Thermally conductive composition, thermally conductive sheet using same, and production method therefor

Abstract

The present invention provides: a thermally conductive composition that has a high thermal conductivity while keeping a low compressive load value; a thermally conductive sheet using the same; and a production method therefor. The present invention comprises a matrix resin (A) and thermally conductive inorganic particles (B). With respect to 100 mass% of the matrix resin (A), an addition-curing silicone polymer (A1) is not less than 30 mass% but less than 100 mass% and a non-reactive silicone oil (A2) is more than 0 mass% but not more than 70 mass%. With respect to 100 parts by mass of the matrix resin (A), the content of the thermally conductive inorganic particles (B) is as follows: 400-1000 parts by mass of thermally conductive inorganic particles having a median diameter D50 of less than 10 μm; 400-1000 parts by mass of thermally conductive inorganic particles having a D50 of not less than 10 μm but less than 100 μm; and 800-1500 parts by mass of thermally conductive inorganic particles having a D50 of not less than 100 μm. The instantaneous load value is not more than 500 N.

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] In recent years, the performance of semiconductors such as CPUs has improved dramatically, resulting in enormous increases in heat generation. Therefore, 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 their integration becomes more advanced, thermally conductive sheets are required to be flexible and have high thermal conductivity. Previously, Japanese Patent Publication Nos. 6246986 and 7039157 proposed polysiloxane compositions containing large-sized aluminum nitride particles and small-sized aluminum nitride particles or alumina particles. Japanese Patent Publication Nos. 7082563 and 7205554 proposed thermally conductive polysiloxane compositions containing aluminum nitride particles.

[0003] The present invention provides a thermally conductive composition comprising a matrix resin (A) and thermally conductive inorganic particles (B), wherein the matrix resin (A) comprises an addition-curable silicone polymer (A1) and a non-reactive silicone oil (A2), and the matrix resin (A) comprises 30% by mass or more and less than 100% by mass of the addition-curable silicone polymer (A1) and more than 0% by mass and 70% by mass or less of the non-reactive silicone oil (A2), when the matrix resin (A) is taken as 100% by mass, and the thermally conductive inorganic particles (B) comprise, relative to 100 parts by mass of the matrix resin (A), 400 to 1000 parts by mass of thermally conductive inorganic particles (B1 component) having a D50 (median diameter) of less than 10 μm, and 400 to 1000 parts by mass of thermally conductive inorganic particles (B2 component) having a D50 (median diameter) of 10 μm or more and less than 100 μm, The thermally conductive composition contains 800 to 1,400 parts by mass of thermally conductive inorganic particles (component B3) having a D50 (median diameter) of 100 μm or more, and the total amount of components B1, B2, and B3 is 2,000 to 3,000 parts by mass per 100 parts by mass of the matrix resin (A).

[0004] 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. FIG. 2 is a schematic side cross-sectional view of a compression load measuring device used in one embodiment of the present invention. FIGS. 3A-B are schematic explanatory diagrams showing a method for measuring the thermal conductivity of a sample according to one embodiment of the present invention. FIG. 4A is a schematic cross-sectional view showing an oil bleed width measurement test in one embodiment of the present invention, and FIG. 4B is a schematic plan view showing the same oil bleed width measurement. FIG. 5 is a scanning electron microscope (SEM, 5000x magnification) photograph of amorphous alumina (D50 = 0.3 μm) according to one embodiment of the present invention. FIG. 6 is a scanning electron microscope (SEM, 100x magnification) photograph of spherical alumina (D50 = 120 μm) according to one embodiment of the present invention. FIG. 7 is a scanning electron microscope (SEM, 500x magnification) photograph of amorphous aluminum nitride (D50 = 20 μm) according to one embodiment of the present invention. Detailed Description of the Invention

[0005] However, conventional thermally conductive compositions and thermally conductive sheets using them have problems with moldability due to the increased plasticity of the composition when the thermal conductivity is increased, and the compressive load value of the cured thermally conductive sheet also increases, leaving further improvements necessary.

[0006] In order to solve the above-mentioned problems of the prior art, the present invention provides a thermally conductive composition having high thermal conductivity and a low compressive load value, a thermally conductive sheet using the same, and a method for producing the same.

[0007] The thermally conductive composition of the present invention is a thermally conductive composition comprising a matrix resin (A) and thermally conductive inorganic particles (B), wherein the matrix resin (A) comprises an addition-curable silicone polymer (A1) and a non-reactive silicone oil (A2), and the matrix resin (A) comprises 30% by mass or more and less than 100% by mass of the addition-curable silicone polymer (A1) and more than 0% by mass and 70% by mass or less of the non-reactive silicone oil (A2), when the matrix resin (A) is taken as 100% by mass, and the thermally conductive inorganic particles (B) comprise, relative to 100 parts by mass of the matrix resin (A), 400 to 1000 parts by mass of thermally conductive inorganic particles (B1 component) having a D50 (median diameter) of less than 10 μm, and 400 to 1000 parts by mass of thermally conductive inorganic particles (B2 component) having a D50 (median diameter) of 10 μm or more and less than 100 μm, The composition contains 800 to 1,400 parts by mass of thermally conductive inorganic particles (B3 component) having a D50 (median diameter) of 100 μm or more, and the total amount of the B1 component, B2 component, and B3 component is 2,000 to 3,000 parts by mass per 100 parts by mass of the matrix resin (A).

[0008] The thermally conductive sheet of the present invention contains the thermally conductive composition described above and is formed into a sheet.

[0009] The method for producing a thermally conductive sheet of the present invention includes the steps of vacuum degassing the thermally conductive composition, rolling it, forming it into a sheet, and then heat-curing it to produce a thermally conductive sheet.

