An insulating, highly thermally conductive flexible silicone sheet and its preparation method

Abstract

This invention provides an insulating, highly thermally conductive flexible silicone sheet and its preparation method. The silicone sheet, by weight, comprises the following components: 1-5 parts of an organoboronide; 1-5 parts of a polysilazane compound; 1-5 parts of hydrogen-containing silicone oil; 5-10 parts of dimethyl silicone oil; 20-30 parts of vinyl silicone oil; 50-80 parts of a thermally conductive filler; and 0.01-0.1 parts of a platinum-based catalyst. The thermally conductive filler comprises thermally conductive filler 1 and thermally conductive filler 2. Thermally conductive filler 1 is selected from any one of boron nitride, alumina, and magnesium oxide, and thermally conductive filler 2 is selected from any one of graphene, silicon carbide, and silicon nitride. The flexible silicone sheet of this invention achieves comprehensive optimization of high thermal conductivity, excellent electrical insulation, thermomechanical stability, and surface flatness.

Description

Technical Field

[0001] This invention relates to the field of thermal conductive materials technology, and in particular to an insulating, highly thermally conductive flexible silicone sheet and its preparation method. Background Technology

[0002] In electronic devices, the development of miniaturization, high power, and functional integration has placed higher demands on heat dissipation materials. Flexible thermally conductive silicone sheets, due to their excellent flexibility, conformability, and thermal conductivity, are widely used in the thermal management of electronic devices. However, existing technologies still have the following problems that urgently need to be solved: On the one hand, to improve thermal conductivity, existing technologies often introduce high thermal conductivity fillers such as silicon carbide, silicon nitride, and graphene. However, some of these fillers are conductive, and in a high-filling state, they are prone to forming local electrical pathways, leading to an increase in the dielectric constant and a decrease in electrical insulation, thereby affecting the safety and stability of electronic devices. Even when using insulating fillers, when the filler ratio is too high or the dispersion is uneven, it can easily cause enhanced interfacial polarization, adversely affecting the reliability of electronic devices. On the other hand, to obtain higher thermal conductivity, an increase in the filler ratio inevitably leads to a significant increase in system viscosity, resulting in difficulties in mixing and residual bubbles. Microbubbles inside the finished product not only become thermal resistance points, reducing the actual thermal conductivity of the material, but are also prone to expansion and cracking under high-temperature operating environments. In addition, high viscosity reduces the leveling and surface adhesion of the sheet, further affecting the fit of flexible silicone sheets in electronic devices.

[0003] Therefore, how to improve thermal conductivity while taking into account the electrical insulation, processability, and structural integrity of the final product remains a pressing issue in the current technology of flexible thermal conductive silicone pads. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes an insulating, highly thermally conductive flexible silicone sheet and its preparation method. The flexible silicone sheet prepared by this invention, while ensuring high thermal conductivity, also exhibits strong insulation, a smooth surface, and low bubble content, facilitating casting and bonding. It can be widely used for heat dissipation in high-density electronic packaging, LED devices, 5G communication modules, and other integrated electronic devices, demonstrating strong practical value and broad industrial prospects.

[0005] This invention provides an insulating and highly thermally conductive flexible silicone sheet, comprising the following components by weight:

[0006] 1 to 5 parts of organoboronide, such as 1, 2, 3, 4, or 5 parts, preferably 2 to 3 parts;

[0007] 1 to 5 parts of polysilazane compound, such as 1, 2, 3, 4, or 5 parts, preferably 2 to 3 parts;

[0008] 1 to 5 parts of hydrogen-containing silicone oil, such as 1, 2, 3, 4, or 5 parts, preferably 2 to 3 parts;

[0009] 5-10 parts of dimethyl silicone oil, such as 5, 6, 7, 8, 9, or 10 parts, preferably 6-8 parts;

[0010] 20-30 parts of vinyl silicone oil, such as 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 parts, preferably 23-28 parts;

[0011] The thermally conductive filler is 50-80 parts, such as 50, 55, 60, 65, 70, 75, or 80 parts, preferably 60-70 parts;

[0012] The platinum-based catalyst is used in amounts of 0.01 to 0.1 parts, such as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1 parts, preferably 0.03 to 0.06 parts;

[0013] The thermally conductive filler includes thermally conductive filler 1 and thermally conductive filler 2. The thermally conductive filler 1 is selected from any one of boron nitride, aluminum oxide, and magnesium oxide, and the thermally conductive filler 2 is selected from any one of graphene, silicon carbide, and silicon nitride.

