (surface-treated with octyltrimethoxysilane) with a D50 of 0.3 μm used in one embodiment of the present invention. FIG. 7 is a 2000x magnification photograph of amorphous alumina (surface-treated with decyltrimethoxysilane) with a D50 of 2.3 μm used in one embodiment of the present invention. Figure 8 is a 2000x magnification photograph of amorphous aluminum nitride (without surface treatment) with a D50 of 15 μm used in one embodiment of the present invention. Figure 9 is a 100x magnification photograph of spherical alumina (without surface treatment) with a D50 of 105 μm used in one embodiment of the present invention. Figure 10 is a photograph of spherical agglomerated boron nitride (without surface treatment) with a D50 of 25 μm used in one embodiment of the present invention. Figure 11 is a photograph of spherical agglomerated boron nitride (without surface treatment) with a D50 of 60 μm used in one embodiment of the present invention. Detailed Description of the Invention

[0006] However, in the above-mentioned conventional technology, a two-component curing thermally conductive material is used in the hope of providing drop resistance, but because the two components are mixed in a dispenser and then applied, if application is not completed immediately after mixing, the thermally conductive material may continue to harden inside the dispenser. To avoid this, the thermally conductive material cannot be stored in the dispenser for a long time after mixing, which creates the problem of time-consuming cleaning of the device.

[0007] In order to solve the above-mentioned problems of the conventional art, the present invention provides a thermally conductive silicone grease composition that can be applied with a dispenser, has good drop resistance, and cures after application, so that curing does not proceed within the dispenser, as well as a method for producing the same.

[0008] The thermally conductive silicone grease composition of the present invention is a thermally conductive silicone grease composition comprising a first thermally conductive silicone grease, a second thermally conductive silicone grease, and a junction therebetween, wherein the first thermally conductive silicone grease contains a curing reaction catalyst but does not contain a crosslinking agent, and the second thermally conductive silicone grease does not contain a curing reaction catalyst but does contain a crosslinking agent, the first and second thermally conductive silicone greases are joined via the junction on at least one opposing surface, the junction being cured, and the first and second thermally conductive silicone greases being in an uncured state apart from the junction.

[0009] The method for producing a thermally conductive silicone grease composition of the present invention is a method for producing the thermally conductive silicone grease composition described above, and includes the steps of: filling dispensers with the first thermally conductive silicone grease and the second thermally conductive silicone grease; alternately discharging and applying the first and second thermally conductive silicone greases from the discharge holes of the dispensers, while leaving a gap of 10% to 90% of the applied thickness so that the thermally conductive silicone greases do not come into contact with each other; and compression-molding the applied first and second thermally conductive silicone greases at a compression ratio of 10% to 90% of the applied thickness, thereby causing an addition reaction at the contact points between the first and second thermally conductive silicone greases to form joints, and joining the first and second thermally conductive silicone greases via these joints to produce a thermally conductive silicone grease composition.

[0010] The thermally conductive silicone grease composition of the present invention is produced by a method comprising the steps of: filling a dispenser with the first thermally conductive silicone grease and the second thermally conductive silicone grease; alternately applying the first and second thermally conductive silicone greases through the nozzles of the dispenser, leaving a gap of 10% to 90% of the applied thickness to prevent contact between the individual thermally conductive silicone greases; and compression-molding the applied first and second thermally conductive silicone greases at a compression ratio of 10% to 90% of the applied thickness, thereby causing an addition reaction at the contact points between the first and second thermally conductive silicone greases to form joints, and bonding the first and second thermally conductive silicone greases via these joints to produce a thermally conductive silicone grease composition. In other words, the joints are cured by the addition reaction, but the first and second thermally conductive silicone greases remain uncured outside the joints. According to this manufacturing method, the first thermally conductive silicone grease and the second thermally conductive silicone grease can be applied using a dispenser, have good drop resistance, and because the first and second thermally conductive silicone greases harden after application, hardening does not progress within the dispenser before application.

[0011] Furthermore, in the thermally conductive silicone grease composition of the present invention, the joints are cured by an addition reaction, while the areas other than the joints remain uncured, so that the cured areas have a high hardness while the uncured areas have a low hardness, allowing them to deform freely and easily conform to the irregularities of the heat-generating and / or heat-dissipating areas.This makes the thermally conductive silicone grease composition of the present invention suitable as a thermal interface material (TIM) to be placed between the heat-generating parts of electrical and electronic components and heat dissipating bodies.

[0012] The present invention provides a thermally conductive silicone grease composition comprising a first thermally conductive silicone grease, a second thermally conductive silicone grease, and a joint therebetween, wherein the first thermally conductive silicone grease contains a curing reaction catalyst but no crosslinking agent, and the second thermally conductive silicone grease does not contain a curing reaction catalyst but does contain a crosslinking agent, the first and second thermally conductive silicone greases being joined via the joint on at least one opposing surface, the joint being cured, and the first and second thermally conductive silicone greases being uncured apart from the joint. In the uncured state, the first and second thermally conductive silicone greases are freely deformable and easily conform to the irregularities of the heat-generating and / or heat-dissipating parts. Furthermore, because the joint is cured by an addition reaction, it also has shape retention and good drop resistance. The good drop resistance of the thermally conductive silicone grease composition of the present invention is presumed to be due to the fact that the cured joint traps leaching components.

[0013] [First and Second Thermally Conductive Silicone Greases] The first and second thermally conductive silicone greases preferably contain a matrix resin and thermally conductive particles, with the matrix resin containing the following components (A) and (C), and the thermally conductive particles containing the following component (B). The compositions below allow the first and second thermally conductive silicone greases to be applied smoothly using a dispenser. The first and second thermally conductive silicone greases each contain a matrix resin and thermally conductive particles, but the matrix resin of the first thermally conductive silicone grease and the matrix resin of the second thermally conductive silicone grease may be the same or different. If they are different, the type and / or content of at least one of the following components (A) and (C) contained in the first and second thermally conductive silicone greases may be different. Furthermore, the thermally conductive particles of the first thermally conductive silicone grease and the thermally conductive particles of the second thermally conductive silicone grease may be the same or different. When the first and second thermally conductive silicone greases are different, the type and / or content of the following component (B) contained in the first and second thermally conductive silicone greases may also be different: (A) a kinematic viscosity at 40°C of 100 to 3,000 mm 2 / s addition reaction curable organopolysiloxane: 100 parts by mass; (B) thermally conductive filler: 200 to 3000 parts by mass relative to 100 parts by mass of the matrix resin; (C) R a Si(OR') 4-a (wherein R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1): 0 to 10 parts by mass of alkoxysilane

[0014] <Matrix Resin> Here, the matrix resin includes the curing reaction catalyst or the crosslinking agent. The matrix resin includes the components (A) and (C), and also includes the following component (D) (non-reactive silicone oil) when added.

[0015] (1) Curing Reaction Catalyst Catalysts used in hydrosilylation reactions can be used as curing reaction catalysts. Examples of the curing reaction catalyst include platinum-based catalysts such as platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins or vinylsiloxanes, platinum group metal catalysts such as platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts, with platinum group metal catalysts being preferred. The curing reaction catalyst is added in an amount of preferably 1 to 3,500 ppm by weight (10 to 35,000 times the effective curing amount), more preferably 5 to 2,000 ppm, and even more preferably 7 to 700 ppm, based on the matrix resin.

[0016] (2) Crosslinking Agents Examples of crosslinking agents include organohydrogenpolysiloxanes. The organohydrogenpolysiloxanes function as crosslinkers, curing the composition by an addition reaction (hydrosilylation) between the SiH groups in the organohydrogenpolysiloxane and the alkenyl groups in the organopolysiloxane (component A). Any organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms (i.e., SiH groups) per molecule can be used as a crosslinking agent. The molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure. Furthermore, organohydrogenpolysiloxanes containing 2 to 1,000 silicon atoms per molecule (i.e., a degree of polymerization) of approximately 2 to 300 are preferably used as crosslinkers.

