Thermally conductive silicone resin composition, method for manufacturing the same, and thermally conductive silicone resin cured sheet

Abstract

To provide a thermally conductive silicone resin composition which has good thermal conductivity and in which a pumping-out phenomenon after extended use is prevented.SOLUTION: The thermally conductive silicone resin composition of the present invention contains the following components (A) to (C): (A) X (X=50-99) pts.mass of a liquid silicone resin, (B) (100-X) pts.mass of a linear organopolysiloxane represented by the following formula, and (C) 50-3000 pts.mass of a thermally conductive filler, and as the thermally conductive inorganic particles (C), contains at least one thermally conductive inorganic particle selected from the group consisting of alumina and aluminum nitride, having a median diameter D50 of a cumulative particle size distribution by volume of 80 μm or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive silicone resin composition suitable for placement between a heat-generating portion of an electric or electronic component or the like and a heat sink, a method for producing the same, and a cured thermally conductive silicone resin sheet. [Background technology]

[0002] In recent years, the performance of semiconductors such as CPUs has improved dramatically, resulting in enormous amounts of heat generation. Heat sinks are therefore attached to heat-generating electronic components, and thermally conductive silicone resins are used to improve adhesion between heat sinks and heat-generating components such as semiconductors. However, when used over a long period of time, thermally conductive silicone resins can flow 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. Patent Document 1 proposes a thermally conductive silicone resin containing a specific cyclic organopolysiloxane and crosslinked. Patent Document 2 proposes a thermally conductive silicone resin crosslinked using hydrosilylation catalyst particles having a microcapsule structure. Patent Document 3 proposes a thermally conductive silicone resin crosslinked using an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-026788 [Patent Document 2] Japanese Patent Application Publication No. 2021-147591 [Patent Document 3] Japanese Patent Publication No. 2021-098804 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the thermally conductive silicone compositions and cured thermally conductive silicone resin sheets of the prior art suffer from the problem of being prone to pumping out when used over an extended period of time.

[0005] In order to solve the above-mentioned problems of the conventional art, the present invention provides a thermally conductive silicone resin composition and a cured thermally conductive silicone resin sheet that have good thermal conductivity and suppress the pumping-out phenomenon during long-term use. [Means for solving the problem]

[0006] One embodiment of the present invention comprises the following components A to C: (A) liquid silicone resin: X (X=50-99) parts by mass, (B) (100-X) parts by mass of a linear organopolysiloxane represented by the following chemical formula (Chemical Formula 1): [ka] (However, R 1 ~R 3 is an alkyl group having 1 to 18 carbon atoms or a phenyl group, R 4 and R 5 are each independently an alkyl group having 1 to 18 carbon atoms or a phenyl group, R 6 and R 8 is an OH group, R 7 is an alkyl group having 1 to 3 carbon atoms or a phenyl group, n is 5 to 1000, and m is 1 to 20. 2 and the R 3 If there are multiple R 2 and R 3 may be the same or different from each other.) (C) Thermally conductive filler: 50 to 3,000 parts by mass The present invention relates to a thermally conductive silicone resin composition comprising, as the thermally conductive inorganic particles (C), at least one thermally conductive inorganic particle selected from the group consisting of alumina and aluminum nitride, having a median diameter D50 of a cumulative particle size distribution on a volume basis of 80 μm or more.

[0007] One embodiment of the method of the present invention relates to a method for producing the thermally conductive silicone resin composition, which comprises mixing and stirring the components A, B, and C. [Effects of the Invention]

[0008] The present invention provides a thermally conductive silicone resin composition and a cured thermally conductive silicone resin sheet that have good thermal conductivity and suppress pumping-out during long-term use. Specifically, the linear organopolysiloxane of component B acts as a coupling agent for the thermally conductive inorganic particles, with the organic group at one end of the molecule chemically reacting with the surface of the thermally conductive inorganic particles to form a covalent bond, and the organic group at the other end having high affinity with the matrix resin. Therefore, pumping-out, such as cracking or fissures, is suppressed even during long-term use. [Brief explanation of the drawings]

