Boron nitride composite microsheet and preparation method thereof, and heat-conducting silicone gel and preparation method thereof

Abstract

The application discloses a boron nitride composite flake and a preparation method thereof. The boron nitride composite flake comprises 40-70% of boron nitride powder, 10-40% of polysiloxane resin, 3-15% of ceramic powder filler, 1-8% of metal powder, 0.1-1% of wetting agent and 0.5-3% of curing agent in percentage by mass. The application further provides a heat-conducting silicone gel and a preparation method thereof. The heat-conducting silicone gel comprises 1-5% of vinyl silicone oil, 5-10% of hydrogen-containing silicone oil, 0.05-0.3% of a catalyst, 50-80% of the boron nitride composite flake and 1-30% of ceramic powder filler in percentage by mass. The boron nitride composite flake has a low oil absorption value, and the prepared heat-conducting silicone gel has good orientation, good heat-conducting performance and high rebound performance.

Description

Technical Field

[0001] This invention relates to the field of thermal interface materials technology, and in particular to a boron nitride composite microsheet and its preparation method, as well as a thermally conductive silica gel containing the boron nitride composite microsheet and its preparation method. Background Technology

[0002] In recent years, with rapid social development, people's awareness of environmental protection has increased significantly, and the requirements for environmental protection have reached a new level. The vigorous development of clean energy is driving the rapid development of photovoltaic power generation, a strategic industry. Among these, the power control components of photovoltaic power generation are a crucial part. Because they need to operate continuously in various outdoor environments for extended periods, the interface material, which plays a role in heat conduction between the heat-generating components and the heat sink, has become a critical element. The weather resistance and lifespan of the interface material directly determine the service life of the power generation components. Currently, most of the materials used are pure alumina or interface materials prepared with aluminum nitride. In pursuit of high thermal conductivity, a large amount of thermally conductive powder is required, inevitably sacrificing the material's mechanical properties, such as resilience. There are also thermal interface materials prepared using conventional boron nitride powder or physically modified boron nitride powder. However, because boron nitride powder has a very high oil absorption value and poor organic compatibility, it is difficult to disperse in silicone resins. Therefore, the resulting interface materials generally have low thermal conductivity and poor mechanical properties, making them unsuitable for applications requiring high thermal conductivity and high reliability.

[0003] Publicly available information shows that current methods for preparing oriented thermally conductive materials using boron nitride involve directly adding boron nitride powder or surface-treated boron nitride powder to silicone resin and then processing it using downstream processes. Because the particle size of boron nitride powder is typically in the micrometer range, with the largest being only a few hundred micrometers, the orientation effect is not ideal, resulting in low thermal conductivity or poor mechanical properties in the final interface material. There are also reports of using special binders to orient boron nitride powder, achieving better orientation results; however, these binders cannot withstand long-term operation in environments exceeding 100°C, making them unsuitable for high-reliability applications. Summary of the Invention

[0004] In view of the above problems, the present invention provides a boron nitride composite microplate, comprising, by mass percentage, 40-70% boron nitride powder, 10-40% polysiloxane resin, 3-15% ceramic powder filler, 1-8% metal powder, 0.1-1% wetting agent and 0.5-3% curing agent.

[0005] In some embodiments, the content of boron nitride powder is 40-70%, preferably 50-60%. As an example, the content of boron nitride powder may be, but is not limited to, 40%, 50%, 60%, or 70%.

[0006] In some embodiments, the boron nitride powder has a morphology of one or a combination of two of the following: flake-like or spherical. Preferably, the boron nitride powder has a morphology of a combination of flake-like and spherical. Further, the particle size of the boron nitride powder is 0.5-200 μm, preferably 1-150 μm, more preferably 5-100 μm. As an example, the particle size of the boron nitride powder is 0.5 μm, 5 μm, 10 μm, 50 μm, 100 μm, or 200 μm.

[0007] In some embodiments, the content of polysiloxane resin is 10-40%, preferably 20-30%. As an example, the content of polysiloxane resin may be, but is not limited to, 10%, 20%, 30%, or 40%.

