1. A low dielectric constant heat conduction membrane is characterized in that: comprises hexagonal boron nitride powder, a defoaming agent, a dispersing agent, an adhesive and a plasticizer.

2. The low dielectric constant thermally conductive film of claim 1, wherein: the low-dielectric constant heat-conducting membrane can also comprise deionized water and absolute ethyl alcohol.

3. The low dielectric constant thermally conductive film of claim 1, wherein: in the low-dielectric-constant heat-conducting membrane, the dosage of the defoaming agent is 0.05-0.4 wt% of the mass of the hexagonal boron nitride powder; the dosage of the dispersant is 0.5 to 3 weight percent of the mass of the hexagonal boron nitride powder; the mass of the adhesive is 30-60 wt% of the mass of the boron nitride powder; the dosage of the plasticizer is 1-5 wt% of the hexagonal boron nitride powder.

4. A method for preparing a low dielectric constant thermal conductive film as defined in any one of claims 1 to 3, wherein: the method comprises the following steps:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

5. The method of claim 4, wherein the method comprises: s1, the mixed solvent comprises deionized water and absolute ethyl alcohol; and the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent of S1 is (5-20): 1.

6. The method of claim 4, wherein the method comprises: s2, the mass of the hexagonal boron nitride powder is 40-70 wt% of the mass of the mixed solvent; s3, the dosage of the defoaming agent is 0.05-0.4 wt% of the mass of the hexagonal boron nitride powder; the dosage of the dispersant S3 is 0.5-3 wt% of the mass of the hexagonal boron nitride powder.

7. The method of claim 4, wherein the method comprises: s3, the dispersion is uniform, and the method specifically comprises the following steps: adding the obtained mixture into a sand mill, and sanding for 1-5h under the conditions that the rotation speed of a main machine is 500-1500rpm and the material temperature is 20-40 ℃.

8. The method of claim 4, wherein the method comprises: s4, the adhesive dispersion liquid comprises an adhesive and deionized water; s4, the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1 (1-4).

9. The method of claim 4, wherein the method comprises: s5, the mass of the adhesive in the adhesive dispersion liquid is 30-60 wt% of the mass of the boron nitride powder in the slurry 3; s5, dispersing, including: the obtained mixture is added into a sand mill and is subjected to sand milling for 2 to 6 hours under the conditions that the rotation speed of a main machine is 700 and 1500rpm and the material temperature is 20 to 40 ℃.

10. The method of claim 4, wherein the method comprises: s6, the dosage of the plasticizer is 1-5 wt% of the mass of the hexagonal boron nitride powder contained in the slurry 5; s6, dispersing uniformly, including: the mixture is added into a sand mill and is milled for 1h under the conditions that the rotation speed of a main machine is 700 and 1500rpm and the material temperature is 20-40 ℃.

Background

With the advent of the 5G era, high-power high-frequency signal transmitting devices/5G devices and mobile terminals are beginning to rapidly move into the production and life of people. The heat conducting film is an important factor for limiting the performance of products in the field of electronic products, and based on the heat conducting (heat dissipation) requirements of circuit boards and devices, low-dielectric-constant high-heat conducting materials are often needed, and especially the circuit boards and the devices are seriously heated due to the characteristics of high power, high frequency, high operating speed and the like of the high-power high-frequency signal transmitting equipment/5G equipment and the mobile terminal, so that new requirements are provided for the heat conducting performance and the dielectric constant of the heat conducting materials.

In the existing method for preparing the low-dielectric-constant heat-conducting membrane, materials such as reinforced fibers and the like are often required to be added in order to ensure the mechanical properties of the membrane, such as mechanical strength and the like, and the materials reduce the heat-conducting property of the product or increase the dielectric constant of the product to a certain extent. In addition, in order to realize effective heat conduction in the heat conducting membrane, a three-dimensional structure in the membrane is required to be prepared by adding material components or reflecting steps, so that the heat dissipation efficiency is improved, however, due to the added material components or reflecting products, the performance of the membrane can be gained only from the three-dimensional structure, and the material properties of the membrane are not helpful, so that the method has no practical value in industrial production on the basis of increasing a large amount of cost and production time.

