Search

JP-2026075501-A - Thermally conductive silicone composition and its cured product

JP2026075501AJP 2026075501 AJP2026075501 AJP 2026075501AJP-2026075501-A

Abstract

[Problem] The present invention provides a thermally conductive silicone composition that, despite being a composition highly filled with inexpensive alumina as a thermally conductive filler, maintains stable quality in that its hardness does not change over time from the completion of mixing when the composition is cured. [Solution] (A) Organopolysiloxane having two or more alkenyl groups in one molecule, (B) Organohydrogenpolysiloxanes having two or more hydrosilyl groups in one molecule, consisting of (B-1) and (B-2) below. (B-1) Organohydrogenpolysiloxane represented by the following formula (1), (B-2) Organohydrogenpolysiloxane having hydrosilyl groups only at both ends, (C) A thermal conductive filler comprising amorphous alumina fillers having a specific particle size and spherical alumina fillers having a specific particle size. (D) A thermally conductive silicone composition comprising a platinum group metal curing catalyst. [Selection Diagram] None

Inventors

  • 塚田 淳一

Assignees

  • 信越化学工業株式会社

Dates

Publication Date
20260508
Application Date
20241022

Claims (7)

  1. A thermally conductive silicone composition, (A) Organopolysiloxane having two or more alkenyl groups in one molecule: 100 parts by mass, (B) An organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, comprising (B-1) and (B-2) below, wherein the molar ratio of the number of molecules of component (B-1) to component (B-2) is 1:0.1 to 1.5: an amount such that the molar ratio of the total amount of hydrosilyl groups in component (B) to the alkenyl groups bonded to silicon atoms in component (A) is 0.5 to 2.0. (B-1) Organohydrogenpolysiloxane represented by the following formula (1), (In the formula, R1 is independently an alkyl group having 1 to 6 carbon atoms, a is an integer from 2 to 10, b is an integer from 20 to 100, and the bonding order of the siloxane units enclosed by a and b may be in blocks or random.) (B-2) Organohydrogenpolysiloxane having hydrosilyl groups only at both ends, represented by the following formula (2), (In the formula, R2 is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer from 40 to 200.) (C) Thermal conductive filler consisting of (C-1) to (C-3) below: 4,000 to 7,000 parts by mass, (C-1) Irregularly shaped alumina filler with an average particle size greater than 0.4 μm and less than or equal to 4 μm: 1,000 to 2,000 parts by mass, (C-2) Spherical alumina filler having an average particle size greater than 8 μm and less than or equal to 40 μm: 1,000 to 2,000 parts by mass, (C-3) Spherical alumina filler having an average particle size greater than 70 μm and less than or equal to 135 μm: 2,000 to 3,000 parts by mass, (D) Platinum group metal-based hardening catalyst: 10 to 2,000 ppm in terms of the mass of platinum group metal elements relative to component (A), A thermally conductive silicone composition characterized by containing [a certain substance].
  2. Furthermore, as component (E), dimethylpolysiloxane is formed in which the molecular chain ends represented by the following formula (3) are sealed with trialkoxy groups. (In the formula, R3 is independently an alkyl group having 1 to 6 carbon atoms, and d is an integer from 5 to 100.) The thermally conductive silicone composition according to claim 1, characterized in that it contains 100 to 200 parts by mass of component (A) per 100 parts by mass of component (A).
  3. The thermally conductive silicone composition according to claim 1, characterized in that the (B-1) component is an organohydrogenpolysiloxane represented by the following formula (4). (In the formula, a is an integer between 2 and 10, b is an integer between 20 and 100, and the bonding order of the siloxane units enclosed by a and b can be either block or random.)
  4. The thermally conductive silicone composition according to claim 1, characterized in that the (B-2) component is an organohydrogenpolysiloxane having hydrosilyl groups only at both ends represented by the following formula (5). (In the formula, c is an integer between 40 and 200.)
  5. The thermally conductive silicone composition according to claim 1, characterized in that the kinematic viscosity of component (A) at 23°C is 10 to 100,000 mm² /s.
  6. The thermally conductive silicone composition according to claim 1, characterized in that the thermal conductivity of the thermally conductive silicone composition is 7.5 W/m·K or higher.
  7. A cured thermally conductive silicone product characterized by being obtained by curing a thermally conductive silicone composition according to any one of claims 1 to 6.

