Thermally conductive silicone grease composition and production method for same

Abstract

The present invention provides: a thermally conductive silicone grease composition which has good viscosity and thermal conductivity, and in which a pump-out phenomenon upon a long period of use thereof is suppressed; and a production method for the same. The present invention comprises a matrix resin and thermally conductive inorganic particles. The matrix resin contains a component (A) and a component (B). The component (A) is an unreactive liquid dimethylpolysiloxane that has a kinematic viscosity of 100 to 10,000 mm2 / s at 25°C. The component (B) is a linear polydimethylsiloxane represented by formula (I) (where Me is methyl, n-Bu is normal butyl, and n = 5 to 1,000). The present invention contains X parts by mass of the component (A) (where X is 50 to 99.9), (100-X) parts by mass of the component (B), and 50 to 3, 000 parts by mass of the thermally conductive inorganic particles. The silicone grease composition is a non-curing product.

Description

Thermally conductive silicone grease composition and method for producing same

[0001] The present invention relates to a thermally conductive silicone grease composition suitable for placement between heat-generating parts of electrical and electronic components and heat sinks, and a method for producing the same.

[0002] In recent years, the performance of semiconductors such as CPUs has improved dramatically, resulting in enormous increases in the amount of heat they generate. Heat sinks are therefore attached to heat-generating electronic components, and thermally conductive silicone grease is used to improve adhesion between the heat sink and the heat-generating component, such as a semiconductor. However, when used over a long period of time, thermally conductive silicone grease can leak out of the heat sink due to the thermal shock of the semiconductor element, creating voids in the heat sink, resulting in the problem of "pumping out."

[0003] Japanese Patent Application Laid-Open No. 2023-026788 proposes a thermally conductive silicone grease containing a specific cyclic organopolysiloxane and crosslinked. Japanese Patent Application Laid-Open No. 2021-147591 proposes a thermally conductive silicone grease crosslinked using hydrosilylation catalyst fine particles having a microcapsule structure. Japanese Patent Application Laid-Open No. 2021-098804 proposes a thermally conductive silicone grease crosslinked using an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule.

[0004] The present invention provides a thermally conductive silicone grease composition comprising a matrix resin and thermally conductive inorganic particles, wherein the matrix resin comprises the following components (A) and (B): (A) is a silicone grease having a kinematic viscosity at 25°C of 100 to 10,000 mm 2 / s, wherein (B) is a linear polydimethylsiloxane represented by the following formula (I):

[0005]

[0006] (where Me is methyl, n-Bu is normal butyl, and n = 5 to 1000) The thermally conductive silicone grease composition comprises X parts by mass of the component (A) (X is 50 to 99.9), (100 - X) parts by mass of the component (B), and 50 to 3000 parts by mass of the thermally conductive inorganic particles, and the thermally conductive silicone grease composition is a non-cured product.

[0007] 1A-B are explanatory diagrams showing a method for measuring the thermal conductivity of a sample in one embodiment of the present invention. FIG. 2 is a photograph of the surface of a sample showing cracks or fissures in a pumping-out test in one embodiment of the present invention. FIG. 3 is a scanning electron microscope (SEM) photograph (magnification: 5000x) of amorphous alumina (D50 = 0.3 μm) (C-1) used in one embodiment of the present invention. FIG. 4 is an SEM photograph (magnification: 3000x) of spherical alumina (D50 = 2.0 μm) (C-2) used in one embodiment of the present invention. FIG. 5 is an SEM photograph (magnification: 1000x) of spherical alumina (D50 = 20 μm) (C-3) used in one embodiment of the present invention. FIG. 6 is an SEM photograph (magnification: 100x) of spherical alumina (D50 = 120 μm) used in one embodiment of the present invention. Detailed Description of the Invention

[0008] However, the thermally conductive silicone grease of the prior art still has the problem of being prone to pumping out when used for a long period of time.

[0009] In order to solve the above-mentioned problems of the prior art, the present invention provides a thermally conductive silicone grease composition that has good viscosity and thermal conductivity and that suppresses pumping-out during long-term use, as well as a method for producing the same.