[0017] The organohydrogenpolysiloxane contains SiH groups as described above. In the organohydrogenpolysiloxane, the position of the SiH groups is not particularly limited, and they may be at the terminals of the molecular chain or at non-terminal locations (in the middle of the molecular chain). Furthermore, examples of organic groups bonded to silicon atoms other than hydrogen atoms include R in the general formula (I). 1 and unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, similar to those shown above.

[0018] The organohydrogenpolysiloxane may be exemplified by the following formula (I):

[0019]

[0020] In the above formula (I), R 6 may be the same or different and are hydrogen, an alkyl group, a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, or an alkoxy group, and at least two are hydrogen. L is an integer of 0 to 1,000, particularly an integer of 0 to 300, and M is an integer of 1 to 200.

[0021] (3) Organopolysiloxane (Component (A)) Organopolysiloxane is the main component (base polymer component) in the matrix resin, and contains, for example, two or more silicon-bonded alkenyl groups per molecule. This organopolysiloxane contains two silicon-bonded alkenyl groups per molecule, such as vinyl or allyl groups, each having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms. From the viewpoint of workability and curability, the viscosity of the organopolysiloxane is preferably 10 to 1,000,000 mPa·s, particularly 100 to 100,000 mPa·s, and more preferably 100 to 3,000 mPa·s at 25°C. The kinematic viscosity of the organopolysiloxane at 40°C is preferably 100 to 3,000 mm 2 / s, preferably 100 to 2,000 mm 2 / s, more preferably 100 to 1,000 mm 2 / s.

[0022] Specifically, a linear organopolysiloxane represented by the following general formula (II) can be used, which contains an average of two or more alkenyl groups per molecule, each of which is bonded to a silicon atom at the molecular chain terminal. From the viewpoint of workability and curability, a viscosity of 10 to 1,000,000 mPa·s at 25°C is desirable. This linear organopolysiloxane may also contain a small amount of branched structures (trifunctional siloxane units) in the molecular chain.

[0023]

[0024] In formula (II), R 1 are the same or different unsubstituted or substituted monovalent hydrocarbon groups that do not contain an aliphatic unsaturated bond, R 2is an alkenyl group, and k is 0 or a positive integer.

[0025] Here, in general formula (II), R 1 The unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond is preferably one having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples of the unsubstituted monovalent hydrocarbon group having no aliphatic unsaturated bond 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; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl. Examples of the substituted monovalent hydrocarbon group having no aliphatic unsaturated bond include the above unsubstituted monovalent hydrocarbon groups in which some or all of the hydrogen atoms have been substituted with halogen atoms such as fluorine, bromine, or chlorine; or with a cyano group, for example, halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl; and the cyanoethyl group.

[0026] In general formula (II), R 2 The alkenyl group preferably has 2 to 6 carbon atoms, particularly 2 to 3 carbon atoms. Specific examples include vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl groups, with vinyl being preferred.

[0027] In general formula (II), k is 0 or a positive integer, for example, 0 or a positive integer satisfying 0≦k≦10000, preferably 5≦k≦2000, more preferably 10≦k≦1200.

[0028] The organopolysiloxane may be used in combination with an organopolysiloxane having three or more, typically 3 to 30, and preferably 3 to 20, alkenyl groups bonded to silicon atoms having 2 to 8, particularly 2 to 6, carbon atoms, such as vinyl groups or allyl groups, per molecule. The molecular structure may be linear, cyclic, branched, or three-dimensional network. A preferred example is a linear organopolysiloxane whose main chain is composed of repeating diorganosiloxane units and whose molecular chain is terminally blocked with triorganosiloxy groups, and whose viscosity at 25°C is 10 to 1,000,000 mPa·s, particularly 100 to 100,000 mPa·s.

[0029] In organopolysiloxanes containing two or more alkenyl groups bonded to silicon atoms per molecule, the alkenyl groups may be bonded to any part of the molecule. For example, they may be bonded to silicon atoms at the molecular chain terminals or non-terminal locations (in the middle of the molecular chain). Among these, linear organopolysiloxanes represented by the following general formula (III), in which one to three alkenyl groups are bonded to silicon atoms at both molecular chain terminals, and which have a viscosity at 25°C of 10 to 1,000,000 mPa·s are preferred from the viewpoints of workability and curability. However, when the total number of alkenyl groups bonded to silicon atoms at the molecular chain terminals of this linear organopolysiloxane is less than three, linear organopolysiloxanes having at least one alkenyl group bonded to a non-terminal location (in the middle of the molecular chain) (e.g., as a substituent in a diorganosiloxane unit) are preferred. As mentioned above, such linear organopolysiloxanes preferably have a viscosity of 10 to 1,000,000 mPa·s at 25° C. from the viewpoint of workability, curability, etc. The linear organopolysiloxane may also contain a small amount of branched structure (trifunctional siloxane units) in the molecular chain.

[0030]

[0031] In formula (III), R 3 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups, at least one of which is an alkenyl group. 4may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds, R 5 is an alkenyl group; l and m are each independently 0 or a positive integer.

[0032] Here, in general formula (III), R 3 The unsubstituted or substituted monovalent hydrocarbon group preferably has 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples of the unsubstituted monovalent hydrocarbon group 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 alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl. Examples of the substituted monovalent hydrocarbon group include those in which some or all of the hydrogen atoms of the unsubstituted monovalent hydrocarbon group have been substituted with halogen atoms such as fluorine, bromine, or chlorine; or a cyano group, such as halogen-substituted alkyl groups such as a chloromethyl group, a chloropropyl group, a bromoethyl group, or a trifluoropropyl group; and a cyanoethyl group.

[0033] In addition, in the general formula (III), R 4 The unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond is preferably one having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. 4 The unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond includes the above-mentioned R 1 Specific examples of the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond are the same as those of the group 1, except that alkenyl groups are not included.

[0034] In general formula (III), R 5 The alkenyl group of the formula (1) is preferably an alkenyl group having 2 to 6 carbon atoms, particularly preferably having 2 to 3 carbon atoms. 2 The preferred is a vinyl group.

[0035] In general formula (III), l and m are 0 or a positive integer, for example, 0 or a positive integer satisfying 0 < l + m ≦ 10000, preferably 5 ≦ l + m ≦ 2000, more preferably 10 ≦ l + m ≦ 1200, and an integer satisfying 0 < l / (l + m) ≦ 0.2, preferably 0.0011 ≦ l / (l + m) ≦ 0.1.

[0036] (4) R a Si(OR') 4-a Alkoxysilane (component (C)) of the formula R a Si(OR') 4-a (wherein R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) alkoxysilane functions as a viscosity modifier. By including component (C), the dischargeability of the thermally conductive silicone grease is further improved, which is preferable.

[0037] Component (C) of formula R a Si(OR') 4-a Examples of alkoxysilanes represented by the formula (R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) include octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane. The alkoxysilanes can be used alone or in combination of two or more. As a surface treatment agent, the alkoxysilanes can be used in combination with one-terminated silanol siloxane.

[0038] (5) Non-reactive silicone oil (component (D)) The matrix resins of the first and second thermally conductive silicone greases may each further contain 1 to 50 mass % of non-reactive silicone oil (D) in the component (A). This allows for smooth application using a dispenser. The non-reactive silicone oils (D) contained in the matrix resins of the first and second thermally conductive silicone greases may be the same or different. If different, the type and / or content of component (D) contained in the first and second thermally conductive silicone greases may be different.

