阅读说明：本技术 复合散热膜及其制备方法 (Composite heat dissipation film and preparation method thereof ) 是由 刘科海 张志强 何梦林 王恩哥 于 2021-03-03 设计创作，主要内容包括：一种复合散热膜及其制备方法,属于散热膜领域。复合散热膜包括导热中间层以及设置在导热中间层的相对两侧表面的第一氮化硼层,导热中间层包括至少一层石墨片。该复合散热膜同时具有良好的电绝缘性和散热效果。(A composite heat dissipation film and a preparation method thereof belong to the field of heat dissipation films. The composite heat dissipation film comprises a heat conduction intermediate layer and first boron nitride layers arranged on the two opposite side surfaces of the heat conduction intermediate layer, and the heat conduction intermediate layer comprises at least one layer of graphite sheet. The composite heat dissipation film has good electrical insulation and heat dissipation effects.)

1. The composite heat dissipation film is characterized by comprising a heat conduction intermediate layer and first boron nitride layers arranged on two opposite side surfaces of the heat conduction intermediate layer, wherein the heat conduction intermediate layer comprises at least one layer of graphite sheet.

2. The composite heat spreading film of claim 1, wherein the thermally conductive intermediate layer further comprises at least one graphene layer disposed between the graphite sheet and the first boron nitride layer.

3. The composite heat dissipation film according to claim 2, wherein the graphene layer is provided with two layers, and the two graphene layers are respectively located at two outermost sides of the heat conductive intermediate layer.

4. The composite heat dissipation film of any of claims 1-3, wherein the first boron nitride layer comprises a boron nitride film that is a two-dimensional material made by a chemical vapor deposition process and a boron nitride sheet made by a high temperature sintering process of a boron nitride slurry.

5. The composite heat dissipation film of claim 4, wherein the thickness of the boron nitride thin film is 0.1-10nm, and the thickness of the boron nitride sheet is 1-50 um.

6. The composite heat spreading film according to claim 2 or 3, wherein the thermally conductive intermediate layer further comprises at least one second boron nitride layer, and the graphite sheets and the second boron nitride layer are alternately arranged.

7. A method of making a composite heat spreading film according to claim 1 comprising: and laminating the heat-conducting intermediate layer and the first boron nitride layer together for calendering treatment, and then carrying out heat treatment at the temperature of 800-1700 ℃.

8. The method for manufacturing a composite heat dissipation film according to claim 7, wherein the step of laminating the heat conductive intermediate layer and the first boron nitride layer together by calendering includes:

growing a boron nitride film on at least one surface of the heat-conducting intermediate layer by adopting a chemical vapor deposition process;

and superposing a boron nitride sheet on the surface of the boron nitride film and then carrying out calendaring treatment.

9. The method for manufacturing a composite heat dissipating film according to claim 8, wherein the step of laminating the heat conductive intermediate layer and the first boron nitride layer together to be subjected to a calendering process includes:

growing a boron nitride film on the surface of the metal substrate by adopting a chemical vapor deposition method, and transferring the boron nitride film to at least one surface of the heat-conducting intermediate layer;

and superposing a boron nitride sheet on the surface of the boron nitride film, and then performing calendering treatment.

10. The method for preparing a composite heat dissipation film according to any one of claims 7-9, wherein the step of preparing the heat conductive intermediate layer comprises: and attaching the graphene oxide dispersion liquid to at least one surface of the at least one layer of graphite sheet, and then carrying out reduction treatment to form a graphene layer on the surface of the at least one layer of graphite sheet.

Technical Field

The application relates to the technical field of heat dissipation films, in particular to a composite heat dissipation film and a preparation method thereof.

Background

With the high-speed performance improvement and the more powerful functions of electronic products, the heating problem gradually appears in the fields of 5G communication equipment, smart phones, notebook computers, communication base stations, LEDs and the like. Taking a mobile phone as an example, under the demand of pursuing lightness and thinness and high endurance, the power consumption of the mobile phone is increased rapidly, the heat productivity is increased rapidly, the service life and the operation performance of a chip are reduced seriously, and the problems of blockage, slow reaction and the like occur.

In the existing electronic product device, a graphite sheet or a graphene film is used as a heat dissipation film, but the graphite sheet or the graphene film is directly used in the electronic product device, and a short circuit risk exists.

