Thermally conductive components, thermally conductive sheets and their manufacturing methods

Abstract

This invention relates to a thermally conductive composition comprising a curable polyorganosiloxane (A) and a thermally conductive inorganic filler (B), wherein, relative to 100 parts by mass of the curable polyorganosiloxane (A), it comprises 500 to 5000 parts by mass of the thermally conductive inorganic filler (B). The thermally conductive inorganic filler (B) comprises spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm, and fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm. Relative to 100 parts by mass of the curable polyorganosiloxane (A), the proportion of spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm is greater than 0 parts by mass and less than 1500 parts by mass, and the proportion of fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm is greater than 0 parts by mass and less than 1000 parts by mass.

Description

Thermally conductive components, thermally conductive sheets and their manufacturing methods This invention relates to a thermally conductive composition, a thermally conductive sheet, and a method for manufacturing the same. In recent years, the performance of semiconductors such as CPUs has significantly improved, resulting in a corresponding increase in heat generation. Therefore, heat sinks are installed on heat-generating electronic components, and thermally conductive sheets are used to improve the contact between heat-generating components such as semiconductors and the heat sinks. However, with the miniaturization and high performance of machines in recent years, there is a growing demand for thermally conductive sheets with high thermal conductivity, low steady load, and flexibility. Patent Document 1 proposes setting the viscosity of the thermally conductive polysiloxane composition before curing to below 800 Pa·s at 23°C to improve compressibility, insulation, and thermal conductivity. Patent Document 2 proposes improving the contact and conformability to electronic components by setting a specific average particle size of the thermally conductive filler. Patent Document 3 proposes forming irregularities on the surface of the thermally conductive sheet to improve flexibility, thereby improving conformability to electronic components. The applicant proposes a thermally conductive sheet in Patent Document 4 that uses a matrix resin with low viscosity after cross-linking, resulting in a low steady load. [Previous Technical Documents] [Patent Documents] Patent Document 1: Japanese Patent Application Publication No. 2013-147600; Patent Document 2: Japanese Patent Application Publication No. 2003-253136; Patent Document 3: Japanese Patent Application Publication No. 2001-217360; Patent Document 4: Specification No. WO2020-179115 [The problem that the invention aims to solve] However, regarding conventional thermally conductive components, the viscosity of the uncured composite (mixed raw materials) is high, which poses problems in formability, and the stable load value of the cured thermally conductive sheet is high, requiring further improvement. To address the aforementioned problems, this invention provides a thermally conductive composition (mixture) with low viscosity and improved formability before curing, and a thermally conductive sheet with low stable load value after curing; a thermally conductive sheet; and a method for manufacturing the same. [Technical Means for Solving the Problem] The thermally conductive composition of this invention comprises a curable polyorganosiloxane (A) and a thermally conductive inorganic filler (B), and comprises 500 to 5000 parts by mass of the thermally conductive inorganic filler (B) relative to 100 parts by mass of the curable polyorganosiloxane (A). The thermally conductive inorganic filler (B) comprises spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm, and fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm. Relative to 100 parts by mass of the curable polyorganosiloxane (A), the proportion of the spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm is more than 0 parts by mass and less than 1500 parts by mass, and the proportion of the fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm is more than 0 parts by mass and less than 1000 parts by mass. The thermally conductive sheet of the present invention is formed by shaping the above-mentioned thermally conductive components into a sheet and then hardening them. The method for manufacturing the thermally conductive sheet of the present invention includes shaping the composite of the above-mentioned thermally conductive components into a sheet shape and then heating and curing it. [Effects of the Invention] The thermally conductive composition of the present invention comprises a curable polyorganosiloxane (A) and a thermally conductive inorganic filler (B), wherein, relative to 100 parts by mass of the curable polyorganosiloxane (A), it comprises 500 to 5000 parts by mass of the thermally conductive inorganic filler (B). The thermally conductive inorganic filler (B) comprises spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm, and fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm. Relative to 100 parts by mass of the curable polyorganosiloxane (A), the proportion of the spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm is greater than 0 parts by mass and less than 1500 parts by mass, and the proportion of the spherical alumina (B2) with an average particle size of 0.01 μm or more but less than 10 μm is less than 0 parts by mass. The ratio of fragmented alumina (B2) with a diameter of μm is greater than 0 parts by mass and less than 1000 parts by mass, thereby providing a thermally conductive composition with lower viscosity, improved formability, and lower instantaneous and stable load values ​​of the thermally conductive sheet before curing, a thermally conductive sheet, and a method for manufacturing the same. This invention relates to a thermally conductive composition comprising a curable polyorganosiloxane (A) and a thermally conductive inorganic filler (B). The curable polyorganosiloxane (A) is composed of a base polymer, a crosslinking component, and a catalyst component, preferably an addition-curable polysiloxane. The thermally conductive component is preferably as follows: (A1) Base polymer: A linear organosiloxane containing, on average, two or more alkenyl groups bonded to silicon atoms at both ends of the molecular chain per molecule. (A2) Crosslinking component: An organohydrogenated polysiloxane containing, on average, two or more hydrogen atoms bonded to silicon atoms per molecule, with an amount of 0.1 mol or more but less than 3 mol relative to the amount of alkenyl groups bonded to silicon atoms in the above-mentioned component A1. (B) Thermally conductive inorganic filler (B): 500 to 5000 parts by mass, more preferably 500 to 4000 parts by mass, and even more preferably 500 to 3000 parts by mass, relative to 100 parts by mass of the curing polyorganosiloxane (A). This results in a thermal conductivity of 2.0 W / m·K or higher, making it suitable as a TIM (Thermal Interface Material). (C) Catalyst composition: 0.01 to 1000 ppm by atomic weight of metal relative to the A1 composition. A platinum-based catalyst is preferred. The thermally conductive inorganic filler (B) comprises spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm and fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm. The ratio of spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm to 100 parts by mass of the curing polyorganosiloxane (A) is greater than 0 parts by mass and less than 1500 parts by mass. The ratio of spherical alumina (B1) to 100 parts by mass of the curing polyorganosiloxane (A) is preferably greater than 0 parts by mass and less than 1000 parts by mass, and more preferably greater than 0 parts by mass and less than 800 parts by mass. This allows for the production of a thermally conductive composition with lower viscosity, improved formability, and lower instantaneous and stable load values ​​in the cured thermally conductive sheet before curing, as well as a thermally conductive sheet formed from this composition. Furthermore, it is preferable that the alumina does not contain non-spherical (fragmented) alumina with an average particle size of 1 μm or more but less than 10 μm. Also, in this specification, "spherical alumina" refers to truly spherical alumina obtained by a melt method. The fraction of fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm relative to 100 parts by mass is more than 0 parts by mass and less than 1000 parts by mass, preferably more than 0 parts by mass and less than 800 parts by mass, and more preferably more than 0 parts by mass and less than 700 parts by mass. The thermally conductive inorganic filler (B) preferably comprises more than 0 parts by mass and less than 3500 parts by mass of spherical alumina (B3) with an average particle size of 10 μm to 150 μm, more preferably more than 0 parts by mass and less than 3000 parts by mass, and even more preferably more than 0 parts by mass and less than 2000 parts by mass. This results in a thermally conductive composition and thermally conductive sheet with lower viscosity of the composite (mixed raw materials) before curing, improved formability, and lower instantaneous and stable load values ​​of the thermally conductive sheet after curing. The thermally conductive inorganic filler (B) preferably comprises more than 0 parts by mass and less than 500 parts by mass of fragmented aluminum nitride (B4) with an average particle size of 10 μm to 100 μm, more preferably more than 0 parts by mass and less than 300 parts by mass, and even more preferably more than 0 parts by mass and less