[0039] The non-reactive silicone oil has a kinematic viscosity at 25°C of, for example, 50 to 3,000 mm 2 / s, preferably 70 to 2,500 mm 2 / s. Viscosity is measured using a Brooklyn Field type rotational viscometer SP No. 2. If the kinematic viscosity is within the above range, oil bleeding is kept low and the filling properties of the thermally conductive particles are also good. The non-reactive silicone oil is a silicone polymer that does not have a reactive group, and examples thereof include dimethylpolysiloxane and diphenylpolysiloxane.

[0040] <Thermal Conductive Particles> The thermally conductive particles are preferably added in an amount of 200 to 3,000 parts by mass per 100 parts by mass of the matrix resin. This allows the thermal conductivity of the thermally conductive silicone grease composition to be maintained at a high level. The material for the thermally conductive particles is preferably at least one selected from the group consisting of alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, quartz, and silica, and more preferably at least one selected from the group consisting of aluminum nitride, boron nitride, and alumina. Various shapes can be used, including spherical, scaly, and polyhedral. When using alumina, α-alumina with a purity of 99.5% by weight or higher is preferred. The specific surface area of ​​the thermally conductive particles should be 0.06 to 10 m 2 / g is preferred. The specific surface area is a BET specific surface area, and the measurement method is in accordance with JIS R1626. The average particle size of the thermally conductive particles is preferably in the range of 0.1 to 100 μm. The particle size is measured by measuring the median size using a laser diffraction light scattering method. An example of an instrument for this measurement is the LA-950S2 laser diffraction / scattering particle distribution analyzer manufactured by Horiba, Ltd.

[0041] The thermally conductive particles may be a mixture of at least two thermally conductive particles with different average particle sizes, because in this case the thermally conductive particles with smaller particle sizes are embedded between the larger particles, allowing for a nearly closest packing state, thereby increasing the thermal conductivity.

[0042] The thermally conductive particles have the formula R a Si(OR')4-a (R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a partial hydrolyzate thereof. a Si(OR') 4-a Examples of alkoxysilanes represented by the formula (where R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) include octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane. These alkoxysilanes can be used alone or in combination. As a surface treatment agent, the alkoxysilanes can be used in combination with single-terminated silanol siloxanes. The term "surface treatment" as used herein includes adsorption as well as covalent bonding. Surface treatment is preferably performed on thermally conductive particles with an average particle size D of 10 μm or less. Thermally conductive particles with D of 10 μm or less have a high specific surface area and are prone to adsorbing platinum catalysts, inhibiting curing. However, this can be prevented by surface treatment.

[0043] The thermally conductive particles contain a thermally conductive filler (component (B)). (1) Thermally conductive filler (component (B)) Thermally conductive fillers include electrically conductive fillers and electrically insulating fillers, and either may be used. Examples of electrically conductive fillers include carbon powders such as carbon black or metal powders. In the case of metal powders, metal powders with a surface resistance of 1 Ω / □ or less are preferred. Specifically, powders made of metals such as gold, silver, platinum, copper, nickel, iron, palladium, cobalt, chromium, and aluminum, or alloys such as stainless steel, or metal powders whose surfaces are coated with precious metals such as gold and silver to reduce electrical resistance are preferred. As the electrically insulating filler, fillers made of alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, quartz, or silica are preferred, and at least one selected from the group consisting of aluminum nitride, boron nitride, and alumina is more preferred. The thermally conductive filler may have various shapes, such as spherical, flaky, and polyhedral. When alumina is used as the thermally conductive filler, α-alumina having a purity of 99.5% by weight or more is preferred. The specific surface area of ​​the thermally conductive filler is 0.06 to 10 m 2 / g is preferred. The specific surface area is a BET specific surface area, and the measurement method is in accordance with JIS R1626. The average particle size of the thermally conductive filler is preferably in the range of 0.1 to 100 μm. The average particle size is the D50 (median diameter) of the cumulative particle size distribution on a volume basis, measured by a laser diffraction light scattering method. An example of an instrument for this measurement is the LA-950S2 laser diffraction / scattering particle distribution analyzer manufactured by Horiba, Ltd.

[0044] The thermally conductive filler may be a mixture of fillers with different particle sizes. Specifically, the following two types of filler mixtures can be exemplified.

[0045] (i) Filler Mixture 1 The thermally conductive filler (B) preferably contains a thermally conductive filler (B1) having a median particle size (D50) of 0.01 to 10 μm, a thermally conductive filler (B2) having a median particle size (D50) of more than 10 μm but not more than 80 μm, and a thermally conductive filler (B3) having a median particle size (D50) of more than 80 μm but not more than 150 μm. By using a thermally conductive filler (B) with such a configuration, the thermally conductive filler (B) can be packed in a state close to closest packing within the thermally conductive silicone grease composition, thereby increasing the thermal conductivity of the thermally conductive silicone grease composition. The median particle size is the D50 (median diameter) of the cumulative particle size distribution on a volume basis measured by laser diffraction light scattering. An example of an instrument for this measurement is the LA-950S2 laser diffraction / scattering particle size distribution analyzer manufactured by Horiba, Ltd.

[0046] The thermally conductive filler (B1) is preferably amorphous alumina, because alumina is inexpensive. The thermally conductive filler (B2) is preferably at least one thermally conductive filler selected from the group consisting of alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon carbide. The thermally conductive filler (B2) is preferably amorphous. The thermally conductive filler (B3) is preferably spherical alumina. When a high proportion of spherical alumina is added as the thermally conductive filler (B3), the thermal conductivity of the thermally conductive silicone grease composition can be increased and costs can be reduced. When alumina is used as the thermally conductive filler (B), it is preferable to use a combination of so-called submicron particles (B1-1) with a D50 (median diameter) of 0.01 μm or more but less than 1 μm, small particles (B1-2) with a D50 (median diameter) of 1 μm or more but less than 10 μm, and large particles (B3) with a D50 (median diameter) of more than 80 μm but less than 150 μm. Using a thermally conductive filler (B) with such a configuration allows for close packing of the thermally conductive filler (B) within the thermally conductive silicone grease composition, thereby increasing the thermal conductivity of the thermally conductive silicone grease composition. Commercially available amorphous alumina is produced by pulverization or crushing, and these thermally conductive fillers (B1), (B2), and (B3) have high thermal conductivity.

[0047] The mass proportions of the thermally conductive fillers (B1), (B2), and (B3) preferably satisfy the relationship (B2)≦(B1)≦(B3), because by satisfying this ratio, the thermally conductive fillers can be packed in a state approaching the closest packing within the thermally conductive silicone grease composition, thereby increasing the thermal conductivity of the thermally conductive silicone grease composition.

[0048] The thermally conductive filler (B) preferably contains 100 to 1,000 parts by mass, more preferably 150 to 1,000 parts by mass, and even more preferably 300 to 850 parts by mass of the thermally conductive filler (B1) per 100 parts by mass of the matrix resin. The thermally conductive filler (B) also preferably contains 100 to 500 parts by mass, more preferably 150 to 500 parts by mass, and even more preferably 200 to 450 parts by mass of the thermally conductive filler (B2) per 100 parts by mass of the matrix resin. The thermally conductive filler (B) also preferably contains 300 to 1,400 parts by mass, more preferably 300 to 1,300 parts by mass, and even more preferably 500 to 1,200 parts by mass of the thermally conductive filler (B3) per 100 parts by mass of the matrix resin. This allows for the production of a thermally conductive silicone grease composition that has high thermal conductivity, is relatively resistant to dripping, and has good dischargeability. For the same reason, the thermally conductive filler (B) preferably contains 100 to 1,000 parts by mass of the thermally conductive filler (B1), 100 to 500 parts by mass of the thermally conductive filler (B2), and 300 to 1,400 parts by mass of the thermally conductive filler (B3) relative to 100 parts by mass of the matrix resin, more preferably 150 to 1,000 parts by mass of the thermally conductive filler (B1), 150 to 500 parts by mass of the thermally conductive filler (B2), and 300 to 1,300 parts by mass of the thermally conductive filler (B3), and even more preferably 300 to 850 parts by mass of the thermally conductive filler (B1), 200 to 450 parts by mass of the thermally conductive filler (B2), and 500 to 1,200 parts by mass of the thermally conductive filler (B3).