Disclosure of Invention

Based on the problems of the existing method for preparing the low-dielectric-constant heat-conducting membrane, the invention provides the low-dielectric-constant heat-conducting membrane with simple components and simple preparation steps and the preparation method thereof, and the scheme is as follows:

the invention provides a low-dielectric-constant heat-conducting membrane, which comprises hexagonal boron nitride powder, a defoaming agent, a dispersing agent, an adhesive and a plasticizer.

Preferably, the low-dielectric constant heat-conducting membrane can also comprise deionized water and absolute ethyl alcohol.

Preferably, the hexagonal boron nitride powder has a particle size of 2 to 50 μm.

Preferably, the defoamer comprises one or both of Staradd DF520 and Staradd DF 535.

Preferably, the Dispersant comprises one or two of SN-5040, Zhongya 5040 and Dispersant-5040.

Preferably, the binder in the binder dispersion comprises one or both of a vinyl acetate resin and an acrylic resin.

Preferably, the plasticizer comprises one or more of DBP, DOP, DBO, DCP, DIDP.

Preferably, in the low-dielectric constant heat-conducting membrane, the dosage of the defoaming agent is 0.05-0.4 wt% of the mass of the hexagonal boron nitride powder.

Preferably, in the low-dielectric constant heat-conducting membrane, the dosage of the dispersant is 0.5-3% wt of the mass of the hexagonal boron nitride powder.

Preferably, in the low-dielectric constant heat-conducting membrane, the mass of the adhesive is 30-60% wt of the mass of the boron nitride powder.

Preferably, in the low-dielectric constant heat-conducting membrane, the amount of the plasticizer is 1-5 wt% of the mass of the hexagonal boron nitride powder.

In addition, the invention also provides a preparation method of the low-dielectric-constant heat-conducting membrane, which comprises the following steps:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Preferably, the mixed solvent of S1 includes deionized water and absolute ethanol.

Preferably, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent of S1 is (5-20): 1.

Preferably, the mass of the hexagonal boron nitride powder S2 is 40-70 wt% of the mass of the mixed solvent.

Preferably, the particle size of the hexagonal boron nitride powder S2 is 2-50 μm.

Preferably, the dispersion in S2 is performed by using a disperser or a homogenizer.

Preferably, the defoamer of S3 comprises one or both of Staradd DF520 and Staradd DF 535.

Preferably, the Dispersant of S3 comprises one or two of SN-5040, Zhongya 5040 and Dispersant-5040.

Preferably, the amount of the defoaming agent S3 is 0.05-0.4% wt of the mass of the hexagonal boron nitride powder.

Preferably, the dispersant of S3 is used in an amount of 0.5-3% wt based on the mass of the hexagonal boron nitride powder.

Preferably, in S3, at concentration C of antifoam_xAfter determination, dispersant C was determined by the following formula_fThe concentration of (a):

wherein, C_xAnd C_fThe meaning of the mass percent concentration is g/100g, m is a constant and takes the value of 65-86, and n is a constant and takes the value of 1-9.

Preferably, the dispersing of S3 is uniform, including: the resulting mixture was added to a sand mill and sanded.

Preferably, the dispersion of S3 is uniform, and specifically includes: adding the obtained mixture into a sand mill, and sanding for 1-5h under the conditions that the rotation speed of a main machine is 500-1500rpm and the material temperature is 20-40 ℃.

Preferably, the adhesive dispersion liquid of S4 includes an adhesive and deionized water.

Preferably, the adhesive in the adhesive dispersion of S4 includes one or both of a vinyl acetate resin and an acrylic resin.

Preferably, the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid of S4 is 1 (1-4).

Preferably, the mass of the binder in the binder dispersion of S5 is 30-60% wt of the mass of the boron nitride powder in slurry 3.

Preferably, the dispersing of S5, comprises: adding the obtained mixture into a sand mill, and sanding for 2-6h under the conditions that the rotation speed of a main machine is 700 and 1500rpm and the material temperature is 20-40 ℃.

Preferably, S6 the plasticizer comprises one or more of DBP, DOP, DBO, DCP, DIDP.

Preferably, the plasticizer of S6 is used in an amount of 1-5% wt based on the mass of hexagonal boron nitride powder contained in slurry 5.

Preferably, the dispersing of S6 is uniform, including: adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 700 and 1500rpm and the material temperature is 20-40 ℃.