Disclosure of Invention

The application provides a composite heat dissipation film and a preparation method thereof, wherein the composite heat dissipation film has good electrical insulation and heat dissipation effects.

The embodiment of the application is realized as follows:

in a first aspect, embodiments of the present application provide a composite heat dissipation film, which includes a thermally conductive intermediate layer and first boron nitride layers disposed on two opposite side surfaces of the thermally conductive intermediate layer, where the thermally conductive intermediate layer includes at least one graphite sheet.

In a second aspect, an embodiment of the present application provides a method for preparing a composite heat dissipation film according to an embodiment of the first aspect, including: the heat-conducting intermediate layer and the first boron nitride layer are laminated together and subjected to calendering treatment, and then subjected to heat treatment at the temperature of 800-1700 ℃.

The composite heat dissipation film and the preparation method thereof have the beneficial effects that:

the heat conducting intermediate layer comprises at least one layer of graphite sheet, and the graphite in the graphite sheet has good heat conductivity and good heat dissipation effect. The relative both sides surface in heat conduction intermediate level has first boron nitride layer, and boron nitride has the hexagonal lamellar structure similar with graphite alkene, not only can heat conduction, has good electrical insulation nature and low dielectric property moreover, and first boron nitride layer setting not only can make compound radiating film have better electrical insulation nature in the relative both sides surface in heat conduction intermediate level, makes compound radiating film also have good radiating effect simultaneously moreover.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 is a schematic structural view of a composite heat dissipation film according to example 1 of the present application;

FIG. 2 is a schematic structural view of a composite heat dissipation film according to example 2 of the present application;

FIG. 3 is a schematic structural view of a composite heat dissipation film according to embodiment 3 of the present application;

FIG. 4 is a schematic structural view of a composite heat dissipating film according to embodiment 4 of the present application;

FIG. 5 shows the structure obtained after the steps S5-1 and S7-1 in the method for manufacturing a composite heat dissipation film of examples 5 and 7 of the present application;

FIG. 6 shows a structure obtained after step S5-2 in the method for manufacturing a composite heat dissipation film according to example 5 of the present application;

FIG. 7 shows a structure obtained after step S6-1 in the method for manufacturing a composite heat dissipating film according to example 6 of the present application;

FIG. 8 is a view showing a structure obtained after the step S6-2 in the method for manufacturing a composite heat dissipating film according to example 6 of the present application;

fig. 9 shows a structure obtained after step S6-3 in the method for manufacturing a composite heat dissipation film according to example 6 of the present application.

Icon: 10-composite heat dissipation film; 11-a thermally conductive intermediate layer; 111-graphite flakes; 112-a graphene layer; 113-a second boron nitride layer; 12-a first boron nitride layer; a 121-boron nitride film; 122-boron nitride wafer.

Detailed Description

Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The following description specifically describes the composite heat dissipation film 10 and the preparation method thereof according to the embodiment of the present application:

in a first aspect, embodiments of the present application provide a composite heat dissipation film 10, referring to fig. 1-4, including a thermally conductive intermediate layer 11 and first boron nitride layers 12 disposed on opposite side surfaces of the thermally conductive intermediate layer 11, where the thermally conductive intermediate layer 11 includes at least one graphite sheet 111. That is, the graphite sheet 111 may be provided in one layer or in a plurality of layers.

The heat conducting intermediate layer 11 comprises at least one layer of graphite sheet 111, and graphite in the graphite sheet 111 has good heat conductivity and good heat dissipation effect. The opposite side surfaces of the heat conduction intermediate layer 11 are provided with the first boron nitride layers 12, the boron nitride layers have a hexagonal layered structure similar to graphene, heat conduction can be achieved, good electric insulation and low dielectric property are achieved, the first boron nitride layers 12 are arranged on the opposite side surfaces of the heat conduction intermediate layer 11, the composite heat dissipation film 10 can have good electric insulation, and the composite heat dissipation film 10 also has a good heat dissipation effect. The composite heat dissipation film 10 of the embodiment of the application has the heat conductivity as high as 2100W/(m.K), the thickness of the composite heat dissipation film can be larger than or equal to 10 micrometers, and the composite heat dissipation film 10 can be applied to the fields of 5G communication equipment, smart phones, notebook computers, 5G communication base stations, LEDs and the like.

