A low-volatility thermally conductive pad and its preparation method

Abstract

This application provides a low-volatility thermally conductive pad, prepared from a parylene-coated thermally conductive filler, a vinyl silicone oil treated to remove volatiles, a hydrogen-containing silicone oil treated to remove volatiles, an inhibitor, and a catalyst. This application also provides a method for preparing the low-volatility thermally conductive pad described above. The low-volatility thermally conductive pad provided by this application, prepared from a parylene-coated thermally conductive filler, a vinyl silicone oil treated to remove volatiles, a hydrogen-containing silicone oil treated to remove volatiles, an inhibitor, and a catalyst, exhibits high thermal conductivity and low volatility. Experimental results show that the low-volatility thermally conductive pad provided by this application has a thermal conductivity of 2 W / (m·K)~6 W / (m·K), a hardness of 25~50 Shore 00, a D3~D20 content of <15 ppm, and no condensable volatiles after >24 hours at 150℃.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a low-volatility thermally conductive pad and its preparation method. Background Technology

[0002] When ordinary thermally conductive materials are used in devices, some small molecules will gradually volatilize, forming an oil film or mist on the device, which will affect the normal use of devices such as optical filters, cameras, lidar, optical modules and lighting components. Summary of the Invention

[0003] In view of this, the technical problem to be solved by the present invention is to provide a low-volatility thermal conductive pad and its preparation method. The thermal conductive pad provided by this application has the characteristics of high thermal conductivity and low volatility, and is not easy to form an oil film.

[0004] This application provides a low-volatility thermally conductive pad, which is prepared from a poly(p-xylene)-coated thermally conductive filler, a vinyl silicone oil treated to remove volatiles, a hydrogen-containing silicone oil treated to remove volatiles, an inhibitor, and a catalyst.

[0005] The low-volatility thermally conductive pad provided in this application uses parylene-coated thermally conductive filler as raw material. The parylene-coated thermally conductive filler includes a thermally conductive filler and a parylene layer coating the surface of the thermally conductive filler. The thickness of the parylene layer is less than or equal to 5 μm, preferably 0.5 μm to 4 μm. The thermally conductive filler includes, but is not limited to, alumina, aluminum nitride, silicon carbide, etc., and can be one or more of these. When multiple thermally conductive fillers are used, this application does not impose any special limitation on their proportions. In some specific implementations, the particle size of the thermally conductive filler is 1 μm to 100 μm, for example, 95 μm, 80 μm, 75 μm, 70 μm, 45 μm, and 5 μm. In some specific implementations, the thermally conductive filler includes a first-size thermally conductive filler and a second-size thermally conductive filler, wherein the first-size filler is 30μm~100μm, preferably 50μm~100μm; the second-size filler is 1μm~20μm, preferably 1μm~10μm; and the mass ratio of the first-size thermally conductive filler to the second-size thermally conductive filler is 1~5:1, preferably 1~3:1. Specifically, the alumina has a particle size (D50) of one or more of about 95μm, about 75μm, about 45μm, and about 5μm; the aluminum nitride has a particle size (D50) of one or more of about 80μm and 5μm; and the silicon carbide has a particle size (D50) of one or more of about 70μm and 45μm.

[0006] This application does not impose any special restrictions on the source of the parylene-coated thermally conductive filler, which can be prepared according to the following method.

[0007] Heat-treat the thermally conductive filler;

[0008] A poly(p-xylene) coating layer is formed on the surface of a heat-treated thermally conductive filler by chemical vapor deposition.

[0009] This application first heat-treats the thermally conductive filler to remove moisture and other impurities. In some specific implementations, the heat treatment temperature is 100℃~200℃, preferably 120℃~180℃, and the time is 5h~10h, preferably 6h~8h. After obtaining the dried thermally conductive filler, a parylene coating layer is formed on its surface by chemical vapor deposition. Specifically, a typical chemical vapor deposition process for forming the parylene coating layer is as follows: using parylene monomer as raw material, chemical vapor deposition is performed on the surface of the thermally conductive filler, with an evaporation source temperature of 180℃~190℃, a pyrolysis temperature of 675℃~685℃, a deposition chamber temperature of 25℃~35℃, and a vacuum of 1Pa~5Pa.