Preferably, the method for preparing the film as described in S7 includes one or more of doctor blade coating, spray coating, spin coating, calendering, suction filtration, and adsorption.

Preferably, the preparation described in S7 is film-formed, the film thickness being 10 to 1000. mu.m.

Preferably, in all the sanding steps, the method for determining the sanding finishing time point is as follows: when Δ u (i) < 0.01;

wherein, the delta u (i) corresponds to the variation of the concentration in the time interval of two times of concentration testing; k_iIs constant and takes the value of 8-13; f (i) is the deviation of the ith sampling time, f (i-1) is the deviation of the ith-1 sampling time, and f (i-2) is the deviation of the ith-2 sampling time; t is_zIs a sampling period of 10-30s, T_IIntegration time is 2-8 min; t is_wDifferentiation time, 2-8 min.

Advantageous effects

The invention has the beneficial effects that:

according to the invention, a reinforced fiber material is not required to be added into the raw material formula, and the mechanical properties of the heat-conducting membrane including the mechanical strength composite application standard can be ensured only by specific limitation of parameters such as material selection, proportion and the like of each component in the formula, so that the cost increase and other property reduction caused by adding the reinforced fiber are avoided.

According to the invention, a three-dimensional structure is not required to be prepared in the heat-conducting membrane through materials or specific reaction, so that high-speed heat conduction is realized, and high heat conductivity and low dielectric constant can be ensured only through a formula and a specific preparation method.

The raw materials used in the invention are all common materials, the cost is low, the preparation steps are simple, no special and unusual equipment is needed, the method is suitable for large-scale industrial production, and the method has very high application value.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

The following examples and comparative examples are parallel runs, with the same processing steps and parameters, unless otherwise indicated.

Example 1 preparation of low dielectric constant thermally conductive film:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Wherein:

s1, the mixed solvent comprises deionized water and absolute ethyl alcohol.

And S1, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent is 5: 1.

And the mass of the hexagonal boron nitride powder S2 is 40 wt% of the mass of the mixed solvent.

And the grain diameter of the hexagonal boron nitride powder S2 is 2-50 μm.

And S2, dispersing by using a dispersing machine.

S3 the defoamer comprises Staradd DF 520.

The dispersant of S3 includes SN-5040.

S3 the dosage of the defoaming agent is 0.05 wt% of the mass of the hexagonal boron nitride powder.

The dosage of the dispersant S3 is 0.5 wt% of the mass of the hexagonal boron nitride powder.

S3, the dispersion is uniform, and the method specifically comprises the following steps: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 500rpm and the material temperature is 20 ℃.

S4 the adhesive dispersion liquid comprises an adhesive and deionized water.

The adhesive in the adhesive dispersion of S4 includes an acrylic resin.

And S4, wherein the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1: 1.

S5 the binder in the binder dispersion liquid accounts for 30 wt% of the mass of the boron nitride powder in the slurry 3.

S5, dispersing, including: and adding the obtained mixture into a sand mill, and sanding for 2 hours under the conditions that the rotation speed of a main machine is 700rpm and the material temperature is 20 ℃.

S6 the plasticizer comprises DOP.

S6 the amount of the plasticizer is 1 wt% of the mass of the hexagonal boron nitride powder contained in the slurry 5.

S6, dispersing uniformly, including: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 700rpm and the material temperature is 20 ℃.

S7 the method for preparing the film includes spraying.

S7 the film is formed, and the thickness of the film is 300 μm.

Example 2 preparation of low dielectric constant thermally conductive film:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Wherein:

s1, the mixed solvent comprises deionized water and absolute ethyl alcohol.

And S1, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent is 20: 1.

And the mass of the hexagonal boron nitride powder S2 is 70 wt% of the mass of the mixed solvent.

And the grain diameter of the hexagonal boron nitride powder S2 is 2-50 μm.

And S2, dispersing by using a dispersing machine.

S3 the defoamer comprises Staradd DF 535.

The dispersant of S3 includes ZHONGYA 5040.

S3 the dosage of the defoaming agent is 0.4 wt% of the mass of the hexagonal boron nitride powder.

S3 the dosage of the dispersant is 3 wt% of the mass of the hexagonal boron nitride powder.

