Thermally conductive silicone gel composition, thermally conductive silicone sheet and method for producing the same

Abstract

The silicone gel composition comprises (A) an organopolysiloxane containing at least two alkenyl groups in one molecule, (B) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to a silicon atom, and (C) a platinum group metal curing catalyst: a catalytic amount, with respect to 100 parts by mass of the total of the components (A) and (C), and (D) 200 to 600 parts by mass of aluminum hydroxide particles as thermally conductive particles, when these are set as a matrix, the composition comprises (D-1) aluminum hydroxide particles having a particle size (D50) of 30 μm or more exceeding 40% by mass and less than 75% by mass, (D-2) aluminum hydroxide particles having a particle size (D50) of less than 30 μm containing 25% by mass and less than 60% by mass, a relative dielectric constant of 5.0 or less at a frequency of 1 MHz by a mutual inductance bridge method, and a Shore-OO hardness of 5 to 60. Thus, a silicone gel composition is provided which uses a substance not classified as a GHS, is highly safe, has flexibility, a low dielectric constant, and is thermally conductive.

Description

Technical Field

[0001] The present invention relates to a thermally conductive silicone gel composition suitable for being sandwiched between a heat generating portion and a heat sink of an electric or electronic component, etc. More preferably, it relates to a silicone gel composition having a low dielectric constant and being thermally conductive, a thermally conductive silicone sheet, and a method for producing the same. Background Art

[0002] The performance of semiconductors such as CPUs has improved dramatically in recent years, and the amount of heat generated has also become huge. Therefore, heat sinks are installed on electronic components that generate heat, and thermally conductive silicone gels are used between heat sinks such as semiconductors and heat sinks. With the miniaturization, high performance, and high integration of equipment, thermally conductive silicone gels are required to have thermal conductivity, electromagnetic wave absorption, noise prevention, etc. Furthermore, in recent years, from the perspective of global environmental issues, a system (Globally Harmonized System of Classification and Labelling of Chemicals; hereinafter referred to as "GHS") regarding classification standards and indication methods (indicated in SDS, etc.) for the harmfulness of handled substances has also been required. Regarding thermally conductive fillers, alumina, crystalline silica, magnesium oxide, etc. comply with GHS and are considered undesirable. In Patent Document 1, it is proposed to add crystalline silica particles and aluminum hydroxide particles to acrylic resin to make a low dielectric constant sheet. In Patent Documents 2 to 4, it is proposed to add alumina particles and various aluminum hydroxide particles to organopolysiloxane to make a thermally conductive silicone composition.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-077777

[0006] Patent Document 2: Japanese Patent No. 5304588

[0007] Patent Document 3: Japanese Patent Application Publication No. 2020-002236

[0008] Patent Document 4: Japanese Patent Application Publication No. 2020-066713 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, Patent Document 1 contains crystalline silica and is a GHS-classified substance, and Patent Documents 2 to 4 contain alumina particles and are therefore GHS-classified substances, and they do not have the problem of being a low dielectric constant sheet.

[0011] The present invention aims to solve the above-mentioned conventional problems and provides a silicone gel composition, a thermally conductive silicone sheet and a method for producing the same which use substances not included in the GHS classification, are highly safe, have flexibility, a low dielectric constant and good thermal conductivity.

[0012] Means for solving problems

[0013] The thermally conductive silicone gel composition of the present invention is characterized by comprising:

[0014] As the component (A), an organopolysiloxane containing at least two alkenyl groups in one molecule,

[0015] As the component (B), an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms,

[0016] As component (C), platinum group metal curing catalyst: catalytic amount,

[0017] With respect to 100 parts by mass of the total of the above-mentioned components (A) to (C),

[0018] As the component (D), 200 to 600 parts by mass of aluminum hydroxide particles as thermally conductive particles are contained, when the aluminum hydroxide particles are taken as 100% by mass:

[0019] (D-1) aluminum hydroxide particles having a median particle size (D50) of 30 μm or more account for more than 40% by mass and less than 75% by mass,

[0020] (D-2) the aluminum hydroxide particles having a median particle size (D50) of less than 30 μm account for 25% by mass or more and 60% by mass or less,

[0021] According to JIS K6911:2006, the relative dielectric constant at a frequency of 1 MHz by the mutual inductance bridge method is 5.0 or less, and the Shore-OO hardness is 5 to 60.