[0010] The low-volatility thermally conductive pad provided in this application uses vinyl silicone oil treated to remove volatiles as raw material. In some specific implementations, the vinyl silicone oil is a double-ended vinyl silicone oil. In some specific implementations, the viscosity of the vinyl silicone oil is 100 mPa·s to 50000 mPa·s, preferably 300 mPa·s to 10000 mPa·s, such as 350 mPa·s, 500 mPa·s, 2000 mPa·s, and 10000 mPa·s. In some specific implementations, the vinyl silicone oil can be a combination of vinyl silicone oils of different viscosities, and this application does not have any special restrictions on their proportions. In some specific implementations, the vinyl content in the vinyl silicone oil is 0.03 mmol / g to 0.39 mmol / g, preferably 0.04 mmol / g to 0.2 mmol / g. In some specific implementations, the vinyl silicone oil treated to remove volatiles is prepared according to the following method:

[0011] Vinyl silicone oil was treated to remove volatiles using a molecular thin-film evaporator at 190℃~220℃ and a vacuum of 0.5Pa~5Pa for a duration of <60s.

[0012] In some specific implementations, the temperature of the molecular thin film evaporator is preferably 200℃~210℃, the vacuum is preferably 0.5Pa~3Pa, and the processing time is preferably <45s.

[0013] The low-volatility thermally conductive pad provided in this application uses hydrogen-containing silicone oil treated to remove volatiles as raw material. In some specific implementations, the hydrogen-containing silicone oil is a component of side-containing and end-containing hydrogen-containing silicone oil, with a viscosity of 200 mPa·s to 2500 mPa·s, preferably 500 mPa·s to 2000 mPa·s, more preferably 800 mPa·s to 1800 mPa·s, and a hydrogen content of 0.2 mmol / g to 0.4 mmol / g, preferably 0.25 mmol / g to 0.35 mmol / g.

[0014] In some specific implementations, the hydrogen-containing silicone oil for removing volatiles is prepared according to the following method:

[0015] Hydrogen-containing silicone oil was treated to remove volatiles using a molecular thin-film evaporator at 190℃~220℃ and a vacuum of 0.1Pa~5Pa for a duration of <60s.

[0016] In some specific implementations, the temperature of the molecular thin film evaporator is preferably 200℃~210℃, the vacuum is preferably 0.1Pa~1Pa, and the processing time is preferably <45s.

[0017] The raw materials for preparing the low-volatility thermally conductive pads provided in this application also include inhibitors and catalysts. In some specific implementations, the catalyst is a platinum catalyst. In some specific implementations, the inhibitors include, but are not limited to, methyltris(1,1-dimethyl-1-ethynylmethoxy)silane, vinyltris(1,1-dimethyl-1-ethynylmethoxy)silane, phenyltris(1,1-dimethyl-1-ethynylmethoxy)silane, 3-methyl-1-butyn-3-ol, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, N,N,N',N'-tetraallylterephthalamide, or monoallyl maleate, etc.

[0018] In some specific implementations, the low-volatility thermally conductive pad is prepared from 83 to 95 parts by weight of a parylene-coated thermally conductive filler, 1 to 20 parts by weight of vinyl silicone oil treated to remove volatiles, 0.1 to 5 parts by weight of a hydrogen-containing silicone oil treated to remove volatiles, 0.003 to 0.015 parts by weight of an inhibitor, and 0.006 to 0.03 parts by weight of a catalyst. In some specific implementations, the low-volatility thermally conductive pad is prepared from 85 to 90 parts by weight of a parylene-coated thermally conductive filler, 5 to 15 parts by weight of a vinyl silicone oil treated to remove volatiles, 0.5 to 2 parts by weight of a hydrogen-containing silicone oil treated to remove volatiles, 0.005 to 0.010 parts by weight of an inhibitor, and 0.01 to 0.02 parts by weight of a catalyst.

