Thermally conductive silicone grease composition and method for producing the same

Abstract

To provide a thermally conductive silicone grease composition which has good viscosity and thermal conductivity, and suppresses a pumping out phenomenon when being used for a long period of time, and a method for producing the same.SOLUTION: A thermally conductive silicone grease composition contains a matrix resin component and thermally conductive inorganic particles, wherein the matrix resin component contains X(X=50 to 99.9) pts.mass of (A) non-reactive liquid dimethyl polysiloxane having dynamic viscosity at 25°C of 100 to 10,000 mm2 / s, and (100-X) pts.mass of (B) linear polydimethylsiloxane represented by the following chemical formula (provided that Me is methyl, n-Bu is normal butyl, and n is 5 to 1,000), 50 to 3,000 pts.mass of the thermally conductive inorganic particles are contained, and the silicone grease composition is a non-cured product.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a thermally conductive silicone grease composition suitable for being interposed between a heat-generating part such as an electric and electronic component and a heat sink, and a method for manufacturing the same.

Background Art

[0002] In recent years, the performance improvement of semiconductors such as CPUs has been remarkable, and along with this, the amount of heat generated has also become enormous. Therefore, a heat sink is attached to the heat-generating electronic component, and a thermally conductive silicone grease is used to improve the adhesion between the heat-generating body such as a semiconductor and the heat sink. However, when the thermally conductive silicone grease is used for a long time, due to the thermal shock of the semiconductor element, it flows out from the heat dissipation part, voids are generated in the heat dissipation part, and there is a problem that a so-called pumping-out phenomenon occurs. Patent Document 1 proposes a crosslinked thermally conductive silicone grease containing a specific cyclic organopolysiloxane. Patent Document 2 proposes a crosslinked thermally conductive silicone grease using hydrosilylation catalyst fine particles having a microcapsule structure. Patent Document 3 proposes a crosslinked thermally conductive silicone grease using an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the conventional thermal conductive silicone grease still has a problem that the pumping-out phenomenon is likely to occur when it is used for a long time.

[0005] In order to solve the above-mentioned conventional problems, the present invention provides a thermal conductive silicone grease composition having good viscosity and thermal conductivity as a thermal conductive silicone grease, and suppressing the pumping-out phenomenon when used for a long time, and a method for producing the same.

Means for Solving the Problems

[0006] One embodiment of the present invention is a silicone grease composition containing a matrix resin component and thermally conductive inorganic particles, wherein the matrix resin component includes the following (A) and (B): (A) A non-reactive liquid dimethylpolysiloxane having a kinematic viscosity at 25°C of 100 to 10,000 mm 2 / s: X (X = 50 to 99.9) parts by mass, (B) A linear polydimethylsiloxane represented by the following chemical formula (Chemical Formula 1): (100 - X) parts by mass,

Chemical Formula

[0007] One embodiment of the method of the present invention relates to a method for producing the above-mentioned thermally conductive silicone grease composition, which is a method for producing a thermally conductive silicone grease composition by mixing and stirring the components A, B, and C.

Effects of the Invention

[0008] The thermally conductive silicone grease composition of the present invention is in an uncured state, has good viscosity and thermal conductivity, and can provide a thermally conductive silicone grease composition in which the pumping-out phenomenon during long-term use is suppressed. That is, the B component acts as a coupling agent for the thermally conductive inorganic particles, the methoxy group at one end of the compound of the chemical formula (Chemical Formula 1) chemically reacts with the surface of the thermally conductive inorganic particles to form a covalent bond, and the organosiloxane group at the other end has a high affinity with the matrix resin. Therefore, the pumping-out phenomenon such as cracks or fissures is suppressed even during long-term use.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Embodiments for Carrying Out the Invention

[0010] The inventors of the present invention studied why the pumping-out phenomenon occurs when a thermally conductive silicone grease composition is used for a long period of time. As a result, they obtained the idea that the interface between the matrix resin and the thermally conductive inorganic particles peels off, leading to the pumping-out phenomenon such as cracks or fissures. In particular, this phenomenon was frequently observed when large-particle thermally conductive inorganic particles were included to increase the thermal conductivity. By including the compound represented by the chemical formula (Chemical Formula 1) together with the matrix resin in the present invention, the methoxy group at one end of the compound of the chemical formula (Chemical Formula 1) chemically reacts with the surface of the thermally conductive inorganic particles to form a covalent bond, and the organosiloxane group at the other end has a high affinity with the matrix resin. Therefore, the pumping-out phenomenon such as cracks or fissures is suppressed even after long-term use.