[0010] One embodiment of the present invention is a thermally conductive silicone grease composition comprising a matrix resin and thermally conductive inorganic particles, wherein the matrix resin comprises the following components (A) and (B), and component (A) has a kinematic viscosity at 25°C of 100 to 10,000 mm 2 The component (B) is a non-reactive liquid dimethylpolysiloxane of the formula (I):

[0011]

[0012] (where Me is methyl, n-Bu is normal butyl, and n = 5 to 1000) The present invention relates to a thermally conductive silicone grease composition comprising X parts by mass of component (A) (X is 50 to 99.9), (100 - X) parts by mass of component (B), and 50 to 3000 parts by mass of the thermally conductive inorganic particles, wherein the silicone grease composition is a non-cured product.

[0013] One embodiment of the method of the present invention relates to a method for producing the thermally conductive silicone grease composition described above, which comprises a step of mixing and stirring the component (A) and the component (B) with thermally conductive inorganic particles.

[0014] The thermally conductive silicone grease composition of the present invention is in an uncured state, has good viscosity and thermal conductivity, and is a thermally conductive silicone grease composition that suppresses pumping-out during long-term use. The methoxy group at one end of the compound of chemical formula (I), component (B), chemically reacts with the surface of the thermally conductive inorganic particles to form a covalent bond, and the organosiloxane group at the other end has high affinity with component (A) of the matrix resin. In other words, component (B) acts as a coupling agent between the thermally conductive inorganic particles and component (A) of the matrix resin. Therefore, pumping-out, such as cracks or fissures, is suppressed even when the thermally conductive silicone grease composition of the present invention is used for long periods of time.

[0015] The present inventors investigated why pumping-out occurs when a thermally conductive silicone grease composition is used for an extended period of time. As a result, they came up with the idea that this may be due to separation at the interface between the matrix resin and the thermally conductive inorganic particles, leading to the pumping-out phenomenon of cracks or fissures. This phenomenon was particularly common when large thermally conductive inorganic particles were included to increase thermal conductivity.

[0016] The methoxy group at one end of the compound of formula (I) (component (B)) chemically reacts with the surface of the thermally conductive inorganic particles to form a covalent bond, while the organosiloxane group at the other end has a high affinity with the matrix resin. In other words, component (B) acts as a coupling agent for the thermally conductive inorganic particles. For this reason, it can be assumed that the thermally conductive silicone grease composition of the present invention, which contains the compound of formula (I) together with a matrix resin, exhibits the effect of suppressing pumping-out, such as cracks, even over long periods of use.

[0017] [Thermal Conductive Silicone Grease Composition] <Matrix Resin> The matrix resin contains X parts by mass of the component (A) and (100-X) parts by mass of the component (B), where X is 50 to 99.9, preferably 60 to 98, and more preferably 70 to 95.

[0018] <<Component (A): kinematic viscosity at 25°C of 100 to 10,000 mm 2 The component (A) is a non-reactive liquid dimethylpolysiloxane having a kinematic viscosity at 25°C of 100 to 10,000 mm 2 The kinematic viscosity is preferably 100 to 5000 mm 2 / s, and more preferably 100 to 3000 mm 2 / s.

[0019] <<Component (B): Linear Polydimethylsiloxane Represented by Formula (I)>> The component B is a linear polydimethylsiloxane represented by formula (I).

[0020]

[0021] n is 5 to 1,000, preferably 10 to 900, more preferably 20 to 500, and even more preferably 30 to 250.

[0022] <Component (C): Thermally Conductive Inorganic Particles> The thermally conductive silicone grease composition of the present invention contains 50 to 3000 parts by mass, preferably 100 to 2800 parts by mass, and more preferably 200 to 2500 parts by mass of thermally conductive inorganic particles, which enables the thermal conductivity of the thermally conductive silicone grease composition to be maintained at a high level.

[0023] The thermally conductive inorganic particles are preferably inorganic particles of aluminum oxide (alumina), zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, silicon carbide, etc. These inorganic particles have high thermal conductivity and are suitable as a TIM (Thermal Interface Material).