[0009] [Figure 1] 1A-B are explanatory diagrams showing a method for measuring the thermal conductivity of a sample in one embodiment of the present invention. [Figure 2] FIG. 2 is a photograph of the surface of a sample showing the state in which cracks or fissures have occurred in a pumping-out test according to an embodiment of the present invention. [Figure 3] FIG. 3 is a scanning electron microscope (SEM) photograph (magnification: 5000 times) of surface-pretreated amorphous alumina (median diameter D50) of 0.3 μm used in one embodiment of the present invention. [Figure 4] FIG. 4 is an SEM photograph (magnification 3000 times) of spherical alumina (median diameter D50 is 2.0 μm) used in one example of the present invention. [Figure 5] FIG. 5 is an SEM photograph (magnification: 5000 times) of crushed alumina (median diameter D50: 2.0 μm) used in one example of the present invention. [Figure 6] FIG. 6 is an SEM photograph (magnification 10,000 times) of spherical alumina (median diameter D50 is 4.0 μm) used in one example of the present invention. [Figure 7]FIG. 7 is an SEM photograph (magnification 1000 times) of spherical alumina (median diameter D50 is 20 μm) used in one example of the present invention. [Figure 8] FIG. 8 is an SEM photograph (magnification: 100 times) of spherical alumina (median diameter D50: 120 μm) used in one example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The inventors of the present invention investigated why pumping-out phenomena such as cracks or fissures occur in conventional technologies after long-term use. As a result, they came up with the idea that pumping-out phenomena such as cracks or fissures may occur when the matrix resin peels off at the interface of the thermally conductive inorganic particles. This phenomenon was particularly common when large thermally conductive inorganic particles were used to increase thermal conductivity. By incorporating the linear organopolysiloxane of component B in addition to the liquid silicone resin, the organic group at one end of the molecule chemically reacts with the surface of the thermally conductive inorganic particles to form a covalent bond, while the organic group at the other end has a high affinity with the matrix resin, thereby suppressing pumping-out phenomena such as cracks and fissures even after long-term use.

[0011] As an example of the linear organopolysiloxane of component B of the present invention, a compound represented by the following chemical formula (Chemical Formula 2) is preferred. [ka] (wherein Me is a methyl group, n-Bu is a normal butyl group, and n=5 to 1000). The OH group at one end of the molecule of this compound reacts chemically with the surface of the thermally conductive inorganic particles to form a covalent bond, while the n-Bu group at the other end has a high affinity with the matrix resin, which prevents pumping-out phenomena such as cracks and fissures even after long-term use.

[0012] The component (A) of the present invention is preferably at least one silicone selected from the group consisting of addition-curing silicone polymers and non-curing silicone oils. Silicones have high heat resistance and fluidity, making them suitable as thermally conductive materials (TIMs). An example of a non-curing silicone oil is a silicone oil made of dimethylpolysiloxane. An example of an addition-curing silicone polymer includes a base polymer (A-1) made of an organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms per molecule, and a crosslinking component (A-2) made of an organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms per molecule.

[0013] The addition-curing silicone polymer will now be described. (1) Base polymer component (Component A-1) The base polymer component is an organopolysiloxane containing two or more silicon-bonded alkenyl groups per molecule, and this organopolysiloxane containing two or more alkenyl groups is the main component (base polymer component) in the silicone rubber composition of the present invention. This organopolysiloxane contains two silicon-bonded alkenyl groups per molecule, such as vinyl or allyl groups, each having 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms. From the standpoint of workability and curability, the viscosity at 25°C is preferably 10 to 1,000,000 mPa·s, and more preferably 100 to 100,000 mPa·s. Specifically, an organopolysiloxane is used, which contains two or more alkenyl groups per molecule, each of which is represented by the following general formula (Chemical Formula 3), and which is bonded to a silicon atom at the molecular chain end. The side chains are linear organopolysiloxanes with alkyl groups capped. From the viewpoint of workability and curability, a viscosity of 10 to 1,000,000 mPa·s at 25°C is desirable. Note that this linear organopolysiloxane may also contain a small amount of branched structure (trifunctional siloxane units) in the molecular chain.