[0010] By using the above composition, the present invention can provide a thermally conductive sheet having high thermal conductivity and a low compressive load value, a thermally conductive composition that is the raw material for the thermally conductive sheet, and a method for producing the thermally conductive sheet. Specifically, the thermal conductivity of the thermally conductive sheet is 8.5 W / mK or higher, and the instantaneous load value at 50% compression of a 28.6 mm diameter, 2 mm thickness sheet is 500 N or less, as measured by the compressive load measurement method in accordance with ASTM D575-91:2012. Furthermore, the method for producing the thermally conductive sheet of the present invention enables continuous sheet molding because the thermally conductive composition of the present invention has low plasticity and good moldability.

[0011] The present invention is a conductive composition comprising a matrix resin (A) and thermally conductive inorganic particles (B).

[0012] <Matrix Resin (A)> The matrix resin (A) contains an addition-curable silicone polymer (component A1) and a non-reactive silicone oil (component A2). When the matrix resin (A) is taken as 100% by mass, the matrix resin (A) contains 30% by mass or more but less than 100% by mass of the component A1 and more than 0% by mass but not more than 70% by mass of the component A2. The matrix resin (A) preferably contains 32% by mass or more but not more than 90% by mass of the component A1 and 10% by mass or more but not more than 68% by mass of the component A2, more preferably 35% by mass or more but not more than 80% by mass of the component A1 and 20% by mass or more but not more than 65% by mass of the component A2, and even more preferably 38% by mass or more but not more than 70% by mass of the component A1 and 30% by mass or more but not more than 62% by mass of the component A2. By achieving a composition within these ranges, the compressive load value of the thermally conductive composition can be kept low, and oil bleeding can be reduced. In particular, if the proportion of the non-reactive silicone oil (component A2) is 70 mass % or less, oil bleeding can be reduced, which is preferable.

[0013] The non-reactive silicone oil (component A2) has a viscosity of 50 to 3000 mm at 25°C. 2 / s is preferred, and more preferably 70 to 2500 mm 2 / s. Viscosity measurement is performed using a Brookfield rotational viscometer Sp No. 2. If the viscosity is within the above range, the thermally conductive inorganic particles contained in the thermally conductive composition will be well filled, and oil bleeding from the thermally conductive sheet will be kept low. The non-reactive silicone oil (component A2) is, for example, dimethylpolysiloxane, diphenylpolysiloxane, dimethylsilicone, etc., and is a silicone polymer without reactive groups.

[0014] The matrix resin (A) preferably further contains a silane coupling agent. The silane coupling agent is preferably added in an amount of 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, per 100 parts by mass of the matrix resin (A). By further including the silane coupling agent, the thermally conductive composition can maintain a low compressive load value. Furthermore, the surfaces of the thermally conductive inorganic particles are coated with the silane coupling agent (surface treatment), which results in the coated thermally conductive inorganic particles (B) being more easily filled into the matrix resin (A) (plasticizer function), preventing the curing catalyst from being adsorbed onto the thermally conductive inorganic particles (B), thereby preventing curing inhibition. This is useful for improving storage stability.

[0015] The silane coupling agent may be, for example, a compound represented by the formula R a Si(OR') 4-a (wherein R is an unsubstituted or substituted hydrocarbon 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 (wherein R is an unsubstituted or substituted hydrocarbon group having 1 to 20 carbon atoms, R' is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1) Examples of alkoxysilane compounds (hereinafter simply referred to as "silane") represented by the formula 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.

[0016] The addition-curable silicone polymer (A1) of the matrix resin preferably contains a base polymer component (component a1) and a crosslinking component (a2). Each component is described below. (1) Base Polymer Component (Component a1) The base polymer component is, for example, an organopolysiloxane containing two or more silicon-bonded alkenyl groups per molecule. The organopolysiloxane is the main component (base polymer component) in the matrix resin of the present invention. This organopolysiloxane contains two or more silicon-bonded alkenyl groups per molecule, such as vinyl groups or allyl groups, each having 2 to 8 carbon atoms, preferably 2 to 6 carbon atoms. From the viewpoint of workability and curability, it is desirable for the viscosity of the organopolysiloxane to be 10 to 1,000,000 mPa·s, and particularly 100 to 100,000 mPa·s, at 25°C.

[0017] Specifically, an organopolysiloxane represented by the following general formula (I) containing alkenyl groups bonded to silicon atoms at both ends of the molecular chain per molecule can be used. This organopolysiloxane is a linear organopolysiloxane whose side chains are blocked with alkyl groups. From the viewpoint of workability, curability, and the like, an organopolysiloxane with 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 structures (trifunctional siloxane units) in the molecular chain.

[0018]

[0019] In the formula, R 1 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, R 2 is an alkenyl group, and k is 0 or a positive integer.

[0020] In general formula (I), R 1Preferred examples of unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds include hydrocarbon groups having 1 to 10 carbon atoms, and particularly 1 to 6 carbon atoms. Specific examples of unsubstituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenylethyl, and phenylpropyl. Examples of unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds include groups in which the above unsubstituted monovalent hydrocarbon groups have been partially or entirely 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.

[0021] In general formula (I), R 2 The alkenyl group is preferably an alkenyl group having 2 to 6 carbon atoms, particularly 2 to 3. Specific examples of the alkenyl group include a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a hexenyl group, and a cyclohexenyl group, and the vinyl group is preferred.

[0022] In general formula (I), k is 0 or a positive integer, preferably 0 or a positive integer satisfying 0≦k≦10,000, more preferably 5≦k≦2000, and even more preferably 10≦k≦1200.