[0049] The thermally conductive filler (B1) having a median particle size (D50) of 0.01 to 10 μm, the thermally conductive filler (B2) having a median particle size (D50) of more than 10 μm but not more than 80 μm, and the thermally conductive filler (B3) having a median particle size (D50) of more than 80 μm but not more than 150 μm may each contain two or more types of thermally conductive fillers with different median particle sizes (D50). Using a thermally conductive filler (B) with such a configuration allows the thermally conductive filler (B) to be closely packed within the thermally conductive silicone grease composition, thereby increasing the thermal conductivity of the thermally conductive silicone grease composition. For example, the thermally conductive filler (B1) preferably contains two or more types of thermally conductive fillers with different median particle sizes (D50). Specifically, the thermally conductive filler (B1) preferably comprises a thermally conductive filler (B1-1) having a median particle size (D50) of 0.01 μm or more and less than 1 μm and a thermally conductive filler (B1-2) having a median particle size (D50) of 1 μm or more and 10 μm or less, more preferably a thermally conductive filler (B1-1) having a median particle size (D50) of 0.05 μm or more and less than 1 μm and a thermally conductive filler (B1-2) having a median particle size (D50) of 1 μm or more and 8 μm or less, and even more preferably a thermally conductive filler (B1-1) having a median particle size (D50) of 0.1 μm or more and less than 1 μm and a thermally conductive filler (B1-2) having a median particle size (D50) of 1 μm or more and 5 μm or less. By using a thermally conductive filler (B) with such a configuration, the thermally conductive filler (B) can be closest packed within the thermally conductive silicone grease composition, and as a result, the thermal conductivity of the thermally conductive silicone grease composition can be increased. When the thermally conductive filler (B1) contains the thermally conductive filler (B1-1) and the thermally conductive filler (B1-2), the thermally conductive inorganic particles (B1) preferably contain 50 to 400 parts by mass of the thermally conductive filler (B1-1) and 50 to 600 parts by mass of the thermally conductive filler (B1-2) relative to 100 parts by mass of the matrix resin, more preferably contain 50 to 400 parts by mass of the thermally conductive filler (B1-1) and 100 to 600 parts by mass of the thermally conductive filler (B1-2), and even more preferably contain 100 to 350 parts by mass of the thermally conductive filler (B1-1) and 200 to 500 parts by mass of the thermally conductive filler (B1-2).By using a thermally conductive filler (B) with such a configuration, the thermally conductive filler (B) can be closest packed within the thermally conductive silicone grease composition, and as a result, the thermal conductivity of the thermally conductive silicone grease composition can be increased.

[0050] A part or all of the thermally conductive filler (B1) having a median particle size (D50) of 0.01 to 10 μm is represented by the formula R a Si(OR') 4-a Preferably, the thermally conductive filler (B1) is surface-treated in advance with an alkoxysilane (similar to component (C) above) represented by the formula: (where R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1). "Pre-surface treatment" refers to pre-treatment before mixing. Surface-treating the thermally conductive filler (B1) in advance not only facilitates filling the thermally conductive filler (B1) into the matrix resin, but also prevents the thermally conductive filler (B1) from adsorbing a curing catalyst (e.g., a platinum-based catalyst), thereby preventing curing inhibition. This is useful for improving storage stability. Small particles with a D50 (median diameter) of 10 μm or less are particularly prone to adsorbing curing catalysts, so it is preferable to surface-treat a thermally conductive filler with a D50 (median diameter) of 10 μm or less. "Surface treatment" as used herein includes not only covalent bonding but also adsorption. Surface-treated thermally conductive filler (B1) exhibits good mixability with the matrix resin. It is preferable to add 0.01 to 10 parts by mass of the non-reactive silicone oil to 100 parts by mass of the thermally conductive filler.

[0051] The content of the filler mixture 1 is 400 to 3,000 parts by mass, preferably 500 to 2,900 parts by mass, and more preferably 600 to 2,800 parts by mass, relative to 100 parts by mass of the matrix resin.

[0052] (ii) Filler Mixture 2 The thermally conductive filler (B) preferably contains spherically agglomerated boron nitride particles. The spherically agglomerated boron nitride particles include spherically agglomerated boron nitride particles (B4) having a median particle diameter D50 of 10 μm or more and 30 μm or less, and spherically agglomerated boron nitride particles (B5) having a median particle diameter D50 at least twice that of B1 and greater than 30 μm and less than 100 μm. The ratio of the amount of spherically agglomerated boron nitride particles (B5) to the amount of spherically agglomerated boron nitride particles (B4) (B5 / B4, mass ratio) is 1.00 to 6.00. The ratio (B5 / B4, mass ratio) is preferably 1.20 to 5.50, more preferably 1.40 to 5.50, and even more preferably 1.60 to 5.40.

[0053] An example of the spherical agglomerated boron nitride particles (B4) that can be used is a product manufactured by Momentive under the trade name "PTX25," and an example of the spherical agglomerated boron nitride particles (B5) that can be used is a product manufactured by Momentive under the trade name "PTX60." Catalogs for "PTX25" and "PTX60" are available on the Internet at the following URL: https: / / www.tomo-e.co.jp / upload / newsJA / 29SVF8R-newsJA#content-012.pdf.

[0054] The content of the filler mixture 2 is 10 to 300 parts by mass, preferably 50 to 250 parts by mass, and more preferably 60 to 200 parts by mass, relative to 100 parts by mass of the matrix resin.

[0055] <Other Components> Components other than those described above can be blended into the thermally conductive silicone grease composition of the present invention as needed. For example, heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardant aids, and alkyltrialkoxysilanes for the purpose of filler surface treatment may be added to the thermally conductive silicone grease composition. Alkoxy group-containing silicones may be added to the thermally conductive silicone grease composition as a material added for filler surface treatment, etc. An adhesion promoter such as a silane coupling agent may be added to the thermally conductive silicone grease composition. Organic or inorganic pigments may be added to the thermally conductive silicone grease composition for the purpose of coloring or toning.

[0056] At least one of the first and second thermally conductive silicone greases preferably has a thermal conductivity of 2.0 W / m K or more, more preferably 3.0 W / m K or more, and even more preferably 4.0 W / m K or more, with the upper limit being 20.0 W / m K or less.

[0057] The first and second thermally conductive silicone greases each preferably have an absolute viscosity, as measured by a Brookfield viscometer at 23° C., in the range of 1,000 to 20,000 Pa s, more preferably 1,500 to 18,000 Pa s, and even more preferably 2,000 to 15,000 Pa s. If the absolute viscosity is within this range, the thermally conductive silicone grease can be smoothly applied using a dispenser.

[0058] The first and second thermally conductive silicone greases are preferably each filled into a 30 mL syringe and discharged in an amount of 2 to 10 g when discharged for 9 seconds with a discharge hole diameter of 2.5 mm and a discharge pressure of 0.5 MPa, allowing for smooth application using a dispenser.