[0014] In this invention, the combination of organoborides and polysilazane compounds optimizes the network structure of the silicone matrix. Organoborides can form complex structures with siloxane groups, increasing the crosslinking density of the system and enhancing electrical insulation and thermomechanical stability; polysilazane compounds possess high thermal stability and a flexible framework, improving the material's toughness and surface leveling, while also enhancing the interfacial wettability between the filler and the matrix, reducing microbubbles and interfacial thermal resistance.

[0015] Preferably, the average particle size of the thermally conductive filler 1 is 1~10 μm, and the average particle size of the thermally conductive filler 2 is 1~2 nm.

[0016] Preferably, if the thermally conductive filler 2 is graphene, its specific surface area is 200~800 m² / g; if it is silicon carbide nanowire, its aspect ratio is 50~200.

[0017] In some embodiments, the organoboronide is selected from any one of trialkoxyborane, trihydroxyborane, or organoboroesters.

[0018] In some embodiments, the mass ratio of the organoboride to the polysilazane compound is (0.8~2):1, such as 0.8:1, 0.9:1, 1:1, 1.2:1, 1.5:1, 2:1, etc., preferably (0.8~1.5):1, more preferably 1:1.

[0019] In this invention, the mass ratio of organoborides to polysilazane compounds is 0.8~1.5:1, which can achieve a synergistic effect between the two, ensuring the flexibility and toughness of the matrix, improving the thermal stability of the material and the wettability of the filler interface, reducing the interfacial thermal resistance, and reducing microbubbles.

[0020] In some embodiments, the mass ratio of the thermally conductive filler 1 to the thermally conductive filler 2 is (3~9):1, such as 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, etc., preferably (4~6):1; this can ensure the overall thermal conductivity of the material while also taking into account the electrical insulation.

[0021] In some embodiments, the platinum-based catalyst is selected from any one of chloroplatinic acid, platinum-vinylsiloxane complex, and platinum-dimethylsiloxane complex; used to catalyze hydrosilylation reactions.

[0022] Preferably, the platinum-based catalyst contains 1000~5000 ppm of platinum. Too low a concentration of platinum-based catalyst can lead to insufficient catalysis, while too high a concentration can reduce insulation and increase costs.

[0023] Preferably, the platinum-based catalyst is a Karstedt catalyst.

[0024] In some embodiments, the vinyl content in the vinyl silicone oil is 0.1~2wt%, such as 0.1, 0.5, 1, 1.5, 2wt%, etc., preferably 0.1~0.5wt%, more preferably 0.1~0.35wt%; within this range, it ensures sufficient crosslinking density to improve the mechanical properties of the material, while avoiding excessive viscosity and poor flowability of the system due to excessive crosslinking.

[0025] The present invention also provides a method for preparing the flexible silicone sheet, comprising the following steps:

[0026] (1) Add vinyl silicone oil to the thermally conductive filler, stir and disperse, then add dimethyl silicone oil, hydrogen-containing silicone oil, polysilazane compound and organoboride in sequence, stir evenly under vacuum to obtain mixture 1;

[0027] (2) Add a platinum-based catalyst to the mixture 1 at 25~50℃ and stir thoroughly to obtain mixture 2;

[0028] (3) Cast mixture 2 into a sheet and cure it in the following two steps:

[0029] In the first stage, the material is pre-cured at 80~100℃ for 0.5~1 h. In the second stage, the material is heated to 130~150℃ and then cured for 1~2 h to obtain the flexible silicone sheet.

[0030] In this invention, the stepwise curing process first pre-cures at low temperature to lock the dispersion state of the filler, and then fully cures at high temperature to form a stable cross-linked network, so that the thermally conductive filler is evenly distributed in the matrix, ensuring high thermal conductivity, while maintaining the surface smoothness and thermomechanical stability of the material.