[0022] The thermally conductive silicone sheet of the present invention is a sheet obtained by forming the thermally conductive silicone gel composition described above into a sheet.

[0023] The method for producing a thermally conductive silicone sheet of the present invention is characterized in that:

[0024] The following components are mixed, sheet-formed, and cured to produce a thermally conductive silicone sheet having a relative dielectric constant of 5.0 or less at a frequency of 1 MHz according to the mutual inductance bridge method and a Shore-OO hardness of 5 to 60 in accordance with JIS K6911:2006.

[0025] The ingredients include:

[0026] Component (A): an organopolysiloxane containing at least two alkenyl groups in one molecule,

[0027] (B) component: an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms,

[0028] (C) Component: Platinum group metal curing catalyst: catalytic amount,

[0029] With respect to 100 parts by mass of the total of the above-mentioned components (A) to (C),

[0030] (D) component: 200 to 600 parts by mass of aluminum hydroxide particles as thermally conductive particles,

[0031] When the aluminum hydroxide particles are set to 100 mass %,

[0032] (D-1) aluminum hydroxide particles having a median particle size (D50) of 30 μm or more account for more than 40% by mass and less than 75% by mass,

[0033] (D-2) The content of aluminum hydroxide particles having a median particle size (D50) of less than 30 μm is 25% by mass or more and 60% by mass or less.

[0034] Effects of the Invention

[0035] The present invention contains the above-mentioned (A)-(D) components, and according to JIS K6911:2006, the relative dielectric constant at a frequency of 1 MHz by the mutual inductance bridge method is 5.0 or less, and the Shore-OO hardness is 5 to 60, thereby providing a silicone gel composition and a thermally conductive silicone sheet and a method for producing the same, which use substances not classified as GHS, are highly safe, have flexibility, a low dielectric constant and are thermally conductive. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1A -B is an explanatory diagram showing a method for measuring the thermal conductivity of a sample in one example of the present invention. DETAILED DESCRIPTION

[0037] The component (A) of the present invention is an organopolysiloxane containing at least two alkenyl groups in one molecule. This component is a component that becomes the base polymer of the silicone gel composition. It preferably has at least two alkenyl groups in one molecule and a viscosity of 100 to 10,000 Pa·s. The viscosity is a value measured at 23°C for 30 seconds using a B-type rotational viscometer at a rotation speed of 20 rpm.

[0038] The component (B) of the present invention is an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms. This component is a crosslinking component of the organosilicon gel composition. It is preferably contained in an amount in which the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from the component (A). The above number of moles is more preferably 0.1 to 4.0 times, and even more preferably 0.1 to 3.0 times.

[0039] The component (C) of the present invention is a platinum group metal curing catalyst. The catalyst is an addition curing reaction catalyst. The content may be a catalytic amount, and specifically, it is preferably 0.1 to 1,000 ppm in terms of mass of the platinum group metal element relative to the component (A).

[0040] The component (D) of the present invention is aluminum hydroxide particles of thermally conductive particles. The component (D) contains 200 to 600 parts by mass relative to 100 parts by mass of the total of the components (A) to (C). The aluminum hydroxide particles have various median particle sizes (D50). When the total of the component (D) is set to 100% by mass,

[0041] (D-1) Aluminum hydroxide particles having a median particle size (D50) of 30 μm or more exceed 40% by mass and are less than 75% by mass

[0042] (D-2) The content of aluminum hydroxide particles having a median particle size (D50) of less than 30 μm is 25% by mass or more and 60% by mass or less.