[0059] [Joint] The first and second thermally conductive silicone greases are joined via the joint on at least one opposing surface. The joint is formed by the first and second thermally conductive silicone greases coming into contact with each other, causing an addition reaction between the curing catalyst of the first thermally conductive silicone grease and the crosslinker of the second thermally conductive silicone grease, resulting in curing. When the first and second thermally conductive silicone greases come into contact in the thickness direction, the curing catalyst contained in the first thermally conductive silicone grease penetrates and then diffuses into the uncured second thermally conductive silicone grease, causing an addition reaction between the curing catalyst and the crosslinker, resulting in curing. The first and second thermally conductive silicone greases are joined via the joint formed by this curing. The first and second thermally conductive silicone greases are in an uncured state except for the joint.

[0060] [Thermal Conductive Silicone Grease Composition] The thermally conductive silicone grease composition of the present invention will now be described with reference to the drawings. In the following drawings, the same reference numerals refer to the same components. FIGS. 1A and 1B are schematic plan views of a thermally conductive silicone grease composition according to one embodiment of the present invention. In FIG. 1A, first thermally conductive silicone greases 2a and 2b and second thermally conductive silicone greases 3a and 3b are alternately dispensed and applied in a cylindrical shape from their respective dispensers to form a cylindrical array 1. In FIG. 1B, the cylindrical array 1 is compression molded into a molded product 4. In FIG. 1B, the first thermally conductive silicone greases 2a and 2b and the second thermally conductive silicone greases 3a and 3b come into contact with each other, causing an addition reaction and curing, thereby forming joints 5a, 5b, and 5c, while the remaining first thermally conductive silicone greases 2a and 2b and second thermally conductive silicone greases 3a and 3b are in an uncured state.

[0061] 2A and 2B are schematic plan views of a thermally conductive silicone grease composition according to another embodiment of the present invention. In Fig. 2A, first thermally conductive silicone greases 7a and 7b and second thermally conductive silicone greases 8a and 8b are alternately dispensed from their respective dispensers in a dot pattern to form a dot array 6. In Fig. 2B, the dot array 6 is compression molded into a molded product 10. In Fig. 2B, the first thermally conductive silicone greases 7a and 7b and the second thermally conductive silicone greases 8a and 8b come into contact with each other, causing an addition reaction and curing, thereby forming joints 9a, 9b, and 9c, while the remaining first thermally conductive silicone greases 7a and 7b and second thermally conductive silicone greases 8a and 8b remain uncured.

[0062] In a heat shock test in which 1.0 g of the thermally conductive silicone grease composition is placed between two plates, compressed to a thickness of 1.0 mm, and the two plates are held vertically and placed in a heat shock tester, and the plates are held at -40°C and 125°C for 30 minutes each, for 500 cycles, the thermally conductive silicone grease composition preferably falls within 5 mm. This allows the thermally conductive silicone grease composition to maintain good drop resistance. High drop resistance in the thermally conductive silicone grease composition is preferred because it prevents leaching from the composition and prevents contamination of the surrounding area after installation in a heat-generating component.

[0063] [Method for producing thermally conductive silicone grease composition] The method for producing the thermally conductive silicone grease composition of the present invention includes the steps of filling dispensers with the first thermally conductive silicone grease and the second thermally conductive silicone grease, respectively; alternately discharging and applying the first and second thermally conductive silicone greases from the discharge holes of the dispensers while leaving a gap of 10% to 90% of the applied thickness so that the thermally conductive silicone greases do not come into contact with each other; and compression-molding the applied first and second thermally conductive silicone greases at a compression ratio of 10% to 90% of the applied thickness, thereby causing an addition reaction at the contact points between the first and second thermally conductive silicone greases to form joints, and joining the first and second thermally conductive silicone greases via these joints to produce the thermally conductive silicone grease composition. For example, if the gap is 10% of the applied thickness, the first and second thermally conductive silicone greases are compression molded at a compression rate of 10%, and if the gap is 90% of the applied thickness, the first and second thermally conductive silicone greases are compression molded at a compression rate of 90%.This allows for the production of a void-free thermally conductive silicone grease composition.

[0064] In the application step of the manufacturing method, the first and second thermally conductive silicone greases may be applied by alternately dispensing them in cylindrical or dot-like shapes. The manufacturing method may also be carried out when mounting the thermally conductive silicone grease composition on a heat-generating component. In the case of a cylindrical shape, the diameter of the cylinder is preferably 0.5 to 3.0 mm and the length is preferably 50 to 1000 mm. In the case of a dot-like shape, the dots are preferably 0.5 to 30 mm in diameter. A thermally conductive silicone grease composition within the above ranges is convenient for incorporation into heat-generating electrical and electronic components. The thermally conductive silicone grease composition may also be formed into a thermally conductive sheet. The thickness of the thermally conductive sheet is preferably 0.1 to 5 mm.

[0065] The compression molding in the above manufacturing method is preferably carried out at a temperature in the range of 80 to 150°C for a period of 5 to 60 minutes. This range allows for more efficient application of the thermally conductive silicone grease composition.

[0066] [Thermal Conductive Sheet] The present invention relates to a thermally conductive sheet formed from the thermally conductive silicone grease composition of the present invention. Figure 3 is a schematic cross-sectional view of a thermally conductive sheet according to one embodiment of the present invention incorporated into a heat dissipation structure 16. The thermally conductive sheet 11b dissipates heat generated by an electronic component 13, such as a semiconductor device. The thermally conductive sheet 11b is fixed to the main surface 12a of the heat spreader 12 facing the electronic component 13 and is sandwiched between the electronic component 13 and the heat spreader 12. The thermally conductive sheet 11a is sandwiched between the heat spreader 12 and a heat sink 15. The thermally conductive sheets 11a and 11b, together with the heat spreader 12, constitute a heat dissipation member that dissipates heat from the electronic component 13. The heat spreader 12 is formed, for example, in the shape of a rectangular plate and has a main surface 12a facing the electronic component 13 and a sidewall 12b extending along the outer periphery of the main surface 12a. The heat spreader 12 has a main surface 12a surrounded by side walls 12b, on which a thermally conductive sheet 11b is provided, and a heat sink 15 is provided on the other surface 12c opposite to the main surface 12a, via the thermally conductive sheet 11a. The electronic component 13 is, for example, a semiconductor element such as a BGA, and is mounted on a wiring board 14.

[0067] In one aspect, the present invention provides a method for producing a thermally conductive sheet, which comprises molding the thermally conductive silicone grease composition of the present invention into a sheet and then curing it. Once molded into a sheet and cured, the thermally conductive silicone grease composition of the present invention is suitable as a thermal interface material (TIM). The sheet molding method may be a roll molding method or a press molding method (mold clamping method). Sheet molding is preferably carried out by sandwiching the compound thermally conductive silicone grease composition between polyethylene terephthalate (PET) films and rolling them, and curing is preferably carried out by heating at 80 to 150°C for 10 to 120 minutes.

[0068] In one aspect, the present invention relates to use of the thermally conductive sheet of the present invention, in which the sheet is interposed between a heat generating body such as an electronic component or an electric component, and a heat dissipating body such as a heat spreader or a heat sink.

[0069] The present invention includes the following aspects.

[0070] [Item 1] A thermally conductive silicone grease composition comprising a first thermally conductive silicone grease, a second thermally conductive silicone grease, and a joint therebetween, wherein the first thermally conductive silicone grease contains a curing reaction catalyst but does not contain a crosslinking agent, the second thermally conductive silicone grease does not contain a curing reaction catalyst but does contain a crosslinking agent, the first and second thermally conductive silicone greases are joined via the joint on at least one opposing surface, the joint is cured, and the first and second thermally conductive silicone greases are in an uncured state apart from the joint.