[0011] Component (A) of the present invention is a non-reactive liquid dimethylpolysiloxane having a kinematic viscosity at 25°C of 100 to 10,000 mm 2 / s. Preferably it is 100 to 5000 mm 2 / s, and more preferably 100 to 3000 mm 2 / s.

[0012] The compound of component B is a linear organopolysiloxane having trimethoxy groups at one end represented by the above (Chemical Formula 1). n is preferably from 10 to 900, more preferably from 20 to 500, and even more preferably from 30 to 250.

[0013] The composition ratios of the above components (A), (B), and (C) are preferably as follows. · Non-reactive liquid dimethylpolysiloxane of (A): X (X = 50 to 99.9) parts by mass, more preferably X is 60 to 98 parts by mass, and even more preferably X is 70 to 95 parts by mass. · Linear organopolysiloxane of (B): (100 - X) parts by mass. ·(C) Thermally conductive inorganic particles: 50 to 3000 parts by mass, more preferably 100 to 2800 parts by mass, even more preferably 200 to 2500 parts by mass. With this addition amount, the thermal conductivity of the composition can be increased, and it is suitable as a thermal conductive material: TIM (Thermal Interface Material).

[0014] Based on the total amount of the thermally conductive inorganic particles (C), the thermally conductive inorganic particles with a median diameter D50 of less than 1 μm in the cumulative particle size distribution by volume are 0 to 30 vol%, the thermally conductive inorganic particles with a diameter of 1 μm or more and less than 10 μm are 15 to 55 vol%, and the thermally conductive inorganic particles with a diameter of 30 μm or more are preferably composed of 5 to 55 vol% of thermally conductive inorganic particles. When large particles, medium particles, and small particles are mixed in this way, the medium particles and small particles are filled between the large particles, and the thermal conductivity can be improved.

[0015] Based on the total amount of the thermally conductive inorganic particles (C), the thermally conductive inorganic particles with a median diameter D50 of less than 1 μm in the cumulative particle size distribution by volume are 3 to 30 vol%, the thermally conductive inorganic particles with a diameter of 1 μm or more and less than 10 μm are 15 to 55 vol%, the thermally conductive inorganic particles with a diameter of 10 μm or more and less than 30 μm are 10 to 50 vol%, and the thermally conductive inorganic particles with a diameter of 30 μm or more are preferably composed of 5 to 55 vol% of thermally conductive inorganic particles. When large particles, medium particles, and small particles are mixed in this way, the medium particles and small particles are filled between the large particles, and the thermal conductivity can be improved. Note that the thermally conductive inorganic particles are also referred to as thermally conductive fillers.

[0016] The thermally conductive inorganic particles with a median diameter D50 of less than 1 μm are preferably at least one selected from the group consisting of alumina (aluminum oxide) and aluminum nitride. This is because alumina particles and aluminum nitride particles themselves have high thermal conductivity.

[0017] It is preferable that the heat-conductive inorganic particle (C) contains at least one selected from the group consisting of alumina and aluminum nitride having a median diameter D50 of 70 μm or more. More preferably, the heat-conductive inorganic particle contains particles having a median diameter D50 of 80 μm or more in the cumulative particle size distribution based on volume, and the ratio is 40% by mass or more and 60% by mass or less with respect to the total amount of the heat-conductive inorganic particles. Adding these large particles can maintain high heat conductivity.

