Composite heat-conducting filler, high-heat-conducting silicone grease, preparation method and application thereof

Abstract

The application belongs to the technical field of heat-conducting materials, and particularly relates to a composite heat-conducting filler, a high-heat-conducting silicone grease and a preparation method and application thereof. The filler comprises spherical boron nitride, flaky boron nitride, spherical alumina and a silane coupling agent. The mass ratio of the spherical boron nitride, the flaky boron nitride and the spherical alumina is (12-15):(5-7):(2-3). The particle size of the spherical boron nitride is 36-65 mu m. The particle size of the flaky boron nitride is 7-14 mu m. The particle size of the spherical alumina is 0.8-3.3 mu m. The silane coupling agent accounts for 0.9-3.3% of the total mass of the spherical boron nitride, the flaky boron nitride and the spherical alumina. The filler has high filling property and high heat-conducting coefficient. When the filler is used in the preparation of the silicone grease, the silicone grease has excellent properties such as high heat-conducting property, low density, low viscosity and good insulation property, can quickly and effectively conduct the heat generated by the heat-dissipating components and devices, and further improves the service life of the components and devices.

Description

Technical Field

[0001] This invention belongs to the field of thermal conductive materials technology, and specifically relates to a composite thermal conductive filler, a high thermal conductivity silicone grease, its preparation method and application. Background Technology

[0002] In recent years, with the development of technology, electronic products have experienced rapid growth. As electronic products continue to evolve towards miniaturization and higher power, higher demands are being placed on their performance, especially heat dissipation. Electronic products commonly suffer from heat accumulation problems, generating a large amount of heat in a short period during use. This heat must be dissipated promptly; otherwise, its reliability and lifespan will be directly affected.

[0003] Thermal grease, as a thermally conductive material, can be used to dissipate heat from heat-generating or heat-dissipating components. It possesses excellent thermal conductivity and is commonly used in electronic products and other fields. Thermal grease can quickly and evenly transfer the heat generated by heat-generating components during operation to the heat sink, thus achieving good heat dissipation. To improve thermal conductivity, traditional thermal greases often add a large amount of filler, typically including aluminum powder and graphene. However, the amount of these fillers is limited, resulting in a still relatively low thermal conductivity. Furthermore, it leads to high viscosity, poor wettability, high density, and poor insulation, hindering the timely conduction of heat. This causes a large amount of heat to accumulate in the components, resulting in poor heat dissipation and hindering the development of miniaturized and lightweight products.

[0004] Therefore, there is an urgent need to provide a filler with high filling volume and high thermal conductivity, so that the prepared silicone grease has excellent properties such as high thermal conductivity, low density, low viscosity and good insulation, which can quickly and effectively conduct away the heat generated by heat dissipation components and improve the service life of the components. Summary of the Invention

[0005] This invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions. This invention provides a composite thermally conductive filler with high filling volume and high thermal conductivity. When used in the preparation of silicone grease, this filler gives the silicone grease excellent properties such as high thermal conductivity, low density, low viscosity, and good insulation, enabling it to quickly and effectively conduct heat generated by heat dissipation components and improve the service life of the components.

[0006] The inventive concept of this invention is as follows: By simultaneously adding spherical boron nitride with a particle size of 36-65 μm, plate-shaped boron nitride with a particle size of 7-14 μm, and spherical alumina with a particle size of 0.8-3.3 μm, the spherical fillers achieve point-to-point contact, while the plate-shaped and spherical fillers achieve surface and point contact. The combination of spherical and plate-shaped fillers generates more contact points, thus improving the thermal conductivity of the filler. Furthermore, the addition of smaller plate-shaped boron nitride and spherical alumina further strengthens the contact between the filler particles. The different particle sizes of spherical boron nitride, plate-shaped boron nitride, and spherical alumina... The combined effect of alumina and spherical boron nitride (BN), lamellar boron nitride (BN), and spherical alumina (Alumina) results in excellent filling properties and thermal conductivity. Furthermore, the mass ratio of spherical BN, lamellar BN, and spherical Alumina is (12-15):(5-7):(2-3). This ratio ensures more contact points between the fillers, leading to higher filler content and thermal conductivity. Additionally, the use of a silane coupling agent to modify the mixture of spherical BN, lamellar BN, and spherical Alumina improves the compatibility between the filler and the base adhesive. This results in a silicone grease with excellent properties such as high thermal conductivity, low density, low viscosity, and good insulation, thereby improving the lifespan and operating efficiency of components.