Alternatively, the process for preparing the graphite sheet 111 includes a thermal expansion method and a high-molecular thermal decomposition method.

Illustratively, the step of preparing the graphite sheet 111 by a thermal expansion method includes:

the graphite powder is subjected to thermal expansion and impurity removal, then mixed with an adhesive, and then subjected to calendering to obtain a graphite sheet 111.

Illustratively, the step of preparing the graphite sheet 111 by the high molecular thermal decomposition method includes:

the polyimide film is subjected to high-temperature heat treatment under the protection of inert atmosphere to carbonize and graphitize the polyimide film, and then rolled to obtain a graphite sheet 111.

Illustratively, in one possible embodiment, the thermally conductive intermediate layer 11 includes a layer of graphite sheet 111, and the opposite side surfaces of the graphite sheet 111 have first boron nitride layers 12 (refer to fig. 3).

Further, in another possible embodiment, the thermally conductive intermediate layer 11 further includes at least one graphene layer 112, and the graphene layer 112 is disposed between the graphite sheet 111 and the first boron nitride layer 12 (refer to fig. 1, 2, and 4).

Illustratively, referring to fig. 4, the thermally conductive intermediate layer 11 includes a graphene sheet 111 and a graphene sheet 112, one surface of the graphene sheet 111 has the graphene sheet 112, the other surface of the graphene sheet 111 has the first boron nitride layer 12, and a surface of the graphene sheet 112 has the first boron nitride layer 12.

Illustratively, the thermally conductive intermediate layer 11 includes a graphene sheet 111 and two graphene sheets 112, the graphene sheet 111 has the graphene sheet 112 on both surfaces, and the first boron nitride layer 12 is provided on both surfaces of the two graphene sheets 112. That is, two graphene layers 112 are respectively disposed on the outermost sides of the heat conductive intermediate layer 11, and the first boron nitride layer 12 is disposed on the opposite side surfaces of the heat conductive intermediate layer 11 (see fig. 1).

It is understood that in the present embodiment, the graphite sheet 111 may be provided in a plurality of sheets, and the plurality of graphite sheets 111 may be disposed adjacent to each other in a stacked manner. For example, the graphite sheet 111 is provided in two layers, two layers of graphite sheets 111 are disposed adjacent to each other, the graphene layer 112 is provided in two layers, and the two graphene layers 112 are respectively disposed outside the two layers of graphite sheets 111.

The thermal conductivity of graphene is higher than that of graphite, and the heat-dissipating capacity is better, and at least one layer of graphene layer 112 is arranged on the basis of at least one layer of graphite sheet 111 in the heat-conducting intermediate layer 11, so that the heat-dissipating effect of the composite heat-dissipating film 10 can be improved. Moreover, the graphene layer 112 is disposed between the graphite sheet 111 and the first boron nitride layer 12, the graphene and the boron nitride have similar layered structures, and the composite film structure formed by the graphene layer 112 and the first boron nitride layer 12 is more stable.

In one possible embodiment, the first boron nitride layer 12 includes a boron nitride film 121 and a boron nitride sheet 122 (refer to fig. 1 to 3), the boron nitride film 121 is a two-dimensional material produced by a chemical vapor deposition method, and the boron nitride sheet 122 is produced by a high temperature sintering method of a boron nitride slurry.

The boron nitride film 121 prepared by the chemical vapor deposition method is a two-dimensional material, and the two-dimensional structure of the boron nitride film 121 is complete, continuous, large in size, high in quality, excellent in heat conduction performance and electrical insulation performance, and better in insulation performance compared with the boron nitride sheet 122. Because the boron nitride film 121 is prepared by the chemical vapor deposition method, the obtained boron nitride film 121 is generally thin, and the boron nitride film 121 alone serving as the outer insulating layer cannot well meet the use requirement of high-reliability electrical insulation, the first boron nitride layer 12 further comprises the boron nitride sheet 122, so that the thickness of the first boron nitride layer 12 can be ensured to better meet the use requirement of electrical insulation.