[0043] Preferably (D-1) component exceeds 45 mass % and is lower than 75 mass %, and (D-2) component exceeds 25 mass % and is lower than 55 mass %. By using aluminum hydroxide particles with different median particle diameters (D50) like this, small particles are present between macroparticles, and are filled in a state close to the densest packing, and thermal conductivity becomes high. Particle diameter is set to 50% of the cumulative particle size distribution based on volume basis in the particle size distribution determination utilizing laser diffraction light scattering method, i.e. D50 (median particle diameter). As this measuring machine, for example, there is a laser diffraction / scattering particle distribution measuring device LA-950S2 made by Horiba Manufacturing Co., Ltd.

[0044] The thermally conductive silicone gel composition of the present invention has a relative dielectric constant of 5.0 or less, preferably 4.8 or less, at a frequency of 1 MHz by the mutual induction bridge method according to JIS K6911:2006. This improves electromagnetic wave absorption and noise prevention. The lower limit of the relative dielectric constant is 2.6 or more, preferably 3.0 or more.

[0045] The Shore-OO hardness of the thermally conductive silicone gel composition of the present invention is 5 to 60, preferably 10 to 55. This allows the composition to exhibit flexibility. If the composition has flexibility, it can improve the adhesion between a heat generating body such as a semiconductor and a heat dissipating body, and is suitable as a TIM (Thermal Interface Material) material.

[0046] The thermally conductive silicone gel composition of the present invention may further contain a surface treatment agent for the thermally conductive particles as component (E). The surface treatment agent includes titanate coupling agents, aluminate coupling agents, stearic acid coupling agents, epoxy silane coupling agents, alkyl silane coupling agents, etc. Among them, the alkyl silane coupling agent is preferred, preferably selected from R a Si(OR') 4-a (R is a non-substituted or substituted organic group with 6 to 12 carbon atoms, R' is an alkyl group with 1 to 4 carbon atoms, and a is 0 or 1) represented by an alkoxysilane compound, a partial hydrolyzate thereof, and at least one silane coupling agent containing an alkoxy-containing silicone with a non-substituted or substituted organic group with 6 to 12 carbon atoms. For example, there are silane compounds such as hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, and dodecyltriethoxysilane. The above-mentioned silane compounds can be used alone or in combination of two or more. As a surface treatment agent, alkoxysilane can also be used in combination with a single-terminal silanol siloxane. The surface treatment mentioned here includes adsorption in addition to covalent bonding.

[0047] The surface treatment agent can be mixed with the thermally conductive particles in advance for pretreatment (pretreatment method), or can be added when the matrix resin and the thermally conductive particles are mixed (overall blending method). In the case of the two-treatment method, the surface treatment agent is preferably added in an amount of 0.01 to 10 parts by mass relative to 100 parts by mass of the thermally conductive particles. By performing the surface treatment, it has the effect of becoming easier to fill into the matrix resin.

[0048] The thermally conductive silicone gel composition of the present invention may contain ingredients other than those mentioned above as needed. For example, addition reaction control agents such as 1-ethynyl-1-cyclohexanol, heat resistance enhancers such as red iron oxide, titanium oxide, cerium oxide, flame retardants, flame retardant aids, etc. may be added. Organic or inorganic particle pigments may be added for the purpose of coloring and toning. Alkoxy-containing silicone may also be added as a material added for the purpose of filler surface treatment, etc.

[0049] Furthermore, as component (F), thermally conductive particles other than the above-mentioned component (D) and not classified under GHS may be included. For example, hexagonal boron nitride, aluminum nitride, amorphous silicon dioxide, calcium carbonate, etc. are preferably added. Alumina particles, crystalline silicon dioxide particles, and magnesium oxide particles are classified under GHS, so they are preferably not added.

[0050] The thermal conductivity of the thermally conductive silicone gel composition is preferably 2.0 W / mK or less, more preferably 0.5 to 2.0 W / mK, and even more preferably 0.7 to 1.8 W / mK. Thus, a silicone gel composition that uses a substance not classified by GHS and has a balanced safety, flexibility, low dielectric constant, and thermal conductivity can be provided.