[0008] In some embodiments, the polysiloxane resin is one or a combination of at least two of methylphenyl polysiloxane resin, methyl polysiloxane resin, or hydroxyl polysiloxane resin. As an example, the polysiloxane resin is methylphenyl polysiloxane resin or methyl polysiloxane resin, but is not limited thereto. Further, the solid content of the polysiloxane resin is 10-40%, preferably 20-30%. As an example, the solid content of the polysiloxane resin may be, but is not limited to, 10%, 20%, 30%, or 40%. In some embodiments, the viscosity of the polysiloxane resin is 10-80 cs, preferably 20-60 cs. As an example, the viscosity of the polysiloxane resin may be, but is not limited to, 10 cs, 20 cs, 40 cs, 60 cs, or 80 cs.

[0009] In some embodiments, the content of ceramic powder filler is 3-15%, preferably 5-10%. For example, the content of ceramic powder filler may be, but is not limited to, 3%, 6%, 9%, or 12%.

[0010] In some embodiments, the ceramic powder filler is one or a combination of at least two of alumina, zinc oxide, magnesium oxide, and aluminum nitride. As an example, the ceramic powder filler is a composition of alumina, zinc oxide, and aluminum nitride, but is not limited thereto. Further, the particle size of the ceramic powder filler is 0.5-50 μm, preferably 1-40 μm, more preferably 5-30 μm. As an example, the particle size of the ceramic powder filler is 0.5 μm, 5 μm, 10 μm, or 50 μm. Even further, the morphology of the ceramic powder is one or a combination of angular, flake-like, quasi-spherical, and spherical shapes.

[0011] In some embodiments, the content of metal powder is 1-8%, preferably 2-6%, and by way of example, the content of metal powder may be, but is not limited to, 1%, 3%, 6%, or 8%.

[0012] In some embodiments, the metal powder is one or a combination of aluminum powder and silver powder. Further, the particle size of the metal powder is 0.5-10 micrometers, preferably 1-8 micrometers. As an example, the particle size of the metal powder may be, but is not limited to, 0.5 micrometers, 2 micrometers, 4 micrometers, 6 micrometers, 8 micrometers, and 10 micrometers.

[0013] In some embodiments, the content of the wetting agent is 0.1-1%, preferably 0.2-0.8%. As examples, the content of the wetting agent may be, but is not limited to, 0.1%, 0.3%, 0.6%, 0.8%, or 1%.

[0014] In some embodiments, the wetting agent has the structural formula shown in structural formula 2:

[0015]

[0016] Wherein, R1 is methyl or hydroxyl, n = 8-17, and R2 is methoxy or ethoxy.

[0017] In some embodiments, the content of the curing agent is 0.5-3%, preferably 1-2%. As examples, the content of the curing agent may be, but is not limited to, 0.5%, 1%, 1.5%, 2%, or 2.5%.

[0018] In some embodiments, the curing agent is one or a combination of at least two of diethylenetriamine, triethylenetetramine, or γ-aminopropyltriethoxysilane.

[0019] Accordingly, the present invention also provides a method for preparing boron nitride composite microsheets, comprising the following steps:

[0020] (1) Mix the boron nitride powder, polysiloxane resin, ceramic powder filler, metal powder and wetting agent in the specified amounts to obtain a slurry;

[0021] (2) The curing agent and the slurry are mixed evenly to obtain a boron nitride-based material;

[0022] (3) The boron nitride base material is fed into a scraper for processing and then cut to obtain boron nitride composite micro flakes.

[0023] On the other hand, the present invention also provides a thermally conductive silicone gel comprising the above-mentioned boron nitride composite microsheets.

[0024] In some embodiments, the thermally conductive silicone gel comprises, by weight percentage, 1-5% vinyl silicone oil, 5-10% hydrogen-containing silicone oil, 0.05-0.3% catalyst, 50-80% of the boron nitride composite microplates, and 1-30% ceramic powder filler.

[0025] In some embodiments, the content of vinyl silicone oil is 1-5%, preferably 2-4%, and by way of example, the content of vinyl silicone oil may be, but is not limited to, 1%, 2%, 3%, 4%, or 5%.

[0026] In some embodiments, the vinyl silicone oil is a compound shown in structural formula 1:

[0027]

[0028] Where n:m = 1:10-20, and R is either methyl or phenyl.

