Low-dielectric fluorine-containing resin-based flexible heat-conducting dielectric sheet and preparation method thereof

Abstract

The invention discloses a low-dielectric fluorine-containing resin-based flexible heat-conducting dielectric sheet and a preparation method thereof, and belongs to the technical field of heat-conducting dielectric materials. The invention relates to a preparation method of a traditional Chinese medicine. Comprising the following components: 70-100 parts of a polytetrafluoroethylene emulsion, 0-20 parts of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion, 0-10 parts of a copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester, 25-30 parts of boron nitride particles, 20-25 parts of silicon dioxide, 0-25 parts of titanium dioxide, 0-10 parts of silicon nitride, 1-2 parts of a fluorine-containing polymer dispersant, and 2-3 parts of an amber ester segmented copolymer and complex wetting agent. 1-2 parts of a modified polyether defoaming agent and 1-2 parts of an acrylate thickening agent. A sizing material is obtained by blending all the materials, and then the dielectric sheet is prepared by utilizing coating and curing means and controlling the temperature. The material has high heat conductivity coefficient, excellent dielectric property and good mechanical property, and can be used as a high-frequency plate material.

Description

Technical Field

[0001] The invention belongs to the technical field of heat-conducting medium materials, and in particular relates to a low-dielectric fluorine-containing resin-based flexible heat-conducting medium sheet and a preparation method thereof. Background Art

[0002] With the development of electronic information technology, printed circuit boards (PCBs) tend to be micro-integrated, high-frequency and high-speed, resulting in high power density of PCBs, which leads to two major problems: first, a large amount of heat is accumulated. If the heat dissipation is not smooth, it will cause circuit failure and reduce the service life of electronic devices; second, the dielectric properties of PCB materials are required to be improved. High dielectric materials affect the transmission rate of signals and are difficult to meet the high-frequency and high-speed requirements of 5G communications. In addition, flexible electronic products often need to be equipped with flexible PCB materials.

[0003] However, traditional epoxy / glass fiber composite boards are difficult to meet the above requirements. Therefore, there is an urgent need to develop high-frequency board materials with excellent thermal conductivity, dielectric properties, and mechanical properties to meet the actual use needs of high-frequency and high-speed flexible electronic products. Summary of the invention

[0004] The first purpose of the present invention is to propose a method for preparing a low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet. First, various materials are blended to form a rubber compound, and then a coating and curing process is used to obtain the medium sheet. The steps are simple and easy to operate, which is conducive to large-scale mass production.

[0005] The second object of the present invention is to provide a low-dielectric fluorine-containing resin-based flexible thermally conductive dielectric sheet, which has a high thermal conductivity, excellent dielectric properties and good mechanical properties.

[0006] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] A low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following components by weight: 70-100 parts of polytetrafluoroethylene emulsion, 0-20 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion, 0-10 parts of copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester, 25-30 parts of boron nitride particles, 20-25 parts of silicon dioxide, 0-25 parts of titanium dioxide, 0-10 parts of silicon nitride, 1-2 parts of fluorine-containing polymer dispersant, 2-3 parts of amber ester block copolymer and complex wetting agent, 1-2 parts of modified polyether defoamer and 1-2 parts of acrylate thickener.

[0008] Furthermore, the following components are included, by weight: 70 parts of polytetrafluoroethylene emulsion, 20 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion, 10 parts of copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester, 25 parts of boron nitride particles, 25 parts of silicon dioxide, 10 parts of titanium dioxide, 10 parts of silicon nitride, 2 parts of fluorine-containing polymer dispersant, 2 parts of amber ester block copolymer and complex wetting agent, 1 part of modified polyether defoamer and 1 part of acrylate thickener.

[0009] Furthermore, the solid content of the polytetrafluoroethylene emulsion is 60%; the solid content of the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion is 50%; the solid content of the copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester is 50%; the boron nitride is hexagonal with a particle size of 5 to 30 μm; the silicon dioxide is crystalline with a particle size not exceeding 5 μm; the silicon nitride is β phase with a particle size not exceeding 5 μm; the titanium dioxide is hydrophilic rutile with a particle size not exceeding 0.3 μm.