Illustratively, the thickness of the boron nitride film 121 is 0.1-10nm and the thickness of the boron nitride sheet 122 is 1-50 um. For example, the boron nitride film 121 has a thickness of 0.1nm, 0.5nm, 1nm, 2nm, 4nm, 5nm, 7nm, 9nm, or 10 nm. For example, the thickness of the boron nitride sheet 122 is 1um, 5um, 10um, 15um, 20um, 30um, 40um, or 50 um.

In other embodiments, the first boron nitride layer 12 may contain only the boron nitride sheet 122 (see fig. 4).

Further, in a possible embodiment, the heat conductive intermediate layer 11 further includes at least one second boron nitride layer 113, and the graphite sheets 111 and the second boron nitride layers 113 are alternately arranged (refer to fig. 2).

The second boron nitride layer 113 is arranged in the heat-conducting middle layer 11, and the graphite sheets 111 and the second boron nitride layer 113 are alternately arranged, so that the insulating property of the heat-conducting middle layer 11 is improved, and the insulating property of the composite heat dissipation film 10 is better.

In a second aspect, an embodiment of the present application provides a method for manufacturing a composite heat dissipation film 10, including: the heat conductive intermediate layer 11 and the first boron nitride layer 12 were laminated together and subjected to a rolling treatment, followed by a heat treatment at a temperature of 800-.

The preparation method can well combine the heat-conducting intermediate layer 11 and the first boron nitride layer 12 together to form the composite heat dissipation film 10 with stable structure.

In one possible embodiment, the step of laminating the thermally conductive intermediate layer 11 and the first boron nitride layer 12 together to be subjected to the rolling treatment includes:

growing a boron nitride film 121 on at least one surface of the heat-conducting intermediate layer 11 by adopting a chemical vapor deposition method;

the boron nitride sheet 122 is laminated on the surface of the boron nitride film 121 and then rolled.

In another possible embodiment, the step of laminating the thermally conductive intermediate layer 11 and the first boron nitride layer 12 together to be subjected to the rolling treatment includes:

growing a boron nitride film 121 on the surface of the metal substrate by adopting a chemical vapor deposition method, and transferring the boron nitride film 121 to at least one surface of the heat-conducting intermediate layer 11;

the boron nitride sheet 122 is laminated on the surface of the boron nitride film 121 and then rolled.

In the two embodiments, compared with the scheme of growing the boron nitride film 121 on the surface of the metal substrate and transferring the boron nitride film 121 to the heat-conducting intermediate layer 11, the boron nitride film 121 is directly grown on the surface of the heat-conducting intermediate layer 11, the boron nitride film 121 can be relatively stably attached to the surface of the heat-conducting intermediate layer 11, and the damage probability of the boron nitride film 121 in the transferring process can be reduced. In addition, in both schemes, the chemical vapor deposition method is adopted to grow the boron nitride film 121, the two-dimensional structure of the boron nitride film 121 prepared by the method is complete and continuous, the boron nitride film 121 has excellent heat conducting performance and electric insulating performance, and the boron nitride film 121 with large size can be prepared.

Illustratively, in the above two embodiments, the step of growing the boron nitride film 121 on at least one surface of the thermally conductive intermediate layer 11 or on the surface of the metal substrate includes:

placing the heat-conducting intermediate layer 11 in a high-temperature annealing device, introducing inert gas, carrying out heating treatment on the interior of the annealing device, moving the heat-conducting intermediate layer 11 to an area with the temperature of 300-2000 ℃, and then carrying out high-temperature annealing.

Optionally, the inert gas comprises N₂Ar or He.

Optionally, the speed of the heat conducting intermediate layer 11 moving to the region with the temperature of 300-2000 ℃ is 0.05-50 cm/min. For example, 0.05cm/min, 0.1cm/min, 0.2cm/min, 0.5cm/min, 1cm/min, 5cm/min, 10cm/min, 20cm/min, 30cm/min, 40cm/min or 50 cm/min.

Optionally, the time of the temperature raising treatment is 1-15 min, for example, 1min, 3min, 5min, 8min, 10min, 12min or 15 min.

After high-temperature annealing, moving the heat-conducting intermediate layer 11 to a growth chamber, introducing a gas source to start to grow the boron nitride film 121, wherein the growth time is 1 s-24 h; and after the growth is finished, stopping introducing the gas source, introducing only inert gas, and cooling to room temperature. Alternatively, the growth time of the boron nitride film 121 is 10s, 30s, 1h, 2h, 5h, 10h, 15h, 20h, or 24 h.