[0019] This application also provides a method for preparing the low-volatility thermally conductive pad described in the above technical solution, comprising the following steps:

[0020] 1) Mix the parylene-coated thermally conductive filler, the vinyl silicone oil treated to remove volatiles, the hydrogen-containing silicone oil treated to remove volatiles, the inhibitor and the catalyst to obtain the adhesive;

[0021] 2) The adhesive is molded into a sheet and cured to obtain a low-volatile thermally conductive pad.

[0022] This application uses parylene-coated thermally conductive filler, vinyl silicone oil treated to remove volatiles, hydrogen-containing silicone oil treated to remove volatiles, inhibitors, and catalysts as raw materials. As described above, these raw materials will not be repeated here.

[0023] Specifically, this application mixes the raw materials in the following manner:

[0024] The thermally conductive filler coated with parylene, the vinyl silicone oil treated to remove volatiles, and the hydrogen-containing silicone oil treated to remove volatiles were stirred in a planetary mixer at a speed of 25 RPM to 40 RPM and a vacuum of ≤-0.09 MPa for 40 min to 90 min to obtain the first mixture.

[0025] The first mixture and the inhibitor were stirred in a planetary mixer at a speed of 15 RPM to 35 RPM and a vacuum of ≤-0.09 MPa for 5 min to 15 min to obtain the second mixture;

[0026] The second mixture and the catalyst were stirred in a planetary mixer at a speed of 15 RPM to 30 RPM and a vacuum of ≤-0.09 MPa for 5 min to 15 min to obtain the rubber compound.

[0027] After obtaining the adhesive compound, it is molded into a sheet, and after curing, a low-volatile thermally conductive pad is obtained. This application does not impose any particular limitation on the molding method; it can be calendering. In some specific implementations, the thickness of the sheet is 1mm to 2mm. In some specific implementations, the curing temperature is 130℃ to 150℃, preferably 135℃ to 145℃, and the curing time is 20min to 30min, preferably 22min to 28min.

[0028] See Figure 1 , Figure 1 The process flow diagram for preparing the low-volatility thermally conductive pads for this application is shown below, with a typical flow as follows:

[0029] The thermally conductive powder (i.e., thermally conductive filler) is baked and dried to obtain dry thermally conductive powder. Then, a parylene coating layer is formed on the surface of the dry thermally conductive powder by chemical vapor deposition to obtain coated thermally conductive powder.

[0030] Vinyl silicone oil is subjected to volatile matter removal treatment to obtain pretreated vinyl silicone oil;

[0031] The hydrogen-containing silicone oil is subjected to a devolatileization treatment to obtain pretreated hydrogen-containing silicone oil;

[0032] The coated thermally conductive powder, pretreated vinyl silicone oil, and pretreated hydrogen-containing silicone oil were mixed under vacuum stirring to obtain the first mixed adhesive.

[0033] The mixed rubber compound and the inhibitor were mixed under vacuum and stirring conditions to obtain a second mixed rubber compound;

[0034] The second mixed rubber compound and the catalyst were mixed under vacuum and stirring conditions to obtain the third mixed rubber compound;

[0035] The third mixed adhesive is calendered into sheets and cured to obtain a low-volatile thermally conductive pad.

[0036] The low-volatility thermally conductive pad provided in this application is prepared from parylene-coated thermally conductive filler, volatile-free vinyl silicone oil, volatile-free hydrogen-containing silicone oil, inhibitors, and catalysts. It exhibits high thermal conductivity and low volatility. Experimental results show that the thermal conductivity of the low-volatility thermally conductive pad provided in this application is 2 W / (m·K)~6 W / (m·K), the hardness is 25~50 Shore 00, the D3~D20 content is <15 ppm, and there are no condensable volatiles after >24 hours at 150℃. Attached Figure Description

[0037] Figure 1 A process flow diagram for preparing the low-volatility thermally conductive pad for this application. Detailed Implementation

[0038] This invention provides a low-volatility thermally conductive pad and its preparation method. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the same result. The method and application of this invention have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the method and application described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0039] The terms “including,” “having,” or “containing,” including the use of their grammatical synonyms, should generally be understood as open-ended and non-restrictive, for example, not excluding other unstated elements or steps, unless otherwise specifically stated or understood from the context.