[0018] The heat-conductive silicone grease composition preferably has a kinematic viscosity at 25°C measured with a rotational viscometer in the range of 200 to 30,000 Pas, more preferably 220 to 2800 Pas, and even more preferably 250 to 2500 Pas. Having such fluidity has the advantage that it can be applied to narrow gaps as a heat-conductive material: TIM (Thermal Interface Material).

[0019] The heat-conductive silicone grease composition has a thermal conductivity of 1.0 W / m·K or more and 30 W / m·K or less, more preferably 2.0 to 30 W / m·K, and even more preferably 3.0 to 30 W / m·K. Such heat-conductive grease is suitable as a TIM (Thermal Interface Material).

[0020] The heat-conductive silicone grease composition is used to compress and sandwich a test piece with an area of 300 mm 2 and a thickness of 2.0 mm between two plates and install it horizontally in a heat shock tester. In the pumping out test where it is held at -40°C and 125°C for 30 minutes each and 100 cycles are passed, it is preferable that there are 2 or fewer cracks with a gap of 1 mm or more. Also, in the same pumping out test, it is preferable that there are 9 or fewer voids with a diameter of 0.3 mm or more. This suppresses the pumping out phenomenon due to the generation of cracks or voids, etc. even after long-term use.

[0021] The thermally conductive silicone grease composition is non-curable because it uses non-reactive liquid dimethylpolysiloxane as the matrix resin. The present invention can prevent pumping out while being non-curable.

[0022] The thermally conductive inorganic particles are preferably inorganic particles such as aluminum oxide (alumina), zinc oxide, magnesium oxide, aluminum nitride, boron nitride, aluminum hydroxide, or silicon carbide. These inorganic particles have high thermal conductivity and are suitable as TIM (Thermal Interface Material).

[0023] It is preferable to pre-treat the small particles with a median diameter D50 of 1 μm or less on the surface with a coupling agent. As an example of the coupling agent, R(CH3) a Si(OR’) 4-a (where R is an unsubstituted or substituted organic group having 1 to 20 carbon atoms, R’ is an alkyl group having 1 to 4 carbon atoms, and a is 0 or 1), or a partial hydrolyzate thereof. The alkoxysilane compound of the above chemical formula (hereinafter simply referred to as “silane”) is, for example, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, pentyltrimethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane and other silane compounds. The silane compounds can be used alone or in combination of two or more. In particular, when the fine thermally conductive particles with a median diameter D = 50 of 1 μm or less are surface-treated with a coupling agent in advance, the miscibility is improved when compounding, and the workability is improved.

[0024] The thermal conductive silicone grease composition of the present invention can be used in greases, pastes, liquids, etc., but is preferably a thermal conductive grease. The thermal conductive grease is preferably filled in a syringe and applied as a thermal conductive material (TIM: Thermal Interface Material) between a heat generating part and a heat radiating part of an electronic component or the like.

[0025] The manufacturing method of the thermal conductive silicone grease composition of the present invention may be heated after mixing and stirring the components A, B, and C. The heating conditions are preferably less than 300 °C and the time is 5 minutes to 48 hours, and the more preferable temperature is 100 to 150. By heating, the one-terminal trimethoxy group of the component (B) chemically reacts with the surface of the thermally conductive inorganic particles, generating low molecular substances such as water or methanol, etc., but they evaporate outside the composition and do not remain inside the composition, so the heat resistance is increased.

[0026] The thermal conductive silicone resin composition of the present invention is a non-curable thermal conductive grease composition. Therefore, a curing catalyst and a curing agent are not required, but they may be added in some cases.

[0027] In the grease of the present invention, components other than those described above can be blended as necessary. For example, heat resistance improvers such as red iron oxide, titanium oxide, and cerium oxide, flame retardants, flame retardant aids, etc. may be added. Organic or inorganic particle pigments may be added for coloring and color adjustment purposes. An alkoxy group-containing silicone may be added as a material added for the purpose of surface treatment of the thermally conductive inorganic particles. The thermal conductive grease composition of the present invention can be filled into various products such as a tin can, a syringe, and a cartridge to form a product.