[0014] [ka] In the formula, R 1 are the same or different unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds, and R 2 is an alkenyl group, and k is 0 or a positive integer. 1 Examples of unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond include those having 1 to 10 carbon atoms, and particularly preferably 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, bromine, or chlorine, or with cyano groups, such as halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl; and cyanoethyl groups. 2 The alkenyl group preferably has 2 to 6 carbon atoms, particularly 2 to 3 carbon atoms, and specific examples include vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl groups, with vinyl being preferred. In general formula (1), k is generally 0 or a positive integer satisfying 0≦k≦10000, preferably 5≦k≦2000, and more preferably 10≦k≦1200. The organopolysiloxane of component (A-1) may be an organopolysiloxane having three or more, typically 3 to 30, and preferably 3 to 20, alkenyl groups, such as vinyl groups or allyl groups, bonded to silicon atoms having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, 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. The alkenyl group may be bonded to any part of the molecule. For example, it may be bonded to a silicon atom at either the molecular chain terminal or a non-terminal (mid-chain) location. Among these, linear organopolysiloxanes represented by the following general formula (Chemical Formula 4) have one to three alkenyl groups on each of the silicon atoms at both molecular chain terminals. However, if the total number of alkenyl groups bonded to the terminal silicon atoms is less than three, linear organopolysiloxanes having at least one alkenyl group bonded to a non-terminal (mid-chain) silicon atom (e.g., as a substituent in a diorganosiloxane unit) at the molecular chain are preferred from the viewpoints of workability and curability. These linear organopolysiloxanes may also contain a small amount of branched structures (trifunctional siloxane units) in the molecular chain.

[0015] [ka] In the formula, R 3 are the same or different unsubstituted or substituted monovalent hydrocarbon groups, and at least one is an alkenyl group. 4 are the same or different unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds, and R 5 is an alkenyl group, and l and m are 0 or positive integers. 3As the monovalent hydrocarbon group, those having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms are preferred. Specifically, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, alkenyl groups such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, octenyl group, and those in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, chlorine, cyano group, etc., for example, halogen-substituted alkyl groups such as chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, and cyanoethyl group, etc. can be mentioned. Also, R 4 As the monovalent hydrocarbon group of, those having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms are preferred, and the same as the specific examples of the above R 1 can be exemplified, but an alkenyl group is not included. As the alkenyl group of R 5 , for example, those having 2 to 6 carbon atoms, particularly 2 to 3 carbon atoms are preferred, and specifically, the same as R of the above formula (Chemical Formula 1) 2 is exemplified, and preferably it is a vinyl group. l and m are generally 0 or positive integers that satisfy 0 < l + m ≦ 10000, preferably 5 ≦ l + m ≦ 2000, more preferably 10 ≦ l + m ≦ 1200, and are integers that satisfy 0 < l / (l + m) ≦ 0.2, preferably 0.0011 ≦ l / (l + m) ≦ 0.1.

[0016] (2) Crosslinking component (A-2 component) The organohydrogenpolysiloxane of component (A-2) of the present invention acts as a crosslinking agent, forming a cured product through an addition reaction (hydrosilylation) between the SiH groups in this component and the alkenyl groups in component (A-1). Any organohydrogenpolysiloxane may be used as long as it has two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) per molecule. The molecular structure of this organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure, but those with a number of silicon atoms per molecule (i.e., degree of polymerization) of 2 to 1000, preferably about 2 to 300, can be used. The position of the silicon atom to which the hydrogen atom is bonded is not particularly limited, and it may be at the end of the molecular chain or at a non-end of the molecular chain (in the middle of the molecular chain). In addition, examples of organic groups bonded to silicon atoms other than hydrogen atoms include R in the general formula (Chemical Formula 3). 1 and unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, similar to those shown above. Examples of organohydrogenpolysiloxanes of component (A-2) include those with the following structures:

[0017] [ka] In the above formula, R 6 are the same or different alkyl groups, phenyl groups, epoxy groups, acryloyl groups, methacryloyl groups, alkoxy groups, or hydrogen atoms, and at least two of them are hydrogen atoms. 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.

[0018] (3) Catalyst component The catalyst component is a catalyst used in hydrosilylation reactions. Examples include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins or vinylsiloxanes, platinum-based catalysts such as platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. Two-component curing silicone polymers contain platinum-based metal catalysts.

[0019] The composition ratio of the components (A), (B), and (C) is preferably as follows: The liquid silicone resin of the component (A): X (X=50 to 99) parts by mass, preferably 55 to 98 parts by mass, and even more preferably 60 to 95 parts by mass. (B) Component linear organopolysiloxane: (100-X) parts by mass Thermally conductive inorganic particles of component (C): 50 to 3000 parts by mass, more preferably 100 to 2800 parts by mass, and even more preferably 200 to 2500 parts by mass. This amount increases the thermal conductivity of the composition, making it suitable as a thermally conductive material: TIM (Thermal Interface Material).