than 150 parts by mass. This results in a thermally conductive composition and a thermally conductive sheet with lower viscosity of the composite (mixed raw materials) before curing, improved formability, and lower instantaneous and stable load values ​​of the thermally conductive sheet after curing. Furthermore, other thermally conductive inorganic fillers besides those mentioned above can be added. Examples include boron nitride, zinc oxide, magnesium oxide, aluminum hydroxide, silicon carbide, and silicon dioxide. These can be used alone or in combination. Preferably, the average particle size is 10–150 μm, and the shape can be any shape, such as broken, spherical, round, or needle-like. 0–3,000 parts by weight can be added relative to 100 parts by weight of the curing polyorganosiloxane (A). Thermally conductive inorganic fillers can be surface-treated using silane compounds, titanate compounds, aluminate compounds, or their partial hydrolysates. This prevents the deactivation of hardening catalysts or crosslinking agents and improves storage stability. The thermally conductive component is sheet-formed and cured to form the thermally conductive sheet of the present invention. This thermally conductive sheet has high versatility and is suitable as a TIM (Thermal Interface Material). The thickness of the thermally conductive sheet is preferably in the range of 0.2–10 mm. Regarding the thermally conductive polysiloxane sheet of the present invention, the instantaneous load at 50% compression of a sheet with a diameter of 28.6 mm and an initial thickness of 2 mm, obtained by the compression load test method according to ASTM D575-91:2012, is preferably 300 N or less, more preferably 1 to 270 N, and even more preferably 1 to 250 N. Furthermore, the stable load value at 50% compression of a sheet with a diameter of 28.6 mm and an initial thickness of 2 mm, obtained by the compression load test method according to ASTM D575-91:2012, is preferably 80 N or less, more preferably 1 to 80 N, and even more preferably 1 to 50 N. In this invention, the curable polyorganosiloxane (A), also known as polysiloxane, has high heat resistance and flexibility, making it a suitable material for heat sinks. Polysiloxanes can be addition-curing, peroxide-curing, or condensation-curing types, with addition-curing polysiloxanes being preferred. The thermally conductive sheet of the present invention is preferably obtained by sheet forming and crosslinking a composite comprising a curable polyorganosiloxane (A) and a thermally conductive inorganic filler (B) according to the following composition. The curable polyorganosiloxane (A) is composed of a base polymer, a crosslinking component, and a catalyst component. (A1) Base polymer: A linear organic polysiloxane containing an average of two or more alkenyl groups bonded to silicon atoms at both ends of the molecular chain in one molecule. (A2) Crosslinking component: An organic hydrogenated polysiloxane containing an average of two or more hydrogen atoms bonded to silicon atoms in one molecule, with an amount of 0.1 mol or more but less than 3 mol relative to 1 mol of alkenyl groups bonded to silicon atoms in the above-mentioned component A1. (B) Thermally conductive inorganic filler: 500 to 5000 parts by mass, more preferably 500 to 4000 parts by mass, and even more preferably 500 to 3000 parts by mass, relative to 100 parts by mass of the curing polyorganosiloxane (A). This results in a thermal conductivity of 2.0 W / m·K or higher for the thermally conductive sheet. (C) Catalyst composition: 0.01 to 1000 ppm by atomic weight of metal relative to composition A1. The catalyst is preferably a platinum-based catalyst. The method for manufacturing the thermally conductive sheet of the present invention includes vacuum defoaming, calendering, sheet forming, and then heat curing of the composite of the above-mentioned thermally conductive components. The thermally conductive components formed into a sheet and then heat-cured become a thermally conductive sheet. In vacuum defoaming, the above-mentioned thermally conductive components (composite) are placed under a pressure of, for example, -0.08 to -0.1 MPa for about 5 to 10 minutes to defoam. As a calendering method, there are rolling processing, pressing processing, etc., and rolling processing is preferred for continuous production. In rolling processing, as an example, the above-mentioned composite is sandwiched between two synthetic resin films and calendered from above using a roller. The heat curing conditions for the above-mentioned formed sheet are preferably a temperature of 90 to 120°C and a time of 5 to 180 minutes. In this specification, curing is the same as crosslinking. The following describes each component. (1) Base polymer (Component A1) The base polymer is an organopolysiloxane containing two or more alkenyl groups bonded to silicon atoms in