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US-12624270-B2 - Silicone composition and a thermally conductive silicone cured product having high thermal conductivity

US12624270B2US 12624270 B2US12624270 B2US 12624270B2US-12624270-B2

Abstract

One of the objects the present invention to provide a cured product of a thermally conductive silicone composition having high thermal conductivity and excellent compressibility. A silicone composition comprising an organo(poly)siloxane and a thermally conductive filler, wherein the organo(poly)siloxane comprises at least one curable organo(poly)siloxane, the thermally conductive filler comprises (B-i) unsintered aluminum nitride having an average particle size of 20 μm or more and 120 μm or less and (B-ii) alumina having an average particle size of 0.1 μm or more and 5 μm or less, the (B-ii) alumina comprises spherical alumina with 25 to 80 mass % of the spherical alumina, based on a total mass of the component (B-ii), a proportion of the component (B-ii) is 25 to 50 mass %, based on a total mass of the components (B-i) and (B-ii), and a proportion of a volume of the thermally conductive filler is 80 to 90 volume %, based on a total volume of the silicone composition.

Inventors

  • Yuya HIRONAKA
  • Yasuhisa Ishihara
  • Katsuyuki Tanaka

Assignees

  • SHIN-ETSU CHEMICAL CO., LTD.

Dates

Publication Date
20260512
Application Date
20210611
Priority Date
20200618

Claims (16)

  1. 1 . A silicone composition comprising an organo(poly) siloxane and a thermally conductive filler, wherein the organo(poly) siloxane comprises at least one curable organo(poly)siloxane, the thermally conductive filler comprises (B-i) unsintered aluminum nitride having an average particle size of 20 μm or more and 120 μm or less and (B-ii) alumina having an average particle size of 0.1 μm or more and 5 μm or less, the (B-ii) alumina comprises spherical alumina with 25 to 80 mass % of the spherical alumina, based on a total mass of the component (B-ii), wherein the spherical alumina has an average particle size of 0.1 μm or more and 2 μm or less, a proportion of the component (B-ii) is 25 to 50 mass %, based on a total mass of the components (B-i) and (B-ii), and a proportion of a volume of the thermally conductive filler is 80 to 90 volume %, based on a total volume of the silicone composition.
  2. 2 . The silicone composition according to claim 1 , wherein the thermally conductive silicone composition further comprises a (C) surface treating agent, and the surface treating agent is at least one selected from a (C-1) alkoxysilane represented by the following general formula (1): R 2 a R 3 b Si(OR 4 ) 4-a-b (1) wherein R 2 is, independently of each other, an alkyl group having 6 to 15 carbon atoms, R 3 is, independently of each other, a group selected from an unsubstituted or substituted alkyl group having 1 to 5 carbon atoms, a cycloalkyl group having 4 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 6 to 12 carbon atoms, R 4 is, independently of each other, an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, and b is an integer of 0 to 2, provided that a+b is an integer of 1 to 3, and a (C-2) dimethylpolysiloxane represented by the following general formula (2): wherein R 5 is, independently of each other, an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.
  3. 3 . The silicone composition according to claim 1 , wherein the at least one curable organo(poly) siloxane comprises an (A) alkenyl group-containing organopolysiloxane.
  4. 4 . The silicone composition according to claim 2 , wherein the at least one curable organo(poly) siloxane comprises an (A) alkenyl group-containing organopolysiloxane, and wherein an amount of the (C) surface treating agent is 50 to 200 parts by mass, relative to 100 parts by mass of the (A) alkenyl group-containing organopolysiloxane.
  5. 5 . A thermally conductive silicone-cured product of curing the silicone composition according to claim 1 .
  6. 6 . The thermally conductive silicone-cured product according to claim 5 , having thermal conductivity of 10 W/m K or more.
  7. 7 . The thermally conductive silicone-cured product according to claim 5 , having an Asker C hardness of 50 or less.
  8. 8 . The silicone composition according to claim 1 , wherein the thermally conductive silicone composition further comprises a (C) surface treating agent, and the surface treating agent is at least one selected from a (C-1) alkoxysilane represented by the following general formula (1): R 2 a R 3 b Si(OR 4 ) 4-a-b (1) wherein R 2 is, independently of each other, an alkyl group having 6 to 15 carbon atoms, R 3 is, independently of each other, a group selected from an unsubstituted or substituted alkyl group having 1 to 5 carbon atoms, a cycloalkyl group having 4 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 6 to 12 carbon atoms, R 4 is, independently of each other, an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, and b is an integer of 0 to 2, provided that a+b is an integer of 1 to 3, and a (C-2) dimethylpolysiloxane represented by the following general formula (2): wherein R 5 is, independently of each other, an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.
  9. 9 . The silicone composition according to claim 8 , wherein the at least one curable organo(poly) siloxane comprises an (A) alkenyl group-containing organopolysiloxane.
  10. 10 . The silicone composition according to claim 2 , wherein the at least one curable organo(poly) siloxane comprises an (A) alkenyl group-containing organopolysiloxane.
  11. 11 . A thermally conductive silicone-cured product of curing the silicone composition according to claim 2 .
  12. 12 . A thermally conductive silicone-cured product of curing the silicone composition according to claim 3 .
  13. 13 . A thermally conductive silicone-cured product of curing the silicone composition according to claim 4 .
  14. 14 . A thermally conductive silicone-cured product of curing the silicone composition according to claim 8 .
  15. 15 . A thermally conductive silicone-cured product of curing the silicone composition according to claim 9 .
  16. 16 . A thermally conductive silicone-cured product of curing the silicone composition according to claim 10 .