[0007] Therefore, a first aspect of the present invention provides a composite thermally conductive filler.

[0008] Specifically, a composite thermally conductive filler includes spherical boron nitride, plate-shaped boron nitride, spherical alumina, and a silane coupling agent;

[0009] The mass ratio of the spherical boron nitride, the plate-shaped boron nitride, and the spherical alumina is (12-15):(5-7):(2-3);

[0010] The spherical boron nitride has a particle size of 36-65 μm; the plate-shaped boron nitride has a particle size of 7-14 μm; and the spherical alumina has a particle size of 0.8-3.3 μm.

[0011] Preferably, the spherical boron nitride has a particle size of 40-60 μm; the plate-shaped boron nitride has a particle size of 8-13 μm; and the spherical alumina has a particle size of 1-3 μm.

[0012] The particle size of the flake boron nitride was obtained by dispersing the flake boron nitride in water and measuring it with a laser particle size analyzer, while the shape was obtained by measuring it with an electron scanning microscope.

[0013] Specifically, spherical boron nitride has a larger particle size, while plate-like boron nitride has a smaller particle size, and spherical alumina has a smaller particle size than plate-like boron nitride. Spherical boron nitride is effective in improving thermal conductivity, but gaps and gaps between the filler particles result in insufficient contact, thus reducing thermal conductivity. Therefore, by adding smaller plate-like boron nitride and spherical alumina, the contact between the filler particles is made closer, significantly improving thermal conductivity. Thus, the combined effect of spherical boron nitride, plate-like boron nitride, and spherical alumina of different particle sizes gives the filler good filling properties and thermal conductivity. In addition, although boron nitride has a higher thermal conductivity than alumina, when the filler particle size is 1-3μm, the particle size is too small, the oil absorption value is high and the filling amount is low, so the effect on improving the thermal conductivity is limited. At the same time, boron nitride is more expensive than alumina. Therefore, using small-particle-size alumina can reduce costs while maintaining the same thermal conductivity. Furthermore, products prepared from small-particle-size spherical alumina have lower viscosity and better flowability.

[0014] Preferably, the silane coupling agent accounts for 0.9-3.3% of the total mass of the spherical boron nitride, the plate-like boron nitride, and the spherical alumina.

[0015] More preferably, the silane coupling agent accounts for 1.0-3.0% of the total mass of the spherical boron nitride, the plate-like boron nitride, and the spherical alumina.

[0016] More preferably, the silane coupling agent accounts for 2.0% of the total mass of the spherical boron nitride, the plate-like boron nitride, and the spherical alumina.

[0017] Specifically, spherical boron nitride, flake boron nitride, and spherical alumina fillers contain hydroxyl groups on their surfaces, making them hydrophilic. When preparing silicone grease, these fillers exhibit poor compatibility with the base adhesive, resulting in high oil absorption and low filler loading, leading to a higher product viscosity. Modifying the filler with a silane coupling agent addresses this issue. The methoxy or ethoxy functional groups of the silane coupling agent hydrolyze into hydroxyl groups, which react with the hydroxyl groups on the filler surface, transforming them into hydrophobic substances. This results in improved compatibility between the modified filler and silicone oil, lower oil absorption, significantly increased filler loading, and a lower viscosity silicone grease.

[0018] Preferably, the silane coupling agent is selected from at least one of vinyltrimethoxysilane, vinyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, and hexadecyltriethoxysilane.

[0019] A second aspect of the present invention provides a method for preparing a composite thermally conductive filler.

[0020] Specifically, a method for preparing a composite thermally conductive filler includes the following steps:

[0021] (1) Mix spherical boron nitride, flake boron nitride, and spherical alumina to obtain a mixture;

[0022] (2) Add the silane coupling agent to the mixture obtained in step (1), stir and react to obtain the composite thermally conductive filler.

[0023] Preferably, in step (1), mixing is carried out by stirring; the stirring speed is 90-160 r / min, and the stirring time is 8-22 min.

[0024] More preferably, in step (1), the stirring speed is 100-150 r / min and the stirring time is 10-20 min.

[0025] Preferably, in step (2), the stirring speed is 360-650 r / min, the stirring time is 55-130 min, and the reaction temperature is 90-130℃.

[0026] More preferably, in step (2), the stirring speed is 400-600 r / min, the stirring time is 60-120 min, and the reaction temperature is 100-120℃.

