Thermally conductive composition, thermally conductive sheet using same, and method for producing same

Abstract

This thermally conductive composition in an uncured state comprises a matrix resin (component A) and thermally conductive particles, wherein the thermally conductive particles include component B and component C. Component B: 220 to 500 parts by mass of alumina having a D50 (median diameter) in a cumulative particle size distribution of 0.01 μm or more and less than 1 μm on a volume basis, based on 100 parts by mass of component A. Component C: 1900 to 2500 parts by mass of aluminum nitride having a D50 (median diameter) of 0.01-150 μm based on 100 parts by mass of component A. Provided thereby are: a thermally conductive composition having high thermal conductivity, low plasticity, and good moldability; a thermally conductive sheet obtained by using the thermally conductive composition; and a method for producing same.

Description

Thermally conductive composition, thermally conductive sheet using the same, and method for manufacturing the same

[0001] The present invention relates to a thermally conductive composition suitable for being interposed between a heat-generating portion of an electric or electronic component or the like and a heat sink, a thermally conductive sheet using the same, and a method for producing the same.

[0002] Recent improvements in the performance of semiconductors such as CPUs have been remarkable, resulting in enormous increases in the amount of heat generated. For this reason, heat-generating electronic components are fitted with heat sinks, and thermally conductive sheets are used to improve adhesion between the semiconductor and the heat sink. As devices become smaller, their performance improves, and they become more highly integrated, thermally conductive sheets are required to be soft and have high thermal conductivity. Patent documents 1 to 3 propose using an addition-curing silicone polymer containing a curing catalyst, with the interior in a low-cured or uncured state and the surface forming a cured skin layer. In patent document 4, the applicant proposes a thermally conductive sheet made by laminating a cured sheet and an uncured sheet.

[0003] Japanese Patent Application Laid-Open No. 2009-203373 Japanese Patent Application Laid-Open No. 2008-280395 Japanese Patent Application Laid-Open No. 2007-224102 Republished No. 2019-206190

[0004] However, conventional thermally conductive compositions and thermally conductive sheets using the same have the problem that increasing the thermal conductivity increases the plasticity of the composition, resulting in poor moldability.

[0005] In order to solve the above-mentioned conventional problems, the present invention provides a thermally conductive composition having high thermal conductivity, low plasticity of the composition, and good moldability, as well as a thermally conductive sheet using the same and a method for producing the same.

[0006] The thermally conductive composition of the present invention is a thermally conductive composition comprising a matrix resin (component A) and thermally conductive particles, wherein the thermally conductive particles comprise the following components B and C: component B: 220 to 500 parts by mass of alumina having a D50 (median diameter) of 0.01 μm or more and less than 1 μm in a cumulative particle size distribution on a volume basis, relative to 100 parts by mass of component A; component C: 1900 to 2500 parts by mass of aluminum nitride having a D50 (median diameter) of 0.01 μm or more and 150 μm or less, relative to 100 parts by mass of component A; and the thermally conductive composition is in an uncured state.

[0007] The thermally conductive sheet of the present invention is characterized in that the thermally conductive composition is formed into a sheet. The method for producing the thermally conductive sheet of the present invention is characterized in that the thermally conductive composition is vacuum degassed, rolled, and formed into a sheet to obtain an uncured thermally conductive sheet.

[0008] The present invention provides a thermally conductive composition that has high thermal conductivity, low plasticity, and good moldability by being in an uncured state and adding a large amount of thermally conductive particles, and a thermally conductive sheet using the same. Specifically, the plasticity of the thermally conductive composition after degassing is preferably less than 100, and the thermal conductivity is preferably 14 W / m·K or more. Furthermore, the method for producing a thermally conductive sheet of the present invention enables continuous sheet molding because the composition has low plasticity and good moldability.

[0009] Fig. 1 is a schematic cross-sectional view showing a method for using a thermally conductive sheet according to one embodiment of the present invention. Figs. 2A and 2B are schematic explanatory views showing a method for measuring the thermal conductivity of a sample according to one embodiment of the present invention.

[0010] The present invention provides an uncured thermally conductive composition containing a matrix resin and thermally conductive particles. The matrix resin is preferably a thermosetting resin such as silicone rubber, silicone gel, unreacted silicone oil, acrylic rubber, fluororubber, epoxy resin, phenolic resin, unsaturated polyester resin, melamine resin, acrylic resin, or fluororesin, or a thermoplastic resin such as polyurethane, polyethylene, polypropylene, polyethylene glycol, or ethylene-α-olefin copolymer. Among these, silicone polymer or unreacted silicone oil is preferred. Silicone is preferred due to its high heat resistance. It is also preferred because it is non-corrosive to the surrounding area and emits few by-products outside the system. By leaving the matrix resin uncured and adding a large amount of thermally conductive particles, the present invention can provide a thermally conductive composition with high thermal conductivity, low plasticity, and good moldability, as well as a thermally conductive sheet using the same.