Description

TECHNICAL FIELD The present invention relates to a silicone composition that provides a thermally conductive silicone-cured product having high thermal conductivity. BACKGROUND OF THE INVENTION As further progress is made in making electronic equipment smaller and more highly integrated, the impact of heat generated from electronic components such as power semiconductors and memory is becoming more serious than ever. When heat accumulates in an electronic component, the temperature of the electronic component rises, which can potentially cause operational failure or breakdown. Many heat dissipation methods and heat dissipation members to be used in these methods have been proposed to efficiently release the heat generated from electronic components to a cooling member, such as a heat sink. Conventionally, heat sinks that employ a metal plate having high thermal conductivity, such as one made of aluminum or copper, have been used in electronic equipment to suppress a rise in temperature of an element during operation. This kind of heat sink carries away heat generated by the element and discharges the heat from surfaces due to the difference in temperature with the air outside. In a case where heating elements are directly brought in contact with a heat sink, air present on an interface there between obstructs thermal conduction, therefore the heat sink needs to be arranged in close vicinity of the elements. Due to differences in height and a tolerance for assembly among elements, a sheet or a grease having flexibility and thermal conductivity is used. Sheets are superior to grease in handleability, and thermally conductive sheets formed of thermally conductive resin have been used in various fields. In the field of in-vehicle devices, long-term reliability at temperatures in the region of approximately −40° C. at the low end in cold areas and temperatures as high as 150° C. or more of a heat generating member is required. Furthermore, in many cases, flame retardance, electrical insulation, and the like are also required. Silicone is suitable as a resin having all these characteristics, and a sheet of thermally conductive silicone comprising a silicone and a thermally conductive filler is used. Thermally conductive silicone sheets are often used in cases where there is some space between the heating elements and a cooling member such as a heat sink or a housing. In many cases it is necessary to ensure that the space is electrically insulated, with the thermally conductive sheet often required to be insulating as well. Consequently, metal particles such as aluminum, copper, and silver cannot be used as the thermally conductive filler, and an insulating thermally conductive filler such as aluminum hydroxide or alumina is often used. However, aluminum hydroxide and alumina have low thermal conductivity by themselves, so that a thermally conductive silicone composition using this kind of thermally conductive filler will have lower thermal conductivity. Recently, heat generated by electronic components has been increasing. Thermally conductive sheets are also required to be have higher thermal conductivity, and aluminum hydroxide and alumina alone cannot sufficiently meet this requirement as a thermally conductive filler. Therefore, the use of boron nitride and aluminum nitride as a highly thermally-conductive filler has been attracting attention. Common scaly boron nitride has a layered crystal structure and exhibits anisotropic thermal conductivity due to a significant difference in thermal conductivity between the surface direction and lamination direction of the crystals. In contrast, aluminum nitride has a wurtzite crystal structure. Therefore, aluminum nitride does not exhibit extreme anisotropy like boron nitride. Accordingly, various heat dissipation materials for which aluminum nitride has been selected as the highly thermally-conductive filler have been disclosed in Patent Literature 1 (JP H03-14873 A) and Patent Literature 2 (Japanese Patent No. 4357064). However, when silicone is filled with aluminum nitride having an average particle size of 3 μm or less at a high density, the viscosity of the material increases and moldability is reduced. Patent Literature 3 (JP 2004-91743 A) discloses a thermally conductive grease that comprises spherical alumina having an average particle size of 0.2 to 1.0 μm and aluminum nitride having an average particle size of 1 to 3 μm and a maximum particle size of 2 to 10 μm to suppress an increase in viscosity. However, aluminum nitride has a small particle diameter and, therefore, it has the problem that it is difficult to provide a high thermal conduction. Therefore, Patent Literature 4 (Japanese Patent No. 6246986) proposes a composition with high thermal conductivity that comprises aluminum nitride having an average particle size of 30 to 150 μm, aluminum nitride or alumina having an average particle size of 1 to 30 μm, and inorganic particles having an average partic