[0024] The thermally conductive inorganic particles can be in a variety of shapes, including spherical, scaly, and polyhedral. When using alumina, α-alumina with a purity of 99.5% by weight or higher is preferred. The average particle size of the thermally conductive inorganic 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.

[0025] The thermally conductive inorganic particles may be used in combination with at least two thermally conductive inorganic particles having different average particle sizes, because in this case, the thermally conductive inorganic particles having a smaller particle size are embedded between the larger particles, allowing for a state of nearly closest packing, thereby increasing thermal conductivity.

[0026] It is preferable that the total amount of thermally conductive inorganic particles (component (C)) is composed of 0 to 30 vol% of thermally conductive inorganic particles with a median diameter D50 of less than 1 μm in the cumulative particle size distribution on a volume basis, 15 to 55 vol% of thermally conductive inorganic particles with a diameter of 1 μm or more but less than 10 μm, and 5 to 55 vol% of thermally conductive inorganic particles with a diameter of 30 μm or more. By mixing large, medium, and small particles in this way, the medium and small particles fill the spaces between the large particles, thereby improving thermal conductivity.

[0027] It is preferable that the total amount of thermally conductive inorganic particles (component (C)) be 3 to 30 vol% thermally conductive inorganic particles with a median diameter D50 of less than 1 μm in the cumulative particle size distribution on a volume basis, 15 to 55 vol% thermally conductive inorganic particles with a diameter of 1 μm or more but less than 10 μm, 10 to 50 vol% thermally conductive inorganic particles with a diameter of 10 μm or more but less than 30 μm, and 5 to 55 vol% thermally conductive inorganic particles with a diameter of 30 μm or more. Mixing large, medium, and small particles in this way allows the medium and small particles to fill in between the large particles, improving thermal conductivity. Thermally conductive inorganic particles are also called thermally conductive fillers.

[0028] Preferably, the thermally conductive inorganic particles contain, relative to 100 parts by mass of the matrix resin, 100 to 400 parts by mass of thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, 200 to 500 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 1 μm or more and less than 10 μm, 100 to 400 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 10 μm or more and less than 30 μm, and 800 to 1,100 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 30 μm or more.

[0029] More preferably, the thermally conductive inorganic particles contain, relative to 100 parts by mass of the matrix resin, 150 to 350 parts by mass of thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, 250 to 450 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 1 μm or more and less than 10 μm, 150 to 350 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 10 μm or more and less than 30 μm, and 750 to 1050 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 30 μm or more.

[0030] The thermally conductive inorganic particles having a median diameter D50 of less than 1 μm are preferably at least one selected from the group consisting of alumina (aluminum oxide) and aluminum nitride, because alumina particles and aluminum nitride particles themselves have high thermal conductivity.

[0031] The thermally conductive inorganic particles having a median diameter D50 of 30 μm or more preferably include thermally conductive inorganic particles having a median diameter D50 of 70 μm or more, and the material of the thermally conductive inorganic particles having a median diameter D50 of 70 μm or more is preferably at least one selected from the group consisting of alumina and aluminum nitride.The thermally conductive inorganic particles having a median diameter D50 of 30 μm or more preferably include thermally conductive inorganic particles having a median diameter D50 of 80 μm or more, and more preferably the proportion of these particles is 40% by mass to 60% by mass of the total amount of the thermally conductive inorganic particles.This is because the addition of these large particles allows the thermal conductivity of the thermally conductive silicone grease composition to be maintained at a high level.

[0032] The small particles having a median diameter D50 of 1 μm or less are preferably surface-pretreated with a coupling agent. Examples of the coupling agent include alkylalkoxysilanes. Examples of the alkylalkoxysilanes include those represented by the formula R(CH3) a Si(OR') 4-a (R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a partial hydrolyzate thereof. Examples of the silane compound include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and the like. These silane compounds can be used alone or in combination. If the fine thermally conductive inorganic particles having a median diameter D=50 of 1 μm or less are surface-treated with a coupling agent in advance, the particles will have better mixability when compounded, improving workability.