Description

This invention relates to a thermally conductive silicone composition and its cured product. In recent years, with the increasing sophistication of electronic devices and the miniaturization and integration of electronic components, the amount of heat generated by electronic devices and components has increased, and the heat density tends to rise. Therefore, countermeasures such as designing devices with excellent heat dissipation and using materials with superior thermal conductivity are necessary. Furthermore, while thermal grease and thermal sheets are used to quickly transfer heat generated from heat-generating components to cooling components such as heat sinks, high thermal conductivity is also required for these thermal dissipation materials. On the other hand, to improve the thermal conductivity of heat dissipation materials, methods include using highly thermally conductive fillers such as aluminum nitride or boron nitride in silicone resins, or increasing the density of the thermally conductive fillers. However, highly thermally conductive fillers are expensive, and increasing the density of the fillers leads to problems such as increased viscosity of the composition. On the other hand, even when using only inexpensive alumina, it is possible to improve the wettability of the alumina and achieve high fill by incorporating it with an alkoxysilane compound into a silicone resin. For example, Patent Document 1 describes a thermally conductive silicone cured product having a thermal conductivity of 6.5 W/m·K or higher, obtained by curing a composition containing spherical alumina and amorphous alumina of different particle sizes. However, when a large amount of alumina is filled using an alkoxysilane compound, some active sites of alumina may remain that cannot be treated even with the excessive inclusion of the alkoxysilane compound. These remaining active sites react, for example, with the hydroxyl groups of organohydrogenpolysiloxanes used in addition crosslinking of the composition, changing the wettability of the alumina over time. Consequently, the viscosity of the composition, or the hardness of the cured product (which depends on the viscosity of the composition), changes over time. In other words, even with the same composition, the hardness of the molded product after curing can vary significantly depending on the time elapsed since manufacturing, which is a problem that drastically reduces the quality of thermally conductive silicone molded products. Japanese Patent Publication No. 2021-176945 As mentioned above, even when using a high concentration of inexpensive alumina as a thermally conductive filler, there was a need to develop a thermally conductive silicone composition with stable quality that maintains its hardness even after time has passed since the completion of mixing during curing. The inventors of this invention, after diligently studying the above-mentioned problems, discovered that a thermally conductive silicone composition containing the following components (A) to (D) can produce a thermally conductive silicone cured product with stable hardness regardless of the elapsed time since the completion of mixing, even if the composition is highly filled with inexpensive alumina as a thermally conductive filler. This led to the completion of the present invention. In other words, the present invention is A thermally conductive silicone composition, (A) Organopolysiloxane having two or more alkenyl groups in one molecule: 100 parts by mass, (B) An organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, comprising (B-1) and (B-2) below, wherein the molar ratio of the number of molecules of component (B-1) to component (B-2) is 1:0.1 to 1.5: an amount such that the molar ratio of the total amount of hydrosilyl groups in component (B) to the alkenyl groups bonded to silicon atoms in component (A) is 0.5 to 2.0. (B-1) Organohydrogenpolysiloxane represented by the following formula (1), (In the formula, R1 is independently an alkyl group having 1 to 6 carbon atoms, a is an integer from 2 to 10, b is an integer from 20 to 100, and the bonding order of the siloxane units enclosed by a and b may be in blocks or random.) (B-2) Organohydrogenpolysiloxane having hydrosilyl groups only at both ends, represented by the following formula (2), (In the formula, R2 is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer from 40 to 200.) (C) Thermal conductive filler consisting of (C-1) to (C-3) below: 4,000 to 7,000 parts by mass, (C-1) Irregularly shaped alumina filler with an average particle size greater than 0.4 μm and less than or equal to 4 μm: 1,000 to 2,000 parts by mass, (C-2) Spherical alumina filler having an average particle size greater than 8 μm and less than or equal to 40 μm: 1,000 to 2,000 parts by mass, (C-3) Spherical alumina filler having an average particle size greater than 70 μm and less than or equal to 135 μm: 2,000 to 3,