[0010] Furthermore, the preparation method of any of the above-mentioned low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheets is as follows: first, a polytetrafluoroethylene emulsion is mixed with a fluorine-containing polymer dispersant, a succinate block copolymer and a complex-type wetting agent, a modified polyether defoaming agent, and an acrylate thickener to obtain an emulsion mixture; then, other thermally conductive powders are added to the emulsion mixture, and after stirring, a fluorine-containing resin-based thermally conductive adhesive is obtained; the prepared fluorine-containing resin-based thermally conductive adhesive is coated on the surface of a glass plate or a PI film, dried, and cured at high temperature, and then peeled off from the glass plate or the PI film to obtain a low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet.

[0011] Furthermore, during the preparation of the emulsion mixture, the mixing and stirring rate is 100 rpm and the mixing time is 15 min.

[0012] Furthermore, the stirring rate is 100 rpm and the time is 30 min.

[0013] Furthermore, during the coating process, a four-sided preparation device or a wire rod is used for coating; the coating thickness is 50 to 250 μm.

[0014] Furthermore, the temperature required for the drying process is 80°C.

[0015] Furthermore, the temperature required for the high temperature curing is 330-390° C., and the curing time is 10 minutes.

[0016] Furthermore, the high temperature curing heating rate is 5°C / min.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] 1) The present invention greatly improves the stability and coating film-forming properties of the fluorine-containing resin-based thermal conductive adhesive due to the addition of the fluorine-containing resin-based and filler-friendly fluorine-containing polymer dispersant.

[0019] 2) The present invention prepares a dielectric sheet having a high thermal conductivity, excellent dielectric properties and good mechanical properties by mixing different fluorine-containing resins, optimizing the ratio of thermally conductive fillers and the synergistic effect of low dielectric constant / loss of fluorine-containing resins.

[0020] 3) The present invention can be used as a high-frequency board material to meet the requirements of high-frequency and high-speed electronic circuit substrates and flexible electronic devices for efficient heat dissipation, low dielectric constant / loss, and low thermal expansion coefficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet prepared in Example 1 of the present invention;

[0022] Figure 2 This is a cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet prepared in Comparative Example 1 of the present invention;

[0023] Figure 3 This is a cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet prepared in Example 4 of the present invention;

[0024] Figure 4 This is a cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet prepared in Comparative Example 4 of the present invention;

[0025] Figure 5 This is a cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet prepared in Example 5 of the present invention;

[0026] Figure 6 This is a cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet prepared in Comparative Example 5 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0028] Unless otherwise specified, the materials or components used in the following examples are all commercially available products or products prepared by conventional methods in the laboratory.

[0029] The method for testing the performance of the dielectric sheets prepared in the following embodiments and comparative examples is as follows:

[0030] Thermal conductivity test: The test is carried out using the steady-state heat flow method (according to the standard: ASTM D5470), and the test conditions are cold stage temperature 20°C and hot stage temperature 80°C;

[0031] Dielectric constant / loss test (D K / D F ): The resonant cavity method (SPDR, according to the standard: IPC-TM-6502.5.5.5) is used for testing, and the test frequency is 10GHz;

[0032] Linear thermal expansion coefficient (CTE) test: The test is carried out using the static thermomechanical method (TMA) with a test temperature range of 50°C-160°C.

[0033] Example 1

[0034] A low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following components by weight: 100 parts of polytetrafluoroethylene emulsion (PTFE, solid content 60%), 25 parts of boron nitride (BN, hexagonal crystal, particle size 30 μm), 25 parts of silicon dioxide (SiO2, crystalline, particle size 5 μm), 10 parts of silicon nitride (Si3N4, β phase, 5 μm), 2 parts of fluorine-containing polymer dispersant, 2 parts of amber ester block copolymer and complex wetting agent, 1 part of modified polyether defoamer and 1 part of acrylic thickener.