[0033] <Thermal Conductive Silicone Grease Composition> The thermally conductive silicone grease composition of the present invention preferably contains the components (A), (B), and (C) in the following proportions: Component (A): X parts by mass (X is 50 to 99.9, more preferably 60 to 98, and even more preferably 70 to 95), Component (B): (100-X) parts by mass (X is 50 to 99.9, more preferably 60 to 98, and even more preferably 70 to 95), and Component (C): 50 to 3,000 parts by mass, preferably 100 to 2,800 parts by mass, and even more preferably 200 to 2,500 parts by mass. A thermally conductive silicone grease composition of the present invention with these proportions can exhibit high thermal conductivity, making it suitable as a thermally conductive material: TIM (Thermal Interface Material).

[0034] The thermally conductive silicone grease composition preferably has a kinematic viscosity at 25°C, as measured with a rotational viscometer, in the range of 200 to 30,000 Pas, more preferably 220 to 2800 Pas, and even more preferably 250 to 2500 Pas. Due to this fluidity, the thermally conductive silicone grease composition of the present invention has the advantage that it can be used as a thermally conductive material (TIM: Thermal Interface Material), even in narrow gaps.

[0035] The thermal conductivity of the thermally conductive silicone grease composition is preferably 1.0 W / m K or more and 30 W / m K or less, more preferably 2.0 to 30 W / m K, and even more preferably 3.0 to 30 W / m K. Such a thermally conductive silicone grease composition is suitable as a TIM (thermal interface material).

[0036] The thermally conductive silicone grease composition was applied to a 300 mm 2In a pumping-out test in which a test piece compressed and clamped to a thickness of 2.0 mm is placed horizontally in a heat shock tester and held at -40°C and 125°C for 30 minutes each, for 100 cycles, it is preferable that no cracks with gaps of 1 mm or more are present, or that if present, there are no more than two. Furthermore, in the same pumping-out test, it is preferable that no voids with a diameter of 0.3 mm or more are present, or that if present, there are no more than nine. With such a thermally conductive silicone grease composition, the pumping-out phenomenon caused by the occurrence of cracks or voids is suppressed even when used for long periods of time.

[0037] The thermally conductive silicone grease composition is non-curing because it uses a matrix resin containing a non-reactive liquid dimethylpolysiloxane. Despite being non-curing, the thermally conductive silicone grease composition of the present invention is able to prevent pumping out.

[0038] The thermally conductive silicone grease composition of the present invention can be used as a grease, putty, liquid, etc., but is preferably used as a thermally conductive grease. This thermally conductive grease is ideally filled into a syringe and applied as a thermal interface material (TIM) between heat-generating and heat-dissipating parts of electronic components, etc.

[0039] [Method for Producing Thermally Conductive Silicone Grease Composition] The method for producing a thermally conductive silicone grease composition of the present invention comprises the step of mixing and stirring the aforementioned components (A), (B), and (C). The production method may further comprise the step of heating after the mixing and stirring. The heating temperature is preferably less than 300°C, more preferably 100 to 150°C. The heating time is preferably 5 minutes to 48 hours. Upon heating, the trimethoxy group at one end of component (B) chemically reacts with the surface of the thermally conductive inorganic particles, generating low-molecular-weight substances such as water or methanol. However, these low-molecular-weight substances evaporate outside the composition and do not remain within the composition, thereby improving the heat resistance of the thermally conductive silicone grease composition.

[0040] The thermally conductive silicone grease composition of the present invention is non-curing, and therefore does not require a curing catalyst or curing agent, although these may be added if desired.

[0041] The thermally conductive silicone grease composition of the present invention may contain other components as needed, such as heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardants, and flame retardant assistants. Furthermore, organic or inorganic particle pigments may be added to the thermally conductive silicone grease composition for the purposes of coloring or toning. Alkoxy group-containing silicones may also be added to the thermally conductive silicone grease composition as a material added for purposes such as surface treatment of the thermally conductive inorganic particles.