S3, the dispersion is uniform, and the method specifically comprises the following steps: and adding the obtained mixture into a sand mill, and sanding for 5 hours at the rotation speed of a main machine of 1500rpm and the material temperature of 40 ℃.

S4 the adhesive dispersion liquid comprises an adhesive and deionized water.

S4 the adhesive in the adhesive dispersion liquid includes vinyl acetate resin.

And S4, wherein the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1: 4.

S5 the mass of the binder in the binder dispersion liquid is 60 wt% of the mass of the boron nitride powder in the slurry 3.

S5, dispersing, including: and adding the obtained mixture into a sand mill, and sanding for 6 hours under the conditions that the rotation speed of a main machine is 1500rpm and the material temperature is 40 ℃.

S6 the plasticizer comprises DBO.

S6 the amount of the plasticizer is 5 wt% of the mass of the hexagonal boron nitride powder contained in the slurry 5.

S6, dispersing uniformly, including: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 1500rpm and the material temperature is 40 ℃.

S7 the method for preparing the film includes suction filtration.

S7 the film is formed, and the thickness of the film is 300 μm.

Example 3 preparation of low dielectric constant thermally conductive film:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Wherein:

s1, the mixed solvent comprises deionized water and absolute ethyl alcohol.

And S1, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent is 15: 1.

And the mass of the hexagonal boron nitride powder S2 is 60 wt% of the mass of the mixed solvent.

And the grain diameter of the hexagonal boron nitride powder S2 is 2-50 μm.

And S2, dispersing by using a dispersing machine.

S3 the defoamer comprises Staradd DF 520.

S3 the Dispersant includes Dispersant-5040.

S3 the dosage of the defoaming agent is 0.2 wt% of the mass of the hexagonal boron nitride powder.

The dosage of the dispersant S3 is 1.5 wt% of the mass of the hexagonal boron nitride powder.

S3, dispersing uniformly, including: the resulting mixture was added to a sand mill and sanded.

S3, the dispersion is uniform, and the method specifically comprises the following steps: and adding the obtained mixture into a sand mill, and sanding for 3 hours under the conditions that the rotation speed of a main machine is 900rpm and the material temperature is 30 ℃.

S4 the adhesive dispersion liquid comprises an adhesive and deionized water.

The adhesive in the adhesive dispersion of S4 includes an acrylic resin.

And S4, wherein the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1: 2.

S5 the binder in the binder dispersion liquid accounts for 50 wt% of the mass of the boron nitride powder in the slurry 3.

S5, dispersing, including: and adding the obtained mixture into a sand mill, and sanding for 4 hours under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S6 the plasticizer comprises DBP.

S6 the amount of the plasticizer is 3 wt% of the hexagonal boron nitride powder contained in the slurry 5.

S6, dispersing uniformly, including: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S7 the method for preparing a film includes knife coating.

S7 the film is formed, and the thickness of the film is 300 μm.

Example 4 preparation of low dielectric constant thermally conductive film:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Wherein:

s1, the mixed solvent comprises deionized water and absolute ethyl alcohol.

And S1, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent is 15: 1.

And the mass of the hexagonal boron nitride powder S2 is 60 wt% of the mass of the mixed solvent.

And the grain diameter of the hexagonal boron nitride powder S2 is 2-50 μm.

And S2, dispersing by using a dispersing machine.

S3 the defoamer comprises Staradd DF 520.

S3 the Dispersant includes Dispersant-5040.

S3 the dosage of the defoaming agent is 0.2 wt% of the mass of the hexagonal boron nitride powder.

The dosage of the dispersant S3 is 1.5 wt% of the mass of the hexagonal boron nitride powder.

S3, dispersing uniformly, including: the resulting mixture was added to a sand mill and sanded.

S3, the dispersion is uniform, and the method specifically comprises the following steps: and adding the obtained mixture into a sand mill, and sanding for 3 hours under the conditions that the rotation speed of a main machine is 900rpm and the material temperature is 30 ℃.

S4 the adhesive dispersion liquid comprises an adhesive and deionized water.

The adhesive in the adhesive dispersion of S4 includes an acrylic resin.

And S4, wherein the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1: 2.

S5 the binder in the binder dispersion liquid accounts for 50 wt% of the mass of the boron nitride powder in the slurry 3.