[0040] It should be understood that the order of the steps or the order in which certain actions are performed is not important as long as the invention remains operational. Furthermore, two or more steps or actions can be performed simultaneously.

[0041] The use of any and all instances or exemplary language such as “e.g.” or “including” in this document is merely intended to better illustrate the invention and is not intended to limit the scope of the invention unless the claims are made. No language in this specification should be construed as indicating that any unclaimed element is essential to the practice of the invention.

[0042] Furthermore, the numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as precisely as possible. However, any value inevitably contains standard deviations due to individual test methods. Therefore, unless explicitly stated otherwise, it should be understood that all ranges, quantities, values, and percentages used in this disclosure are modified with the word "approximately". Here, "approximately" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a specific value or range.

[0043] This application provides a low-volatility thermally conductive pad, which is prepared from a poly(p-xylene)-coated thermally conductive filler, a vinyl silicone oil treated to remove volatiles, a hydrogen-containing silicone oil treated to remove volatiles, an inhibitor, and a catalyst.

[0044] This application also provides a method for preparing the low-volatility thermally conductive pad described in the above technical solution, comprising the following steps:

[0045] 1) Mix the parylene-coated thermally conductive filler, the vinyl silicone oil treated to remove volatiles, the hydrogen-containing silicone oil treated to remove volatiles, the inhibitor and the catalyst to obtain the adhesive;

[0046] 2) The adhesive is molded into a sheet and cured to obtain a low-volatile thermally conductive pad.

[0047] The low-volatility thermally conductive pad provided in this application is prepared from parylene-coated thermally conductive filler, volatile-free vinyl silicone oil, volatile-free hydrogen-containing silicone oil, inhibitors, and catalysts. It exhibits high thermal conductivity and low volatility. Experimental results show that the thermal conductivity of the low-volatility thermally conductive pad provided in this application is 2 W / (m·K)~6 W / (m·K), the hardness is 25~50 Shore 00, the D3~D20 content is <15 ppm, and there are no condensable volatiles after >24 hours at 150℃.

[0048] The present application will be further described below with reference to the embodiments.

[0049] Example 1

[0050] (1) Alumina powders with particle sizes (D50) of about 45 μm and about 5 μm were baked at 150 °C for 6 h to obtain corresponding dry alumina powders. The aforementioned dry alumina powders were coated with parylene using a vacuum coating machine by chemical vapor deposition (evaporation source temperature 180 °C~190 °C, pyrolysis temperature 675 °C~685 °C, deposition chamber temperature 25 °C~35 °C, vacuum 1 Pa~5 Pa). The coating layer thickness was 1 μm~3 μm to obtain the corresponding coated alumina powders.

[0051] (2) Vinyl silicone oil with a viscosity of about 10000 mPa·s was treated with a molecular thin film evaporator at 200℃ and under vacuum conditions of 0.7 Pa to 2.3 Pa to remove volatiles, and pretreated vinyl silicone oil was obtained.

[0052] (3) Hydrogen-containing silicone oil (hydrogen content 0.2 mmol / g to 0.4 mmol / g) was treated with a molecular thin film evaporator at a temperature of 180℃ and a vacuum of 0.3 Pa to 0.85 Pa to remove volatiles, and pretreated hydrogen-containing silicone oil was obtained;

[0053] (4) 14 parts of the pretreated vinyl silicone oil with a viscosity of 10000 mPa·s, 1.03 parts of the pretreated hydrogen-containing silicone oil, 63.3 parts of coated alumina with a particle size (D50) of about 45 μm, and 31.7 parts of coated alumina with a particle size (D50) of about 5 μm were added to a planetary mixer and stirred for 60 min at 30 RPM and ≤-0.09 MPa vacuum. Then, 0.01 parts of the inhibitor vinyltris(1,1-dimethyl-1-ethynylmethoxy)silane were added and stirred for 10 min at 25 RPM and ≤-0.09 MPa vacuum. After that, 0.02 parts of platinum catalyst were added and stirred for 10 min at 25 RPM and ≤-0.09 MPa vacuum to obtain a mixed adhesive.