[0020] The thermally conductive silicone resin composition preferably has a kinematic viscosity at 23°C measured with a rotational viscometer in the range of 200 to 20,000 Pas, more preferably 300 to 18,000 Pas, and even more preferably 400 to 15,000 Pas, which provides excellent workability and makes the composition suitable for use as a TIM (thermal interface material).

[0021] The thermal conductivity of the thermally conductive silicone resin 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 resin composition is suitable as a TIM (Thermal Interface Material).

[0022] The thermally conductive composition is placed between two plates with a thickness of 1.0 mm or 2.0 mm and a contact area with the plates of 300 mm 2In a pumping-out test, the test specimen is placed horizontally in a heat shock tester, and held at -40°C and 125°C for 30 minutes each, for 100 cycles. When the appearance is checked after 100 cycles, it is preferable that there are no more than two cracks with a gap of 1 mm or more, or no more than two cracks with a length of 10 mm or more. This will prevent the pumping-out phenomenon caused by the occurrence of cracks or voids, even when used for a long period of time.

[0023] The thermally conductive inorganic particles are preferably at least one inorganic particle selected from the group consisting of aluminum oxide (alumina), zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon carbide. These inorganic particles have high thermal conductivity and are suitable as TIM (Thermal Interface Material). The D50 (median diameter) of the cumulative particle size distribution on a volume basis of the thermally conductive particles is preferably 0.01 to 150 μm, more preferably 0.05 to 130 μm, and even more preferably 0.1 to 120 μm. The thermally conductive inorganic particles are also called thermally conductive fillers.

[0024] The thermally conductive inorganic particles preferably contain particles with a median diameter D50 of 1 μm or less in the cumulative particle size distribution on a volume basis, particles greater than 1 μm and less than 80 μm, and particles with a diameter of 80 μm or more and 200 μm or less. By mixing large, medium, and small particles in this way, the medium and small particles fill the spaces between the large particles, thereby increasing the thermal conductivity of the thermally conductive silicone resin composition.

[0025] The thermally conductive inorganic particles may comprise 40% by mass or more and 60% by mass or less of thermally conductive inorganic particles having a median diameter D50 of 80 μm or more in the cumulative particle size distribution on a volume basis, relative to 100% by mass. By using a relatively large amount of large particles, the thermal conductivity of the thermally conductive silicone resin composition can be increased.

[0026] The small particles having a median diameter D50 of 1 μm or less are preferably surface-pretreated with a coupling agent. An example of the coupling agent is R(CH3) aSi(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 alkoxysilane compounds (hereinafter simply referred to as "silane") having the above chemical formula include methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane. The above silane compounds can be used alone or in combination. In particular, if fine thermally conductive particles with a median diameter D=50 of 1 μm or less are surface pretreated with a coupling agent in advance, they will be easier to mix when compounded, improving workability, and will not absorb the platinum catalyst during the compounding process, preventing the curing reaction from being inhibited.

[0027] The method for producing the thermally conductive silicone resin composition of the present invention involves mixing and stirring the aforementioned components A, B, and C. After mixing and stirring, the mixture may be heated at a temperature of less than 300°C for 5 minutes to 48 hours. By heating, the diol group at one end of component (B) chemically reacts with the surface of the thermally conductive inorganic particles, generating low-molecular substances such as water or methanol. However, these evaporate outside the composition and do not remain within the composition, thereby improving heat resistance. Furthermore, heating can accelerate the addition curing reaction.

[0028] The composition of the present invention may contain other components as needed. For example, heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardants, and flame retardant assistants may be added. Organic or inorganic particle pigments may be added for coloring or toning purposes. Alkoxy group-containing silicones may be added as materials for surface treatment of thermally conductive inorganic particles.