Illustratively, the source gas for growing the boron nitride film 121 includes H₂、N₂、CH₄And borazine at a gas flow rate of 0.1 to 2000 sccm. Optionally, the gas source has a gas flow rate of 1sccm, 10sccm, 50sccm, 100sccm, 500sccm, 1000sccm, 1500sccm, or 2000 sccm.

Illustratively, in both embodiments described above, the step of preparing the boron nitride wafer 122 includes: the boron nitride slurry is formed on a substrate and rolled to form a primary boron nitride on the surface of the substrate, the primary boron nitride is stripped from the substrate, and then sintered at the temperature of 800-1700 ℃ to obtain the boron nitride sheet 122. Illustratively, the material of the substrate may be a polymer material or a metal material. Illustratively, the boron nitride slurry is sprayed, coated or dipped onto the substrate.

Further, when the heat conductive intermediate layer 11 includes at least one graphite sheet 111 and at least one graphene layer 112, and the graphene layer 112 is disposed between the graphite sheet 111 and the first boron nitride layer 12, the heat conductive intermediate layer 11 is prepared by: the graphene oxide dispersion is attached to at least one surface of at least one graphite sheet 111, and then reduction treatment is performed to form a graphene layer 112 on the surface of at least one graphite sheet 111.

The graphene layer 112 obtained by reducing graphene oxide has better heat conduction property. Illustratively, the method of attaching the graphene oxide dispersion to at least one surface of the at least one layer of graphite sheets 111 comprises coating or dipping.

The composite heat dissipation film 10 and the method for manufacturing the same according to the present application will be described in further detail with reference to examples.

Example 1

The present embodiment provides a composite heat dissipation film 10, referring to fig. 1, which includes a graphite sheet 111 with a thickness of 20um, two opposite surfaces of the graphite sheet 111 both have a graphene layer 112 with a thickness of 0.7nm, the surface of each graphene layer 112 has a boron nitride film with a thickness of 1.4nm, and the surface of each boron nitride film has a boron nitride sheet 122 with a thickness of 15 um.

Example 2

The present embodiment provides a composite heat dissipation film 10, referring to fig. 2, it includes three layers of graphite sheets 111 with a thickness of 20um and two layers of second boron nitride layers 113 with a thickness of 15um, two layers of second boron nitride layers 113 and three layers of graphite sheets 111 are alternately disposed, two opposite surfaces of graphite sheet 111 all have graphene layer 112 with a thickness of 0.7nm, the surface of each graphene layer 112 all has a boron nitride film with a thickness of 1.4nm, and the surface of each boron nitride film all has a boron nitride sheet 122 with a thickness of 15 um.

Example 3

The present embodiment provides a composite heat dissipation film 10, referring to fig. 3, which includes a graphite sheet 111 with a thickness of 20um, two opposite surfaces of the graphite sheet 111 have a boron nitride film with a thickness of 1.4nm, and each surface of the boron nitride film has a boron nitride sheet 122 with a thickness of 15 um.

Example 4

The present embodiment provides a composite heat dissipation film 10, referring to fig. 4, which includes a graphite sheet 111 with a thickness of 20um, one surface of the graphite sheet 111 has a graphene layer 112 with a thickness of 0.7nm, the other surface of the graphite sheet 111 has a boron nitride sheet 122 with a thickness of 15um, and the surface of the graphene layer 112 has a boron nitride sheet 122 with a thickness of 15 um.

Example 5

The present embodiment provides a method for preparing the composite heat dissipation film 10 of embodiment 1, which includes:

s5-1, coating the graphene oxide dispersion liquid on both surfaces of the graphite sheet 111, and performing a reduction process to form graphene layers 112 on both surfaces of the graphite sheet 111 (see fig. 5);

s5-2, respectively growing boron nitride films on the surfaces of the two graphene layers 112 by adopting a chemical vapor deposition method (refer to FIG. 6);

s5-3, laminating a layer of boron nitride sheet 122 on both surfaces of the two boron nitride films, rolling, and heat-treating at 1600 ℃ to obtain the composite heat dissipation film 10 of example 1 (see FIG. 1).