[0023] The organopolysiloxane of component a1 may be an organopolysiloxane having three or more, typically 3 to 30, and preferably about 3 to 20, alkenyl groups, such as vinyl groups or allyl groups, bonded to silicon atoms having 2 to 8, particularly 2 to 6, carbon atoms per molecule. The molecular structure of the organopolysiloxane used in combination may be linear, cyclic, branched, or three-dimensional network. The organopolysiloxane used in combination is preferably a linear organopolysiloxane whose main chain is composed of repeating diorganosiloxane units, 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.

[0024] In organopolysiloxanes containing two or more alkenyl groups bonded to silicon atoms per molecule, the alkenyl groups may be bonded to any part of the molecule. For example, they may be bonded to silicon atoms at the molecular chain terminals or non-terminal locations (in the middle of the molecular chain). Among these, linear organopolysiloxanes represented by the following general formula (II), in which one to three alkenyl groups are bonded to silicon atoms at both molecular chain terminals, and which have a viscosity at 25°C of 10 to 1,000,000 mPa·s are preferred from the viewpoints of workability and curability. However, when the number of alkenyl groups bonded to silicon atoms at the molecular chain terminals of this linear organopolysiloxane is one or two in total, linear organopolysiloxanes in which the alkenyl groups bonded to non-terminal locations (in the middle of the molecular chain) are used as substituents in, for example, diorganosiloxane units are preferred. This linear organopolysiloxane may contain a small amount of branched structure (trifunctional siloxane unit) in the molecular chain.

[0025]

[0026] In the formula, R 3 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups, at least one of which is an alkenyl group; 4 may be the same or different and are unsubstituted or substituted monovalent hydrocarbon groups that do not have an aliphatic unsaturated bond, R5 is an alkenyl group, and l and m are each independently 0 or a positive integer.

[0027] In general formula (II), R 3 The unsubstituted or substituted monovalent hydrocarbon group is preferably a hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms. Specific examples of the unsubstituted monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl, aryl groups such as phenyl, tolyl, xylyl, and naphthyl, aralkyl groups such as benzyl, phenylethyl, and phenylpropyl, and alkenyl groups such as nyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl. Examples of the substituted monovalent hydrocarbon group include groups in which some or all of the hydrogen atoms of the unsubstituted monovalent hydrocarbon group have been substituted with halogen atoms such as fluorine, bromine, or chlorine; or a cyano group, such as halogen-substituted alkyl groups such as a chloromethyl group, a chloropropyl group, a bromoethyl group, or a trifluoropropyl group; and a cyanoethyl group.

[0028] In general formula (II), R 4 As the unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, a hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, is preferred. 4 The unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond includes the above-mentioned R 1 Specific examples are the same as those of 1, except that alkenyl groups are not included.

[0029] In general formula (II), R 5 The alkenyl group in the formula (I) is preferably an alkenyl group having 2 to 6 carbon atoms, particularly preferably an alkenyl group having 2 to 3 carbon atoms. 2 Examples of the alkyl group include the same as the alkenyl group, and a vinyl group is preferred.

[0030] In general formula (II), l and m are each independently 0 or a positive integer, preferably 0 or a positive integer that satisfies 0 < l + m ≦ 10,000, preferably 5 ≦ l + m ≦ 2,000, more preferably 10 ≦ l + m ≦ 1,200, and preferably an integer that satisfies 0 < l / (l + m) ≦ 0.2, more preferably 0.0011 ≦ l / (l + m) ≦ 0.1.

[0031] (2) Crosslinking Component (Component a2) The organohydrogenpolysiloxane of component a2 of the present invention is, for example, an organohydrogenpolysiloxane. This organohydrogenpolysiloxane acts as a crosslinking agent. A cured product is formed by addition reaction (hydrosilylation) between SiH groups in this organohydrogenpolysiloxane and alkenyl groups in the organopolysiloxane of component a1. Any organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms (i.e., SiH groups) per molecule can be used as the crosslinking component (component a2). The molecular structure of this organohydrogenpolysiloxane may be linear, cyclic, branched, or a three-dimensional network structure. Furthermore, organohydrogenpolysiloxanes having a number of silicon atoms in one molecule (ie, degree of polymerization) of 2 to 1,000, and particularly 2 to 300, can be preferably used as the crosslinking component (component a2).

[0032] The organohydrogenpolysiloxane contains SiH groups as described above. In the organohydrogenpolysiloxane, the position of the SiH groups is not particularly limited, and they may be at the terminals of the molecular chain or at non-terminal locations (in the middle of the molecular chain). Furthermore, examples of organic groups bonded to silicon atoms other than hydrogen atoms include R in the general formula (I). 1 and unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, similar to those shown above.

[0033] An example of the organohydrogenpolysiloxane of component a2 is one represented by the following formula (III).

[0034]

[0035] In the above formula, each R6 may be the same or different and are an alkyl group, a phenyl group, an epoxy group, an acryloyl group, a methacryloyl group, an alkoxy group, or a hydrogen atom, 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.

[0036] (3) Catalyst Component (Component c) The catalyst component c can be a catalyst used in hydrosilylation reactions. Examples of the curing catalyst 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 typically contain a platinum-group metal catalyst. However, even when the thermally conductive composition of the present invention contains a two-component curing silicone polymer, an additional platinum-group metal catalyst is preferably used. The platinum-group metal catalyst is added to control the curing rate of the thermally conductive composition.

[0037] The curing catalyst is contained in the thermally conductive composition in an amount of, for example, 0.01 to 1000 parts by mass, preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 50 parts by mass, per 100 parts by mass of the matrix resin (component A).