[0029] The composition of the present invention can also be formed into a sheet and cured. The composition is vacuum degassed, rolled, and formed into a sheet. Vacuum degassing involves reducing the pressure of the composition (compound) to -0.08 to -0.1 Pa and leaving it for 5 to 10 minutes to degas. Rolling can be performed by roll rolling or press working, with roll rolling being preferred due to its ability to allow continuous production. The resulting sheet has a substantially uniform composition from the inside to the outside. A sheet with a uniform composition exhibits uniform physical properties even after being mounted on an electrical or electronic component as a TIM. In roll rolling, for example, the compound is sandwiched between two synthetic resin films and then rolled with rolls. The heat curing conditions for the molded sheet are preferably a temperature of 90 to 120°C and a time of 5 to 180 minutes. In this specification, curing and crosslinking are the same. A sheet is highly versatile and suitable as a TIM. The thickness of the sheet is preferably in the range of 0.2 to 10 mm. [Example]

[0030] The present invention will be described below using examples, but is not limited to these examples. Various parameters were measured by the following methods. <Thermal conductivity> The thermal conductivity of the thermally conductive silicone composition was measured using a hot disk (ISO 22007-2:2008 compliant). As shown in Figure 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. The thermal characteristics are analyzed based on the temperature rise of the sensor 2. The sensor 2 has a 7 mm diameter tip 4 and, as shown in Figure 1B, a double spiral electrode structure, with an applied current electrode 5 and a resistance 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).

number

[0031] (Examples 1 to 6, Comparative Examples 1 to 6) 1. Raw material ingredients (1) Component A (A-1) Dimethyl silicone oil (manufactured by Momentive Performance Materials Japan, product number TSF458-100, kinematic viscosity at 23°C measured with a rotational viscometer of 100 mm) was used as a non-curing base polymer. 2 / s range) was used. (A-2, A-3) An addition-cure reaction-type silicone polymer (manufactured by Dow-Toray Industries, Inc., product name "CF5036") was used. This silicone polymer was divided into liquid A (A-2) and liquid B (A-3). Liquid A contained a base polymer made of organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms per molecule and a platinum catalyst, while liquid B contained a crosslinking component made of organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to silicon atoms per molecule. The viscosity of liquid A at 23°C was 450cs. (2)B component The component (B) used was a linear organopolysiloxane (Mn=5000) having a diol group at one end, as shown in Chemical Formula 2. (2) Thermally conductive inorganic particles (component C) As the component (C-1), an octyltrimethoxysilane pretreated amorphous alumina (median diameter D50) of 0.3 μm shown in FIG. 3 was used. As the component (C-2), spherical alumina D50=2.0 μm (75 μm top cut product) shown in FIG. 4 was used. As the component (C-3), crushed alumina D50=2.0 μm shown in FIG. 5 was used. As the component (C-4), spherical alumina D50=4.0 μm (75 μm top cut product) shown in FIG. 6 was used. As the component (C-5), spherical alumina D50=20 μm (55 μm top cut product) shown in FIG. 7 was used. As the component (C-6), spherical alumina D50=90 μm was used. As the component (C-7), spherical alumina D50=120 μm shown in FIG. 8 was used. As the component (C-8), spherical alumina D50=150 μm was used. <Procedure for preparing non-hardening liquid grease composition> Examples 1 to 3, Comparative Examples 1 to 3 Procedure: Components A, B, and C were mixed and degassed using a 1L planetary mixer. <Procedure for preparing a liquid grease composition containing hardened components> Example 4, Comparative Example 4 Procedure 1: Component A was mixed and degassed using a 1 L planetary mixer. Step 2: The kneaded component A was placed in an electric furnace and heated at 100°C for 30 minutes to completely harden it. Step 3: The above components A and B and the thermally conductive inorganic particles were kneaded using a 1 L planetary mixer, and the mixture was defoamed. <Cured sheet production procedure> Examples 5-6, Comparative Examples 5-6 Procedure 1: Components A, B, and C were mixed and degassed using a 1 L planetary mixer. Step 2: Rolled into a sheet. Step 3: Heat-hardened in an electric furnace at 100°C for 15 minutes. The silicone compositions and cured sheets obtained in this manner were evaluated. The conditions and results are summarized in Tables 1 and 2 below.