Example 6

The present embodiment provides a method for preparing the composite heat dissipation film 10 of embodiment 2, which includes:

s6-1, coating the single surfaces of two graphite sheets 111 with graphene oxide dispersion liquid, and then carrying out reduction treatment to respectively form a graphene layer 112 on the single surfaces of the two graphite sheets 111 (refer to FIG. 7);

s6-2, laminating the graphite sheet 111 having the graphene layer 112 on the surface, the second boron nitride layer 113, the single graphite sheet 111, the second boron nitride layer 113, and the graphite sheet 111 having the graphene layer 112 on the surface in this order to obtain the heat-conducting intermediate layer 11, and making the graphene layer 112 on the outermost sides of the heat-conducting intermediate layer 11 (refer to fig. 8);

s6-3, respectively growing boron nitride films on the surfaces of the two graphene layers 112 by adopting a chemical vapor deposition method (refer to FIG. 9);

s6-4, laminating a layer of boron nitride sheet 122 on both surfaces of the two boron nitride films, rolling, and heat-treating at 1600 ℃ to obtain the composite heat dissipation film 10 of example 2 (see FIG. 2).

Example 7

The present embodiment provides a method for preparing the composite heat dissipation film 10 of embodiment 3, including:

s7-1, growing a layer of boron nitride film on both surfaces of the graphite sheet 111 by adopting a chemical vapor deposition method (refer to FIG. 5);

s7-2, laminating a layer of boron nitride sheet 122 on both surfaces of the two boron nitride films, rolling, and heat-treating at 1600 ℃ to obtain the composite heat dissipation film 10 of example 3 (see FIG. 3).

Comparative example 1

This comparative example provides a heat dissipating film which is a layer of a graphite sheet having a thickness of 20 um.

Comparative example 2

This comparative example provides a heat-dissipating film, and it includes that one deck thickness is 20 um's graphite flake, and the relative two surfaces of graphite flake all have one deck thickness to be 0.7 nm's graphite layer.

Test examples

The composite heat dissipation films of examples 1 to 4 and the heat dissipation films of comparative examples 1 to 3 were subjected to a breakdown-resistant threshold voltage test and a thermal conductivity test, wherein the breakdown-resistant threshold voltage test can represent the insulation performance of the composite material, and the thermal conductivity test can represent the heat dissipation performance of the material, and the test methods are as follows:

breakdown-resistant critical voltage test: the composite heat dissipation films of examples 1 to 4 and the heat dissipation films of comparative examples 1 to 3 were subjected to a breakdown voltage test using an insulation withstand voltage tester, wherein the voltage was set at 1000 to 2000V and alternating current was continuously applied for 60 seconds, and if the test was not reported, it was indicated that the sample could withstand the breakdown voltage test at the set voltage, and the breakdown threshold voltages of the composite heat dissipation films of examples 1 to 4 and the heat dissipation films of comparative examples 1 to 3 were recorded in table 1. It should be noted that the breakdown-resistant threshold voltage refers to a threshold voltage capable of breaking down the heat dissipation film, wherein the higher the breakdown-resistant threshold voltage is, the better the insulation performance is.

Testing the thermal conductivity coefficient: the composite heat dissipation films of examples 1 to 4 and the heat dissipation films of comparative examples 1 to 3 were tested for thermal conductivity using a thermal conductivity analyzer by a flash method, and the results are shown in table 1.

TABLE 1 breakdown Voltage resistance test results and thermal conductivity of composite Heat spreading films and Heat spreading films

As can be seen from the results in table 1, the breakdown threshold voltages of the composite heat dissipation films of examples 1 to 4 are higher than those of comparative examples 1 to 2, which indicates that the composite heat dissipation films of examples of the present application all have better insulating properties. In addition, the thermal conductivity coefficients of the composite heat dissipation film of the embodiments 1 to 4 are all high, which indicates that the composite heat dissipation film of the embodiments has good insulating property and heat dissipation effect.

In addition, it is found by comparing example 2 and example 1 that example 2 in which the second boron nitride layer is provided in the heat conductive intermediate layer and the second boron nitride layer and the graphite sheet are alternately provided has a higher breakdown voltage resistance and better insulation performance than example 1.

The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.