S5, dispersing, including: and adding the obtained mixture into a sand mill, and sanding for 4 hours under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S6 the plasticizer comprises DBP.

S6 the amount of the plasticizer is 3 wt% of the hexagonal boron nitride powder contained in the slurry 5.

S6, dispersing uniformly, including: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S7 the method for preparing a film includes knife coating.

S7 the film is formed, and the thickness of the film is 500 μm.

Example 5 preparation of low dielectric constant thermally conductive film:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Wherein:

s1, the mixed solvent comprises deionized water and absolute ethyl alcohol.

And S1, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent is 15: 1.

And the mass of the hexagonal boron nitride powder S2 is 60 wt% of the mass of the mixed solvent.

And the grain diameter of the hexagonal boron nitride powder S2 is 2-50 μm.

And S2, dispersing by using a dispersing machine.

S3 the defoamer comprises Staradd DF 520.

S3 the Dispersant includes Dispersant-5040.

S3 the dosage of the defoaming agent is 0.2 wt% of the mass of the hexagonal boron nitride powder.

The dosage of the dispersant S3 is 1.5 wt% of the mass of the hexagonal boron nitride powder.

S3, dispersing uniformly, including: the resulting mixture was added to a sand mill and sanded.

S3, the dispersion is uniform, and the method specifically comprises the following steps: and adding the obtained mixture into a sand mill, and sanding for 3 hours under the conditions that the rotation speed of a main machine is 900rpm and the material temperature is 30 ℃.

S4 the adhesive dispersion liquid comprises an adhesive and deionized water.

The adhesive in the adhesive dispersion of S4 includes an acrylic resin.

And S4, wherein the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1: 2.

S5 the binder in the binder dispersion liquid accounts for 50 wt% of the mass of the boron nitride powder in the slurry 3.

S5, dispersing, including: and adding the obtained mixture into a sand mill, and sanding for 4 hours under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S6 the plasticizer comprises DOP.

S6 the amount of the plasticizer is 3 wt% of the hexagonal boron nitride powder contained in the slurry 5.

S6, dispersing uniformly, including: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S7 the method for preparing a film includes spin coating.

S7 is prepared into a film with the thickness of 700 μm.

Example 6 preparation of low dielectric constant thermally conductive film:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Wherein:

s1, the mixed solvent comprises deionized water and absolute ethyl alcohol.

And S1, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent is 15: 1.

And the mass of the hexagonal boron nitride powder S2 is 60 wt% of the mass of the mixed solvent.

And the grain diameter of the hexagonal boron nitride powder S2 is 2-50 μm.

And S2, dispersing by using a dispersing machine.

S3 the defoamer comprises Staradd DF 520.

S3 the Dispersant includes Dispersant-5040.

At concentration C of antifoaming agent in S3_xAfter determination, dispersant C was determined by the following formula_fThe concentration of (a):

wherein, C_xAnd C_fThe meaning of the mass percent concentration is g/100g, m is a constant and takes the value of 65-86, and n is a constant and takes the value of 1-9.

S3, dispersing uniformly, including: the resulting mixture was added to a sand mill and sanded.

S3, the dispersion is uniform, and the method specifically comprises the following steps: and adding the obtained mixture into a sand mill, and sanding for 3 hours under the conditions that the rotation speed of a main machine is 900rpm and the material temperature is 30 ℃.

S4 the adhesive dispersion liquid comprises an adhesive and deionized water.

The adhesive in the adhesive dispersion of S4 includes an acrylic resin.

And S4, wherein the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1: 2.

S5 the binder in the binder dispersion liquid accounts for 50 wt% of the mass of the boron nitride powder in the slurry 3.

S5, dispersing, including: and adding the obtained mixture into a sand mill, and sanding for 4 hours under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S6 the plasticizer comprises DOP.

S6 the amount of the plasticizer is 3 wt% of the hexagonal boron nitride powder contained in the slurry 5.

S6, dispersing uniformly, including: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S7 the method for preparing a film includes spin coating.

S7 the film is formed, and the thickness of the film is 300 μm.

In the embodiment, a specific concentration ratio parameter of the defoaming agent and the dispersing agent is adopted, the specific ratio can ensure that the finished heat-conducting membrane does not contain bubbles and breakpoints, and compared with the product in the embodiment 3, the membrane prepared in the embodiment still contains a very small amount of bubbles, and the membrane prepared in the embodiment does not contain any bubbles and breakpoints.