[0042] The thermally conductive silicone grease composition of the present invention can be filled into a variety of containers, such as pails, syringes, and cartridges, to produce a finished product.

[0043] The present invention includes the following aspects.

[0044] [Item 1] A thermally conductive silicone grease composition containing a matrix resin and thermally conductive inorganic particles, wherein the matrix resin contains the following components (A) and (B): Component (A) has a kinematic viscosity at 25°C of 100 to 10,000 mm 2 / s (preferably 100 to 5000 mm 2 / s, and more preferably 100 to 3000 mm 2 / s), and the component (B) is a linear polydimethylsiloxane represented by the following formula (I):

[0045]

[0046] (where Me is methyl, n-Bu is normal butyl, and n is 5 to 1000, preferably 10 to 900, more preferably 20 to 500, and even more preferably 30 to 250), a thermally conductive silicone grease composition comprising: X parts by mass of component (A) (X is 50 to 99.9, preferably 60 to 98, and more preferably 70 to 95); (100-X) parts by mass of component (B) (X is 50 to 99.9, more preferably 60 to 98, and even more preferably 70 to 95); and 50 to 3000 parts by mass, preferably 100 to 2800 parts by mass, and more preferably 200 to 2500 parts by mass of the thermally conductive inorganic particles, wherein the thermally conductive silicone grease composition is an uncured product.

[0047] [Item 2] The thermally conductive silicone grease composition according to Item 1, wherein the thermally conductive inorganic particles are inorganic particles such as aluminum oxide (alumina), zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, or silicon carbide.

[0048] [Item 3] The thermally conductive silicone grease composition according to Item 1 or 2, wherein the thermally conductive inorganic particles contain, per 100 parts by mass of the matrix resin: 100 to 400 parts by mass of thermally conductive inorganic particles having a median diameter D50 of less than 1 μm; 200 to 500 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 1 μm or more and less than 10 μm; 100 to 400 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 10 μm or more and less than 30 μm; and 800 to 1,100 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 30 μm or more.

[0049] [Item 4] The thermally conductive silicone grease composition according to any one of Items 1 to 3, wherein the thermally conductive inorganic particles contain, per 100 parts by mass of the matrix resin: 150 to 350 parts by mass of thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, 250 to 450 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 1 μm or more and less than 10 μm, 150 to 350 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 10 μm or more and less than 30 μm, and 750 to 1,050 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 30 μm or more.

[0050] [Item 5] The thermally conductive silicone grease composition according to any one of Items 1 to 4, wherein the thermally conductive inorganic particles comprise thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, and the material of the thermally conductive inorganic particles having a D50 of less than 1 μm is at least one selected from the group consisting of alumina and aluminum nitride.

[0051] [Item 6] The thermally conductive silicone grease composition according to any one of Items 1 to 5, wherein the thermally conductive inorganic particles comprise thermally conductive inorganic particles having a median diameter D50 of 70 μm or greater, and the material of the thermally conductive inorganic particles having a D50 of 70 μm or greater is at least one selected from the group consisting of alumina and aluminum nitride.

[0052] [Item 7] The thermally conductive silicone grease composition according to any one of Items 1 to 6, wherein the thermally conductive inorganic particles comprise thermally conductive inorganic particles having a median diameter D50 of 80 μm or greater, and the proportion of these particles relative to the total amount of the thermally conductive inorganic particles is 40% by mass or greater and 60% by mass or less.

[0053] [Item 8] The thermally conductive silicone grease composition according to any one of Items 1 to 7, wherein the thermally conductive inorganic particles comprise thermally conductive inorganic particles having a median diameter D50 of 1 μm or less, and the thermally conductive inorganic particles having a median diameter D50 of 1 μm or less have been surface pretreated with an alkylalkoxysilane.

[0054] [Item 9] The thermally conductive silicone grease composition according to any one of Items 1 to 8, wherein the kinematic viscosity at 25°C measured with a rotational viscometer is in the range of 200 to 30,000 Pas, preferably 220 to 2800 Pas, and more preferably 250 to 2500 Pas.