[0035] The preparation method of the above-mentioned low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following steps:

[0036] (1) First, polytetrafluoroethylene emulsion, fluorine-containing polymer dispersant, amber ester block copolymer and complex wetting agent, modified polyether defoamer, and acrylic thickener were mixed at 100 rpm for 15 minutes, various thermal conductive powders were pre-mixed by dry method (manual shaking), and then added to the emulsion mixture in small amounts, and stirred at 100 rpm for 15 minutes to obtain a uniform fluorine-containing resin-based thermal conductive adhesive;

[0037] (2) applying the fluorine-containing resin-based thermally conductive adhesive prepared in step (1) to the surface of the glass plate using a wire rod and a four-sided preparation device, respectively, with a coating thickness of 100 μm;

[0038] (3) Place the coated rubber in an oven at 80°C for surface drying;

[0039] (4) The surface-dried coating is placed in a high-temperature oven for curing. The temperature control process during high-temperature curing is as follows: the temperature is gradually increased from room temperature to 390°C, the heating rate is controlled at 5°C / min, the temperature is maintained at 390°C for 10 minutes, and then the temperature is reduced from 390°C to room temperature, and the cooling rate is controlled at 1°C / min;

[0040] (5) Peeling the cured coating off the glass plate to obtain a low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet. The cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet is as follows: Figure 1 shown.

[0041] Example 2

[0042] A low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following components by weight: 100 parts of polytetrafluoroethylene emulsion (PTFE, solid content 60%), 25 parts of boron nitride (BN, hexagonal crystal, particle size 30 μm), 25 parts of silicon dioxide (SiO2, crystalline, particle size 5 μm), 25 parts of titanium dioxide (TiO2, hydrophilic rutile type, 0.3 μm), 2 parts of fluorine-containing copolymer dispersant, 2 parts of amber ester block copolymer and complex wetting agent, 1 part of modified polyether defoamer and 1 part of acrylic thickener.

[0043] The preparation method of the above-mentioned low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following steps:

[0044] (1) First, a polytetrafluoroethylene emulsion, a fluorine-containing copolymer dispersant, an amber ester block copolymer and a complex wetting agent, a modified polyether defoamer, and an acrylate thickener are mixed at 100 rpm for 15 minutes, various thermal conductive powders are pre-mixed by dry method (manual shaking), and then gradually added to the emulsion mixture. After stirring at 100 rpm for 15 minutes, a uniform fluorine-containing resin-based thermal conductive adhesive is obtained;

[0045] (2) coating the fluorine-containing resin-based thermally conductive adhesive prepared in step (1) on the surface of the PI film using a wire rod, with a coating thickness of 100 μm;

[0046] (3) Place the coated rubber in an oven at 80°C for surface drying;

[0047] (4) The surface-dried coating is placed in a high-temperature oven for curing. The temperature control process during high-temperature curing is as follows: the temperature is gradually increased from room temperature to 390°C, the heating rate is controlled at 5°C / min, the temperature is maintained at 390°C for 10 minutes, and then the temperature is reduced from 390°C to room temperature, and the cooling rate is controlled at 1°C / min;

[0048] (5) Peeling off the cured coating from the PI film, thus obtaining a low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet.

[0049] Example 3

[0050] A low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following components by weight: 90 parts of polytetrafluoroethylene emulsion (PTFE, solid content 60%), 10 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion (PFA, solid content 50%), 25 parts of boron nitride (BN, hexagonal crystal type, particle size 30μm), 25 parts of silicon dioxide (SiO2, crystalline type, particle size 5μm), 25 parts of titanium dioxide (TiO2, hydrophilic rutile type, 0.3μm), 2 parts of fluorine-containing copolymer dispersant, 2 parts of succinate block copolymer and complex wetting agent, 1 part of modified polyether defoamer and 1 part of acrylic thickener.