[0031] In some embodiments, the vacuum condition is -0.06 to -0.09 MPa; this can effectively remove air and microbubbles during the mixing process, reduce the internal porosity of the material, thereby reducing interfacial thermal resistance, improving thermal conductivity, and ensuring the smoothness of the material surface and the density of the structure after curing.

[0032] In some embodiments, in step (2), the stirring speed is 500~1500 rpm and the time is 0.5~1.5 h; this can not only fully disperse the thermally conductive filler and compound components to ensure the homogeneity of the matrix, but also avoid generating a large number of shear bubbles or damaging the structure of the filler due to excessive stirring, thus achieving good flowability and surface smoothness during casting.

[0033] In some embodiments, in step (3), the heating rate between the first stage and the second stage is 2~5℃ / min; the control between the first stage and the second stage of curing can slowly release the residual stress inside the system, so that the network structure formed by pre-curing can be stably transitioned, avoiding cracking, warping or bubble expansion of the material during high-temperature curing, while ensuring that the thermally conductive filler is evenly distributed in the matrix, improving thermal conductivity and thermomechanical stability.

[0034] The materials, components, additives, and process conditions described in this invention can be appropriately varied within a certain range without departing from the scope of protection of this invention. For example, the type, particle size, and dispersion method of the thermally conductive filler, the content and ratio of silicone oil and organoborides, and parameters such as curing temperature, time, and heating rate can all be adjusted according to actual production needs.

[0035] In summary, compared with the prior art, the present invention achieves the following technical effects:

[0036] (1) The flexible silicone sheet of the present invention has excellent electrical insulation while maintaining high thermal conductivity.

[0037] (2) The flexible silicone sheet of the present invention introduces organic borosilicates and polysilazane compounds and combines them with a step-by-step curing process, so that the flexible silicone sheet maintains high insulation while reducing the linear thermal expansion coefficient, effectively avoiding expansion and cracking under high temperature use, significantly improving thermomechanical stability, and thus extending the service life of electronic devices.

[0038] (3) The flexible silicone sheet of the present invention has low surface roughness and low bubble content, which ensures the leveling and adhesion of the flexible silicone sheet, and improves the reliability of the sheet manufacturing process and the quality of the finished product. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a flowchart illustrating the preparation method of the insulating, highly thermally conductive flexible silicone sheet of the present invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0042] In this invention, the components used are not limited to specific sources or manufacturers, nor are they limited to specific synthetic routes, raw material sources, or purification methods. Any corresponding materials that can be prepared or obtained by those skilled in the art through conventional methods can be used in the implementation of this invention without departing from the scope of protection of this invention. The materials of this invention can be commercially available, laboratory-made, or other equivalent sources, all of which fall within the scope of this invention.

[0043] In the description of this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0044] It should be understood that the weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope of this invention. Specifically, the weights mentioned in the embodiments of this invention can be well-known mass units in the chemical industry, such as μg, mg, g, and kg. Furthermore, unless the context explicitly uses it otherwise, the singular form of a word should be understood as including the plural form of the word. The terms "comprising" or "having" are intended to specify the presence of a feature, quantity, step, operation, element, part, or combination thereof, but are not intended to exclude the presence or possible addition of one or more other features, quantities, steps, operations, elements, parts, or combinations thereof.

[0045] A component or a combination thereof.

[0046] I. The sources of raw materials and equipment used in the embodiments of this invention are as follows:

[0047] Organoboronides: Trimethoxyboroxane, 089153, Hubei Nuona Technology Co., Ltd.

[0048] Polysilazane #1: Polysilazane, PB36769, Wengjiang Reagent.

[0049] Polysilazane #2: Vinyl polysilazane, TC-P11, Hangzhou Qingci New Materials.

[0050] Hydrogen-containing silicone oil: Hubei Dongcao Chemical Technology Co., Ltd., the same substance was used in parallel experiments.

[0051] Dimethyl silicone oil: PMX50-12500CS, Shenzhen Chonghuaxin Technology Co., Ltd.