[0032] [Table 1] [Table 2]

[0033] From the above results, the following can be seen: (1) In Examples 1 to 6, it was confirmed that cracks were suppressed in the pumping-out test due to the effect of adding component B. (2) In Comparative Examples 1 to 6, cracks occurred in the pumping-out test because component B was not added. An example of the cracks in Comparative Example 1 is shown in Figure 2. In Figure 2, the cracks are cracks. [Industrial Applicability]

[0034] The thermally conductive silicone resin composition and cured sheet of the present invention are suitable as a thermally conductive material (TIM: Thermal Interface Material) to be interposed between a heat-generating part of an electric or electronic part and a heat sink. [Explanation of symbols]

[0035] 1. Thermal conductivity measuring device 2 sensors 3a,3b Sample 4 Sensor tip 5 Electrode for applied current 6 Resistance electrode (temperature measurement electrode)

Claims

1. It contains the following ingredients A to C, (A) Liquid silicone resin: X (X = 50 - 99) parts by mass, (B) Linear organopolysiloxane represented by the following chemical formula (Chemical Formula 1): (100-X) parts by mass, 【Chemistry 1】 (However, R 1 ~R 3 is an alkyl group or a phenyl group having 1 to 18 carbon atoms, R 4 and R 5 are each independently an alkyl group or a phenyl group having 1 to 18 carbon atoms, R 6 and R 8 is an OH group, R 7 is an alkyl group or a phenyl group having 1 to 3 carbon atoms, n is 5 to 1000, and m is 1 to 20. The above R 2 and the above R 3 When there are a plurality of them, the plurality of R 2 and R 3 may be the same as or different from each other.) (C) Thermally conductive filler: 50 to 3000 parts by mass A thermally conductive silicone resin composition characterized in that the thermally conductive inorganic particles (C) include at least one thermally conductive inorganic particle selected from the group consisting of alumina and aluminum nitride, having a median diameter D50 of 80 μm or more in the cumulative particle size distribution based on volume.

2. The thermally conductive silicone resin composition according to claim 1, wherein component (A) is at least one silicone selected from the group consisting of addition-curing silicone polymers and non-curing silicone oils.

3. The thermally conductive silicone resin composition according to claim 1, wherein the proportion of thermally conductive inorganic particles with a median diameter D50 of the cumulative particle size distribution based on volume of 80 μm or more is 40% by mass or more and 60% by mass or less with respect to 100% by mass of the aforementioned component (C).

4. The thermally conductive silicone resin composition according to claim 1, wherein the kinematic viscosity at 23°C, as measured by a rotational viscometer, is in the range of 200 to 30,000 Pas.

5. The thermally conductive silicone resin composition according to claim 1, wherein the thermal conductivity of the thermally conductive silicone resin composition is 1.0 W / m·K or more and 30 W / m·K or less.

6. The aforementioned thermal conductive composition is placed between two plates with a thickness of 1.0 mm or 2.0 mm and a contact area of ​​300 mm² with the plates. 2 The thermally conductive silicone resin composition according to claim 1, wherein the test specimen is arranged in such a manner, compressed and clamped, and then placed horizontally in a heat shock tester, held at -40°C and 125°C for 30 minutes each, and after 100 cycles, the pumping-out test is performed, and when the appearance is checked after 100 cycles, there are no more than two cracks with a gap of 1 mm or more, or no more than two cracks with a length of 10 mm or more.

7. The thermally conductive silicone resin composition according to claim 1, wherein the thermally conductive inorganic particles are at least one inorganic particle selected from the group consisting of aluminum oxide (alumina), zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, and silicon carbide.

8. The thermally conductive inorganic particles include particles with a median diameter D50 of 1 μm or less in the cumulative particle size distribution based on volume, particles with a diameter greater than 1 μm and less than 80 μm, and particles with a diameter of 80 μm or more and less than 200 μm, wherein the particles with a median diameter D50 of 1 μm or less are surface-pretreated with alkylalkoxysilane, as described in claim 1.

9. The thermally conductive silicone resin composition according to claim 1, wherein the linear organopolysiloxane is a compound represented by the following chemical formula (Chemical Formula 2). 【Chemistry 2】 (However, Me represents a methyl group, n-Bu represents a n-butyl group, and n = 5 to 1000)

10. A method for producing a thermally conductive silicone resin composition according to any one of claims 1 to 9, characterized by mixing and stirring the components A, B, and C.

11. A method for producing a thermally conductive silicone resin composition according to claim 10, wherein the mixture is heated after stirring, and the heating conditions are: temperature: less than 300°C, time: 5 minutes to 48 hours.

12. A heat-conductive silicone resin cured sheet characterized by being formed in a sheet and cured, according to any one of claims 1 to 9.

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