[0029] In some embodiments, the vinyl silicone oil has a viscosity of 50-300 cp and a vinyl content of 1.5-3.6%.

[0030] In some embodiments, the content of hydrogen-containing silicone oil is 5-10%, preferably 6-9%. As an example, the content of hydrogen-containing silicone oil may be, but is not limited to, 5%, 6%, 7%, 8%, 9%, or 10%.

[0031] In some embodiments, the hydrogen-containing silicone oil is a double-ended hydrogen-containing linear silicone oil, and its molecular formula is shown in structural formula 3:

[0032]

[0033] The value of n is 70-250. Select the hydrogen-containing silicone oil with the corresponding viscosity according to the value of n.

[0034] Furthermore, the viscosity of the hydrogen-containing silicone oil is 100-500 cp.

[0035] In some embodiments, the catalyst content is 0.05-0.3%, preferably 0.1-0.2%, and as examples, the catalyst content may be, but is not limited to, 0.05%, 0.1%, 0.2%, or 0.3%.

[0036] In some embodiments, the catalyst is a microencapsulated castor platinum catalyst with a Pt content of 50-2000 ppm, and further, the activation temperature of the microencapsulated castor platinum catalyst is 60-90°C.

[0037] In some embodiments, the content of boron nitride composite microflakes is 50-80%, preferably 55-70%. As an example, the content of boron nitride composite microflakes may be, but is not limited to, 50%, 60%, 70%, or 80%.

[0038] In some embodiments, the content of ceramic powder filler is 1-30%, preferably 5-20%. As an example, the content of ceramic powder filler may be, but is not limited to, 1%, 2%, 5%, 10%, 15%, 20%, 25%, and 30%.

[0039] In some embodiments, the ceramic powder filler is at least one of alumina, zinc oxide, and aluminum nitride. Preferably, the ceramic powder filler is a combination of alumina and zinc oxide or a combination of aluminum nitride and zinc oxide. Further, in the combination of alumina and zinc oxide, the mass ratio of alumina:zinc oxide is 10:1-5; and in the combination of aluminum nitride and zinc oxide, the mass ratio of aluminum nitride:zinc oxide is 10:1-3.

[0040] In some embodiments, the particle size of the ceramic powder is 0.5-120 μm, preferably 1-100 μm, and more preferably 5-80 μm. For example, the particle size of the ceramic powder filler is 0.5 μm, 5 μm, 10 μm, 50 μm, 80 μm, 100 μm, or 120 μm. Furthermore, the morphology of the ceramic powder is one or more combinations of angular, flake-like, quasi-spherical, and spherical shapes.

[0041] Accordingly, the present invention also provides a method for preparing thermally conductive silicone gel, comprising the following steps:

[0042] (1) Mix the vinyl silicone oil, hydrogen-containing silicone oil, boron nitride composite microplates and ceramic powder filler in the specified amounts evenly to obtain material A;

[0043] (2) Mix the catalyst with the material A evenly to obtain a gel base material;

[0044] (3) The gel base material is extruded and then cut to obtain a semi-finished product. The semi-finished product is then heated and cured, and cut to the required thickness along the extrusion direction to obtain thermally conductive silicone gel.

[0045] In some embodiments, the extrusion port 10 of the extrusion molding machine is designed in a trapezoidal shape (see reference). Figure 1 (Structure shown).

[0046] The beneficial effects of this invention are as follows:

[0047] (1) Due to its small particle size, boron nitride powder has poor orientation and is not easy to obtain an efficient thermal conduction path to achieve high thermal conductivity. The technical solution of this invention first prepares boron nitride composite microplates with good orientation, and then prepares thermally conductive silicon gel to obtain high thermal conductivity.

[0048] (2) Boron nitride powder has a very high oil absorption value, making it difficult to fill and prepare a high thermal conductivity interface material directly. In the boron nitride composite microplate, the inclusion of organosilicon material effectively reduces the oil absorption value, making it very easy to fill into silicone oil, which significantly helps to improve the thermal conductivity of the gel.

[0049] (3) Metal powder itself has a high thermal conductivity, but it is difficult to use general insulating thermal interface materials, and its conductivity cannot be avoided. The technical solution of the present invention is to premix the metal powder in the boron nitride composite microplate, which effectively solves the overall conductivity problem and improves the thermal conductivity of the gel.