[0038] <Thermal conductive inorganic particles (B)> The thermal conductive inorganic particles (B) comprise, relative to 100 parts by mass of the matrix resin (A), 400 to 1000 parts by mass, preferably 410 to 950 parts by mass, more preferably 420 to 900 parts by mass, and even more preferably 430 to 850 parts by mass of thermal conductive inorganic particles (B1) having a D50 (median diameter) of less than 10 μm, and 400 to 1000 parts by mass, preferably 420 to 950 parts by mass, more preferably 440 to 900 parts by mass, and even more preferably 460 to 800 parts by mass of thermal conductive inorganic particles (B2) having a D50 (median diameter) of 10 μm or more and less than 100 μm, The composition contains 800 to 1,400 parts by mass, preferably 820 to 1,400 parts by mass, more preferably 840 to 1,350 parts by mass, and even more preferably 860 to 1,300 parts by mass of thermally conductive inorganic particles (component B3) having a D50 (median diameter) of 100 μm or more. This is because using such a blending ratio allows for the production of a thermally conductive sheet with high thermal conductivity and low plasticity.

[0039] The thermally conductive inorganic particles (B) preferably contain, relative to the total amount of the matrix resin (A), 10 to 45 mass%, more preferably 12 to 40 mass%, and even more preferably 15 to 35 mass% of thermally conductive inorganic particles (B1) having a D50 (median diameter) of less than 10 μm, 10 to 45 mass%, more preferably 12 to 40 mass%, and even more preferably 15 to 35 mass% of thermally conductive inorganic particles (B2) having a D50 (median diameter) of 10 μm or more but less than 100 μm, and 25 to 65 mass%, more preferably 30 to 60 mass%, and even more preferably 35 to 55 mass% of thermally conductive inorganic particles (B3) having a D50 (median diameter) of 100 μm or more. Using these blending ratios results in a thermally conductive sheet with high thermal conductivity and low plasticity.

[0040] Furthermore, the total of the B1, B2, and B3 components is 2,000 to 3,000 parts by mass per 100 parts by mass of the matrix resin (A). The total of the B1, B2, and B3 components is preferably 2,000 to 2,800 parts by mass, and more preferably 2,000 to 2,600 parts by mass per 100 parts by mass of the matrix resin (A). This is because using such a blending ratio allows for the production of a thermally conductive sheet with high thermal conductivity and low plasticity.

[0041] In the present invention, the thermally conductive particles (component B) are made up of multiple types of inorganic particles with different average particle sizes. This allows smaller thermally conductive inorganic particles to be embedded between larger particles, resulting in a nearly close-packed structure, enhancing the thermal conductivity of the thermally conductive sheet. This also results in a thermally conductive composition with low plasticity and excellent moldability. This also allows the thermally conductive sheet to be molded into a thermal interface material (TIM), a heat-dissipating sheet with a low compressive load and easier handling than putty-like materials.

[0042] The thermally conductive inorganic particles of the B1, B2, and B3 components are preferably, independently of one another, at least one selected from the group consisting of amorphous alumina, spherical alumina, and amorphous aluminum nitride. Using these particles can enhance thermal conductivity. "Amorphous" refers to irregularly shaped particles. Figure 5 shows a scanning electron microscope (SEM, magnification 5000x) photograph of amorphous alumina (D50 = 0.3 μm), Figure 6 shows a scanning electron microscope (SEM, magnification 100x) photograph of spherical alumina (D50 = 120 μm), and Figure 7 shows a scanning electron microscope (SEM, magnification 500x) photograph of amorphous aluminum nitride (D50 = 20 μm).

[0043] The mass % of alumina relative to the total thermally conductive inorganic particles is preferably 40 to 80 mass %, more preferably 45 to 75 mass %, and even more preferably 50 to 70 mass %. The mass % of aluminum nitride relative to the total thermally conductive inorganic particles is preferably 10 to 55 mass %, more preferably 15 to 50 mass %, and even more preferably 20 to 45 mass %. By making the mass % of alumina in the thermally conductive inorganic particles higher than the mass % of aluminum nitride, the production costs of the thermally conductive composition can be reduced, which is preferable.

[0044] <Other Additives> The thermally conductive composition of the present invention may contain components other than those described above, as needed. For example, the thermally conductive composition may contain heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardant assistants, and curing retarders. The thermally conductive composition may also contain organic or inorganic pigments for coloring or toning purposes. The thermally conductive composition may also contain the above-mentioned silane coupling agent.

[0045] <Thermal Conductive Composition> The plasticity of the thermally conductive composition after degassing before curing is preferably 65 or less, more preferably 64 or less, and even more preferably 63 or less. The plasticity is preferably 5 or more, more preferably 10 or more, and even more preferably 15 or more. Thermally conductive compositions with such low plasticity have good moldability. The plasticity is determined in accordance with JIS K6300-3 and ISO2007:1991 using a Wallace plastometer at a measurement temperature of 25°C. The sample is compressed between two metal plates at a constant load (100 N) for a fixed time (15 seconds). The plasticity is calculated by dividing the thickness (t) of the sample by the thickness (t) of the sample before compression (P0 = t / t0 × 100). A smaller P0 indicates greater flexibility. Because the thermally conductive composition is degassed before being molded into a sheet, the plasticity before curing and after degassing is important.

[0046] A preferred example of the thermally conductive composition of the present invention is a compound having the following composition. A. Matrix Resin The addition-curable silicone polymer (A1) contains the following (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 of less than 1 mole per mole of silicon-bonded alkenyl groups in component A. Non-reactive silicone oil (A2), for example, a dialkylpolysiloxane such as dimethylpolysiloxane, or a diphenylpolysiloxane. C. Platinum group metal catalyst: An amount of 0.01 to 1,000 ppm by mass relative to the matrix resin. D. Other additives: A silane coupling agent, a cure retarder, a colorant, etc.; any amount.