[0054] (5) The aforementioned mixed rubber compound is calendered into a sheet with a thickness of 1 mm or 2 mm and cured by baking at 140°C for 30 min to obtain a low-volatility thermally conductive pad.

[0055] Example 2

[0056] (1) Alumina powders with particle sizes (D50) of about 75 μm and about 5 μm were baked at 150 °C for 6 h to obtain corresponding dry alumina powders. The aforementioned dry alumina powders were coated with parylene by chemical vapor deposition (evaporation source temperature 180 °C~190 °C, pyrolysis temperature 675 °C~685 °C, deposition chamber temperature 25 °C~35 °C, vacuum 1 Pa~5 Pa) to obtain corresponding coated alumina powders.

[0057] (2) A vinyl silicone oil with a viscosity of about 2000 mPa·s was treated to remove volatiles using a molecular thin film evaporator at 210°C and 0.5 Pa to 2.7 Pa vacuum conditions, and a vinyl silicone oil with a viscosity of about 500 mPa·s was treated to remove volatiles at 220°C and 0.9 Pa to 2.6 Pa vacuum conditions to obtain pretreated vinyl silicone oil;

[0058] (3) Hydrogen-containing silicone oil (hydrogen content 0.2mmol / g~0.4mmol / g) was treated with a molecular thin film evaporator at a temperature of 180℃ and a vacuum of 0.3Pa~0.85Pa to remove volatiles, and pretreated hydrogen-containing silicone oil was obtained;

[0059] (4) Add 5 parts of pretreated vinyl silicone oil with a viscosity of 2000 mPa·s, 3 parts of pretreated vinyl silicone oil with a viscosity of 500 mPa·s, 0.9 parts of pretreated hydrogen-containing silicone oil, 55 parts of coated alumina with a particle size (D50) of about 75 μm, and 36 parts of coated alumina with a particle size (D50) of about 5 μm to a planetary mixer and stir for 60 min at 30 RPM and ≤-0.09 MPa vacuum. Then add 0.006 parts of the inhibitor vinyltris(1,1-dimethyl-1-ethynylmethoxy)silane and stir for 10 min at 20 RPM and ≤-0.09 MPa vacuum. Then add 0.012 parts of platinum catalyst and stir for 10 min at 20 RPM and ≤-0.09 MPa vacuum to obtain a mixed adhesive.

[0060] (5) The aforementioned mixed rubber compound is calendered into sheets with thicknesses of 1 mm and 2 mm, and cured by baking at 140°C for 30 min to obtain a low-volatility thermally conductive pad.

[0061] Example 3

[0062] (1) Alumina powders with particle sizes (D50) of about 95 μm and about 5 μm were baked at 150 °C for 6 h to obtain corresponding dry alumina powders. The aforementioned dry alumina powders were coated with parylene by chemical vapor deposition (evaporation source temperature 180 °C~190 °C, pyrolysis temperature 675 °C~685 °C, deposition chamber temperature 25 °C~35 °C, vacuum 1 Pa~5 Pa) to obtain corresponding coated alumina powders.

[0063] (2) Silicon carbide powder with a particle size (D50) of about 70 μm was baked at 150 °C for 6 h to obtain the corresponding dry silicon carbide powder. The aforementioned dry silicon carbide powder was coated with parylene by chemical vapor deposition (evaporation source temperature 180 °C~190 °C, pyrolysis temperature 675 °C~685 °C, deposition chamber temperature 25 °C~35 °C, vacuum 1 Pa~5 Pa) to obtain the corresponding coated silicon carbide powder.