[0050] (4) The gel crosslinking system of the present invention contains vinyl silicone oil and hydrogen-containing silicone oil. The vinyl silicone oil is the compound shown in structural formula 1. Using vinyl silicone oil as a crosslinking bridge is more conducive to obtaining more spatial three-dimensional structures rather than nonlinear structures through molecular crosslinking, so that the gel can obtain better resilience.

[0051] (5) The extrusion port 10 of the extrusion molding machine of the present invention is designed in a trapezoidal shape (see reference). Figure 1 The structure shown further improves the orientation effect of the boron nitride composite microsheets and enhances their thermal conductivity. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the extrusion port of the extrusion molding machine of the present invention. Detailed Implementation

[0053] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0054] Example 1

[0055] A method for preparing boron nitride composite microsheets includes the following steps:

[0056] (1) Add 7000g of measured boron nitride powder, 1650g of polysiloxane resin, 450g of ceramic powder filler, 700g of metal powder and 90g of wetting agent to a low-speed disperser and disperse evenly in a temperature environment of 20-27℃. The disperser speed is 140rpm and the dispersion time is 50 minutes to obtain a slurry.

[0057] (2) Add 110g of the measured curing agent to the dispersed slurry, disperse it evenly in a temperature environment of 20-27℃, the speed of the disperser is 90rpm, the dispersion time is 50 minutes, and the boron nitride base material is obtained.

[0058] (3) The boron nitride base material is fed into a vertical scraper for processing. The scraper speed is 15cm / min, the scraping thickness of the boron nitride base material is controlled at 1.1mm, the temperature of the forming section of the scraper is 60℃, the passing distance is 2.1m, the temperature of the curing section of the scraper is 210℃, and the passing distance is 3.4m.

[0059] (4) Cut the product after the coating machine is processed. The cutting width is 1.7 mm and the cutting length is 11 mm to obtain boron nitride composite micro flakes.

[0060] Among them, the boron nitride powder is flake boron nitride and spherical boron nitride, with a mass ratio of flake boron nitride to spherical boron nitride of 1:4. The particle size of the flake boron nitride is 2±0.2μm, and the particle size of the spherical boron nitride is 60±5μm.

[0061] The polysiloxane resin is a methylphenyl polysiloxane resin with a phenyl content of 10%, a solid content of 35%, and a viscosity of 30 cs.

[0062] The ceramic powder filler is a composition of alumina, zinc oxide and aluminum nitride, with a mass ratio of alumina, zinc oxide and aluminum nitride of 5:1:2. The alumina has a spherical morphology with a medium particle size of 10±2μm, the zinc oxide has a angular morphology with a medium particle size of 0.8±0.1μm, and the aluminum nitride has a angular morphology with a medium particle size of 5±2μm.

[0063] The metal powder is aluminum powder with a medium particle size of 1μm;

[0064] The wetting agent is the compound described in structural formula 2, where R1 is methyl, n = 8, and R2 is methoxy.

[0065] The curing agent is a combination of diethylenetriamine and γ-aminopropyltriethoxysilane in a mass ratio of 4:1.

[0066] Example 2

[0067] A method for preparing boron nitride composite microsheets includes the following steps:

[0068] (1) Add 4000g of measured boron nitride powder, 3920g of polysiloxane resin, 1500g of ceramic powder filler, 500g of metal powder and 20g of wetting agent to a low-speed disperser and disperse evenly in a temperature environment of 20-27℃. The disperser speed is 38rpm and the dispersion time is 110 minutes to obtain a slurry.

[0069] (2) Add 60g of the measured curing agent to the dispersed slurry, disperse it evenly in a temperature environment of 20-27℃, the speed of the disperser is 180rpm, the dispersion time is 15 minutes, and the boron nitride base material is obtained.

[0070] (3) The boron nitride base material is fed into a vertical scraper for processing. The scraper speed is maintained at 30 cm / min. The scraping thickness of the boron nitride base material is controlled at 0.8 mm. The temperature of the forming section of the scraper is 90℃ and the passing distance is 2.5 meters. The temperature of the curing section of the scraper is 120℃ and the passing distance is 4.5 meters.