[0051] The preparation method of the above-mentioned low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following steps:

[0052] (1) First, a polytetrafluoroethylene emulsion, a fluorine-containing copolymer dispersant, an amber ester block copolymer and a complex wetting agent, a modified polyether defoamer, and an acrylate thickener are mixed at 100 rpm for 15 minutes, various thermal conductive powders are pre-mixed by dry method (manual shaking), and then gradually added to the emulsion mixture. After stirring at 100 rpm for 15 minutes, a uniform fluorine-containing resin-based thermal conductive adhesive is obtained;

[0053] (2) coating the fluorine-containing resin-based thermally conductive adhesive prepared in step (1) on the surface of the PI film using a four-sided coating device, with a coating thickness of 100 μm;

[0054] (3) Place the coated rubber in an oven at 80°C for surface drying;

[0055] (4) The surface-dried coating is placed in a high-temperature oven for curing. The temperature control process during high-temperature curing is as follows: the temperature is gradually increased from room temperature to 360°C, the heating rate is controlled at 5°C / min, the temperature is maintained at 360°C for 10 minutes, and then the temperature is reduced from 360°C to room temperature, and the cooling rate is controlled at 1°C / min;

[0056] (5) Peeling off the cured coating from the PI film, thus obtaining a low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet.

[0057] Example 4

[0058] A low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following components by weight: 90 parts of polytetrafluoroethylene emulsion (PTFE, solid content 60%), 10 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion (PFA, solid content 50%), 25 parts of boron nitride (BN, hexagonal crystal type, particle size 30μm), 25 parts of silicon dioxide (SiO2, crystalline type, particle size 5μm), 10 parts of silicon nitride (Si3N4, β phase, 5μm), 10 parts of titanium dioxide (TiO2, hydrophilic rutile type, 0.3μm), 2 parts of fluorine-containing copolymer dispersant, 2 parts of succinate block copolymer and complex wetting agent, 1 part of modified polyether defoamer and 1 part of acrylic thickener.

[0059] The preparation method of the above-mentioned low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following steps:

[0060] (1) First, a polytetrafluoroethylene emulsion, a fluorine-containing copolymer dispersant, an amber ester block copolymer and a complex wetting agent, a modified polyether defoamer, and an acrylate thickener are mixed at 100 rpm for 15 minutes, various thermal conductive powders are pre-mixed by dry method (manual shaking), and then gradually added to the emulsion mixture. After stirring at 100 rpm for 15 minutes, a uniform fluorine-containing resin-based thermal conductive adhesive is obtained;

[0061] (2) coating the fluorine-containing resin-based thermally conductive adhesive prepared in step (1) on the surface of the PI film using a four-sided coating device, with a coating thickness of 100 μm;

[0062] (3) Place the coated rubber in an oven at 80°C for surface drying;

[0063] (4) The surface-dried coating is placed in a high-temperature oven for curing. The temperature control process during high-temperature curing is as follows: the temperature is gradually increased from room temperature to 360°C, the heating rate is controlled at 5°C / min, the temperature is maintained at 360°C for 10 minutes, and then the temperature is reduced from 360°C to room temperature, and the cooling rate is controlled at 1°C / min;

[0064] (5) Peeling off the cured coating from the PI film, a low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet is obtained. The cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet is as follows: Figure 3 shown.

[0065] Example 5

[0066] A low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following components by weight: 70 parts of polytetrafluoroethylene emulsion (PTFE, solid content 60%), 20 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion (PFA, solid content 50%), 10 parts of fluoroolefin and alkyl vinyl ether or ester copolymer emulsion (FEVE, solid content 50%), 25 parts of boron nitride (BN, hexagonal crystal type, particle size 30μm), 25 parts of silicon dioxide (SiO2, crystalline type, particle size 5μm), 10 parts of silicon nitride (Si3N4, β phase, 5μm), 10 parts of titanium dioxide (TiO2, hydrophilic rutile type, 0.3μm), 2 parts of fluorine-containing copolymer dispersant, 2 parts of succinate block copolymer and complex wetting agent, 1 part of modified polyether defoamer and 1 part of acrylic thickener.