[0064] (3) Using a molecular thin film evaporator, the vinyl silicone oil with a viscosity of about 500 mPa·s was subjected to volatile matter removal treatment at 220℃ and 0.9 Pa~2.6 Pa vacuum conditions to obtain pretreated vinyl silicone oil;

[0065] (4) Hydrogen-containing silicone oil (hydrogen content 0.2mmol / g~0.4mmol / g) was treated with a molecular thin film evaporator at a temperature of 180℃ and a vacuum of 0.3Pa~0.85Pa to remove volatiles, and pretreated hydrogen-containing silicone oil was obtained;

[0066] (5) Add 6 parts of the pretreated vinyl silicone oil with a viscosity of 500 mPa·s, 0.89 parts of the pretreated hydrogen-containing silicone oil, 33 parts of coated alumina with a particle size (D50) of about 95 μm, 33 parts of coated silicon carbide with a particle size (D50) of about 70 μm, and 27 parts of coated alumina with a particle size (D50) of about 5 μm to a planetary mixer and stir for 60 min at a speed of 35 RPM and a vacuum of ≤-0.09 MPa; then add 0.005 parts of the inhibitor vinyltris(1,1-dimethyl-1-ethynylmethoxy)silane and stir for 10 min at a speed of 15 RPM and a vacuum of ≤-0.09 MPa; then add 0.01 parts of platinum catalyst and stir for 10 min at a speed of 15 RPM and a vacuum of ≤-0.09 MPa to obtain a mixed adhesive.

[0067] (6) The aforementioned mixed rubber compound is calendered into sheets with thicknesses of 1 mm and 2 mm, and cured by baking at 140°C for 30 min to obtain a low-volatility thermally conductive pad.

[0068] Example 4

[0069] (1) Alumina powders with particle sizes (D50) of about 75 μm and about 5 μm were baked at 150 °C for 6 h to obtain corresponding dry alumina powders. The aforementioned dry alumina powders were coated with parylene by chemical vapor deposition (evaporation source temperature 180 °C~190 °C, pyrolysis temperature 675 °C~685 °C, deposition chamber temperature 25 °C~35 °C, vacuum 1 Pa~5 Pa) to obtain corresponding coated alumina powders.

[0070] (2) Aluminum nitride powder with a particle size (D50) of about 80 μm was baked at 150℃ for 6 h to obtain the corresponding dry aluminum nitride powder. The aforementioned dry silicon carbide powder was coated with parylene by chemical vapor deposition (evaporation source temperature 180℃~190℃, pyrolysis temperature 675℃~685℃, deposition chamber temperature 25℃~35℃, vacuum 1Pa~5Pa) to obtain the corresponding coated aluminum nitride powder.

[0071] (3) Using a molecular thin film evaporator at 220°C and 0.5Pa~1.9Pa vacuum conditions, the vinyl silicone oil with a viscosity of about 300mPa·s was subjected to volatile matter removal treatment to obtain pretreated vinyl silicone oil;

[0072] (4) Hydrogen-containing silicone oil (hydrogen content 0.2mmol / g~0.4mmol / g) was treated with a molecular thin film evaporator at a temperature of 180℃ and a vacuum of 0.3Pa~0.85Pa to remove volatiles, and pretreated hydrogen-containing silicone oil was obtained;

[0073] (5) 5.1 parts of the pretreated vinyl silicone oil with a viscosity of 300 mPa·s, 0.8 parts of the pretreated hydrogen-containing silicone oil, 36 parts of coated aluminum nitride with a particle size (D50) of about 80 μm, 32.5 parts of coated alumina with a particle size (D50) of about 75 μm, and 25 parts of coated alumina with a particle size (D50) of about 5 μm were added to a planetary mixer and stirred for 60 min at 35 RPM and ≤-0.09 MPa vacuum. Then, 0.004 parts of the inhibitor vinyltris(1,1-dimethyl-1-ethynylmethoxy)silane were added and stirred for 10 min at 15 RPM and ≤-0.09 MPa vacuum. After that, 0.08 parts of platinum catalyst were added and stirred for 10 min at 15 RPM and ≤-0.09 MPa vacuum to obtain a mixed adhesive.

[0074] (6) The aforementioned mixed rubber compound is calendered into a sheet with a thickness of 1 mm or 2 mm and cured by baking at 140°C for 30 min to obtain a low-volatility thermally conductive pad.