[0071] (4) Cut the product after the coating machine is processed. The cutting width is 0.8 mm and the cutting length is 20 mm to obtain boron nitride composite micro flakes.

[0072] Among them, the boron nitride powder is flake boron nitride and spherical boron nitride, with a mass ratio of flake boron nitride to spherical boron nitride of 5:3. The particle size of the flake boron nitride is 10±0.3μm, and the particle size of the spherical boron nitride is 160±5μm.

[0073] The polysiloxane resin is a methyl polysiloxane resin with a solid content of 16% and a viscosity of 70 cs.

[0074] The ceramic powder filler is a composition of alumina, magnesium oxide and aluminum nitride, with a mass ratio of alumina, magnesium oxide and aluminum nitride of 1:6:3. The alumina has a spherical morphology with a medium particle size of 0.5±0.1μm, the magnesium oxide has a spherical morphology with a medium particle size of 30±5μm, and the aluminum nitride has an angular morphology with a medium particle size of 2±0.5μm.

[0075] The metal powder is a combination of silver powder and aluminum powder in a mass ratio of 6:1, and both have a medium particle size of 5μm.

[0076] The wetting agent is the compound shown in structural formula 2, where R1 is a hydroxyl group, n = 16, and R2 is an ethyloxy group;

[0077] The curing agent is a combination of triethylenetetramine and γ-aminopropyltriethoxysilane in a mass ratio of 3:2.

[0078] Example 3

[0079] A method for preparing thermally conductive silicone gel, wherein the boron nitride composite microsheets obtained in Example 1 are used to prepare the thermally conductive silicone gel, and the specific steps include:

[0080] (1) 150g of vinyl silicone oil, 800g of hydrogen-containing silicone oil, 7800g of boron nitride composite microplates and 1244g of ceramic powder filler were put into a 20L kneader and dispersed evenly. The rotation speed was 15rpm, the material temperature was controlled below 50℃ by cooling water, and the dispersion time was 3.5 hours to obtain material A.

[0081] (2) Add 6g of the measured catalyst to the mixed material A, continue to disperse evenly, rotate at 12 rpm, keep the material temperature below 50℃ by cooling water, and disperse for 1 hour to obtain the gel base material.

[0082] (3) The gel base material is fed into an extrusion molding machine. The extrusion port 10 of the extrusion molding machine is designed in a trapezoidal shape (see reference). Figure 1 (Structure shown) The pressure is set to 18 MPa and the temperature is set to 120℃. The extruded product is cut into several segments to obtain a semi-finished product. Then, the semi-finished product is placed in an oven and the temperature is set to 125℃ and kept constant for 20 minutes for deep curing. The product that has completed deep curing is cut into the required thickness along the extrusion direction to obtain a highly resilient and thermally conductive silicone gel with orientation.

[0083] Among them, the vinyl silicone oil adopts the compound shown in structural formula 1, in which n:m=1:10, R is phenyl, the viscosity is 70cp, and the vinyl content is 3.0%;

[0084] The hydrogen-containing silicone oil is a structurally type 3 double-ended hydrogen-containing linear silicone oil with a viscosity of 300 cp; the catalyst is a microencapsulated castor platinum catalyst with a Pt content of 1500 ppm and an activation temperature of 65℃.

[0085] The ceramic powder filler is a combination of aluminum nitride and zinc oxide in a mass ratio of 10:1. The aluminum nitride has a spherical morphology with a medium particle size of 80 μm, while the zinc oxide has a angular morphology with a medium particle size of 1.2 μm.

[0086] Example 4

[0087] A method for preparing thermally conductive silicone gel, wherein the boron nitride composite microsheets obtained in Example 2 are used to prepare the thermally conductive silicone gel, specifically including the following steps:

[0088] (1) 450g of vinyl silicone oil, 1000g of hydrogen-containing silicone oil, 5600g of boron nitride composite microplates and 2390g of ceramic powder filler were put into a 20L kneader and dispersed evenly. The rotation speed was 30rpm, the material temperature was controlled below 50℃ by cooling water, and the dispersion time was 2 hours to obtain material A.