[0052] Vinyl silicone oil #1: Vinyl content 0.15%~0.35%, CR-F23A, Wuhan Kewode.

[0053] Vinyl silicone oil #2: Vinyl content 1.45%, RH-Vi70E, Ningbo Runhe High-tech Materials.

[0054] Thermally conductive filler #1: Boron nitride and graphene are mixed in a 6:1 ratio.

[0055] Thermally conductive filler #2: Alumina and silicon carbide are mixed in a 3:1 ratio.

[0056] Thermally conductive filler #3: Magnesium oxide and silicon nitride are mixed in a 9:1 ratio.

[0057] Platinum-based catalysts: Karstedt catalyst, Merck, the same substance was used in parallel experiments.

[0058] Vacuum mixer: IKA RW20 Digital, impeller diameter 10 mm.

[0059] Constant temperature heating and stirring equipment: IKA C-MAG HS 7.

[0060] Casting machine: Labcast 300, squeegee width 300 mm, adjustable gap 0.1~2 mm, casting speed 5~10 mm / s.

[0061] Drying / curing oven: Memmert UF110 oven, temperature control accuracy ±1℃.

[0062] Vacuum pump: Edwards RV3.

[0063] II. The preparation methods of the insulating, highly thermally conductive flexible silicone sheets of Examples 1-8 and Comparative Examples 1-5 of the present invention are as follows:

[0064] (1) Add the thermally conductive filler to the vacuum mixer, add vinyl silicone oil, and stir at 1000 rpm for 30 minutes under vacuum conditions (vacuum degree about -0.08 MPa) to fully wet and disperse the powder evenly.

[0065] (2) Add dimethyl silicone oil, hydrogen-containing silicone oil, polysilazane compound and organoboronide in sequence, and continue stirring under vacuum for 1 hour.

[0066] (3) Transfer to a constant temperature heating stirrer, heat to 40°C, add platinum catalyst, and stir for 1 hour at 1000 rpm.

[0067] (4) Pour into the laboratory flat plate casting device, set the scraper gap to 1 mm, and cast evenly into a sheet.

[0068] (5) Place the cast film in an oven for step-by-step curing: the first stage is pre-curing at 80°C for 0.8 hours; then the second stage is curing at 140°C at a heating rate of about 3°C / min for 1.5 hours. After curing, remove the flexible silicone sheet and allow it to cool naturally to room temperature to obtain the final product.

[0069] Table 1. Technical solutions for each embodiment (unit: parts by weight)

[0070] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 organoborides 3 3 3 3 1 5 3 4 Polysilazane #1 3 3 3 1 5 3 2 Polysilazane #2 3 Hydrogen-containing silicone oil 3 3 3 3 1 5 3 3 Dimethyl silicone oil 8 8 8 8 5 10 8 8 Vinyl silicone oil #1 25 25 25 25 20 30 25 Vinyl silicone oil #2 25 Thermally conductive filler #1 65 65 50 80 65 65 Thermally conductive filler #2 65 Thermally conductive filler #3 65 Platinum catalysts 0.05 0.05 0.05 0.05 0.01 0.1 0.05 0.05

[0071] Table 2 Technical solutions for each comparative example (unit: parts by weight)

[0072] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 organoborides 3 10 3 3 Polysilazane #1 3 3 10 3 Hydrogen-containing silicone oil 3 3 3 3 3 Dimethyl silicone oil 8 8 8 8 8 Vinyl silicone oil #1 25 25 25 25 25 Thermally conductive filler #1 65 65 65 65 100 Platinum catalysts 0.05 0.05 0.05 0.05 0.05

[0073] Comparative Example 6: The components are the same as those in Example 1, but the preparation method is different: it is cured once in an oven at a temperature of 140°C for 2.3 h.