[0075] Comparative Example 1

[0076] (1) Alumina powders with particle sizes (D50) of approximately 45 μm and approximately 5 μm were baked at 150 °C for 6 h to obtain the corresponding dried alumina powders;

[0077] (2) Vinyl silicone oil with a viscosity of about 10000 mPa·s was treated with a molecular thin film evaporator at 200℃ and under vacuum conditions of 0.7 Pa to 2.3 Pa to remove volatiles, and pretreated vinyl silicone oil was obtained.

[0078] (3) Hydrogen-containing silicone oil (hydrogen content 0.2mmol / g~0.4mmol / g) was treated with a molecular thin film evaporator at a temperature of 180℃ and a vacuum of 0.3Pa~0.85Pa to remove volatiles, and pretreated hydrogen-containing silicone oil was obtained;

[0079] (4) 14 parts of the pretreated vinyl silicone oil with a viscosity of 10000 mPa·s, 1.03 parts of the pretreated hydrogen-containing silicone oil, 63.3 parts of dried alumina with a particle size (D50) of about 45 μm, and 31.7 parts of dried alumina with a particle size (D50) of about 5 μm were added to a planetary mixer and stirred for 60 min at 30 RPM and ≤-0.09 MPa vacuum. Then, 0.01 parts of the inhibitor vinyltris(1,1-dimethyl-1-ethynylmethoxy)silane were added and stirred for 10 min at 25 RPM and ≤-0.09 MPa vacuum. After that, 0.02 parts of platinum catalyst were added and stirred for 10 min at 25 RPM and ≤-0.09 MPa vacuum to obtain a mixed adhesive.

[0080] (5) The aforementioned mixed rubber compound is calendered into a sheet with a thickness of 1 mm or 2 mm and cured by baking at 140°C for 30 min to obtain a low-volatility thermally conductive pad.

[0081] Comparative Example 2

[0082] (1) Alumina powders with particle sizes (D50) of approximately 45 μm and approximately 5 μm were baked at 150 °C for 6 h to obtain the corresponding dried alumina powders;

[0083] (2) 14 parts of vinyl silicone oil with a viscosity of 10000 mPa·s, 1.03 parts of hydrogen-containing silicone oil (hydrogen content 0.2 mmol / g~0.4 mmol / g), 63.3 parts of the aforementioned dried alumina with a particle size (D50) of about 45 μm, and 31.7 parts of dried alumina with a particle size (D50) of about 5 μm were added to a planetary mixer and stirred for 60 min at 30 RPM and ≤-0.09 MPa vacuum. Then, 0.01 parts of the inhibitor vinyltris(1,1-dimethyl-1-ethynylmethoxy)silane were added and stirred for 10 min at 25 RPM and ≤-0.09 MPa vacuum. After that, 0.02 parts of platinum catalyst were added and stirred for 10 min at 25 RPM and ≤-0.09 MPa vacuum to obtain a mixed adhesive.

[0084] (3) The aforementioned mixed rubber compound is calendered into a sheet with a thickness of 1 mm or 2 mm and cured by baking at 140°C for 30 min to obtain a low-volatility thermally conductive pad.

[0085] Experimental Example 1

[0086] The thermal pads obtained in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests:

[0087] (1) Hardness test: Tested according to ASTM D2240 standard;

[0088] (2) Thermal conductivity: tested according to ISO 22007-2 standard;

[0089] (3) D3~D20 content: tested according to GB / T 28112-2011 standard;

[0090] (4) Volatilization time test: Take a 1mm thick thermal pad, die-cut it into a 10×10mm piece, place one 10×10mm piece at the bottom of a 5mL glass bottle, cover it with a glass plate, and then place it on a 150℃ heating platform for continuous heating. Record the time and state at which condensable volatiles begin to appear on the glass plate.

[0091] The test results are shown in Table 1:

[0092] Table 1. Test results of the thermal pads in the examples and comparative examples.

[0093]

[0094] As shown in Table 1, the gasket provided in this application has a high thermal conductivity and low volatility, and is not prone to forming an oil film.