[0055] [Item 10] The thermally conductive silicone grease composition according to any one of Items 1 to 9, wherein the thermal conductivity of the thermally conductive silicone grease composition is 1.0 W / m K or more and 30 W / m K or less, preferably 2.0 to 30 W / m K, and more preferably 3.0 to 30 W / m K.

[0056] [Item 11] The thermally conductive silicone grease composition is applied between two plates with an area of ​​300 mm 211. The thermally conductive silicone grease composition according to any one of Items 1 to 10, wherein a test piece compressed and clamped to a thickness of 2.0 mm is placed horizontally in a heat shock testing machine and held at -40°C and 125°C for 30 minutes each, for 100 cycles. In this test, the composition has no cracks with a gap of 1 mm or more, or no more than two cracks if present, or no cracks with a length of 10 mm or more, or no more than two cracks if present.

[0057] [Item 12] The thermally conductive silicone grease composition according to Item 11, wherein, when the appearance of the thermally conductive silicone grease composition is inspected after the pumping-out test, there are no cracks with gaps of 1 mm or more, or if present, there are no more than two cracks, and there are no voids with a diameter of 0.3 mm or more, or if present, there are no more than nine voids.

[0058] [Item 13] A method for producing the thermally conductive silicone grease composition according to any one of Items 1 to 12, comprising the step of mixing and stirring the component A, the component B, and thermally conductive inorganic particles.

[0059] [Item 14] The method for producing a thermally conductive silicone grease composition according to Item 13, further comprising, after the mixing and stirring, a step of heating at a temperature of less than 300°C for 5 minutes to 48 hours.

[0060] [Examples] The present invention will be described below using examples, but is not limited to these examples. Various parameters were measured by the following methods.

[0061] <Thermal Conductivity> The thermal conductivity of the thermally conductive silicone grease composition was measured using a hot disk (in accordance with ISO 22007-2:2008). As shown in FIG. 1A, this thermal conductivity measuring device 1 sandwiches a polyimide film sensor 2 between two samples 3a and 3b. A constant power is applied to the sensor 2, generating a constant amount of heat, and the thermal characteristics are analyzed from the temperature rise of the sensor 2. The sensor 2 has a 7 mm diameter tip 4 and, as shown in FIG. 1B, has a double spiral electrode structure, with an applied current electrode 5 and a resistance value electrode (temperature measurement electrode) 6 located at the bottom. Measurement samples can be obtained by rolling a degassed thermally conductive liquid composition to a thickness of 7 mm or more. The thermal conductivity is calculated using the following equation (Equation 1):

[0062]

[0063] <Pumping-out test> The pumping-out test for the thermally conductive silicone grease composition was carried out by applying the thermally conductive silicone grease composition between an aluminum plate measuring 40 mm in length, 100 mm in width, and 5 mm in thickness and a glass plate measuring 40 mm in length, 100 mm in width, and 5 mm in thickness, and placing a spacer between the plates so that the area of ​​the thermally conductive silicone grease composition was 300 mm 2 , and sandwiched so that the thickness was 2.0 mm. Next, the aluminum plate and glass plate were placed in a heat cycle tester so that their main surfaces were parallel to the ground. In this state, the test piece was held at -40°C for 30 minutes, then heated to 125°C, and then held at 125°C for 30 minutes before cooling to -40°C. This cycle was repeated 100 times. After 100 cycles, the test piece of the thermally conductive silicone grease composition was removed and its appearance was observed. The temperature transition times from -40°C to 125°C and from 125°C to -40°C were each within 10 minutes.

[0064] Evaluation criteria (1): Presence or absence of cracks OK: When visually inspected, no cracks with a gap of 1 mm or more are present on the test piece, or if present, no more than two are observed. Alternatively, no cracks with a length of 10 mm or more are present, or if present, no more than two are observed. In other words, this includes cases where no cracks are observed. NG: When visually inspected, cracks with a gap of 1 mm or more are observed in three or more places on the test piece, or cracks with a length of 10 mm or more are observed in three or more places.