[0011] The thermally conductive particles (components B and C) are added to 100 parts by mass of the matrix resin (component A) as follows: (1) Component B: 220 to 500 parts by mass of alumina having a D50 (median diameter) of 0.01 μm or more and less than 1 μm in the cumulative particle size distribution on a volume basis is added to 100 parts by mass of the component A. The preferred amount is 230 to 480 parts by mass, and more preferably 240 to 440 parts by mass. Component B preferably contains the following components B-1 and B-2. Component B-1: Alumina having a D50 (median diameter) of 0.01 μm or more and less than 0.3 μm, and a BET specific surface area of ​​9 m 2 / g or more of alumina is 30 to 100 mass % relative to 100 mass % of component B. The preferred D50 (median diameter) is 0.1 μm or more and less than 0.3 μm. The preferred BET specific surface area is 9 to 20 m 2 / g, and more preferably 10 to 18m 2 / g. The BET specific surface area is measured according to the standards of JIS R 1626-1996. Component B-2: Alumina having a D50 (median diameter) of 0.3 μm or more and less than 1 μm accounts for 0 to 70 mass% of Component B (100 mass%). The preferred D50 (median diameter) is 0.3 μm or more and 1.0 μm or less. (2) Component C: 1900 to 2500 mass parts of aluminum nitride having a D50 (median diameter) of 0.01 μm or more and 150 μm or less is added to 100 mass parts of Component A. The preferred D50 (median diameter) is 0.1 μm or more and 120 μm or less. The preferred amount added is 1920 to 2400 mass parts, and more preferably 1940 to 2300 mass parts. Component C preferably contains the following components C-1 and C-2. - Component C-1: D50 (median diameter) is 0.01 μm or more and less than 30 μm. - Component C-2: D50 (median diameter) is 30 μm or more and 150 μm or less. However, the abundance ratio of component C-1 and component C-2 is expressed as a mass ratio, and is C-2 component≦component C-1.

[0012] In the present invention, the thermally conductive particles are a mixture of multiple types of inorganic particles with different average particle sizes. This allows the smaller particles to be embedded between the larger particles, resulting in a nearly close-packed state and high thermal conductivity. Furthermore, the resulting thermally conductive composition has low plasticity and good moldability.

[0013] The thermally conductive composition preferably has a plasticity of less than 100 after vacuum degassing, more preferably 10 to 99, even more preferably 20 to 99, and particularly preferably 30 to 99. This results in a thermally conductive composition with low plasticity and excellent moldability. Plasticity is measured using a Wallace plastometer in accordance with JIS K 6300-3 and ISO 2007:1991 at a measurement temperature of 25°C. The plasticity is calculated by dividing the thickness (t) of a sample compressed between two metal plates at a constant load (100 N) for a constant time (15 seconds) by the thickness (t) before compression (P0 = t / t0 × 100). A smaller P0 indicates greater flexibility.

[0014] The thermal conductivity of the thermally conductive composition is preferably 14 W / m K or more, more preferably 14 to 20 W / m K, and even more preferably 14.5 to 20 W / m K. This provides high thermal conductivity and makes the composition suitable for use as a heat dissipation sheet: TIM (Thermal Interface Material).

[0015] The thermally conductive composition preferably has a SHORE 00 hardness of 75 or less, more preferably 10 to 75, and even more preferably 15 to 72. This improves conformability to heat generating bodies and heat dissipating bodies (heat sinks).

[0016] Preferably, 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, of a silane coupling agent is added to 100 parts by mass of the matrix resin. The silane coupling agent coats the surfaces of the thermally conductive particles (surface treatment) and facilitates filling of the particles into the matrix resin (plasticizer function).

[0017] The silane coupling agent is 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. a Si(OR') 4-a Examples of alkoxysilane compounds (hereinafter simply referred to as "silanes") represented by the formula (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 methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane. These silane compounds can be used alone or in combination.

[0018] At least one component selected from the group consisting of alumina (aluminum oxide) as component B and aluminum nitride as component C is preferably in the form of irregularly pulverized particles. Irregularly pulverized particles are readily available. Hereinafter, "irregularly pulverized" may also be simply referred to as "irregular."