[0047] <Thermal Conductive Sheet> The thermally conductive composition of the present invention can be cured by heating or the like. When the thermally conductive composition of the present invention is formed into a sheet, it has high versatility and is suitable as a TIM. The thickness of the sheet containing the thermally conductive composition (i.e., the thermally conductive sheet) is preferably in the range of 0.2 to 10 mm.

[0048] The instantaneous load value of a thermally conductive sheet containing the thermally conductive composition and formed into a sheet, when compressed by 50% to a diameter of 28.6 mm and a thickness of 2 mm, is preferably 500 N or less, more preferably 100 to 500 N, even more preferably 100 to 480 N, and still more preferably 100 to 450 N. Such a thermally conductive sheet is easily crushed, and when interposed between a heat generating part and a heat sink, it can reduce the physical load on the heat sink, making it suitable as a heat sink sheet: TIM (Thermal Interface Material).

[0049] The thermal conductivity of the thermally conductive sheet formed from the thermally conductive composition is preferably 8.5 W / mK or more, more preferably 8.5 to 20 W / m K, and even more preferably 9 to 15 W / m K. This provides high thermal conductivity and makes the sheet suitable as a heat dissipation sheet: TIM (Thermal Interface Material).

[0050] The thermally conductive sheet containing the thermally conductive composition and formed into a sheet preferably has a length of 25 mm, a width of 25 mm, and a thickness of 2 mm, and when sandwiched between a glass plate and a medicine wrapping paper at a compression ratio of 50%, and held at 125°C for 72 hours, the oil-bleed width is preferably 10 mm or less. The oil-bleed width is more preferably 8 mm or less, and even more preferably 6 mm or less. This allows oil-bleed to be kept low.

[0051] <Method for manufacturing a thermally conductive sheet> The method for manufacturing a thermally conductive sheet of the present invention includes the steps of vacuum-degassing the thermally conductive composition, rolling it, forming it into a sheet, and then heat-curing it to obtain a thermally conductive sheet. The vacuum degassing can be performed by reducing the pressure of the thermally conductive composition (compound) to -0.08 to -0.1 Pa and leaving it for about 5 to 10 minutes to degas it. The rolling can be performed by roll-rolling, press-forming, or the like, but roll-rolling is preferred because it allows for continuous production.

[0052] 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.

[0053] 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.

[0054] 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 1 incorporating thermally conductive sheets 2a and 2b according to one embodiment of the present invention. The thermally conductive sheet 2b dissipates heat generated by an electronic component 4, such as a semiconductor device. The thermally conductive sheet 2b is fixed to a main surface 3a of the heat spreader 3 facing the electronic component 4, and is sandwiched between the electronic component 4 and the heat spreader 3. The thermally conductive sheet 2a is sandwiched between the heat spreader 3 and a heat sink 6. The thermally conductive sheets 2a and 2b, together with the heat spreader 3, constitute a heat dissipation member that dissipates heat from the electronic component 4. The heat spreader 3 is formed, for example, in the shape of a rectangular plate, and has a main surface 3a facing the electronic component 4 and a sidewall 3b extending along the outer periphery of the main surface 3a. The heat spreader 3 has a thermally conductive sheet 2b on a main surface 3a surrounded by side walls 3b, and a heat sink 6 on another surface 3c opposite the main surface 2a, with the thermally conductive sheet 2a interposed therebetween. The electronic component 4 is, for example, a semiconductor element such as a BGA, and is mounted on a wiring board 5.

[0055] The present invention includes the following aspects: [Item 1] A thermally conductive composition comprising a matrix resin (A) and thermally conductive inorganic particles (B), wherein the matrix resin (A) comprises an addition-curable silicone polymer (A1) and a non-reactive silicone oil (A2), and the matrix resin (A) comprises 30% by mass or more and less than 100% by mass of the addition-curable silicone polymer (A1) and more than 0% by mass and 70% by mass or less of the non-reactive silicone oil (A2), relative to 100 parts by mass of the matrix resin (A), and the thermally conductive inorganic particles (B) comprise, per 100 parts by mass of the matrix resin (A), 400 to 1000 parts by mass of thermally conductive inorganic particles (B1) having a D50 (median diameter) of less than 10 μm, and 400 to 1000 parts by mass of thermally conductive inorganic particles (B2) having a D50 (median diameter) of 10 μm or more and less than 100 μm, A thermally conductive composition comprising 800 to 1400 parts by mass of thermally conductive inorganic particles (component B3) having a D50 (median diameter) of 100 μm or more, wherein the total amount of components B1, B2 and B3 is 2000 to 3000 parts by mass per 100 parts by mass of the matrix resin (A).

[0056] [Item 2] The thermally conductive composition according to Item 1, wherein, when the matrix resin (A) is taken as 100% by mass, the matrix resin (A) preferably contains 32% by mass or more and 90% by mass or less of the A1 component and 10% by mass or more and 68% by mass or less of the A2 component, more preferably 35% by mass or more and 80% by mass or less of the A1 component and 20% by mass or more and 65% by mass or less of the A2 component, and even more preferably 38% by mass or more and 70% by mass or less of the A1 component and 30% by mass or more and 62% by mass or less of the A2 component.

[0057] [Item 3] The non-reactive silicone oil (component A2) has a viscosity of 50 to 3000 mm at 25°C. 2 / s is preferred, and more preferably 70 to 2500 mm 2 Item 3. The thermally conductive composition of item 1 or 2, wherein:

[0058] [Item 4] The thermally conductive composition according to any one of Items 1 to 3, wherein the non-reactive silicone oil (Component A2) is selected from the group consisting of dimethylpolysiloxane, diphenylpolysiloxane, and dimethylsilicone.