[0071] [Item 2] The thermally conductive silicone grease composition according to Item 1, wherein the curing reaction catalyst is a catalyst used in a hydrosilylation reaction.

[0072] [Item 3] The thermally conductive silicone grease composition according to Item 1 or 2, wherein the curing reaction catalyst is a platinum-based catalyst such as platinum black, platinic chloride, chloroplatinic acid, a reaction product of chloroplatinic acid with a monohydric alcohol, a complex of chloroplatinic acid with an olefin or vinylsiloxane, platinum bisacetoacetate, or a platinum group metal catalyst such as a palladium-based catalyst or a rhodium-based catalyst, preferably a platinum-based metal catalyst.

[0073] [Item 4] The thermally conductive silicone grease composition according to any one of Items 1 to 3, wherein the crosslinking agent is an organohydrogenpolysiloxane.

[0074] [Item 5] The thermally conductive silicone grease composition according to Item 4, wherein the organohydrogenpolysiloxane has two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) per molecule.

[0075] [Item 6] The thermally conductive silicone grease composition according to any one of Items 1 to 5, wherein the first and second thermally conductive silicone greases contain a matrix resin and thermally conductive particles.

[0076] [Item 7] The thermally conductive silicone grease composition according to Item 6, wherein the matrix resin comprises the following components (A) and (C): (A) a kinematic viscosity at 40°C of 100 to 3,000 mm 2 / s addition reaction curable organopolysiloxane: 100 parts by mass (C)R a Si(OR') 4-a (wherein R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1): 0 to 10 parts by mass of alkoxysilane

[0077] [Item 8] The thermally conductive silicone grease composition according to Item 7, wherein the organopolysiloxane contains two silicon-bonded alkenyl groups per molecule, the alkenyl groups being vinyl groups, allyl groups, or the like, having 2 to 8 carbon atoms, and particularly 2 to 6 carbon atoms.

[0078] [Item 9] The thermally conductive silicone grease composition according to Item 7 or 8, wherein the alkoxysilane is one or more selected from the group consisting of octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane.

[0079] [Item 10] The thermally conductive silicone grease composition according to any one of Items 7 to 9, wherein the matrix resin of the first and second thermally conductive silicone greases further contains 1 to 50 mass% of a non-reactive silicone oil (D) in component (A).

[0080] [Item 11] The non-reactive silicone oil has a kinematic viscosity at 25°C of, for example, 50 to 3,000 mm 2 / s, preferably 70 to 2,500 mm 2 Item 11. The thermally conductive silicone grease composition according to Item 10, wherein

[0081] [Item 12] The thermally conductive silicone grease composition according to Item 10 or 11, wherein the non-reactive silicone oil is dimethylpolysiloxane and / or diphenylpolysiloxane.

[0082] [Item 13] The thermally conductive silicone grease composition according to any one of Items 6 to 12, wherein the thermally conductive particles contain the following component (B): (B) 200 to 3,000 parts by mass of a thermally conductive filler per 100 parts by mass of the matrix resin.

[0083] [Item 14] The thermally conductive silicone grease composition according to any one of Items 6 to 13, wherein the material of the thermally conductive particles is preferably at least one selected from the group consisting of alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, quartz, and silica, and more preferably at least one selected from the group consisting of aluminum nitride, boron nitride, and alumina.

[0084] [Item 15] The thermally conductive silicone grease composition according to Item 13 or 14, wherein the thermally conductive filler (B) comprises a thermally conductive filler (B1) having a median particle size (D50) of 0.01 to 10 μm, a thermally conductive filler (B2) having a median particle size (D50) of more than 10 μm and not more than 80 μm, and a thermally conductive filler (B3) having a median particle size (D50) of more than 80 μm and not more than 150 μm.

[0085] [Item 16] The thermally conductive silicone grease composition according to Item 15, wherein the thermally conductive filler (B) preferably contains 100 to 1,000 parts by mass, more preferably 150 to 1,000 parts by mass, and even more preferably 300 to 850 parts by mass of the thermally conductive filler (B1) per 100 parts by mass of the matrix resin; the thermally conductive filler (B) preferably contains 100 to 500 parts by mass, more preferably 150 to 500 parts by mass, and even more preferably 200 to 450 parts by mass of the thermally conductive filler (B2) per 100 parts by mass of the matrix resin; and the thermally conductive filler (B) preferably contains 300 to 1,400 parts by mass, more preferably 300 to 1,300 parts by mass, and even more preferably 500 to 1,200 parts by mass of the thermally conductive filler (B3) per 100 parts by mass of the matrix resin.

[0086] [Item 17] The thermally conductive silicone grease composition according to Item 13, wherein the thermally conductive filler (B) comprises spherical agglomerated boron nitride particles.

[0087] [Item 18] The thermally conductive silicone grease composition according to Item 17, wherein the spherical agglomerated boron nitride particles comprise spherical agglomerated boron nitride particles (B4) having a median particle diameter D50 of 10 μm or more and 30 μm or less, and spherical agglomerated boron nitride particles (B5) having a median particle diameter D50 that is at least twice that of B1 and greater than 30 μm and less than 100 μm.

[0088] [Item 19] The thermally conductive silicone grease composition according to any one of Items 1 to 18, wherein at least one of the first and second thermally conductive silicone greases has a thermal conductivity of preferably 2.0 W / m K or more, more preferably 3.0 W / m K or more, even more preferably 4.0 W / m K or more, and preferably 20.0 W / m K or less.

[0089] [Item 20] The thermally conductive silicone grease composition according to any one of Items 1 to 19, wherein the first and second thermally conductive silicone greases each have an absolute viscosity at 23°C as measured with a Brookfield viscometer of preferably 1,000 to 20,000 Pa s, more preferably 1,500 to 18,000 Pa s, and even more preferably 2,000 to 15,000 Pa s.

[0090] [Item 21] The thermally conductive silicone grease composition according to any one of Items 1 to 20, wherein the first and second thermally conductive silicone greases each have a discharge amount of 2 to 10 g when filled into a 30 mL syringe and discharged for 9 seconds at a discharge pressure of 0.5 MPa through a discharge hole diameter of 2.5 mm.

[0091] [Item 22] The thermally conductive silicone grease composition according to any one of Items 1 to 21, wherein 1.0 g of the thermally conductive silicone grease composition is placed between two plates, compressed to a thickness of 1.0 mm, and the two plates are held vertically in a heat shock tester, where the composition is held at -40°C and 125°C for 30 minutes each, for 500 cycles, and the thermally conductive silicone grease composition falls no more than 5 mm.

[0092] [Item 23] A method for producing a thermally conductive silicone grease composition according to any one of Items 1 to 22, comprising the steps of: filling dispensers with the first thermally conductive silicone grease and the second thermally conductive silicone grease; applying the first and second thermally conductive silicone greases by alternately discharging them from the discharge holes of the dispensers, while leaving a gap of 10% to 90% of the applied thickness so that the thermally conductive silicone greases do not come into contact with each other; and compression-molding the applied first and second thermally conductive silicone greases at a compression rate of 10% to 90% of the applied thickness, thereby causing an addition reaction at the contacting portions of the first and second thermally conductive silicone greases to form joints, and joining the first and second thermally conductive silicone greases via these joints to produce a thermally conductive silicone grease composition.

[0093] [Item 24] The method for producing a thermally conductive silicone grease according to Item 23, wherein the applying step is carried out by alternately discharging the first and second thermally conductive silicone greases in cylindrical shapes and applying them.

[0094] [Item 25] The method for producing a thermally conductive silicone grease according to Item 24, wherein the cylindrical shape has a diameter of 0.5 to 3.0 mm and a length of 50 to 1000 mm.