[0027] Specifically, the reaction temperature should be 90-130℃. The temperature should not be too high or too low. If the reaction temperature is too low, the hydroxyl groups of the coupling agent hydrolyzed will not react sufficiently with the hydroxyl groups on the surface of the filler, and the modification effect will be weakened. If the reaction temperature is too high, the coupling agent will easily volatilize, which will also weaken the modification effect. Therefore, a reaction temperature of 90-130℃ can ensure a good modification effect of the coupling agent on the filler.

[0028] A third aspect of the present invention provides a high thermal conductivity silicone grease.

[0029] Specifically, a high thermal conductivity silicone grease includes a base adhesive and fillers.

[0030] Preferably, by weight, it includes 100 parts of base adhesive and 900-1600 parts of filler.

[0031] A further preferred embodiment, by weight, comprises 100 parts of base adhesive and 1000-1500 parts of filler.

[0032] Preferably, the base adhesive is selected from at least one of dimethyl silicone oil, phenyl silicone oil, and vinyl silicone oil.

[0033] Preferably, the viscosity of the dimethyl silicone oil is 100-2000 mPa·s; more preferably, the viscosity of the dimethyl silicone oil is 100-1000 Pa·s; and even more preferably, the viscosity of the dimethyl silicone oil is 300-500 Pa·s.

[0034] Preferably, the viscosity of the phenyl silicone oil is 100-2000 mPa·s; more preferably, the viscosity of the phenyl silicone oil is 100-1000 Pa·s; and even more preferably, the viscosity of the phenyl silicone oil is 300-500 Pa·s.

[0035] Preferably, the viscosity of the vinyl silicone oil is 100-2000 mPa·s; more preferably, the viscosity of the vinyl silicone oil is 100-1000 Pa·s; and even more preferably, the viscosity of the vinyl silicone oil is 300-500 Pa·s.

[0036] A fourth aspect of the present invention provides a method for preparing a high thermal conductivity silicone grease, comprising the following steps:

[0037] (1) Mix the base adhesive and filler to obtain a mixture;

[0038] (2) The mixture obtained in step (1) is heated and stirred under vacuum to obtain the high thermal conductivity silicone grease.

[0039] Preferably, in step (1), mixing is carried out by stirring, the stirring speed is 27-45 r / min, and the stirring time is 55-130 min.

[0040] More preferably, in step (1), the stirring speed is 30-40 r / min and the stirring time is 60-120 min.

[0041] More preferably, in step (1), the stirring speed is 35 r / min and the stirring time is 90 min.

[0042] Preferably, in step (1), dispersion is performed after stirring and mixing, and the dispersion speed is 270-440 r / min; more preferably, the dispersion speed is 300-400 r / min; and even more preferably, the dispersion speed is 350 r / min.

[0043] Preferably, in step (2), the vacuum degree of the vacuum condition is -0.08 to -0.1 MPa.

[0044] More preferably, in step (2), the vacuum degree of the vacuum condition is -0.09 to -0.1 MPa.

[0045] Preferably, in step (2), the heating temperature is 75-130°C.

[0046] More preferably, in step (2), the heating temperature is 80-120℃.

[0047] More preferably, in step (2), the heating temperature is 100°C.

[0048] Preferably, in step (2), the stirring speed is 35-65 r / min and the stirring time is 27-65 min.

[0049] More preferably, in step (2), the stirring speed is 40-60 r / min and the stirring time is 30-60 min.

[0050] More preferably, in step (2), the stirring speed is 50 r / min and the stirring time is 45 min.

[0051] Preferably, in step (2), dispersion is carried out after stirring, and the dispersion speed is 180-330 r / min.

[0052] More preferably, the dispersion speed is 200-300 r / min.

[0053] More preferably, the dispersion speed is 250 r / min.

[0054] Preferably, in step (2), after dispersion, the temperature is lowered to below 40°C to obtain the high thermal conductivity silicone grease.

[0055] The fifth aspect of the present invention provides the application of composite thermally conductive fillers and / or high thermal conductivity silicone grease in the field of electronics and electrical appliances.

[0056] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0057] (1) By simultaneously adding spherical boron nitride, flake boron nitride, and spherical alumina, the spherical fillers make point-to-point contact with each other, and the flake and spherical fillers make surface and point contact with each other. The combination of spherical and flake fillers can generate more contact points and improve the thermal conductivity of the fillers. At the same time, the combination of spherical boron nitride, flake boron nitride, and spherical alumina in a certain addition ratio results in a high filler content and a high thermal conductivity.