[0059] [Item 5] The thermally conductive composition according to any one of Items 1 to 4, wherein the matrix resin (A) further contains a silane coupling agent.

[0060] [Item 6] The silane coupling agent is preferably added in an amount of 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, per 100 parts by mass of the matrix resin (A). The thermally conductive composition according to Item 5.

[0061] [Item 7] The thermally conductive composition according to Item 5 or 6, wherein the silane coupling agent is selected from the group consisting of methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane.

[0062] [Item 8] The thermally conductive inorganic particles (B) are, relative to 100 parts by mass of the matrix resin (A), preferably 410 to 950 parts by mass, more preferably 420 to 900 parts by mass, and even more preferably 430 to 850 parts by mass of thermally conductive inorganic particles (B1 component) having a D50 (median diameter) of less than 10 μm, and preferably 420 to 950 parts by mass, more preferably 440 to 900 parts by mass, and even more preferably 460 to 800 parts by mass of thermally conductive inorganic particles (B2 component) having a D50 (median diameter) of 10 μm or more and less than 100 μm, and preferably 820 to 1400 parts by mass, more preferably 840 to 1350 parts by mass, and even more preferably 860 to 1300 parts by mass of thermally conductive inorganic particles (B3 component) having a D50 (median diameter) of 100 μm or more.

[0063] [Item 9] The thermally conductive inorganic particles (B) are, relative to the entire matrix resin (A), preferably 10 to 45% by mass, more preferably 12 to 40% by mass, and even more preferably 15 to 35% by mass of thermally conductive inorganic particles (B1 component) having a D50 (median diameter) of less than 10 μm, and preferably 10 to 45% by mass, more preferably 12 to 40% by mass, and even more preferably 15 to 35% by mass of thermally conductive inorganic particles (B2 component) having a D50 (median diameter) of 10 μm or more and less than 100 μm, and preferably 10 to 45% by mass, more preferably 12 to 40% by mass, and even more preferably 15 to 35% by mass of thermally conductive inorganic particles (B3 component) having a D50 (median diameter) of 100 μm or more. The thermally conductive composition according to any one of Items 1 to 8, further comprising:

[0064] [Item 10] The total amount of the B1 component, the B2 component, and the B3 component relative to 100 parts by mass of the matrix resin (A) is preferably 2000 to 2800 parts by mass, more preferably 2000 to 2600 parts by mass. The thermally conductive composition according to any one of items 1 to 9.

[0065] [Item 11] The thermally conductive inorganic particles of the B1 component, the B2 component, and the B3 component are each independently at least one selected from the group consisting of amorphous alumina, spherical alumina, and amorphous aluminum nitride. The thermally conductive composition according to any one of items 1 to 10.

[0066] [Item 12] The thermally conductive composition according to any one of Items 1 to 11, wherein the thermally conductive particles (component B) are a combination of multiple types of inorganic particles having different average particle diameters.

[0067] [Item 13] The alumina mass% relative to the total thermally conductive inorganic particles (component B) is preferably 40 to 80 mass%, more preferably 45 to 75 mass%, and even more preferably 50 to 70 mass%. The thermally conductive composition according to any one of items 1 to 12.

[0068] [Item 14] The mass% of aluminum nitride relative to the total thermally conductive inorganic particles (component B) is preferably 10 to 55 mass%, more preferably 15 to 50 mass%, and even more preferably 20 to 45 mass%. The thermally conductive composition according to any one of items 1 to 13.

[0069] [Item 15] The thermally conductive composition according to any one of Items 1 to 14, wherein the plasticity after degassing before curing is preferably 65 or less, more preferably 64 or less, even more preferably 63 or less, preferably 5 or more, more preferably 10 or more, and even more preferably 15 or more.

[0070] [Item 16] A thermally conductive sheet comprising the thermally conductive composition according to any one of items 1 to 15 and formed into a sheet.

[0071] [Item 17] The thermally conductive sheet according to Item 16, having a thickness of 0.2 to 10 mm.

[0072] [Item 18] The instantaneous load value at 50% compression of the thermally conductive sheet having a diameter of 28.6 mm and a thickness of 2 mm, as measured by a compression load measurement method according to ASTM D575-91:2012, is preferably 500 N or less, more preferably 100 to 500 N, even more preferably 100 to 480 N, and even more preferably 100 to 450 N. The thermally conductive sheet according to item 16 or 17.

[0073] [Item 19] The thermal conductivity of the thermally conductive sheet is preferably 8.5 W / mK or more, more preferably 8.5 to 20 W / m K, and even more preferably 9 to 15 W / m K. The thermally conductive sheet according to any one of items 16 to 18.

[0074] [Item 20] The thermally conductive sheet has a length of 25 mm, a width of 25 mm, and a thickness of 2 mm, is sandwiched between a glass plate and a medicine wrapping paper at a compression rate of 50%, and is kept at 125 ° C. for 72 hours. The oil bleed width is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 6 mm or less. The thermally conductive sheet according to any one of items 16 to 19.

[0075] [Item 21] A method for producing a thermally conductive sheet, comprising the steps of vacuum degassing the thermally conductive composition according to any one of Items 1 to 15, rolling it, forming it into a sheet, and then heat-curing it to produce a thermally conductive sheet.

[0076] [Examples] The present invention will be explained below using examples, but is not limited to these examples. Various parameters were measured by the methods described below.