one molecule. The organopolysiloxane containing two or more alkenyl groups is the main agent in the thermally conductive composition of the present invention. The organopolysiloxane has two or more alkenyl groups, such as vinyl or allyl groups, with 2 to 8 carbon atoms, preferably 2 to 6, bonded to silicon atoms in one molecule. From the viewpoint of workability and hardenability, it is ideal for the viscosity of the base polymer at 25°C to be 10 to 100,000 mPa·s, especially 100 to 10,000 mPa·s. Specifically, for example, an organopolysiloxane, represented by the following general formula (Chem. 1), containing an average of two or more alkenyl groups bonded to the silicon atoms at both ends of the molecular chain in one molecule, can be used as the base polymer. It is a linear organopolysiloxane with alkyl-terminated side chains. From the viewpoint of workability and curability, it is ideal for the base polymer to have a viscosity of 10–100,000 mPa·s at 25°C. Furthermore, this linear organopolysiloxane may also contain a small amount of branched structures (trifunctional siloxane units) in the molecular chain. [Chem. 1] In the formula, R 1 R refers to unsubstituted or substituted monovalent hydrocarbon groups that are the same as or different from each other and do not have aliphatic unsaturated bonds. 2 It is an alkenyl group, and k is 0 or a positive integer. Wherein, as R... 1 The unsubstituted or substituted monovalent hydrocarbon group without aliphatic unsaturated bonds is preferably a monovalent hydrocarbon group with 1 to 10 carbon atoms, especially 1 to 6 carbon atoms. Specifically, examples include: alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tributyl, 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 those in which one or all of the hydrogen atoms are substituted with halogen atoms such as fluorine, bromine, and chlorine, or cyano groups, such as halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl, or cyanoethyl groups. As R 2 The alkenyl group is preferably an alkenyl group with 2 to 6 carbon atoms, especially 2 to 3. Specifically, examples include: vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, cyclohexenyl, etc., with vinyl being preferred. In general formula (1), k is usually a 0 or positive integer satisfying 0 ≤ k ≤ 10000, preferably an integer satisfying 5 ≤ k ≤ 2000, and more preferably an integer satisfying 10 ≤ k ≤ 1200. Regarding the organopolysiloxane as component A1, organopolysiloxanes having 3 or more, typically 3 to 30, preferably 3 to 20, alkenyl groups (e.g., vinyl, allyl, etc.) with 2 to 8, especially 2 to 6, carbon atoms bonded to silicon atoms in one molecule, can also be used with the organopolysiloxane represented by the above general formula (Chemical 1). The molecular structure can be any of the following: linear, cyclic, branched, or three-dimensional network. Preferably, it is a linear organopolysiloxane with a viscosity of 10 to 100,000 mPa·s, especially 100 to 10,000 mPa·s, at 25°C, consisting of a main chain composed of repeating two organosiloxane units and end-capped with three organosilyloxy groups. The alkenyl group can be bonded to any part of the molecule. For example, it can also contain silicon atoms bonded to the ends of the molecular chain or to non-ends (midway) of the molecular chain. Among these, in terms of workability, hardening properties, etc., it is more ideal to have a linear organopolysiloxane represented by the following general formula (Chemical 2) with 1 to 3 alkenyl groups on the silicon atoms at both ends of the molecular chain (wherein, if the total number of alkenyl groups bonded to the silicon atoms at the ends of the molecular chain is less than 3, at least 1 alkenyl group bonded to a silicon atom at a non-end (midway) of the molecular chain (e.g., as a substituent in a diorganosiloxane unit) and a viscosity of 10 to 100,000 mPa·s at 25°C as described above. Furthermore, the linear organopolysiloxane may also contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain. [Chemical 2] In the formula, R 3 Each of the following groups consists of unsubstituted or substituted monovalent hydrocarbon groups, which may be the same as or different from each other, and at least one of them is an alkenyl group. R 4 R refers to unsubstituted or substituted monovalent hydrocarbon groups that are the same as or different from each other and do not have aliphatic unsaturated bonds. 5 It is an alkenyl group, where l and m are 0 or positive integers. Wherein, as R... 3 The monovalent hydrocarbon group preferably has 1 to 10 carbon atoms, especially 1 to 6. Specifically, examples include: alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tributyl, 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; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl; or groups in which one or all of the hydrogen atoms are replaced by halogen atoms such as fluorine, bromine, and chlorine, or cyano groups, such as halogen-substituted alkyl groups or cyanoethyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl. Furthermore, as R 4 The monovalent hydrocarbon group is also preferably composed of 1 to 10 carbon atoms, especially 1 to 6, as exemplified by the R group mentioned above. 