[0095] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-volatility thermally conductive pad, characterized in that, It was prepared from 83 to 95 parts by mass of a thermally conductive filler coated with parylene, 1 to 20 parts by mass of vinyl silicone oil treated to remove volatiles, 0.1 to 5 parts by mass of hydrogen-containing silicone oil treated to remove volatiles, 0.003 to 0.015 parts by mass of an inhibitor, and 0.006 to 0.03 parts by mass of a catalyst; The thermally conductive filler is alumina, or alumina and aluminum nitride, or alumina and silicon carbide; The particle size of the thermally conductive filler is 1μm to 100μm; the thickness of the parylene-coated thermally conductive filler is 0.5μm to 5μm; the parylene-coated thermally conductive filler is prepared according to the following method: Heat-treat the thermally conductive filler; A poly(p-xylene) coating layer is formed on the surface of a heat-treated thermally conductive filler by chemical vapor deposition.

2. The low-volatility thermally conductive pad according to claim 1, characterized in that, The heat treatment temperature is 100℃~200℃, and the time is 5h~10h.

3. The low-volatility thermally conductive pad according to claim 1, characterized in that, The thermally conductive filler includes a first-size thermally conductive filler and a second-size thermally conductive filler. The first particle size is 30μm~100μm; The second particle size is 1μm~20μm; The mass ratio of the first particle size thermally conductive filler to the second particle size thermally conductive filler is 1~3:

1.

4. The low-volatility thermally conductive pad according to any one of claims 1 to 3, characterized in that, The vinyl silicone oil is a double-ended vinyl silicone oil, the viscosity of the vinyl silicone oil is 100 mPa·s to 50000 mPa·s, and the vinyl content in the vinyl silicone oil is 0.03 mmol / g to 0.39 mmol / g; The hydrogen-containing silicone oil is a combination of side-containing hydrogen-containing silicone oil and end-containing hydrogen-containing silicone oil, with a viscosity of 200 mPa·s to 2500 mPa·s and a hydrogen content of 0.2 mmol / g to 0.4 mmol / g.

5. The low-volatility thermally conductive pad according to claim 4, characterized in that, The vinyl silicone oil treated to remove volatiles is prepared according to the following method: Vinyl silicone oil was treated to remove volatiles using a molecular thin-film evaporator at 190℃~220℃ and a vacuum of 0.5Pa~5Pa for a duration of <60s. The hydrogen-containing silicone oil, after volatile matter removal treatment, is prepared according to the following method: Hydrogen-containing silicone oil was treated to remove volatiles using a molecular thin-film evaporator at 190℃~220℃ and a vacuum of 0.1Pa~5Pa for a duration of <60s.

6. A method for preparing the low-volatility thermally conductive pad according to any one of claims 1 to 5, comprising the following steps: 1) Mix the parylene-coated thermally conductive filler, the vinyl silicone oil treated to remove volatiles, the hydrogen-containing silicone oil treated to remove volatiles, the inhibitor and the catalyst to obtain the adhesive; 2) The adhesive is molded into a sheet and cured to obtain a low-volatile thermally conductive pad.

7. The preparation method according to claim 6, characterized in that, Step 1) includes the following steps: The thermally conductive filler coated with parylene, the vinyl silicone oil treated to remove volatiles, and the hydrogen-containing silicone oil treated to remove volatiles were stirred in a planetary mixer at a speed of 25 RPM to 40 RPM and a vacuum of ≤-0.09 MPa for 40 min to 90 min to obtain the first mixture. The first mixture and the inhibitor were stirred in a planetary mixer at a speed of 15 RPM to 35 RPM and a vacuum of ≤-0.09 MPa for 5 min to 15 min to obtain the second mixture; The second mixture and the catalyst were stirred in a planetary mixer at a speed of 15 RPM to 30 RPM and a vacuum of ≤-0.09 MPa for 5 min to 15 min to obtain the rubber compound.

8. The preparation method according to claim 6, characterized in that, The curing temperature is 130℃~150℃, and the time is 20min~30min.

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