[0077] <50% Compression Load Value> The compression load was measured in accordance with ASTM D575-91:2012. FIG. 2 is a schematic side cross-sectional view of a compression load measuring device used in one embodiment of the present invention. This compression load measuring device 7 includes a sample stage 8 and a load cell 12. A thermally conductive sheet sample 10 is sandwiched between aluminum plates 9 and 11, mounted as shown in FIG. 2, and compressed to a specified thickness using the load cell 12. The maximum load value (instantaneous load value) when the thickness is compressed by 50% is recorded.

[0078] Measurement conditions Sample: Circular (diameter 28.6 mm, thickness 2 mm) Compression rate: 50% Aluminum plate size: Circular (diameter 28.6 mm) (compression surface) Compression speed: 5 mm / min Compression method: TRIGGER method (method in which the point at which a load of 2 N is detected is the measurement start position) Measuring device: Aiko Engineering, MODEL-1311NW (load cell 2 kN)

[0079] <Thermal Conductivity> The thermal conductivity of the thermally conductive sheet was measured using a hot disk (compliant with ISO 22007-2:2008). As shown in FIG. 3A, this thermal conductivity measuring device 13 sandwiches a polyimide film sensor 14 between two thermally conductive sheet samples 15a and 15b, applies a constant power to the sensor 14, and analyzes the thermal characteristics from the temperature rise of the sensor 14. The sensor 14 has a 7 mm diameter tip 16 and, as shown in FIG. 3B, has a double spiral electrode structure, with an applied current electrode 17 and a resistance value electrode (temperature measurement electrode) 18 located at the bottom. The thermal conductivity was calculated using the following equation (Equation 1):

[0080] <Method for Measuring Oil-Bleed Width> Figure 4A is a schematic cross-sectional view showing an oil-bleed width measurement test device 21 in one embodiment of the present invention. A thermally conductive sheet sample 22 measuring 25 mm in length, 25 mm in width, and 2 mm in thickness is sandwiched between two sheets of medicine wrapping paper 23a and 23b on an aluminum plate 24 and a glass plate 25. The sample is compressed to a compression ratio of 50% and held at 125°C for 72 hours. The oil-bleed width (spread) from the thermally conductive sheet sample 22 is measured. Figure 4B is a schematic plan view showing the same oil-bleed width (spread). When the size of the thermally conductive sheet sample 22 on the medicine wrapping paper 23a after compression to a compression ratio of 50% is D2 and the length from end to end of the oil-bleed region 26 from the thermally conductive sheet sample 22 is D1, the oil-bleed width is calculated using the following formula: Oil-bleed width = (D1 - D2) / 2 (units: mm).

[0081] <Viscosity of Non-reactive Silicone Oil> The viscosity at 25°C was measured using a Brookfield rotational viscometer Sp No. 2.

[0082] <Plasticity> Plasticity was measured in accordance with JIS K 6300-3 and ISO 2007:1991 using a Wallace plastometer. A sample of the thermally conductive composition was compressed between two metal plates at a measurement temperature of 23°C under a constant load (100 N) for a fixed time (15 seconds). The thickness (t) of the thermally conductive composition after compression was then divided by the thickness (t) before compression to obtain the plasticity (P0 = t / t0 × 100). A smaller P0 indicates a more flexible thermally conductive composition. The post-degassing plasticity is the plasticity measured after the compound is prepared and degassed for 5 minutes under a reduced pressure of -0.1 Pa. Since the compound is degassed before being molded into a sheet, the post-degassing plasticity is important.

[0083] (Examples 1-10, Comparative Examples 1-5) 1. Material Components (1) Matrix Resin (Component A) (a) Addition-Cure Silicone Polymer (Component A1) A commercially available two-component room-temperature-curing silicone polymer (silicone component) containing polyorganosiloxane was used. One component (Component A) contains a base polymer component (polyorganosiloxane, Component A1 of Component A) and a platinum group metal catalyst, while the other component (Component B) contains a base polymer component (polyorganosiloxane, Component A1 of Component A) and a crosslinker component, organohydrogenpolysiloxane. The mass ratio of Components A and B was A:B = 100:100. This two-component room-temperature addition-curing silicone polymer undergoes addition curing when mixed at room temperature to form a silicone resin.

[0084] (b) Non-reactive silicone oil (component A2) As the non-reactive silicone oil (A2), commercially available dimethyl silicone oil (viscosity at 25°C: 100 mm 2 / s) was used.

[0085] (2) Thermally conductive inorganic particles (component B) The thermally conductive inorganic particles listed in Tables 1 and 2 were used. The average particle size of the thermally conductive inorganic particles is the D50 (median diameter) of the cumulative particle size distribution on a volume basis, measured by a laser diffraction light scattering method. An example of the measuring device is the LA-950S2 laser diffraction / scattering particle distribution measuring device manufactured by Horiba, Ltd. Additionally, AlN in the tables is an abbreviation for aluminum nitride.

[0086] (3) Platinum Group Metal Catalyst A platinum-vinyldisiloxane complex (platinum group metal catalyst) was used as the additional platinum group metal catalyst. As described above, the two-component curing silicone polymer (silicone component) contains a platinum group metal catalyst. When preparing the thermally conductive composition of each example, an additional platinum group metal catalyst was added to the thermally conductive composition so that the polyorganosiloxane would be sufficiently cured. (4) Silane Coupling Agent Decyltrimethoxysilane was used as the silane coupling agent.

[0087] 2. Thermally conductive composition (compound) The amounts of each material shown in Tables 1 and 2 were weighed out and placed in a mixer to produce a thermally conductive composition. In Tables 1 and 2, the amount of each material is listed in parts by mass, assuming that the matrix resin (addition-curable silicone polymer and non-reactive silicone oil) is 100 parts by mass (100 g). This thermally conductive composition was degassed for 5 minutes under a reduced pressure of -0.1 Pa.