[0019] The thermally conductive composition of the present invention is highly versatile when molded into a thermally conductive sheet, and is therefore suitable as a TIM. The thickness of the thermally conductive sheet is preferably in the range of 0.2 to 10 mm.

[0020] The method for producing a thermally conductive sheet of the present invention involves vacuum degassing the thermally conductive composition, rolling it, and forming it into a sheet to produce a thermally conductive sheet. Vacuum degassing involves reducing the pressure of the thermally conductive composition (compound) to -0.08 to -0.1 Pa and leaving it for approximately 5 to 10 minutes to degas it. Rolling can be performed by roll rolling or press working, with roll rolling being preferred because it allows for continuous production. The resulting thermally conductive sheet has a substantially uniform composition from the inside to the outside. A sheet with a uniform composition will exhibit uniform physical properties even after being mounted on an electrical or electronic component as a TIM.

[0021] The thermally conductive composition preferably has a breakdown voltage (JIS K6249) of 7 to 16 kV / mm, thereby providing a thermally conductive sheet with high electrical insulation.

[0022] The volume resistivity (JIS K6249) of the thermally conductive composition is 10 10 ~10 14 It is preferable that the resistance is Ω·cm, which makes it possible to provide a thermally conductive sheet with high electrical insulation properties.

[0023] Silicone polymers will be described as matrix resins. Examples of silicone polymers include addition-curable silicone polymers, peroxide-curable silicone polymers, condensation-type silicone polymers, and unreacted silicone oils. These may be used alone or in combination. Each silicone polymer will be described. (1) Addition-Curable Silicone Polymers Addition-curable silicone polymers use either part A or part B of a commercially available two-component silicone polymer containing polyorganosiloxane. In this two-component silicone polymer, one part (part A or part A) contains a base polymer component (component A1 below) and a platinum group metal catalyst, while the other part (part B or part B) contains a base polymer component (component A1 below) and a crosslinker component (component A2 below), which is an organohydrogenpolysiloxane. The mass ratio of part A to part B is A:B = 100:100. Either part A or part B is used alone. Unreacted silicone oil may be added to each part. Materials without the platinum group metal catalyst of Part A may be used. (2) Peroxide-curable silicone polymers Peroxide-curable silicone polymers may or may not contain a catalyst as long as they are not heat-cured. (3) Condensation-type silicone polymers Condensation-type silicone polymers are used without a curing catalyst. As a result of the above, a thermally conductive composition and a thermally conductive sheet are obtained that are in an uncured state, have low plasticity, and have good moldability.

[0024] The addition-curable silicone polymer is composed of the following components (A1) and (A2): (A1) base polymer component: a linear organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule; (A2) crosslinking component: an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule, in an amount less than 1 mole per mole of silicon-bonded alkenyl groups in component A; and (A2) an organopolysiloxane having no reactive groups other than components (A1) and (A2). For example, unreacted silicone oil, such as dimethylpolysiloxane, is used. In this specification, the total of the liquid component, i.e., the silicone polymer, and, if necessary, the unreacted silicone oil and silane coupling agent, is defined as 100 parts by mass.

[0025] Each component is described below. (1) Base Polymer Component (Component A1) The base polymer component is an organopolysiloxane containing two or more silicon-bonded alkenyl groups per molecule. This organopolysiloxane contains two silicon-bonded alkenyl groups per molecule, such as vinyl or allyl groups, each having 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms. From the standpoint of workability, a viscosity of 10 to 1,000,000 mPa·s at 25°C, and particularly 100 to 100,000 mPa·s, is desirable. Specifically, an organopolysiloxane is used that contains two or more silicon-bonded alkenyl groups per molecule, each alkenyl group being represented by the following general formula (Chemical Formula 1): The side chains are linear organopolysiloxanes blocked with alkyl groups. From the viewpoint of workability, a viscosity of 10 to 1,000,000 mPa·s at 25°C is desirable. This linear organopolysiloxane may contain a small amount of branched structure (trifunctional siloxane units) in the molecular chain.