[0095] [Item 26] The method for producing a thermally conductive silicone grease composition according to Item 23, wherein the applying step is carried out by alternately discharging and applying the first and second thermally conductive silicone greases in the form of dots.

[0096] [Item 27] ​​The method for producing a thermally conductive silicone grease composition according to Item 26, wherein the dots have a diameter of 0.5 to 30 mm.

[0097] [Item 28] The method for producing a thermally conductive silicone grease composition according to any one of Items 23 to 27, wherein the compression molding is carried out at a temperature in the range of 80 to 150°C for 5 to 60 minutes.

[0098] [Item 29] The method for producing a thermally conductive silicone grease composition according to any one of Items 23 to 28, wherein the method is carried out when mounting the thermally conductive silicone grease composition on a heat-generating component.

[0099] [Item 30] A thermally conductive sheet in which the thermally conductive silicone grease composition of any one of Items 1 to 22 is formed into a sheet.

[0100] [Item 31] A method for producing a thermally conductive sheet, comprising forming the thermally conductive silicone grease composition of any one of Items 1 to 22 into a sheet, and then curing the sheet.

[0101] [Item 32] The method for producing a thermally conductive sheet according to Item 31, wherein the forming into a sheet is preferably carried out by sandwiching the compound thermally conductive silicone grease composition between polyethylene terephthalate (PET) films and rolling, and the curing is preferably carried out by heating at 80 to 150°C for 10 to 120 minutes.

[0102] [Item 33] Use of a thermally conductive sheet, in which the thermally conductive sheet of Item 30 is interposed between a heat generating body and a heat dissipating body.

[0103] [Examples] The present invention will be described below using examples, but the present invention is not limited to these examples. First, the measurement method will be described.

[0104] <Thermal Conductivity> The thermal conductivity of the thermally conductive silicone grease was measured using a hot disk (compliant with ISO 22007-2:2008). As shown in FIG. 4A, this thermal conductivity measuring device 19 sandwiches a polyimide film sensor 17 between two samples 18a and 18b, applies a constant power to the sensor 17, and generates a constant amount of heat, analyzing the thermal characteristics from the temperature rise of the sensor 17. As shown in FIG. 4B, the tip 20 of the sensor 17 has a diameter of 7 mm and a double spiral electrode structure, with an applied current electrode 21 and a resistance value electrode (temperature measurement electrode) 22 located at the bottom. The thermal conductivity is calculated using the following equation (Equation 1):

[0105]

[0106] <Drop Test> Measurements were performed using the drop test shown in Figures 5A-D. 1.0 g of thermally conductive silicone grease 26 was applied between an aluminum plate 24 measuring 40 mm in length, 100 mm in width, and 5 mm thick and a glass plate 23 measuring 40 mm in length, 100 mm in width, and 5 mm thick (Figure 5A). The plates were compressed to a thickness of 1.0 mm using a spacer 25 (Figure 5B). 27 represents the thermally conductive silicone grease compressed to a thickness of 1.0 mm. The plate was then placed in a heat cycle tester so that the gap between the aluminum plate 24 and the glass plate 23 was perpendicular (Figure 5C). 28 represents the test specimen before testing. In this state, a heat cycle test was performed, holding the plate at -40°C and 125°C for 30 minutes each. After 500 cycles, the test specimen was removed and observed for any drop of the thermally conductive silicone grease 27. 29 represents the test specimen after testing (Figure 5D), and 30 represents the drop distance. The drop test for the thermally conductive silicone grease composition was carried out in the same manner as above, except that "thermally conductive silicone grease" was changed to "thermally conductive silicone grease composition." Evaluation criteria: A: The grease fell within 5 mm; B: The grease fell more than 5 mm.

[0107] <Absolute Viscosity of Thermally Conductive Silicone Grease> The absolute viscosity of the thermally conductive silicone grease was measured using a Brookfield HBDV2T viscometer. The spindle used was a T-E spindle, and the absolute viscosity was measured at a rotation speed of 5 rpm and 23°C.

[0108] <Ejection Test> A 30 mL syringe PSY-30F manufactured by Musashi Engineering was filled with thermally conductive silicone grease, and the ejection amount was measured when the grease was ejected for 9 seconds at an ejection pressure of 0.5 MPa.

[0109] 1. Matrix Resin (1) Organopolysiloxane (Component A), Curing Reaction Catalyst, Crosslinker A commercially available two-component addition reaction curing silicone liquid was used as Component A. One of the components (Component A) contained organopolysiloxane (base polymer component, Component A, kinematic viscosity at 40°C: 450 mm 2The other liquid (liquid B) contains organopolysiloxane (base polymer component, component A, kinematic viscosity at 40°C 450 mm 2 / s) and organohydrogenpolysiloxane (crosslinking agent), and does not contain a platinum group metal catalyst (curing reaction catalyst). In the examples, liquid (i) contains liquid A, and liquid (ii) contains liquid B. The mass ratio of liquid A to liquid B in the examples is A:B = 100:100. (2) Non-reactive silicone oil (component D) Dimethylpolysiloxane (kinetic viscosity at 25°C: 110 mm using a Brooklyn Field type rotational viscometer SP No. 2) was used as the non-reactive silicone oil. 2 (3) Alkoxysilane (Component C) Decyltrimethoxysilane was used as component (C).

[0110] 2. Thermally conductive particles (Component B) The thermally conductive particles listed in Table 1 were used as component (B). The average particle size is the D50 (median diameter) of the cumulative particle size distribution on a volume basis, measured using a laser diffraction / light scattering method. An example of a measuring instrument for this is the LA-950S2 laser diffraction / scattering particle distribution analyzer manufactured by Horiba, Ltd. The number before μm in the table indicates the average particle size of each particle. - Amorphous alumina (D50 = 0.3 μm) (Figure 6): Surface-treated with octyltrimethoxysilane. - Amorphous alumina (D50 = 2.3 μm) (Figure 7): Surface-treated with decyltrimethoxysilane. - Spherical alumina (D50 = 105 μm) (Figure 9): No surface treatment. - Aluminum nitride (D50 = 15 μm) (Figure 8): No surface treatment. Spherical agglomerated boron nitride (D50 = 25 μm) (FIG. 10): No surface treatment. Spherical agglomerated boron nitride (D50 = 60 μm) (FIG. 11): No surface treatment.

[0111] Example 1 (a) Thermally conductive silicone grease composition shown in Figure 1B The amounts of each material shown in Table 1 were weighed out, placed in a mixer, and mixed uniformly to prepare two types of thermally conductive silicone grease: liquid (i) (first thermally conductive silicone grease) and liquid (ii) (second thermally conductive silicone grease). Liquids (i) and (ii) of this thermally conductive silicone grease were each filled into a 30 mL syringe PSY-30F manufactured by Musashi Engineering, Inc., and alternately dispensed onto a plate as shown in Figure 1A at a dispensing pressure of 0.3 MPa. The dispensed thermally conductive silicone grease liquids (i) and (ii) were cylindrical with an average diameter of 3 mm and an average length of 15 mm. A gap of 20% of the coating thickness was provided.

[0112] As shown in Figure 1A, the cylindrical thermally conductive silicone grease liquids (i) and (ii) were extruded and compressed to a thickness of 1.0 mm using a spacer, and then compression-molded by leaving the cylinders in an oven at 100°C for 10 minutes. The compression ratio of the cylindrical bodies was 66%. The resulting thermally conductive silicone grease composition had a thickness of 1 mm.