[0074] III. Performance Testing Methods

[0075] (1) Thermal conductivity test

[0076] Thermal conductivity testing was conducted using a DRL thermal conductivity meter, following the ASTM D5470-2017 standard. The specific steps were as follows: The prepared flexible silicone sheet was cut into test samples measuring 20 mm × 20 mm × 3 mm, ensuring both sides of the sample were flat and free of bubbles or impurities. The sample was placed between the upper and lower measuring modules of the DRL thermal conductivity meter and clamped under constant pressure (0.5 MPa). The test temperature was set to 25℃, and the relative humidity to 50%. After the temperature stabilized, the heat flux density and temperature difference data were recorded, and the steady-state thermal conductivity of the sample was calculated. Each group of samples was tested in triplicate, and the average value was taken as the final test result.

[0077] (2) Volume resistivity test

[0078] Tests were conducted according to ASTM D257-14 (2019) standard. Flexible silicone sheets were cut into 50 mm × 50 mm × 3 mm test samples, placed on a resistivity testing instrument, and a DC voltage of 500 V was applied for 60 s under ambient conditions of 23°C and 50% RH. Current values ​​were recorded during the measurement, and volume resistivity was calculated. Each sample was tested in triplicate, and the average value was taken as the final result.

[0079] (3) Linear thermal expansion coefficient (CTE) test

[0080] The measurements were performed using a TMA (Thermomechanical Analyzer, model TAInstruments Q400) according to ASTM E831-14 (2019) standard. Flexible silicone sheets were cut into 10 mm × 5 mm × 3 mm samples, and measurements were taken using indenter mode. The samples were heated within a temperature range of 25–200 °C at a heating rate of 5 °C / min. Length changes were recorded during the test, and the linear coefficient of thermal expansion was calculated. Each sample was tested in triplicate, and the average value was taken as the final result.

[0081] (4) Surface roughness test

[0082] To evaluate the surface flatness of the flexible silicone sheet, a profilometer (Mitutoyo SJ-210) was used for measurement. The test procedure was as follows: the sample was cut into small pieces of 20 mm × 20 mm × 3 mm, placed on a sample holder, and a probe was used to scan three different straight lines along the sample surface at a scanning speed of 0.5 mm / s and a measurement range of 5 mm. The change in surface profile height was measured and recorded, and the average arithmetic roughness was calculated. R a Each group of samples was tested in parallel three times, and the average value was taken as the final result.

[0083] The test results are shown in Table 3:

[0084] Table 3 Performance Test Results

[0085] Thermal conductivity (W / m·K) Volume resistivity (Ω·cm) <![CDATA[CTE(×10 -6 / ℃)]]> <![CDATA[Roughness R a (μm)]]> Example 1 26 <![CDATA[1.2×10 15 ]]> 120 0.52 Example 2 24 <![CDATA[1.0×10 15 ]]> 132 0.61 Example 3 25 <![CDATA[9.5×10 14 ]]> 126 0.76 Example 4 25 <![CDATA[5.0×10 14 ]]> 121 0.63 Example 5 20 <![CDATA[3.3×10 14 ]]> 136 0.66 Example 6 22 <![CDATA[4.7×10 14 ]]> 133 0.71 Example 7 23 <![CDATA[1.0×10 15 ]]> 120 0.84 Example 8 23 <![CDATA[8.4×10 14 ]]> 126 0.53 Comparative Example 1 20 <![CDATA[1.2×10 11 ]]> 150 0.93 Comparative Example 2 21 <![CDATA[7.5×10 11 ]]> 154 1.36 Comparative Example 3 16 <![CDATA[8.1×10 14 ]]> 143 1.28 Comparative Example 4 14 <![CDATA[6.6×10 14 ]]> 136 1.53 Comparative Example 5 23 <![CDATA[1.2×10 10 ]]> 160 1.44 Comparative Example 6 24 <![CDATA[2.2×10 12 ]]> 154 1.63

[0086] The thermal conductivity, volume resistivity, and coefficient of linear thermal expansion (CTE) of the flexible silicone sheets of Examples 1-8 and Comparative Examples 1-6 of the present invention were tested. The results show that the thermal conductivity of the embodiments of the present invention can be maintained above 20 W / m·K, reaching a maximum of 26 W / m·K, and the volume resistivity is maintained at 3.3 × 10⁻⁶ W / m·K. 14 The material retains good electrical insulation properties even above Ω·cm; the CTE test result is 144×10 -6 The temperature is below / ℃, which is lower than that of the comparative sample, indicating that the silicone sheet of the present invention has better dimensional stability during the heating process and can effectively reduce the interfacial stress caused by thermal expansion.