[0026] 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 2is an alkenyl group, and k is 0 or a positive integer. 1 Examples of unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds include those having 1 to 10 carbon atoms, and particularly preferably 1 to 6 carbon atoms, and specific examples thereof 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, and 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 in (A1) preferably has 2 to 6 carbon atoms, particularly 2 to 3 carbon atoms. Specific examples include vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, and cyclohexenyl groups, with vinyl being preferred. In general formula (1), k is generally 0 or a positive integer satisfying 0≦k≦10,000, preferably 5≦k≦2,000, and more preferably 10≦k≦1,200. The organopolysiloxane of component A1 may also be used in combination with an organopolysiloxane having three or more, typically 3 to 30, and preferably about 3 to 20, alkenyl groups bonded to silicon atoms having 2 to 8 carbon atoms, particularly 2 to 6 carbon atoms, such as vinyl or allyl groups, per molecule. The molecular structure may be linear, cyclic, branched, or three-dimensionally networked. Preferably, the polymer 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, and particularly 100 to 100,000 mPa·s.

[0027] The alkenyl groups may be bonded to any part of the molecule. For example, they may be bonded to a silicon atom at either the molecular chain terminal or a non-terminal (mid-chain) location. Among these, linear organopolysiloxanes are those represented by the following general formula (Chemical Formula 2): These 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, then at least one alkenyl group (e.g., as a substituent in a diorganosiloxane unit) bonded to a non-terminal (mid-chain) silicon atom is required.) As mentioned above, from the viewpoint of workability, those with a viscosity of 10 to 1,000,000 mPa·s at 25°C are desirable. These linear organopolysiloxanes may also contain a small amount of branched structures (trifunctional siloxane units) in the molecular chain.

[0028]

[0029] 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. 3The monovalent hydrocarbon group preferably has 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, and specific examples thereof 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; alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, bromine, and chlorine, or with cyano groups, such as halogen-substituted alkyl groups such as chloromethyl, chloropropyl, bromoethyl, and trifluoropropyl, and cyanoethyl groups. 4 The monovalent hydrocarbon group of R preferably has 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. 1 Specific examples of R include the same as those of R, except that alkenyl groups are not included. 5 The alkenyl group of the formula (1) is preferably an alkenyl group having 2 to 6 carbon atoms, particularly preferably having 2 to 3 carbon atoms. 2 Examples of l and m are the same as those shown in the above, and a vinyl group is preferred. l and m are generally 0 or a positive integer satisfying 0 < l + m ≦ 10000, preferably 5 ≦ l + m ≦ 2000, more preferably 10 ≦ l + m ≦ 1200, and are integers satisfying 0 < l / (l + m) ≦ 0.2, preferably 0.0011 ≦ l / (l + m) ≦ 0.1.

[0030] (2) Crosslinking Component (Component A2) The organohydrogenpolysiloxane of Component A2 of the present invention functions as a crosslinking agent, where SiH groups in this component and alkenyl groups in Component A undergo an addition reaction (hydrosilylation) to crosslink (cure). However, the composition of the present invention is in an uncured state. The organohydrogenpolysiloxane may be any organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms (i.e., SiH groups) per molecule. The molecular structure of this organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure. However, those having a number of silicon atoms per molecule (i.e., a degree of polymerization) of 2 to 1000, preferably about 2 to 300, can be used.

[0031] 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, the organic group bonded to the silicon atom other than a hydrogen atom is R in the general formula (Chemical Formula 1). 1 and unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, similar to those shown above.

[0032] Examples of organohydrogenpolysiloxanes of component A2 include those with the following structures:

[0033] 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.

[0034] (3) Unreacted Silicone Oil Unreacted silicone oil can also be used as the matrix resin. As the unreacted silicone oil, dialkyl polysiloxanes such as dimethyl polysiloxane, or linear organo polysiloxanes such as diphenyl polysiloxane are preferred. The unreacted silicone oil has a viscosity of 1 to 10,000 mm at 25°C. 2 / s is preferred.

[0035] (4) Thermally conductive particles (component B and component C) In the present invention, it is preferable to use three or more types of inorganic particles with different average particle sizes in combination as the thermally conductive particles. When three types are used, they are component B-1, component C-1, and component C-2, and when four types are used, component B-2 is added to these. In this way, the thermally conductive inorganic particles with smaller particle sizes are buried between the larger particles, allowing for filling in a state close to close packing, thereby increasing thermal conductivity.

[0036] (5) Other Additives 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, and flame retardant assistants may be added. Organic or inorganic pigments may be added for coloring or color matching. The above-mentioned silane coupling agents may also be added.