[0089] (2) Add 20g of the measured catalyst to the mixed material A, continue to disperse evenly, rotate at 20rpm, keep the material temperature below 50℃ by cooling water, and disperse for 0.5 hours to obtain gel base material;

[0090] (3) The gel base material is fed into an extrusion molding machine. The extrusion port 10 of the extrusion molding machine is designed in a trapezoidal shape (see reference). Figure 1(Structure shown), pressure set to 6.5 MPa, temperature set to 95℃, extruded product cut into several segments to obtain semi-finished product, then the semi-finished product is placed in baking oven, temperature set to 130℃, kept constant for 18 minutes for deep curing, the deep-cured product is cut into the required thickness along the extrusion direction to obtain oriented high-resilience thermally conductive silicone gel.

[0091] Among them, the vinyl silicone oil adopts the compound shown in structural formula 1, in which n:m=1:15, R is methyl, the viscosity is 280cp, and the vinyl content is 1.8%;

[0092] Hydrogen-containing silicone oil is a structural type 3 double-ended hydrogen-containing linear silicone oil with a viscosity of 500 cp.

[0093] The catalyst is a microencapsulated castor platinum catalyst with a Pt content of 500 ppm and an activation temperature of 80℃.

[0094] The ceramic powder filler is a combination of aluminum nitride and zinc oxide in a mass ratio of 10:3. The aluminum nitride has a spherical morphology with a medium particle size of 120 μm, while the zinc oxide has a angular morphology with a medium particle size of 0.8 μm.

[0095] Comparative Example 1

[0096] A method for preparing boron nitride composite microsheets includes the following steps:

[0097] (1) 1200g of vinyl silicone oil, 56g of hydrogen-containing silicone oil, 3200g of boron nitride powder and 1120g of ceramic powder filler were put into a 20L kneader and dispersed evenly. The rotation speed was 30rpm, the material temperature was controlled below 50℃ by cooling water, and the dispersion time was 2.5 hours to obtain material A.

[0098] (2) Add 20g of the measured catalyst to the mixed material A, continue to disperse evenly, rotate at 20rpm, keep the material temperature below 50℃ by cooling water, and disperse for 0.5 hours to obtain gel base material;

[0099] (3) The gel base material is put into the extrusion molding machine, the pressure is set to 6.5 MPa, and the temperature is set to 95℃.

[0100] The extruded product is cut into several segments to obtain a semi-finished product. The semi-finished product is then placed in an oven and the temperature is set to 130℃ and kept constant for 20 minutes for deep curing. The product that has completed deep curing is then cut into the required thickness along the extrusion direction to obtain an oriented, highly resilient, thermally conductive silicone gel.

[0101] The vinyl silicone oil and hydrogen-containing silicone oil used are the same as those used in Example 3.

[0102] The catalyst is a Castrol Pt catalyst with a Pt content of 1500 ppm;

[0103] The boron nitride powder is a combination of flake and spherical boron nitride in a mass ratio of 4:7.

[0104] The ceramic powder is a combination of alumina and zinc oxide in a mass ratio of 10:3. The alumina has a spherical morphology with a medium particle size of 90 μm, while the zinc oxide has a angular morphology with a medium particle size of 1.0 μm.

[0105] Comparative Example 2

[0106] The comparative example is basically the same as Example 3, except that in Comparative Example 2, the vinyl silicone oil used is terminal vinyl silicone oil (CAS: 68083-19-2), with a viscosity of 200 cp and a vinyl content of 0.68%; the hydrogen-containing silicone oil is side-hydrogen-containing silicone oil (CAS: 63148-57-2), with a viscosity of 110 cp and a hydrogen content of 0.2%; while in Example 3, the vinyl silicone oil used is the compound shown in structural formula 1, where n:m = 1:10, R is phenyl, the viscosity is 70 cp, the vinyl content is 3.0%, and the hydrogen-containing silicone oil is a double-terminated hydrogen-containing linear silicone oil with a viscosity of 300 cp; the rest is the same as in Example 3, and will not be described here.