1 Similar to the specific examples, but without containing an alkenyl group. As R 5 The alkenyl group is preferably composed of 2 to 6 carbons, especially 2 to 3 carbons. Specifically, R can be exemplified as in the above formula (Chemical 1). 2 Of the same type, vinyl is preferred. l and m are usually 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. (2) Crosslinking Component (A2 Component) The organohydrogenated polysiloxane of the A2 component of the present invention acts as a crosslinking agent, forming a hardened product by the addition reaction (hydrosilicification) between the SiH group in this component and the alkenyl group in the A1 component. The organohydrogenated polysiloxane only needs to have two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) in one molecule, and can be any organohydrogenated polysiloxane. The molecular structure of the organohydrogenated polysiloxane can be any of the following: linear, cyclic, branched, or three-dimensional network structure. The number of silicon atoms in one molecule (i.e., degree of polymerization) can be 2 to 1000, especially around 2 to 300. The position of the silicon atom bonded to the hydrogen atom is not particularly restricted; it can be at the end of the molecular chain or at a non-end (midway). Furthermore, as an organic group other than a hydrogen atom bonded to a silicon atom, examples include R in the above general formula (Chemistry 1). 1 The same as an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond. Organohydrogenated polysiloxanes as components A2 can be exemplified by the following structures. [Chemical 3] In the above formula, R 6 The hydrogen, alkyl, phenyl, epoxy, acrylonitrile, methacrylonitrile, and alkoxy groups are the same or different from each other, and at least two of them are hydrogen. L is an integer from 0 to 1,000, especially from 0 to 300, and M is an integer from 1 to 200. (3) Catalyst Component (C Component) The catalyst component of C component is the component that promotes the first stage of curing of this composition. As C component, catalysts used in hydrosilicification reactions can be used. Examples include: platinum black, hexachloroplatinic acid, chloroplatinic acid, reactants of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins or vinyl siloxanes, platinum group metal catalysts such as diacetyl acetate platinum, palladium group metal catalysts, and rhodium group metal catalysts. The amount of C component added only needs to be the amount required for curing and can be adjusted appropriately according to the required curing speed, etc. Preferably, it is added at 0.01 to 1000 ppm relative to A1 component by metal atomic weight. (4) Thermally conductive inorganic filler (component B) The thermally conductive inorganic filler of component B is as described above. Furthermore, alumina is preferably α-alumina with a purity of 99.5% or higher. The average particle size is the D50 (median particle size) of the cumulative particle size distribution on a volume basis, determined by laser diffraction light scattering method. For example, the laser diffraction / scattering type inorganic filler distribution measuring device LA-950S2 manufactured by Arihoba Corporation is used as the measuring instrument. Inorganic fillers with good thermal conductivity are preferred for utilizing R a Si(OR') 4-a Surface treatment is performed on silane compounds or their partial hydrolysates represented by (R is an unsubstituted or substituted organic group with 1 to 20 carbon atoms, R' is an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1). Regarding R... a Si(OR') 4-a Alkoxysilane compounds (hereinafter referred to as "silanes") represented by (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) include, for example, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltrimethoxysilane, and other silane compounds. The aforementioned silane compounds may be used individually or in combination. As a surface treatment agent, the aforementioned alkoxysilane compounds may also be used in combination with monoterminated silanol siloxanes. The surface treatment referred to here includes adsorption, in addition to covalent bonding. (5) Other components may be added to the composition of the present invention as needed. For example, inorganic pigments such as iron oxide or alkyltrialkoxysilanes may be added for the purpose of surface treatment of fillers. As a material added for the purpose of surface treatment of fillers, polysiloxanes containing alkoxy groups may be added. The following description uses drawings. In