[0058] (2) This invention uses fillers of different particle sizes. The spherical boron nitride particles are larger, the plate-shaped boron nitride particles are smaller, and the spherical alumina particles are smaller than the plate-shaped boron nitride particles. By using fillers of different particle sizes in combination, the contact between the filler particles is made closer, improving the filler's filling capacity and thermal conductivity, thereby giving the prepared silicone grease excellent properties such as high thermal conductivity, low density, low viscosity, and good insulation.

[0059] (3) The present invention uses a silane coupling agent to modify the filler after mixing spherical boron nitride, plate boron nitride and spherical alumina, so that it has hydrophobicity, improves the compatibility between the filler and the base adhesive, and thus makes the prepared silicone grease have excellent properties of high thermal conductivity, low density, low viscosity and good insulation, which significantly improves the service life and working efficiency of the components. Detailed Implementation

[0060] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0061] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0062] Example 1

[0063] A composite thermally conductive filler comprises: spherical boron nitride with a particle size of 45 μm, plate-shaped boron nitride with a particle size of 10 μm, spherical alumina with a particle size of 2 μm, and vinyltrimethoxysilane; wherein the mass ratio of spherical boron nitride, plate-shaped boron nitride, and spherical alumina is 12:5:2, and vinyltrimethoxysilane accounts for 2% of the total mass of spherical boron nitride, plate-shaped boron nitride, and spherical alumina.

[0064] A method for preparing a composite thermally conductive filler includes the following steps:

[0065] (1) Add spherical boron nitride with a particle size of 45 μm, plate-shaped boron nitride with a particle size of 10 μm, and spherical alumina with a particle size of 2 μm to a high-speed mixer at a mass ratio of 12:5:2, mix and stir at a speed of 120 r / min for 15 min to obtain a mixture;

[0066] (2) Add 2% of the total mass of spherical boron nitride, plate boron nitride and spherical alumina of vinyltrimethoxysilane to the mixture obtained in step (1), stir at a stirring speed of 500 r / min for 90 min, and react at a temperature of 105 °C to obtain the product.

[0067] A high thermal conductivity silicone grease comprises 100 parts of dimethyl silicone oil and 1200 parts of composite thermally conductive filler.

[0068] A method for preparing a high thermal conductivity silicone grease includes the following steps:

[0069] (1) According to the weight parts, add dimethyl silicone oil and composite thermally conductive filler into the planetary machine, stir and disperse. The stirring speed is 35 r / min, the stirring time is 90 min, and the dispersion speed is 350 r / min to obtain a mixture;

[0070] (2) The mixture obtained in step (1) is heated, stirred and dispersed under a vacuum of -0.1 MPa. The heating temperature is 100℃, the stirring speed is 50 r / min, the stirring time is 45 min, the dispersion speed is 250 r / min, and the temperature is lowered to 35℃ to obtain the mixture.

[0071] Example 2

[0072] A composite thermally conductive filler comprises: spherical boron nitride with a particle size of 60 μm, plate-like boron nitride with a particle size of 12 μm, spherical alumina with a particle size of 1 μm, and vinyltriethoxysilane; wherein the mass ratio of spherical boron nitride, plate-like boron nitride, and spherical alumina is 15:7:2, and vinyltriethoxysilane accounts for 2.5% of the total mass of spherical boron nitride, plate-like boron nitride, and spherical alumina.

[0073] A method for preparing a composite thermally conductive filler includes the following steps:

[0074] (1) Add spherical boron nitride with a particle size of 60 μm, plate-shaped boron nitride with a particle size of 12 μm, and spherical alumina with a particle size of 1 μm to a high-speed mixer at a mass ratio of 15:7:2, mix and stir at a speed of 100 r / min for 20 min to obtain a mixture;

[0075] (2) Add 2.5% of the total mass of spherical boron nitride, plate boron nitride and spherical alumina to the mixture obtained in step (1), stir at a stirring speed of 450 r / min for 100 min, and react at a temperature of 110 °C to obtain the product.

[0076] A high thermal conductivity silicone grease comprises 100 parts of dimethyl silicone oil and 1500 parts of composite thermally conductive filler.