[0051] The specific gravity of the thermally conductive silicone gel composition is preferably 2.2 or less, and more preferably 2.0 or less. This makes it a lightweight TIM material. The lower limit of the specific gravity of the composition is preferably 1.2 or more, and more preferably 1.4 or more.

[0052] The thermally conductive silicone gel composition of the present invention is preferably a thermally conductive silicone sheet formed into a sheet. If formed into a sheet, it is suitable for TIM applications.

[0053] The method for producing the thermally conductive silicone sheet of the present invention comprises mixing the above-mentioned components (A), (B), (C), and (D) and other components added as needed, forming a sheet, and curing the sheet to produce a thermally conductive silicone sheet having a relative dielectric constant of 5.0 or less at a frequency of 1 MHz according to the mutual inductance bridge method and a Shore-OO hardness of 5 to 60 in accordance with JIS K6911:2006.

[0054] The sheet forming is preferably performed by mixing the above-mentioned raw material components, sandwiching them between polyethylene terephthalate (PET) films, rolling them to form a sheet, and curing them at 80 to 120° C. for 5 to 40 minutes.

[0055] Example

[0056] The following is an explanation using examples. The present invention is not limited to the examples. Various parameters were measured by the following methods.

[0057] <Thermal conductivity>

[0058] The thermal conductivity of the thermally conductive grease is measured by Hot Disk (according to ISO / CD 22007-2). Figure 1A As shown in FIG. 1 , a polyimide film sensor 2 is sandwiched between two samples 3a and 3b, and constant power is applied to the sensor 2 to make it constantly release heat. The thermal characteristics are analyzed based on the temperature rise value of the sensor 2. The front end 4 of the sensor 2 has a diameter of 7 mm. Figure 1B As shown in Figure 1B , it becomes a double - helix structure of an electrode, and an electrode 5 for applying current and an electrode for resistance value (electrode for temperature measurement) 6 are arranged at the lower part. The thermal conductivity is calculated by the following formula (Mathematical Formula 1).

[0059] [Mathematical Formula 1]

[0060]

[0061] λ: Thermal conductivity (W / m·K)

[0062] P0: Constant power (W)

[0063] r: Radius of the sensor (m)

[0064]

[0065] α: Thermal diffusivity of the specimen (m 2 / s)

[0066] t: Measurement time (s)

[0067] D(τ): Function of dimensionless τ

[0068] ΔT(τ): Temperature rise of the sensor (K)

[0069] <Relative dielectric constant>

[0070] According to JIS K6911:2006, a sheet with a thickness of 2 mm is used to measure the relative dielectric constant at a frequency of 1 MHz by the mutual - inductance bridge method.

[0071] <Shore - OO hardness>

[0072] According to ASTM D2240, four sheets with a thickness of 3 mm are overlapped and measured using an automatic Durometer rebound hardness tester bench.

[0073] (Example 1)

[0074] 1. Raw material components

[0075] As components (A) - (C), a two - component room - temperature - curable silicone polymer was used. Component (A) and component (C) were pre - added to liquid A of the two - component room - temperature - curable silicone polymer, and component (A) and component (B) were pre - added to liquid B.

[0076] Viscosity of liquid A: 3000 mPas

[0077] Viscosity of liquid B: 1000 mPas

[0078] A total of 100 parts by mass of the two - component room - temperature - curable silicone polymer

[0079] (D) Ingredients

[0080] (D-1) Aluminum hydroxide particles "without surface treatment" having a median particle size (D50) of 55 μm (HIGILITE H-10, manufactured by Showa Denko K.K.): 240 wt.

[0081] (D-2a) Aluminum hydroxide particles having a median particle size (D50) of 4 μm (CL-303, manufactured by Sumitomo Chemical Co., Ltd., epoxy silane coupling agent treated product): 100 parts by weight

[0082] 2. Mixing and forming methods

[0083] The above raw material components were mixed, sandwiched between PET films, and rolled to form a sheet, which was then cured at 100° C. for 10 minutes. The thickness of the thermally conductive silicone sheet was set to 2 mm and 3 mm.