the following drawings, the same symbols represent the same object. FIG1 is a schematic cross-sectional view of a thermally conductive sheet according to one embodiment of the present invention assembled into a heat dissipation structure 30. The thermally conductive sheet 31b dissipates heat generated by electronic components 33 such as semiconductor elements, and is fixed to the main surface 32a of the heat spreader 32 opposite to the electronic component 33, and is sandwiched between the electronic component 33 and the heat spreader 32. The thermally conductive sheet 31a is also sandwiched between the heat spreader 32 and the heat sink 35. Furthermore, the thermally conductive sheets 31a and 31b together with the heat spreader 32 constitute a heat dissipation member for dissipating heat from the electronic component 33. The heat spreader 32 is formed, for example, in the shape of a square plate, having a main surface 32a opposite to the electronic component 33, and sidewalls 32b erected along the outer periphery of the main surface 32a. A heat-conducting sheet 31b is provided on the main surface 32a surrounded by the sidewall 32b of the heat sink 32. A heat sink 35 is provided on the other side 32c opposite to the main surface 32a, insulated from the heat-conducting sheet 31a. The electronic component 33 is, for example, a semiconductor element such as a BGA, and is mounted on the wiring board 34. Figure 2 is a scanning electron microscope (SEM) image (10,000x magnification) of spherical alumina (B1) according to one embodiment of the present invention. This spherical alumina is manufactured by a melt process and is commercially available (e.g., the trade name "AZ2-75" manufactured by Nippon Steel Chemical Materials Co., Ltd., with an average particle size of 2 μm). Figure 3 is a scanning electron microscope (SEM) image of polygonal or circular alumina not included in the spherical alumina (B1) of the present invention. [Examples] The following description uses examples. This invention is not limited to these examples. <Compression Load> The method for measuring compression load is based on ASTM D575-91:2012. Figure 4 is a schematic side sectional view of a compression load measuring device used in one embodiment of this invention. The compression load measuring device 1 includes a sample stage 2 and a load cell 6. A thermally conductive sheet sample 4 is held between aluminum plates 3 and 5, as shown in Figure 4. The load cell 6 compresses the thermally conductive sheet sample 4 to a specified thickness. The maximum load value (instantaneous load value) when the sample thickness is compressed to 50%, and the load value (steady-state load value) after maintaining this compression for 1 minute are recorded. Test conditions: Sample: Circular (diameter 28.6 mm, thickness 2 mm) Compression ratio: 50% Aluminum plate size: Circular (diameter 28.6 mm) (compression surface) Compression speed: 5 mm / min Compression method: TRIGGER method (measurement starts at the point where the load of 2 N is sensed) Testing device: Aikoh Engineering, MODEL-1310NW (load cell 200 kgf) <Thermal conductivity> The thermal conductivity of the thermally conductive sheet was measured using a Hot Disk (according to ISO 22007-2:2008). As shown in Figure 5A, the thermal conductivity measuring device 11 uses two thermally conductive sheet samples 13a and 13b to clamp a polyimide film sensor 12, applies a constant power to the sensor 12 to make it constantly heated, and analyzes the thermal characteristics based on the temperature rise of the sensor 12. The front end 14 of the sensor 12 has a diameter of 7 mm, as shown in Figure 5B, and forms a double helix structure for the electrodes. An electrode 15 for applying current and an electrode 16 for measuring resistance (temperature measurement) are arranged at the bottom. The thermal conductivity is calculated using the following formula (Equation 1). [Number 1] λ: Thermal conductivity (W / m·K) Po: Constant power (W) r: Sensor radius (m) τ: α: Thermal diffusivity of the sample (m) 2 / s) t: Measurement time (s) D(τ): Dimensionless function of τ ΔT(τ): Temperature rise of the sensor (K) <Processability> Since the uncured composite is a clay-like solid, its processability is determined by its roll formability during sheet forming. The evaluation criteria are as follows: A: Good calendering formability. B: Calendering is difficult, but formable. C: Cannot be calendered. <Hardness> The hardness of the cured sheet is determined according to Shore 00 as specified in ASTM D2240:2021. (Example 1) (1) The matrix resin component used was a commercially available two-component room temperature curing polysiloxane. The base polymer and platinum group metal catalyst were pre-added to the A component of the two-component room temperature curing polysiloxane, and the base polymer and crosslinking component were pre-added to the