[0067] The preparation method of the above-mentioned low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet comprises the following steps:

[0068] (1) First, a polytetrafluoroethylene emulsion, a fluorine-containing copolymer dispersant, an amber ester block copolymer and a complex wetting agent, a modified polyether defoamer, and an acrylate thickener are mixed at 100 rpm for 15 minutes, various thermal conductive powders are pre-mixed by dry method (manual shaking), and then gradually added to the emulsion mixture. After stirring at 100 rpm for 15 minutes, a uniform fluorine-containing resin-based thermal conductive adhesive is obtained;

[0069] (2) coating the fluorine-containing resin-based thermally conductive adhesive prepared in step (1) on the surface of the PI film using a four-sided coating device, with a coating thickness of 100 μm;

[0070] (3) Place the coated rubber in an oven at 80°C for surface drying;

[0071] (4) The surface-dried coating is placed in a high-temperature oven for curing. The temperature control process during high-temperature curing is as follows: the temperature is gradually increased from room temperature to 330°C, the heating rate is controlled at 5°C / min, the temperature is maintained at 330°C for 10 minutes, and then the temperature is reduced from 330°C to room temperature, and the cooling rate is controlled at 1°C / min;

[0072] (5) Peeling off the cured coating from the PI film, a low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet is obtained. The cross-sectional SEM image of the low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet is as follows: Figure 5 shown.

[0073] Comparative Example 1

[0074] Different from Example 1, the type of dispersant is changed, and the dispersant used is a fluorine-free polymer dispersant. The other components and steps are the same as Example 1. The cross-sectional SEM of the prepared thermal conductive medium sheet is as follows: Figure 2 shown.

[0075] Comparative Example 2

[0076] Different from Example 2, the type of dispersant is changed, and the dispersant used is a fluorine-free polymer dispersant. The other components and steps are the same as those in Example 2.

[0077] Comparative Example 3

[0078] Different from Example 3, the type of dispersant is changed, and the dispersant used is a fluorine-free polymer dispersant. The other components and steps are the same as those in Example 3.

[0079] Comparative Example 4

[0080] Different from Example 4, the particle size of the boron nitride used is 5 μm, and the other components and steps are the same as those of Example 4. The cross-sectional SEM of the prepared thermal conductive medium sheet is as follows: Figure 4 shown.

[0081] Comparative Example 5

[0082] Different from Example 5, the copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester (FEVE, solid content 50%) is replaced by ethylene-tetrafluoroethylene copolymer emulsion (ETFE, solid content 50%), and the remaining components and steps are the same as Example 5. The cross-sectional SEM of the prepared thermal conductive medium sheet is as follows: Figure 6 shown.

[0083] The dielectric sheets prepared in the above-mentioned Examples 1 to 5 and Comparative Examples 1 to 5 were respectively subjected to thermal conductivity test, dielectric constant / loss test (DK / DF) and linear thermal expansion coefficient (CTE) test, and the specific test results are shown in Table 1 below:

[0084] Table 1 Comparison of various performance tests of dielectric sheets prepared in Examples 1 to 5 and Comparative Examples 1 to 5

[0085]

[0086] It can be seen from the data in Table 1 that the results of Examples 1-3 and Comparative Examples 1-3 show that the addition of fluorinated polymer dispersants significantly improves the thermal conductivity of dielectric sheets with different thermal conductive fillers or composite fluorinated emulsions. Figure 1 and Figure 2As shown, it is shown that Example 1 has a denser microstructure. The main reason is that, on the one hand, the fluorine atoms in the fluorine-containing polymer dispersant replace the hydrogen atoms on the alkyl chain, and the formed fluorocarbon chain greatly reduces the surface tension of the entire system, plays the role of a surfactant, and makes the thermal conductive filler uniformly dispersed in the continuous phase to form a stable suspension; on the other hand, the fluorine-containing polymer dispersant contains filler-friendly groups, which improves the interface compatibility between the organic matrix and the inorganic powder, plays the role of a coupling agent, greatly reduces the interface thermal resistance of the composite material itself, and thus improves the thermal conductivity.

[0087] As shown in Example 4 and Comparative Example 4, the particle size of boron nitride has a greater influence on the thermal conductivity, and the large-size boron nitride has a more obvious effect on the thermal conductivity of the dielectric sheet. Figure 3 and Figure 4 As shown, large-sized boron nitride is more conducive to the construction of thermal conductive paths.