[0077] A method for preparing a high thermal conductivity silicone grease includes the following steps:

[0078] (1) According to the weight parts, add dimethyl silicone oil and composite thermally conductive filler into the planetary machine, stir and disperse. The stirring speed is 30 r / min, the stirring time is 110 min, and the dispersion speed is 380 r / min to obtain a mixture;

[0079] (2) The mixture obtained in step (1) is heated, stirred and dispersed under a vacuum of -0.1 MPa. The heating temperature is 110℃, the stirring speed is 55 r / min, the stirring time is 45 min, the dispersion speed is 220 r / min, and the temperature is lowered to 30℃ to obtain the mixture.

[0080] Example 3

[0081] A composite thermally conductive filler comprises: spherical boron nitride with a particle size of 60 μm, plate-like boron nitride with a particle size of 10 μm, spherical alumina with a particle size of 2 μm, and dodecyltriethoxysilane; wherein the mass ratio of spherical boron nitride, plate-like boron nitride, and spherical alumina is 14:6:3, and dodecyltriethoxysilane accounts for 1.5% of the total mass of spherical boron nitride, plate-like boron nitride, and spherical alumina.

[0082] A method for preparing a composite thermally conductive filler includes the following steps:

[0083] (1) Add spherical boron nitride with a particle size of 60 μm, plate-shaped boron nitride with a particle size of 10 μm, and spherical alumina with a particle size of 2 μm to a high-speed mixer at a mass ratio of 14:6:3. Mix and stir at a speed of 140 r / min for 15 min to obtain a mixture.

[0084] (2) Add 1.5% of the total mass of spherical boron nitride, plate boron nitride and spherical alumina to the mixture obtained in step (1), stir at a stirring speed of 550 r / min for 80 min, and react at a temperature of 115 °C to obtain the product.

[0085] A high thermal conductivity silicone grease comprises 100 parts of dimethyl silicone oil and 1300 parts of composite thermally conductive filler.

[0086] A method for preparing a high thermal conductivity silicone grease includes the following steps:

[0087] (1) According to the weight parts, add dimethyl silicone oil and composite thermally conductive filler into the planetary machine, stir and disperse. The stirring speed is 38 r / min, the stirring time is 80 min, and the dispersion speed is 320 r / min to obtain a mixture;

[0088] (2) The mixture obtained in step (1) is heated, stirred and dispersed under a vacuum of -0.1 MPa. The heating temperature is 90°C, the stirring speed is 45 r / min, the stirring time is 55 min, the dispersion speed is 280 r / min, and the temperature is lowered to 37°C to obtain the mixture.

[0089] Comparative Example 1

[0090] The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 omits spherical alumina when preparing the composite thermally conductive filler; otherwise, it is the same as Example 1.

[0091] Comparative Example 2

[0092] The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 omits the sheet-like boron nitride when preparing the composite thermally conductive filler; otherwise, it is the same as Example 1.

[0093] Comparative Example 3

[0094] The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 omitted spherical boron nitride when preparing the composite thermally conductive filler; otherwise, it is the same as Example 1.

[0095] Comparative Example 4

[0096] The only difference between Comparative Example 4 and Example 1 is that Comparative Example 4 uses an equal amount of spherical alumina with the same particle size to replace spherical boron nitride, while the rest is the same as Example 1.

[0097] Comparative Example 5

[0098] The only difference between Comparative Example 5 and Example 1 is that Comparative Example 5 uses an equal amount of flake alumina with the same particle size to replace flake boron nitride, while the rest is the same as Example 1.

[0099] Comparative Example 6

[0100] The only difference between Comparative Example 6 and Example 1 is that Comparative Example 6 uses an equal amount of flake boron nitride with the same particle size to replace spherical alumina, while the rest is the same as Example 1.

[0101] Comparative Example 7

[0102] The only difference between Comparative Example 7 and Example 1 is that in Comparative Example 7, the mass ratio of 45 μm spherical boron nitride: 10 μm flake boron nitride: 2 μm spherical alumina is 6:9:5, and the rest is the same as in Example 1.

[0103] Performance testing:

[0104] The high thermal conductivity silicone greases prepared in Examples 1-3 and Comparative Examples 1-7 were tested, and the test items are as follows.

[0105] Viscosity: Tested according to GB / T 2794-2013.

[0106] Density: Tested according to GB / T 13354-1992.

[0107] Thermal conductivity: tested according to ISO / DIS 22007.