[0065] Evaluation criterion (2): Presence or absence of voids OK: Voids with a diameter of 0.3 mm or more are visually observed in 9 or less places on the test piece. This includes cases where no voids are observed. NG: Voids with a diameter of 0.3 mm or more are visually observed in 10 or more places on the test piece. However, this does not pose a problem in practical use.

[0066] <Kinematic Viscosity> The kinematic viscosity of the thermally conductive silicone grease composition was measured using a MARSIII viscosity and viscoelasticity measuring device manufactured by HAAKE Corporation at a temperature of 25°C, a measurement thickness of 0.5 mm, and a rotation speed of 1.0 (1 / s). The average value measured from 30 seconds to 1 minute after the start of rotation was recorded as the kinematic viscosity. The catalog value was used for the kinematic viscosity of the raw material dimethylpolysiloxane.

[0067] (Examples 1 to 8, Comparative Example 1) 1. Raw material components (1) Matrix resin (component A+B) Component (A) is a matrix resin having a kinematic viscosity of 100 mm at 25°C. 2 A non-reactive liquid dimethylpolysiloxane having a viscosity of 1 / s (product number TSF458-100, manufactured by Momentive Performance Materials Japan Co., Ltd.) was used. A linear polydimethylsiloxane represented by chemical formula I-1 was used as component (B).

[0068]

[0069] (2) Thermally conductive inorganic particles (component (C)) Thermally conductive particles (C-1), (C-2), (C-3), and (C-4) listed in Table 1 were used. The average 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 a measuring instrument for this is the LA-950S2 laser diffraction / scattering particle distribution analyzer manufactured by Horiba, Ltd. As component (C-1), amorphous alumina D50 = 0.3 μm, pretreated with octyltrimethoxysilane, was used. As component (C-2), spherical alumina D50 = 2 μm (75 μm top cut product) was used. As component (C-3), spherical alumina D50 = 20 μm (55 μm top cut product) was used. As component (C-4), spherical alumina D50=120 μm (150 μm top cut product) was used.

[0070] 2. Mixing Method The thermally conductive inorganic particles were added to the matrix resin and mixed and stirred using a planetary mixer to obtain a thermally conductive silicone grease composition. When heating was performed after mixing and stirring, the heating temperature and time are shown in Table 1. The thermally conductive silicone grease compositions obtained in this manner were evaluated. The conditions and results are summarized in Table 1 below.

[0071]

[0072] The above results reveal the following: (1) In Examples 1 to 8, the pumping-out test found no more than two cracks with gaps of 1 mm or more, and the pumping-out test was successful. (2) In Examples 2 to 4, the pumping-out test found no less than 10 voids with a diameter of 0.3 mm or more, but this posed no practical problems. (3) In Examples 5 to 8, heat treatment was performed at 100 to 250°C for 24 hours, and the pumping-out test found no more than nine voids with a diameter of 0.3 mm or more, which was superior to Examples 2 to 4. (4) In contrast, in Comparative Example 1, which did not contain component (B), the pumping-out test found no more than three cracks with gaps of 1 mm or more, and the pumping-out test was unsuccessful. An example of cracks that occurred in the silicone grease composition of Comparative Example 1 is shown in Figure 2. The cracks in Figure 2 are cracks.

[0073] The thermally conductive silicone grease composition of the present invention is suitable as a thermally conductive material (TIM) to be placed between the heat-generating parts of electrical and electronic components and heat sinks.

[0074] [Explanation of symbols] 1 Thermal conductivity measuring device 2 Sensor 3a, 3b Sample 4 Sensor tip 5 Applied current electrode 6 Resistance value electrode (temperature measurement electrode)

Claims

1. A thermally conductive silicone grease composition comprising a matrix resin and thermally conductive inorganic particles, wherein the matrix resin contains the following components (A) and (B), and the component (A) has a kinematic viscosity at 25 °C of 100 to 10,000 mm 2 / s of non-reactive liquid dimethylpolysiloxane, and the component (B) is linear polydimethylsiloxane represented by the following formula (I), (wherein Me is methyl, n-Bu is normal butyl, and n = 5 to 1000) The component (A) is X parts by mass (X is 50 to 99.9), the component (B) is (100 - X) parts by mass, and the thermally conductive inorganic particles are contained in an amount of 50 to 3000 parts by mass. The thermally conductive silicone grease composition is a non-cured thermally conductive silicone grease composition.