[0037] The following description will be made with reference to the drawings. In the following drawings, the same reference numerals indicate the same components. FIG. 1 is a schematic cross-sectional view of a heat dissipation structure 10 incorporating a thermally conductive sheet according to one embodiment of the present invention. The thermally conductive sheet 11b dissipates heat generated by an electronic component 13, such as a semiconductor device. The thermally conductive sheet 11b is fixed to a main surface 12a of the heat spreader 12 facing the electronic component 13, and is sandwiched between the electronic component 13 and the heat spreader 2. The thermally conductive sheet 11a is sandwiched between the heat spreader 12 and a heat sink 15. The thermally conductive sheets 11a and 11b, together with the heat spreader 2, constitute a heat dissipation member that dissipates heat from the electronic component 13. The heat spreader 12 is formed, for example, in the shape of a rectangular plate, and has a main surface 12a facing the electronic component 13 and a sidewall 12b extending along the outer periphery of the main surface 12a. The heat spreader 2 has a thermally conductive sheet 11b on a main surface 12a surrounded by side walls 12b, and a heat sink 15 on another surface 12c opposite to the main surface 12a, with the thermally conductive sheet 11a interposed therebetween. The electronic component 13 is, for example, a semiconductor element such as a BGA, and is mounted on a wiring board 14.

[0038] The following examples are provided for illustrative purposes only. The present invention is not limited to these examples. Various parameters were measured using the methods described below. <Thermal Conductivity> The thermal conductivity of a thermally conductive silicone rubber sheet was measured using a hot disk (in accordance with ISO 22007-2:2008). As shown in FIG. 2A, 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 to generate a constant amount of heat, and 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 FIG. 2B, a double spiral electrode structure, with an applied current electrode 5 and a resistance electrode (temperature measurement electrode) 6 located at the bottom. The thermal conductivity is calculated using the following formula (Equation 1): <Hardness> The hardness of the thermally conductive silicone rubber sheet was measured in accordance with SHORE 00. <Plasticity> Plasticity was measured using a Wallace plastometer in accordance with JIS K 6300-3 and ISO 2007:1991. The plasticity was determined by dividing the thickness (t) of the sample between two metal plates at a measurement temperature of 23°C with a constant load (100 N) and a constant time (15 seconds) by the thickness before compression (t0). This was used to calculate plasticity (P0 = t / t0 × 100). A higher P0 indicates greater flexibility. The pre-vacuum plasticity is the plasticity of the compound after preparation. The post-degassing plasticity is the plasticity after preparation of the compound and degassing for 5 minutes at a reduced pressure of -0.1 Pa. Since the compound is degassed before being molded into a sheet, the post-degassing plasticity is important. <Moldability> A 6-10 mm thick material was sandwiched between PET films and rolled to 2 mm, and the ability to form a sheet was judged. The criteria for judgment were as follows: A: A uniform sheet was formed. B: The sheet was not uniform and was partially broken. <Fillability> When creating the compound, measurements were made to see if the matrix resin and thermally conductive particles could be mixed uniformly. The criteria for judgment were as follows: A: A uniform mixture was possible and the thermally conductive particles could be filled. B: The mixture was not uniform and the thermally conductive particles could not be filled. <BET specific surface area> The BET specific surface area of ​​the thermally conductive particles was measured according to JIS R 1626-1996. The larger the BET specific surface area, the smaller the D50 (median diameter) of the cumulative particle size distribution based on volume of the thermally conductive particles.

[0039] (Examples 1 to 7, Comparative Examples 1 to 3) 1. Material Components (1) Matrix Resin (Component A) The following materials were used: A part of a commercially available two-component silicone polymer (silicone component) containing polyorganosiloxane; B part of the same; Dimethylpolysiloxane (viscosity at 25°C: 100 mm) as unreacted silicone oil. 2 / s) Decyltrimethoxysilane was used as a silane coupling agent. (2) Thermally conductive particles (component B) The thermally conductive particles 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 when particle size distribution is measured by laser diffraction light scattering. An example of this measuring instrument is the LA-950S2 laser diffraction / scattering particle distribution measuring instrument manufactured by Horiba, Ltd. (3) Thermally conductive particles (component C) The thermally conductive particles 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 when particle size distribution is measured by laser diffraction light scattering. An example of this measuring instrument is the LA-950S2 laser diffraction / scattering particle distribution measuring instrument manufactured by Horiba, Ltd. Also, AlN in the table is an abbreviation for aluminum nitride.

[0040] 2. Compound The amounts of each material shown in Table 1 were weighed out and placed in a mixer to form a compound. In Tables 1 and 2, the amount of each material is listed in parts by mass, assuming that the total amount of silicone polymer, unreacted silicone oil used if necessary, and silane coupling agent is 100 parts by mass (100 g). This compound was degassed for 5 minutes under a reduced pressure of -0.1 Pa.