[0088] 3. Sheet molding The thermally conductive composition was sandwiched between release-treated polyethylene terephthalate (PET) films, and rolled using a constant speed roll to form a sheet with a thickness of 2.0 mm. In this state, the composition was heated and cured at 100°C for 10 minutes to obtain a thermally conductive sheet. The moldability was judged as "possible" if molding was possible under the above conditions, and "NG" if not.

[0089]

[0090]

[0091]

[0092]

[0093] The conditions and results of the examples and comparative examples are shown in Tables 1-2 and Tables 3-4. Tables 1-4 reveal the following: (1) In Examples 1-10, the thermal conductivity of the thermally conductive sheets was high, and the compressive load value and plasticity were low. Furthermore, oil bleeding from the thermally conductive sheets was also low. (2) In Comparative Example 1, non-reactive silicone oil (A2) was added to the thermally conductive composition in an amount exceeding the upper limit, resulting in a low compressive load value and plasticity of the thermally conductive sheet, but increased oil bleeding, which was undesirable. (3) In Comparative Example 2, the matrix resin (A) was not made of non-reactive silicone oil (A2), and the thermally conductive composition contained only the addition-curable silicone polymer (A1). This resulted in a high compressive load value and high plasticity of the thermally conductive sheet, which was undesirable. (4) Comparative Example 3 is a thermally conductive composition in which the amount of thermally conductive inorganic particles (B3) having a D50 (median diameter) of 100 μm or more exceeds the upper limit, resulting in high compression load values ​​and plasticity of the thermally conductive sheet, which is undesirable. (5) Comparative Example 4 is a thermally conductive composition in which the amount of thermally conductive inorganic particles (B1) having a D50 (median diameter) of less than 10 μm falls below the lower limit, so kneading was not possible. (6) Comparative Example 5 is a thermally conductive composition in which the amount of thermally conductive inorganic particles (B2) having a D50 (median diameter) of 10 μm or more but less than 100 μm falls below the lower limit, resulting in low plasticity but an increased compression load value of the thermally conductive sheet, which is undesirable.

[0094] 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.

[0095] [Explanation of symbols] 1 Heat dissipation structure 2a, 2b Thermally conductive sheet 3 Heat spreader 4 Electronic component 5 Wiring board 6 Heat sink 7 Compression load measuring device 8 Sample stage 9, 11 Aluminum plate 10, 15a, 15b Thermally conductive sheet sample 12 Load cell 13 Thermal conductivity measuring device 14 Polyimide film sensor 16 Sensor tip 17 Applied current electrode 18 Resistance value electrode (temperature measurement electrode) 21 Oil bleed width measuring test device 22 Thermally conductive cured sheet sample 23a, 23b Medicine wrapping paper 24 Aluminum plate 25 Glass plate

Claims

1. A thermally conductive composition comprising a matrix resin (A) and thermally conductive inorganic particles (B), wherein the matrix resin (A) comprises an addition-curable silicone polymer (A1) and a non-reactive silicone oil (A2), and the matrix resin (A) comprises 30% by mass or more and less than 100% by mass of the addition-curable silicone polymer (A1) and more than 0% by mass and 70% by mass or less of the non-reactive silicone oil (A2), when the matrix resin (A) is taken as 100% by mass, and the thermally conductive inorganic particles (B) comprise, per 100 parts by mass of the matrix resin (A), 400 to 1,000 parts by mass of thermally conductive inorganic particles (B1 component) having a D50 (median diameter) of less than 10 μm, and 400 to 1,000 parts by mass of thermally conductive inorganic particles (B2 component) having a D50 (median diameter) of 10 μm or more and less than 100 μm, A thermally conductive composition comprising 800 to 1400 parts by mass of thermally conductive inorganic particles (component B3) having a D50 (median diameter) of 100 μm or more, wherein the total amount of components B1, B2 and B3 is 2000 to 3000 parts by mass per 100 parts by mass of the matrix resin (A).

2. The thermally conductive composition according to claim 1, wherein the thermally conductive inorganic particles of components B1, B2 and B3 are, independently of one another, at least one selected from the group consisting of amorphous alumina, spherical alumina and amorphous aluminum nitride.

3. The thermally conductive composition according to claim 1 or 2, wherein the matrix resin (A) further contains a silane coupling agent.

4. The thermally conductive composition according to any one of claims 1 to 3, wherein the thermally conductive composition has a plasticity of 65 or less after degassing before curing.

5. A thermally conductive sheet comprising the thermally conductive composition according to any one of claims 1 to 4 and formed into a sheet.

6. The thermally conductive sheet according to claim 5, wherein the instantaneous load value at 50% compression of the thermally conductive sheet having a diameter of 28.6 mm and a thickness of 2 mm is 500 N or less, as measured by the compression load measurement method in accordance with ASTM D575-91:2012.

7. The thermally conductive sheet according to claim 5 or 6, wherein the thermal conductivity of the thermally conductive sheet is 8.5 W / mK or more.

8. A thermally conductive sheet according to any one of claims 5 to 7, wherein the thermally conductive sheet is 25 mm long, 25 mm wide and 2 mm thick, and when sandwiched between a glass plate and a medicine wrapping paper at a compression rate of 50%, and held at 125°C for 72 hours, the oil bleed width is 10 mm or less.

9. A method for producing a thermally conductive sheet, comprising the steps of vacuum degassing the thermally conductive composition according to any one of claims 1 to 4, rolling it, forming it into a sheet, and then heat-curing it to produce a thermally conductive sheet.

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