Examples

[0028] The following examples will be used for explanation. The present invention is not limited to the examples. Various parameters were measured by the following methods.

[0029] <Thermal conductivity> The thermal conductivity of the thermal conductive grease was measured by a hot disk (conforming to ISO 22007-2:2008). As shown in Fig. 1A, this thermal conductivity measuring device 1 sandwiches a sensor 2 made of a polyimide film with two samples 3a and 3b, applies a constant power to the sensor 2 to generate heat constantly, and analyzes the thermal characteristics from the temperature rise value of the sensor 2. The tip 4 of the sensor 2 has a diameter of 7 mm, and as shown in Fig. 1B, it has a double spiral structure of electrodes, 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 measurement sample can be obtained by roll-molding a defoamed thermally conductive liquid composition to a thickness of 7 mm or more. The thermal conductivity is calculated by the following formula (Equation 1).

Equation

[0030] (Examples 1 to 8, Comparative Example 1) 1. Raw material components (1) Matrix resin components (A + B components) As component (A), a non-reactive liquid dimethylpolysiloxane with a kinematic viscosity of 100 mm 2 / s (manufactured by Momentive Performance Materials Japan, product number TSF458-100) was used at 25 °C. As component (B), the one-terminal trimethoxy linear organopolysiloxane (n = 197) represented by the above chemical formula (Chemical Formula 1) was used. (2) Thermally conductive inorganic particles (C component) As component (C-1), amorphous alumina D50 = 0.3 μm, an octyltrimethoxysilane pretreated product was used. As component (C-2), spherical alumina D50 = 2 μm (75 μm top cut product) was used. As component (C-3), spherical alumina D50 = 20 μm (55 μm top cut product) was used. As component (C-4), spherical alumina D50 = 120 μm (150 μm top cut product) was used. 2. Mixing method Thermally conductive inorganic particles were added to the above matrix components, and they were mixed and stirred using a planetary mixer to obtain a thermal conductive grease composition. When heated after mixing and stirring, the heating temperature and time are shown in Table 1. The grease obtained as described above was evaluated. The conditions and results are summarized in Table 1 below.

[0031]

Table 1

[0032] From the above results, the following can be understood. (1) In Examples 1 to 8, the number of cracks with a gap of 1 mm or more was two or less in the pumping-out test, and the pumping-out test passed. (2) In Examples 2 - 4, there were 10 or more voids with a diameter of 0.3 mm or more in the pumping-out test, but there was no problem in practical use. (3) In Examples 5 - 8, since heat treatment was performed at 100 to 250 °C for 24 hours, the number of voids with a diameter of 0.3 mm or more was nine or less in the pumping-out test, and they were superior to Examples 2 - 4. (4) On the other hand, Comparative Example 1 did not contain component (B), so the number of cracks with a gap of 1 mm or more was three or more in the pumping-out test, and the pumping-out test failed. An example of the crack in Comparative Example 1 is shown in Fig. 2. In Fig. 2, the crack is the fissure.

Industrial Applicability

[0033] The thermally conductive silicone grease composition of the present invention is suitable as a thermally conductive material: TIM (Thermal Interface Material) interposed between a heat generating part of electrical and electronic components, etc. and a heat sink.

Explanation of Signs

[0034] 1 Thermal conductivity measuring device 2 Sensor 3a, 3b Samples 4 Tip of the sensor 5 Electrode for applied current 6 Electrode for resistance value (electrode for temperature measurement)

Claims

1. A silicone grease composition containing a matrix resin component and thermally conductive inorganic particles, wherein the matrix resin component contains the following (A) and (B): (A) a non-reactive liquid dimethylpolysiloxane having a kinematic viscosity at 25 °C of 100 to 10,000 mm 2 / s: X (X = 50 to 99.9) parts by mass, (B) Linear polydimethylsiloxane represented by the following chemical formula (Formula 1): (100 - X) parts by mass, 【Chemical Formula 1】 (However, Me is methyl, n-Bu is normal butyl, n = 5 to 1000) The thermally conductive inorganic particles are contained in an amount of 50 to 3000 parts by mass, The silicone grease composition is a non-cured product, and is characterized by being a thermally conductive silicone grease composition.