[0084] The thermally conductive silicone sheet obtained as described above was evaluated. The conditions and results are summarized in Table 1 below.

[0085] (Example 2)

[0086] The amount of component (D-1) was 150 parts by mass.

[0087] (D-2b) Aluminum hydroxide particles "without surface treatment" (HIGILITE H-32, manufactured by Showa Denko K.K.) having a median particle size (D50) of 10 μm were used in an amount of 100 parts by mass.

[0088] (F) Amorphous silica having a median particle size (D50) of 7 μm is set to 100 parts by mass,

[0089] The same procedure as in Example 1 was carried out except for this point.

[0090] (Example 3)

[0091] The component (D-1) was set to 92 parts by mass.

[0092] The component (D-2a) was set at 118 parts by mass.

[0093] The same procedure as in Example 1 was carried out except for this point.

[0094] (Example 4)

[0095] As components (A) to (C), a two-component room temperature curing silicone polymer is used.

[0096] The viscosity of liquid A is 300mPas.

[0097] Liquid B viscosity: 300mPas,

[0098] The total amount is set to 100 parts by mass.

[0099] The amount of component (D-1) was set to 250 parts by mass.

[0100] The component (D-2a) was set at 130 parts by mass.

[0101] (D-2c) Particles obtained by titanate coupling treatment of aluminum hydroxide particles having a median particle size (D50) of 18 μm (manufactured by Showa Denko K.K., trade name “HIGILITE H-31T”) were set at 70 parts by mass,

[0102] The amount of decyltrimethoxysilane as the component (E) was set to 1 part by mass,

[0103] The same procedure as in Example 1 was carried out except for this point.

[0104] The above conditions and results are summarized in Table 1.

[0105] [Table 1]

[0106]

[0107] (Comparative Examples 1 to 5)

[0108] The same procedure as in Example 1 was carried out except for the following Table 2.

[0109] [Table 2]

[0110]

[0111] (Note: Comparative Examples 1 and 2 could not be filled with (D-1) or (D-2), and could not be formed into sheets.)

[0112] From the above results, it was confirmed that Examples 1 to 4 are silicone gel compositions that use substances not included in the GHS classification and have a good balance of safety, flexibility, low dielectric constant, and thermal conductivity.

[0113] Industrial Applicability

[0114] The thermally conductive silicone gel composition of the present invention is suitable for being sandwiched between a heat generating portion and a heat sink of an electric or electronic component or the like.

[0115] Explanation of symbols

[0116] 1 Thermal conductivity measurement device

[0117] 2 Sensors

[0118] 3a, 3b samples

[0119] 4 Sensor front end

[0120] 5 Electrodes for applying current

[0121] 6 Resistance value electrode (temperature measurement electrode)

Claims

1. A thermally conductive silicone gel composition, characterized in that: Include: (A) component: an organopolysiloxane containing at least two alkenyl groups in one molecule, (B) component: an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms, (C) component: platinum group metal curing catalyst: catalytic amount, With respect to 100 parts by weight of the total of the components (A) to (C), (D) component: 200 to 600 parts by mass of aluminum hydroxide particles as thermally conductive particles, When the aluminum hydroxide particles are set to 100 mass %, the aluminum hydroxide particles contain: (D-1) the content of aluminum hydroxide particles having a median diameter D50 of 30 μm or more, which is 50% of the volume-based cumulative particle size distribution in a particle size distribution measurement by a laser diffraction light scattering method, exceeds 45% by mass and is less than 75% by mass; (D-2) the amount of aluminum hydroxide particles having a median diameter D50 of less than 30 μm, i.e., 50% of the cumulative particle size distribution on a volume basis in a particle size distribution measurement by a laser diffraction light scattering method, exceeds 25% by mass and is less than 55% by mass, The thermally conductive silicone gel composition does not contain aluminum oxide particles, crystalline silicon dioxide particles, and magnesium oxide particles. The thermally conductive silicone gel composition has a relative dielectric constant of 5.0 or less at a frequency of 1 MHz according to a mutual inductance bridge method according to JIS K6911:2006, and a Shore-OO hardness of 5 to 60.