2. The thermally conductive silicone grease composition according to claim 1, wherein, based on 100 parts by mass of the matrix resin, the thermally conductive inorganic particles include 100 to 400 parts by mass of thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, 200 to 500 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 1 μm or more and less than 10 μm, 100 to 400 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 10 μm or more and less than 30 μm, and 800 to 1100 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 30 μm or more.

3. The thermally conductive silicone grease composition according to claim 1 or 2, wherein, based on 100 parts by mass of the matrix resin, the thermally conductive inorganic particles include 150 to 350 parts by mass of thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, 250 to 450 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 1 μm or more and less than 10 μm, 150 to 350 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 10 μm or more and less than 30 μm, and 750 to 1050 parts by mass of thermally conductive inorganic particles having a median diameter D50 of 30 μm or more.

4. The thermally conductive silicone grease composition according to any one of claims 1 to 3, wherein the thermally conductive inorganic particles include thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, and the material of the thermally conductive inorganic particles having a D50 of less than 1 μm is at least one selected from the group consisting of alumina and aluminum nitride.

5. The thermally conductive silicone grease composition according to any one of claims 1 to 4, wherein the thermally conductive inorganic particles include thermally conductive inorganic particles having a median diameter D50 of 70 μm or more, and the material of the thermally conductive inorganic particles having a D50 of 70 μm or more is at least one selected from the group consisting of alumina and aluminum nitride.

6. The thermally conductive silicone grease composition according to any one of claims 1 to 5, wherein the kinematic viscosity at 25°C measured with a rotational viscometer is in the range of 200 to 30,000 Pa·s.

7. The thermally conductive silicone grease composition according to any one of claims 1 to 6, wherein the thermal conductivity is 1.0 W / m·K or more and 30 W / m·K or less.

8. The thermally conductive silicone grease composition is horizontally installed in a heat shock tester with a test piece compressed and clamped between two plates with an area of 300 mm 2 and a thickness of 2.0 mm. In the pumping out test, where it is held at -40°C and 125°C for 30 minutes each and 100 cycles are allowed to elapse, there are no cracks with a gap of 1 mm or more, or if there are any, there are two or fewer, or there are no cracks with a length of 10 mm or more, or if there are any, there are two or fewer. The thermally conductive silicone grease composition according to any one of claims 1 to 7.

9. The heat-conductive silicone grease composition has no cracks with a gap of 1 mm or more or, if any, has two or less cracks when the appearance after the pumping-out test is checked, and has no voids with a diameter of 0.3 mm or more or, if any, has nine or less voids. The heat-conductive silicone grease composition according to claim 8.

10. The heat-conductive inorganic particles include heat-conductive inorganic particles having a median diameter D50 of 1 μm or less, and the heat-conductive inorganic particles having a median diameter D50 of 1 μm or less are surface-treated with an alkylalkoxysilane. The heat-conductive silicone grease composition according to any one of claims 1 to 9.

11. The heat-conductive inorganic particles include heat-conductive inorganic particles having a median diameter D50 of the cumulative particle size distribution on a volume basis of 80 μm or more, and the ratio thereof is 40% by mass or more and 60% by mass or less based on the total amount of the heat-conductive inorganic particles. The heat-conductive silicone grease composition according to any one of claims 1 to 10.

12. A method for producing a heat-conductive silicone grease composition according to any one of claims 1 to 11, the method including a step of mixing and stirring the component (A), the component (B), and heat-conductive inorganic particles.

13. The method for producing a heat-conductive silicone grease composition according to claim 12, further including a step of heating at a temperature of less than 300 °C for 5 minutes to 48 hours after the mixing and stirring.

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