B component. The commercially available two-component room temperature curing polysiloxane used was an addition reaction polysiloxane. (2) The thermally conductive inorganic filler was set to 1890 g relative to 100 g of the addition reaction polysiloxane. The details of the thermally conductive inorganic filler relative to 100 g of the addition reaction polysiloxane are as follows. (i) Fragmented alumina (B2), average particle size 0.4 μm: 290 g (ii) Spherical alumina (B1), average particle size 4 μm: 330 g (iii) Spherical alumina (B3), average particle size 75 μm: 1200 g (iv) Fragmented aluminum nitride (B4), average particle size 14 μm: 70 g (3) Forming of thermally conductive sheets The above uncured two-component room temperature curing polysiloxane polymer was uniformly mixed with thermally conductive inorganic filler to form a composite. The composite was defoamed for 5 minutes under a pressure of -0.1 MPa (under reduced pressure). Then, it was sandwiched between two polyester (PET) films and rolled to a thickness of 2 mm, and cured at 100°C for 120 minutes. The physical properties of the obtained thermally conductive sheets are shown in Table 1. (Examples 2-5, Comparative Examples 1-6) Except as shown in Tables 1 and 2, the procedures were carried out in the same manner as in Example 1. The spherical alumina of Examples 2, 3, 5, and 6 were as shown in the photograph in Figure 2. The circular alumina of Comparative Examples 7 and 9 were as shown in the photograph in Figure 3. The above conditions and results are shown together in Tables 1 and 2. [Table 1] [Table 2] As shown in Tables 1 and 2, it was confirmed that in each embodiment, the thermal conductivity was higher, the instantaneous and stable load values ​​were lower, and the compression was more gradual. By compressing slowly, clamping with a low load was possible, resulting in less damage to the clamping body. Due to the lower load value and flexibility, the conformability to the bumps and dents of electronic components was better. Furthermore, the presence of an initial load value ensured good operability of the sheet. Examples 6 and 7 were embodiments using only spherical alumina with an average particle size of 1-10 μm and fragmented alumina with an average particle size of less than 1 μm, without using large-particle-size fillers, but the effects of the present invention were still confirmed. In contrast, Comparative Example 8 did not include fragmented alumina with an average particle size of less than 1 μm. To maintain a consistent total filler weight, other fillers were added in a constant ratio. As a result, good bonding was not achieved, and processability (formability) was significantly reduced. Furthermore, Comparative Example 9 contained only round alumina with an average particle size of 1–10 μm and fragmented alumina with an average particle size of less than 1 μm, thus exhibiting a higher 50% compressive load value (both instantaneous and stable). Comparative Example 10 contained only fragmented alumina with an average particle size of 1–10 μm and fragmented alumina with an average particle size of less than 1 μm, resulting in poor processability and a higher 50% compressive load value (both instantaneous and stable), thus being unsatisfactory. [Industrial Applicability] The thermally conductive sheet of the present invention can be used as a heat sink between the heat-generating and heat-dissipating parts in electronic components such as semiconductors, LEDs, and home appliances, data communication modules including optical communication equipment, and automotive applications. 1: Compression load measuring device; 2: Sample stage; 3, 5: Aluminum plate; 4: Thermally conductive sheet sample; 6: Load cell; 11: Thermal conductivity measuring device; 12: Sensor; 13a, 13b: Thermally conductive sheet sample; 14: Front end of sensor; 15: Electrode for applying current; 16: Electrode for resistance value (electrode for temperature measurement); 30: Heat dissipation structure; 31a, 31b: Thermally conductive sheet; 32: Heat sink; 32b: Heat sink sidewall; 33: Electronic component; 34: Wiring board; 35: Heat sink fin. [Figure 1] is a schematic cross-sectional view showing the method of using the thermally conductive sheet according to one embodiment of the present invention. [Figure 2] is a scanning electron microscope (SEM) image (10,000x magnification) of spherical alumina (B1) according to one embodiment of the present invention. [Figure 3] is a scanning electron microscope (SEM) image of polygonal or circular alumina not included in the spherical alumina (B1) of the present invention. [Figure 4] is a schematic side cross-sectional view of the compressive load measuring device used in one embodiment of the present invention. [Figures 5A-B] are explanatory diagrams showing the method of measuring thermal conductivity used in one embodiment of the present invention.