2. The thermally conductive silicone grease composition according to Claim 1, wherein, based on the total amount of the thermally conductive inorganic particles (C), the thermally conductive inorganic particles having a median diameter D50 of less than 1 μm in the cumulative particle size distribution by volume are 0 to 30 vol%, the thermally conductive inorganic particles having a size of 1 μm or more and less than 10 μm are 15 to 55 vol%, and the thermally conductive inorganic particles having a size of 30 μm or more are 5 to 55 vol%.

3. The thermally conductive silicone grease composition according to Claim 1, wherein, based on the total amount of the thermally conductive inorganic particles (C), the thermally conductive inorganic particles having a median diameter D50 of less than 1 μm in the cumulative particle size distribution by volume are 3 to 30 vol%, the thermally conductive inorganic particles having a size of 1 μm or more and less than 10 μm are 15 to 55 vol%, the thermally conductive inorganic particles having a size of 10 μm or more and less than 30 μm are 10 to 50 vol%, and the thermally conductive inorganic particles having a size of 30 μm or more are 5 to 55 vol%.

4. The thermally conductive silicone grease composition according to Claim 1, wherein the thermally conductive inorganic particles (C) contain thermally conductive inorganic particles having a median diameter D50 of less than 1 μm, and the thermally conductive inorganic particles having a D50 of less than 1 μm are at least one selected from the group consisting of alumina and aluminum nitride.

5. The thermally conductive silicone grease composition according to Claim 1, wherein the thermally conductive inorganic particles (C) contain at least one selected from the group consisting of alumina and aluminum nitride having a median diameter D50 of 70 μm or more.

6. The thermally conductive silicone grease composition according to Claim 1, wherein the kinematic viscosity at 25°C measured by a rotational viscometer is in the range of 200 to 30,000 Pa·s.

7. The thermally conductive silicone grease composition according to Claim 1, wherein the thermal conductivity is 1.0 W / m·K or more and 30 W / m·K or less.

8. The heat-conductive silicone grease composition is used to horizontally install a test piece compressed and sandwiched between two plates with an area of 300 mm 2 and a thickness of 2.0 mm in a heat shock tester, hold it at -40°C and 125°C for 30 minutes each, and in a pumping out test where 100 cycles are passed, the heat-conductive silicone grease composition according to claim 1, wherein there are two or more cracks with a gap of 1 mm or more, or two or fewer cracks with a length of 10 mm or more.

9. The heat-conductive silicone grease composition according to claim 8, wherein, in the pumping-out test, when the appearance after the test is checked, the number of cracks with a gap of 1 mm or more is 2 or less, and the number of voids with a diameter of 0.3 mm or more is 9 or less.

10. The heat-conductive silicone grease composition according to claim 1, wherein the heat-conductive inorganic particles contain particles with a median diameter D50 of 1 μm or less, and the particles with a median diameter D50 of 1 μm or less are surface-treated with an alkylalkoxysilane.

11. The heat-conductive silicone grease composition according to claim 1, wherein the heat-conductive inorganic particles contain particles with a median diameter D50 of the cumulative particle size distribution based on volume of 80 μm or more, and the proportion is 40% by mass or more and 60% by mass or less with respect to the total amount of the heat-conductive inorganic particles.

12. A method for producing a heat-conductive silicone grease composition according to any one of claims 1 to 11, characterized by mixing and stirring the A and B components and the heat-conductive inorganic particles.

13. The method for producing a heat-conductive silicone grease composition according to claim 12, wherein after the mixing and stirring, heating is performed, and the heating conditions at that time are temperature: less than 300 °C, time: 5 minutes to 48 hours.

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