[0107] Comparative Example 3

[0108] This comparative example is basically the same as Comparative Example 1, except that in Comparative Example 3, the vinyl silicone oil used is terminal vinyl silicone oil (CAS: 68083-19-2), with a viscosity of 200 cp and a vinyl content of 0.68%; the hydrogen-containing silicone oil is side-hydrogen-containing silicone oil (CAS: 63148-57-2), with a viscosity of 110 cp and a hydrogen content of 0.2%; while in Comparative Example 1, the vinyl silicone oil used is the compound shown in structural formula 1, where n:m = 1:10, R is phenyl, the viscosity is 70 cp, the vinyl content is 3.0%, and the hydrogen-containing silicone oil is a double-terminated hydrogen-containing linear silicone oil with a viscosity of 300 cp; the rest is the same as Comparative Example 1, and will not be elaborated here.

[0109] The boron nitride composite microplates of Examples 1-2 and the boron nitride powder of Comparative Example 1 were subjected to oil absorption value tests, and the results are shown in Table 1.

[0110] Table 1 Oil Absorption Value Test Results

[0111] project Example 1 Example 2 Comparative Example 1 powder Boron nitride composite microplates Boron nitride composite microplates Boron nitride raw powder Oil absorption value results 6.7g / 100g 8.5g / 100g 56g / 100g

[0112] The thermally conductive silicone gels of Examples 3-4 and Comparative Examples 1-3 were subjected to thermal conductivity and rebound tests, and the results are shown in Table 2.

[0113] Table 2. Test results of thermally conductive silicone gel properties

[0114]

[0115] As can be seen from the data in Table 1-2, the oil absorption value of boron nitride raw powder is relatively high, making it difficult to fill and prepare a high thermal conductivity interface material directly. However, the modified boron nitride composite microplate of the present invention has a very low oil absorption value because the boron nitride composite microplate is composited with organosilicon material, which makes the oil absorption value very low and easy to fill into silicone oil, significantly improving the thermal conductivity of the gel.

[0116] Finally, it should be noted that 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, it is not limited to those listed in the 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 boron nitride composite microsheet, characterized in that, By mass percentage, it comprises 40-70% boron nitride powder, 10-40% polysiloxane resin, 3-15% ceramic powder filler, 1-8% metal powder, 0.1-1% wetting agent and 0.5-3% curing agent, wherein the metal powder is one or a combination of aluminum powder and silver powder.

2. The boron nitride composite microsheet according to claim 1, characterized in that, The polysiloxane resin is one or a combination of at least two of methylphenyl polysiloxane resin, methyl polysiloxane resin, or hydroxyl polysiloxane resin.

3. The boron nitride composite microsheet according to claim 1, characterized in that, The ceramic powder filler is one or a combination of at least two of alumina, zinc oxide, magnesium oxide, and aluminum nitride.

4. The method for preparing boron nitride composite microsheets according to any one of claims 1-3, characterized in that, Including the following steps: (1) Mix the boron nitride powder, polysiloxane resin, ceramic powder filler, metal powder and wetting agent in the specified amounts to obtain a slurry; (2) Mix the curing agent and the slurry evenly to obtain a boron nitride base material; (3) The boron nitride base material is fed into a scraper for processing and then cut to obtain boron nitride composite micro flakes.

5. A thermally conductive silicone gel, characterized in that, The boron nitride composite microsheets are prepared by the method of any one of claims 1-3 or claim 4.

6. The thermally conductive silicone gel according to claim 5, characterized in that, By weight percentage, it includes 1-5% vinyl silicone oil, 5-10% hydrogen-containing silicone oil, 0.05-0.3% catalyst, 50-80% of the boron nitride composite microplates, and 1-30% ceramic powder filler.

7. The thermally conductive silicone gel according to claim 6, characterized in that, The vinyl silicone oil is a compound shown in structural formula 1: Where n:m = 1:10-20, and R is either methyl or phenyl.

8. The method for preparing thermally conductive silicone gel according to any one of claims 5-7, characterized in that, Including the following steps: (1) Mix the vinyl silicone oil, hydrogen-containing silicone oil, boron nitride composite microplates and ceramic powder filler in the specified amounts evenly to obtain material A; (2) Mix the catalyst with the material A evenly to obtain a gel base material; (3) The gel base material is extruded and then cut to obtain a semi-finished product. The semi-finished product is then heated and cured, and cut to the required thickness along the extrusion direction to obtain thermally conductive silicone gel.

9. The method for preparing thermally conductive silicone gel according to claim 8, characterized in that, The extrusion port of the extrusion molding machine is designed in a trapezoidal shape.

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