[0041] 3. Sheet molding The compound was sandwiched between release-treated polyethylene terephthalate (PET) films and rolled using a constant speed roll into a 2.0 mm thick sheet to form a thermally conductive silicone rubber sheet. If molding was possible under the above conditions, the moldability was judged to be "possible," and if not, it was judged to be "NG." The above conditions and results are shown in Table 1.

[0042]

[0043] As can be seen from Table 1, in Examples 1 to 7, thermally conductive compositions and thermally conductive sheets were obtained that had high thermal conductivity, low plasticity, good moldability, and low plasticity. In contrast, Comparative Example 1 had high plasticity and could not be molded, so a sheet could not be obtained. Comparative Example 2 had a low amount of alumina added, which was undesirable, resulting in low thermal conductivity. Comparative Example 3 had a low amount of aluminum nitride added, which was undesirable, resulting in low thermal conductivity.

[0044] The thermally conductive composition and thermally conductive sheet of the present invention are suitable as a thermal interface material (TIM) that is placed between a heat-generating portion of an electric or electronic part and a heat sink.

[0045] REFERENCE SIGNS LIST 1 Thermal conductivity measuring device 2 Sensor 3a, 3b Sample 4 Sensor tip 5 Electrode for applied current 6 Electrode for resistance value (electrode for temperature measurement) 10 Heat dissipation structure 11a, 11b Thermally conductive sheet 12 Heat spreader 13 Electronic component 14 Wiring board 15 Heat sink

Claims

1. A thermally conductive composition comprising a matrix resin (component A) and thermally conductive particles, wherein the thermally conductive particles comprise the following components B and C: Component B: 220 to 500 parts by mass of alumina having a D50 (median diameter) of 0.01 μm or more and less than 1 μm in a cumulative particle size distribution based on volume, relative to 100 parts by mass of component A; Component C: 1,900 to 2,500 parts by mass of aluminum nitride having a D50 (median diameter) of 0.01 μm or more and 150 μm or less, relative to 100 parts by mass of component A; The thermally conductive composition is in an uncured state.

2. The thermally conductive composition according to claim 1, wherein the component B comprises the following components B-1 and B-2: Component B-1: D50 (median diameter) of 0.01 μm or more and less than 0.3 μm, BET specific surface area of ​​9 m 2 / g or more is 30 to 100 mass% relative to 100 mass% of component B. Component B-2: Alumina having a D50 (median diameter) of 0.3 μm or more and less than 1 μm is 0 to 70 mass% relative to 100 mass% of component B.

3. The thermally conductive composition according to claim 1 or 2, wherein the C component contains the following C-1 and C-2 components: C-1 component: D50 (median diameter) is 0.01 μm or more and less than 30 μm C-2 component: D50 (median diameter) is 30 μm or more and 150 μm or less The mass ratio of C-1 component and C-2 component is C-2 component≦C-1 component 4. The thermally conductive composition according to any one of claims 1 to 3, wherein the thermal conductivity of the thermally conductive composition is 14 W / m·K or more.

5. The thermally conductive composition according to any one of claims 1 to 4, wherein the thermally conductive composition has a SHORE 00 hardness of 75 or less.

6. The thermally conductive composition according to any one of claims 1 to 5, wherein the matrix resin is at least one selected from the group consisting of a silicone polymer and an unreacted silicone oil.

7. The thermally conductive composition according to claim 1, further comprising 0.1 to 10 parts by mass of a silane coupling agent per 100 parts by mass of the matrix resin.

8. A thermally conductive composition according to any one of claims 1 to 7, wherein at least one component selected from the group consisting of alumina (B) and aluminum nitride (C) is in the form of irregularly pulverized particles.

9. The thermally conductive composition according to any one of claims 1 to 8, wherein the thermally conductive composition has a plasticity of less than 100 after vacuum degassing.

10. A thermally conductive sheet, characterized in that the thermally conductive composition according to any one of claims 1 to 9 is formed into a sheet.

11. The thermally conductive sheet according to claim 10, wherein the thickness of the thermally conductive sheet is in the range of 0.2 to 10 mm.

12. A method for producing a thermally conductive sheet, comprising vacuum degassing the thermally conductive composition according to any one of claims 1 to 9, rolling it, and forming it into a sheet to obtain an uncured thermally conductive sheet.

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