[0087] Compared to Example 1, Comparative Examples 1 and 2 lacked organoborides and polysilazane compounds, respectively, resulting in reduced electrical insulation performance of the silicone sheets and increased linear thermal expansion coefficient, leading to decreased thermomechanical stability. Comparative Examples 3 and 4 used excessive amounts of organoborides and polysilazane compounds, improving electrical insulation but significantly reducing thermal conductivity, failing to achieve a balance between thermal conductivity and insulation. Comparative Example 5 had an excessively high proportion of thermally conductive filler; while the material's thermal conductivity improved somewhat, local filler aggregation formed conductive pathways, reducing electrical insulation. Comparative Example 6 did not undergo secondary curing, resulting in significant dimensional changes in the silicone sheet at high temperatures and insufficient thermomechanical stability. The flexible silicone sheets of the embodiments of the present invention have a smooth surface and few microbubbles. In contrast, the comparative examples, due to uneven filler dispersion or lack of secondary curing, exhibited micro-protrusions, and their surface smoothness and internal bubble control were inferior to the embodiments.

[0088] Therefore, it can be seen that by rationally compounding organoborides and polysilazane compounds, optimizing the amount of thermally conductive fillers, and adopting a stepwise curing process, this invention can maintain high thermal conductivity while taking into account good electrical insulation and thermomechanical stability, fully demonstrating the synergistic innovative advantages of the material combination and preparation method of this invention.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An insulating high thermal conductive flexible silicone sheet, characterized by, Based on parts by weight, it comprises the following components: 1-5 parts of organoboronide; 1-5 parts of polysilazane compound; 1-5 parts of hydrogen-containing silicone oil; 5-10 parts of dimethyl silicone oil; 20-30 parts of vinyl silicone oil; 50-80 parts of thermally conductive filler; 0.01~0.1 parts of platinum-based catalyst; The thermally conductive filler includes thermally conductive filler 1 and thermally conductive filler 2. The thermally conductive filler 1 is selected from any one of boron nitride, aluminum oxide, and magnesium oxide, and the thermally conductive filler 2 is selected from any one of graphene, silicon carbide, and silicon nitride. The organoboronide is selected from either trialkoxyborane or trihydroxyborane; The mass ratio of the organoboronide to the polysilazane compound is (0.8~1.5):1; The method for preparing the flexible silicone sheet includes the following steps: (1) Add vinyl silicone oil to the thermally conductive filler, stir and disperse, then add dimethyl silicone oil, hydrogen-containing silicone oil, polysilazane compound and organoboride in sequence, stir evenly under vacuum to obtain mixture 1; (2) Add a platinum-based catalyst to the mixture 1 at 25~50℃ and stir thoroughly to obtain mixture 2; (3) Cast mixture 2 into a sheet and cure it in the following two steps: In the first stage, the material is pre-cured at 80~100℃ for 0.5~1 h. In the second stage, the material is heated to 130~150℃ and then cured for 1~2 h to obtain the flexible silicone sheet.

2. The flexible silicone sheet according to claim 1, characterized in that, The mass ratio of thermally conductive filler 1 to thermally conductive filler 2 is (3~9):

1.

3. The flexible silicone sheet according to claim 1, characterized in that, The platinum-based catalyst is selected from any one of chloroplatinic acid, platinum-vinylsiloxane complex, and platinum-dimethylsiloxane complex.

4. The flexible silicone sheet according to claim 1, characterized in that, The vinyl content in the vinyl silicone oil is 0.1~2wt%.

5. The flexible silicone sheet according to claim 1, characterized in that, Under the specified vacuum conditions, the vacuum level is -0.06 to -0.09 MPa.

6. The flexible silicone sheet according to claim 1, characterized in that, In step (2), the stirring speed is 500~1500 rpm and the time is 0.5~1.5 h.

7. The flexible silicone sheet according to claim 1, characterized in that, In step (3), the heating rate between the first stage and the second stage is 2~5℃ / min.

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