[0113] (b) Thermally conductive silicone grease composition shown in Figure 2B The amounts of each material shown in Table 1 were weighed out, placed in a mixing device, and mixed uniformly to prepare two types of thermally conductive silicone grease: liquid (i) (first thermally conductive silicone grease) and liquid (ii) (second thermally conductive silicone grease). Liquids (i) and (ii) of this thermally conductive silicone grease were each filled into a 30 mL syringe PSY-30F manufactured by Musashi Engineering, Inc., and ejected at a discharge pressure of 0.3 MPa as shown in Figure 2A. Figure 2A shows dots (spherical bodies) with an average diameter of 3 mm. A gap of 20% was provided relative to the coating thickness.

[0114] As shown in Figure 2A, the dot-shaped (spherical) thermally conductive silicone grease liquids (i) and (ii) were ejected and compressed to a thickness of 1.0 mm using spacers, and then compression-molded by leaving the dot-shaped (spherical) bodies in an oven at 100°C for 10 minutes. The compression ratio of the dot-shaped (spherical) bodies was 66%. The resulting thermally conductive silicone grease composition had a thickness of 1 mm.

[0115] Example 2 (a) Thermally conductive silicone grease composition shown in Figure 1B A thermally conductive silicone grease composition was produced in the same manner as Example 1(a), except that the amounts of each material were changed to the amounts shown in Table 1. (b) Thermally conductive silicone grease composition shown in Figure 2B A thermally conductive silicone grease composition was produced in the same manner as Example 1(b), except that the amounts of each material were changed to the amounts shown in Table 1.

[0116] Comparative Examples 1 and 2 The amounts of each material shown in Table 1 were weighed out and placed in a mixer to uniformly mix, thereby preparing a thermally conductive silicone grease.

[0117] The above conditions and results are summarized in Table 1. In Table 1, the amount of each material is shown in parts by mass when the matrix resin is taken as 100 parts by mass (100 g).

[0118]

[0119] The above results reveal the following. (1) From the results of Examples 1 and 2, the first thermally conductive silicone grease (liquid i) and the second thermally conductive silicone grease (liquid ii) were both rated B in the drop test, while the thermally conductive silicone grease composition shown in Figures 1B and 2B was rated A in the drop test. This is presumably because the junction between the first and second thermally conductive silicone greases was cured, trapping leached components in the first and second thermally conductive silicone greases. (2) From the results of Examples 1 and 2, the first thermally conductive silicone grease (liquid i) and the second thermally conductive silicone grease (liquid ii) had good dischargeability. This means that the first and second thermally conductive silicone greases can be stored for long periods of time because they do not harden in the dispenser. (3) Comparative Example 1 was rated B in the drop test. This result is presumably due to the fact that in Comparative Example 1, non-reactive silicone oil is the main component of the matrix resin, and therefore it is not expected that the exuded components will be trapped by the curing of the matrix resin.

[0120] The thermally conductive silicone grease composition of the present invention is suitable as a thermal interface material (TIM) that is a heat-dissipating sheet to be placed between the heat-generating parts of electrical and electronic components and heat sinks.

[0121] REFERENCE SIGNS LIST 1 Cylindrical array 2a, 2b, 7a, 7b First thermally conductive silicone grease 3a, 3b, 8a, 8b Second thermally conductive silicone grease 4, 10 Molded body 5a, 5b, 5c, 9a, 9b, 9c Joint 6 Dot array 11a, 11b Thermally conductive sheet 12 Heat spreader 13 Electronic component 14 Wiring board 15 Heat sink 16 Heat dissipation structure 17 Sensor 18a, 18b Sample 19 Thermal conductivity measuring device 20 Sensor tip 21 Applied current electrode 22 Resistance value electrode (temperature measurement electrode) 23 Glass plate 24 Aluminum plate 25 Spacer 26 Thermally conductive silicone grease 27 Compressed thermally conductive silicone grease 28 Test piece before test 29 Test piece after test 30 Fall distance

Claims

1. A thermally conductive silicone grease composition comprising a first thermally conductive silicone grease, a second thermally conductive silicone grease, and a junction therebetween, wherein the first thermally conductive silicone grease contains a curing reaction catalyst but does not contain a crosslinking agent, the second thermally conductive silicone grease does not contain a curing reaction catalyst but does contain a crosslinking agent, the first and second thermally conductive silicone greases are joined via the junction on at least one opposing surface, the junction is cured, and the first and second thermally conductive silicone greases are in an uncured state apart from the junction.

2. The thermally conductive silicone grease composition according to claim 1, wherein the first and second thermally conductive silicone greases contain a matrix resin and thermally conductive particles, the matrix resin contains the following components (A) and (C), and the thermally conductive particles contain the following component (B). (A) A kinetic viscosity at 40°C of 100 to 3000 mm 2 (B) Organopolysiloxane capable of addition reaction curing of the matrix resin: 100 parts by mass; (C) Thermally conductive filler: 200 to 3,000 parts by mass relative to 100 parts by mass of the matrix resin; a Si(OR′) 4-a (wherein R is an unsubstituted or substituted organic group having 8 to 12 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1): 0 to 10 parts by mass of alkoxysilane 3. A thermally conductive silicone grease composition according to claim 2, wherein the matrix resin of the first and second thermally conductive silicone greases further contains (D) 1 to 50 mass % of a non-reactive silicone oil in the component (A).

4. The thermally conductive silicone grease composition according to claim 2 or 3, wherein the material of the thermally conductive particles is at least one selected from the group consisting of alumina, zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, quartz, and silica.

5. A thermally conductive silicone grease composition according to any one of claims 1 to 4, wherein at least one of the first and second thermally conductive silicone greases has a thermal conductivity of 2.0 W / m·K or higher.

6. A thermally conductive silicone grease composition according to any one of claims 1 to 5, wherein the first and second thermally conductive silicone greases each have an absolute viscosity, as measured by a B-type viscometer at 23°C, in the range of 1,000 to 20,000 Pa·s.

7. A thermally conductive silicone grease composition according to any one of claims 1 to 6, wherein the first and second thermally conductive silicone greases are each filled into a 30 mL syringe and discharged in an amount of 2 to 10 g when discharged for 9 seconds with a discharge hole diameter of 2.5 mm and a discharge pressure of 0.5 MPa.

8. The thermally conductive silicone grease composition according to any one of claims 1 to 7, wherein 1.0 g of the thermally conductive silicone grease composition is placed between two plates, compressed and held to a thickness of 1.0 mm, the two plates are held vertically and placed in a heat shock tester, and held at -40°C and 125°C for 30 minutes each, for 500 cycles, in which the thermally conductive silicone grease composition falls no more than 5 mm.

9. A method for producing a thermally conductive silicone grease composition as defined in any one of claims 1 to 8, comprising the steps of: filling a dispenser with each of the first and second thermally conductive silicone greases; alternately discharging and applying the first and second thermally conductive silicone greases from a discharge hole of the dispenser while leaving a gap of 10% to 90% of the application thickness so that the respective thermally conductive silicone greases do not come into contact with each other; and compression molding the applied first and second thermally conductive silicone greases at a compression rate of 10% to 90% of the application thickness, thereby causing an addition reaction at the contact portions of the first and second thermally conductive silicone greases to form joints, and joining the first and second thermally conductive silicone greases via these joints to produce a thermally conductive silicone grease composition.

10. A method for producing a thermally conductive silicone grease as described in claim 9, wherein the applying step is carried out by alternately discharging and applying the first and second thermally conductive silicone grease in cylindrical form.

11. A method for producing a thermally conductive silicone grease composition as described in claim 9, wherein the applying step is carried out by alternately discharging and applying the first and second thermally conductive silicone greases in the form of dots.

12. A method for producing a thermally conductive silicone grease composition according to claim 9, which is carried out when mounting the thermally conductive silicone grease composition on a heat-generating component.

13. A thermally conductive sheet in which the thermally conductive silicone grease composition according to any one of claims 1 to 8 is formed into a sheet.

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