[0108] Surface insulation resistance: tested according to IPC-TM-650.

[0109] The performance test results of the high thermal conductivity silicone greases in Examples 1-3 and Comparative Examples 1-7 are shown in Table 1.

[0110] Table 1

[0111]

[0112] As shown in Table 1, the silicone greases of Examples 1-3 of the present invention have excellent properties such as low density, low viscosity, high thermal conductivity and good insulation. They can quickly and effectively conduct away the heat generated by heat dissipation components, thereby improving the service life and working efficiency of the components.

[0113] Compared to Example 1, Comparative Examples 1-3 omitted spherical alumina, flake boron nitride, and spherical boron nitride, respectively, resulting in silicone greases prepared in Comparative Examples 1-3 having generally inferior performance compared to Example 1, particularly in viscosity, thermal conductivity, and insulation properties. Comparative Examples 4-6, by replacing the spherical boron nitride, flake boron nitride, and spherical alumina of equal amounts and particle sizes with those of Example 1, resulted in silicone greases prepared in Comparative Examples 4-6 having generally inferior performance compared to Example 1 in terms of density, viscosity, thermal conductivity, and insulation properties. The explanation is that only by simultaneously adding spherical boron nitride, flake boron nitride, and spherical alumina can a low-density, low-viscosity, high thermal conductivity, and good insulation silicone grease be obtained. This is because the spherical fillers make point-to-point contact with each other, while the flake-shaped fillers make surface and point contact with the spherical fillers. The combination of spherical and flake fillers can generate more contact points, improve the thermal conductivity and filling capacity of the fillers, and thus enable the silicone grease to meet the requirements of low density, low viscosity, high thermal conductivity, and good insulation, which can effectively conduct away the heat generated by heat dissipation components.

[0114] Compared to Example 1, in Comparative Example 7, the mass ratio of 45 μm spherical boron nitride, 10 μm flake boron nitride, and 2 μm spherical alumina was 6:9:5. This mass ratio was outside the range of (12-15):(5-7):(2-3), resulting in the silicone grease of Comparative Example 7 exhibiting significantly inferior performance in terms of density, viscosity, thermal conductivity, and insulation compared to Example 1. This demonstrates that by controlling the mass ratio of spherical boron nitride, flake boron nitride, and spherical alumina within the range of (12-15):(5-7):(2-3), the silicone grease prepared in this invention possesses low density, low viscosity, high thermal conductivity, and good insulation.

[0115] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A packing material, characterized in that, Including spherical boron nitride, plate-shaped boron nitride, spherical alumina, and silane coupling agents; The mass ratio of the spherical boron nitride, the plate-shaped boron nitride, and the spherical alumina is (12-15):(5-7):(2-3); The spherical boron nitride has a particle size of 40-60 μm; the plate-shaped boron nitride has a particle size of 8-13 μm; and the spherical alumina has a particle size of 1-3 μm.

2. The packing material according to claim 1, characterized in that, The silane coupling agent accounts for 0.9-3.3% of the total mass of the spherical boron nitride, the plate-like boron nitride, and the spherical alumina.

3. The packing material according to claim 2, characterized in that, The silane coupling agent accounts for 1.0-3.0% of the total mass of the spherical boron nitride, the plate-like boron nitride, and the spherical alumina.

4. The method for preparing the filler according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Mix spherical boron nitride, flake boron nitride, and spherical alumina to obtain a mixture; (2) Add the silane coupling agent to the mixture obtained in step (1), stir and react to obtain the filler.

5. The preparation method according to claim 4, characterized in that, In step (1), the mixture is stirred at a speed of 90-160 r / min for 8-22 min; in step (2), the stirring speed is 360-650 r / min for 55-130 min; and the reaction temperature is 90-130℃.

6. A silicone grease, characterized in that, It includes the base adhesive and the filler as described in any one of claims 1-3.

7. The silicone grease according to claim 6, characterized in that, By weight, it includes 100 parts base adhesive and 900-1600 parts filler.

8. The method for preparing silicone grease according to any one of claims 6-7, characterized in that, Includes the following steps: (1) Mix the base adhesive and filler to obtain a mixture; (2) The mixture obtained in step (1) is heated and stirred under vacuum to obtain the silicone grease.

9. The application of the filler according to any one of claims 1-3 and / or the silicone grease according to any one of claims 6-7 in the field of electronics and electrical appliances.

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