2. The thermally conductive silicone gel composition according to claim 1, wherein: The viscosity of the organopolysiloxane of the component (A) is 100 to 10,000 Pa·s.

3. The thermally conductive silicone gel composition according to claim 1 or 2, wherein: In the organohydrogenpolysiloxane of the component (B), the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from the component (A).

4. The thermally conductive silicone gel composition according to claim 1 or 2, wherein: The surface treatment agent for the thermally conductive particles is further contained as the (E) component.

5. The thermally conductive silicone gel composition according to claim 4, wherein: The surface treatment agent is at least one coupling agent selected from titanate coupling agents, aluminate coupling agents, stearic acid coupling agents, epoxy silane coupling agents and alkyl silane coupling agents.

6. The thermally conductive silicone gel composition according to claim 5, wherein: The alkyl silane coupling agent is selected from R a Si(OR') 4-a The alkoxysilane compound, its partial hydrolyzate, and at least one silane coupling agent containing an alkoxy-containing silicone having a carbon number of 6 to 12, wherein R is a carbon number of 6 to 12 unsubstituted or substituted organic group, R' is a carbon number of 1 to 4 alkyl group, and a is 0 or 1.

7. The thermally conductive silicone gel composition according to claim 4, wherein: The surface treatment agent is added in an amount of 0.01 to 10 parts by mass based on 100 parts by mass of the thermally conductive particles.

8. The thermally conductive silicone gel composition according to claim 1 or 2, wherein: The invention further comprises at least one thermally conductive particle selected from the group consisting of hexagonal boron nitride, aluminum nitride, amorphous silicon dioxide and calcium carbonate as component (F).

9. The thermally conductive silicone gel composition according to claim 1 or 2, wherein: The thermal conductivity of the thermally conductive silicone gel composition is less than 2.0 W / mK.

10. The thermally conductive silicone gel composition according to claim 1 or 2, wherein: The thermally conductive silicone gel composition has a specific gravity of 2.2 or less.

11. The thermally conductive silicone gel composition according to claim 5, wherein: The surface treatment agent is added in an amount of 0.01 to 10 parts by mass based on 100 parts by mass of the thermally conductive particles. 12 . A thermally conductive silicone sheet obtained by forming the thermally conductive silicone gel composition according to claim 1 into a sheet.

13. A method for producing a thermally conductive silicone sheet, characterized in that: The method for producing a thermally conductive silicone sheet according to claim 12, wherein: The following components are mixed, sheet-formed, and cured to produce a thermally conductive silicone sheet having a relative dielectric constant of 5.0 or less at a frequency of 1 MHz according to the mutual inductance bridge method and a Shore-OO hardness of 5 to 60 in accordance with JIS K6911:2006. The ingredients include: (A) component: an organopolysiloxane containing at least two alkenyl groups in one molecule, (B) component: an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms, (C) Component: Platinum group metal curing catalyst: catalytic amount, With respect to 100 parts by mass of the total of the components (A) to (C), (D) component: 200 to 600 parts by mass of aluminum hydroxide particles as thermally conductive particles, When the aluminum hydroxide particles are set to 100 mass %, (D-1) the content of aluminum hydroxide particles having a median diameter D50 of 30 μm or more, which is 50% of the volume-based cumulative particle size distribution in a particle size distribution measurement by a laser diffraction light scattering method, exceeds 45% by mass and is less than 75% by mass; (D-2) the amount of aluminum hydroxide particles having a median diameter D50 of less than 30 μm, i.e., 50% of the cumulative particle size distribution on a volume basis in a particle size distribution measurement by a laser diffraction light scattering method, exceeds 25% by mass and is less than 55% by mass, The composition does not contain aluminum oxide particles, crystalline silicon dioxide particles, and magnesium oxide particles.

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