[0088] As shown in Example 5 and Comparative Example 5, compared with ETFE, the addition of FEVE can greatly improve the thermal conductivity, dielectric properties and mechanical properties of the dielectric sheet. This is mainly because the introduction of the alkyl vinyl ether or ester segment in FEVE makes the melt viscosity reach a suitable level, while improving the melt processability without destroying the overall structural strength, so that the thermal conductive powder is more densely packed. Figure 5 and Figure 6 It shows that adding more ETFE dielectric sheets will result in fewer heat conduction paths, which will comprehensively improve the performance of the dielectric sheet and have important practical significance for the preparation of fluorine-containing resin thermal conductive dielectric sheets.

[0089] The preparation process adopted by the present invention produces a synergistic effect by optimizing the material types and ratios, and can take into account the thermal conductivity, dielectric properties, and mechanical properties to prepare a low-dielectric fluorine-containing resin-based flexible thermal conductive medium sheet, which can be used as a high-frequency board material to meet the requirements of high-frequency and high-speed electronic circuit substrates and flexible electronic devices for efficient heat dissipation, low dielectric constant / loss, and low thermal expansion coefficient.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low dielectric fluorine-containing resin-based flexible thermal conductive medium sheet, characterized in that: The invention comprises the following components by weight: 70-100 parts of polytetrafluoroethylene emulsion, 0-20 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion, 0-10 parts of copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester, 25-30 parts of boron nitride particles, 20-25 parts of silicon dioxide, 0-25 parts of titanium dioxide, 0-10 parts of silicon nitride, 1-2 parts of fluorine-containing polymer dispersant, 2-3 parts of succinate block copolymer and complex wetting agent, 1-2 parts of modified polyether defoamer and 1-2 parts of acrylate thickener.

2. The low dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 1, characterized in that: The invention comprises the following components by weight: 70 parts of polytetrafluoroethylene emulsion, 20 parts of tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion, 10 parts of copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester, 25 parts of boron nitride particles, 25 parts of silicon dioxide, 10 parts of titanium dioxide, 10 parts of silicon nitride, 2 parts of fluorine-containing polymer dispersant, 2 parts of succinate block copolymer and complex wetting agent, 1 part of modified polyether defoamer and 1 part of acrylate thickener.

3. The low dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 1 or 2, characterized in that: The solid content of the polytetrafluoroethylene emulsion is 60%; the solid content of the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer emulsion is 50%; the solid content of the copolymer emulsion of fluoroolefin and alkyl vinyl ether or ester is 50%; the boron nitride is hexagonal with a particle size of 5 to 30 μm; the silicon dioxide is crystalline with a particle size not exceeding 5 μm; the silicon nitride is β phase with a particle size not exceeding 5 μm; the titanium dioxide is hydrophilic rutile with a particle size not exceeding 0.3 μm.

4. A method for preparing a low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet as claimed in any one of claims 1 to 3, characterized in that: First, polytetrafluoroethylene emulsion is mixed with fluorine-containing polymer dispersant, amber ester block copolymer and complex wetting agent, modified polyether defoamer, and acrylate thickener to obtain an emulsion mixture; then other thermally conductive powders are added to the emulsion mixture, and after stirring, a fluorine-containing resin-based thermally conductive adhesive is obtained; the prepared fluorine-containing resin-based thermally conductive adhesive is coated on the surface of a glass plate or a PI film, dried, and cured at high temperature, and then peeled off from the glass plate or the PI film to obtain a low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet.

5. The method for preparing the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 4, characterized in that: During the preparation of the emulsion mixture, the mixing and stirring rate was 100 rpm and the mixing time was 15 min.

6. The method for preparing the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 4, characterized in that: The stirring speed is 100 rpm and the time is 30 min.

7. The method for preparing a low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 4, characterized in that: During the coating process, a four-sided preparation device or a wire rod is used for coating; the coating thickness is 50 to 250 μm.

8. The method for preparing a low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 4, characterized in that: The temperature required for the drying process is 80°C.

9. The method for preparing a low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 4, characterized in that: The temperature required for the high temperature curing is 330-390° C., and the curing time is 10 minutes.

10. The method for preparing the low-dielectric fluorine-containing resin-based flexible thermally conductive medium sheet according to claim 9, characterized in that: The high temperature curing heating rate is 5°C / min.

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