Claims

1. A thermally conductive composition comprising an addition-curing polyorganosiloxane (A) and a thermally conductive inorganic filler (B), characterized in that: relative to 100 parts by mass of the addition-curing polyorganosiloxane (A), it comprises 500 to 5000 parts by mass of the thermally conductive inorganic filler (B); the addition-curing polyorganosiloxane (A) is composed of a base polymer (A1), a crosslinking component (A2), and a catalyst component (C); the thermally conductive inorganic filler (B) comprises spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm, and fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm; and relative to 100 parts by mass of the addition-curing polyorganosiloxane (A), the average particle size of the filler comprises spherical alumina (B1) with an average particle size of 1 μm or more but less than 10 μm. The proportion of spherical alumina (B1) with an average particle size of μm is greater than 0 parts by mass and less than 1500 parts by mass; the proportion of fragmented alumina (B2) with an average particle size of 0.01 μm or more but less than 1 μm is greater than 0 parts by mass and less than 1000 parts by mass; excluding non-spherical and fragmented alumina with an average particle size of 1 μm or more but less than 10 μm; (A1) Base polymer: linear organopolysiloxane, which contains an average of 2 or more alkenyl groups bonded to silicon atoms at both ends of the molecular chain in one molecule; (A2) Crosslinking component: organohydrogenated polysiloxane containing an average of 2 or more hydrogen atoms bonded to silicon atoms in one molecule; relative to 1 mol of alkenyl groups bonded to silicon atoms in component A1, the amount of SiH groups in component A2 is 0.1 mol or more but less than 3 mol; (C) Catalyst composition: Platinum-based catalyst, relative to the above A1 composition, is 0.01 to 1000 ppm by metal atomic weight.

2. As in claim 1, the thermally conductive component, wherein, The aforementioned thermally conductive inorganic filler (B) further comprises spherical alumina (B3) with an average particle size of 10 μm to 150 μm and a mass of more than 0 parts by mass and less than 3500 parts by mass.

3. As in claim 2, the thermally conductive component, wherein, The aforementioned thermally conductive inorganic filler (B) further comprises more than 0 parts by mass and less than 500 parts by mass of fragmented aluminum nitride (B4) with an average particle size of more than 10 μm and less than 100 μm.

4. The thermally conductive component as claimed in claim 3, wherein, Compared to 100 parts by mass of the addition-curing polyorganosiloxane (A) mentioned above, (B2) is more than 0 parts by mass and less than 800 parts by mass, (B3) is more than 0 parts by mass and less than 3000 parts by mass, and (B4) is more than 0 parts by mass and less than 300 parts by mass.

5. The thermally conductive component as claimed in claim 1 or 2, wherein, The aforementioned thermally conductive inorganic fillers are surface-treated using silane compounds, titanate compounds, aluminate compounds, or their partial hydrolysates.

6. A thermally conductive sheet, which is formed by shaping and hardening the thermally conductive composition of any one of claims 1 to 5 into a sheet.

7. As in request item 6, the thermally conductive sheet, wherein, The instantaneous load value of the above-mentioned thermally conductive sheet with a diameter of 28.6 mm and an initial thickness of 2 mm under 50% compression, obtained by the compression load test method according to ASTM D575-91:2012, is less than 300 N.

8. As in request item 6, the thermally conductive sheet, wherein, The stable load value of the above-mentioned thermally conductive sheet with a diameter of 28.6 mm and an initial thickness of 2 mm under 50% compression, obtained by the compression load test method according to ASTM D575-91:2012, is less than 80 N.

9. A method for manufacturing a thermally conductive sheet, which is the method for manufacturing a thermally conductive sheet according to claim 6, comprising forming a composite of the thermally conductive components of any one of claims 1 to 5 into a sheet and then heating and hardening it.

10. A method for manufacturing a thermally conductive sheet as described in claim 9, wherein, The above-mentioned heat hardening conditions are a temperature of 90–120°C and a time of 5–180 minutes.

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