Example 7 preparation of low dielectric constant thermally conductive film:

s1, preparing a mixed solvent;

s2, dispersing the hexagonal boron nitride powder into the mixed solvent to obtain a mixed system 2;

s3, sequentially adding a defoaming agent and a dispersing agent into the mixed system 2, and uniformly dispersing to obtain slurry 3;

s4, preparing an adhesive dispersion liquid;

s5, adding the adhesive dispersion liquid into the slurry 3, and uniformly dispersing to obtain slurry 5;

s6, adding a plasticizer into the slurry 5, and uniformly dispersing to obtain low-dielectric-constant heat-conducting membrane slurry;

s7, preparing the low-dielectric-constant heat-conducting membrane slurry into a membrane.

Wherein:

s1, the mixed solvent comprises deionized water and absolute ethyl alcohol.

And S1, the volume ratio of the deionized water to the absolute ethyl alcohol in the mixed solvent is 15: 1.

And the mass of the hexagonal boron nitride powder S2 is 60 wt% of the mass of the mixed solvent.

And the grain diameter of the hexagonal boron nitride powder S2 is 2-50 μm.

And S2, dispersing by using a dispersing machine.

S3 the defoamer comprises Staradd DF 520.

S3 the Dispersant includes Dispersant-5040.

S3 the dosage of the defoaming agent is 0.2 wt% of the mass of the hexagonal boron nitride powder.

The dosage of the dispersant S3 is 1.5 wt% of the mass of the hexagonal boron nitride powder.

S3, dispersing uniformly, including: the resulting mixture was added to a sand mill and sanded.

S3, the dispersion is uniform, and the method specifically comprises the following steps: and adding the obtained mixture into a sand mill, and sanding for 3 hours under the conditions that the rotation speed of a main machine is 900rpm and the material temperature is 30 ℃.

S4 the adhesive dispersion liquid comprises an adhesive and deionized water.

The adhesive in the adhesive dispersion of S4 includes an acrylic resin.

And S4, wherein the volume ratio of the adhesive to the deionized water in the adhesive dispersion liquid is 1: 2.

S5 the binder in the binder dispersion liquid accounts for 50 wt% of the mass of the boron nitride powder in the slurry 3.

S5, dispersing, including: and adding the obtained mixture into a sand mill, and sanding for 4 hours under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S6 the plasticizer comprises DOP.

S6 the amount of the plasticizer is 3 wt% of the hexagonal boron nitride powder contained in the slurry 5.

S6, dispersing uniformly, including: and adding the obtained mixture into a sand mill, and sanding for 1h under the conditions that the rotation speed of a main machine is 1000rpm and the material temperature is 30 ℃.

S7 the method for preparing a film includes spin coating.

S7 the film is formed, and the thickness of the film is 300 μm.

In all the sanding steps, the method for determining the sanding finishing time point comprises the following steps: when Δ u (i) < 0.01;

wherein, the delta u (i) corresponds to the variation of the concentration in the time interval of two times of concentration testing; k_iIs constant and takes the value of 8-13; f (i) is the deviation of the ith sampling time, f (i-1) is the deviation of the ith-1 sampling time, and f (i-2) is the deviation of the ith-2 sampling time; t is_zIs a sampling period of 10-30s, T_IIntegration time is 2-8 min; t is_wDifferentiation time, 2-8 min.

In the embodiment, a method for determining the sanding finishing time point is specified by a specific algorithm, the next step can be performed after complete material mixing is ensured through real-time feedback, the problems of non-uniformity, poor mechanical performance and the like of a product membrane caused by incomplete material mixing are avoided, and compared with embodiment 3, the membrane prepared by the embodiment is more uniform, and the mechanical performance (tensile strength) is better.

The films obtained in examples 1-7 were individually tested for performance using the test criteria set forth in the following table, wherein the test results for examples 1-5 are set forth in the following table:

the product performance is as follows:

coefficient of thermal conductivity	Unit of	Numerical value	Test standard
				Volume resistivity	Ω*cm	1.03*1016-1.20*1016	ASTMD257
Dielectric constant	@1MHz	4.0-4.2	ASTMD150
				Dielectric loss	@1MHz	0.001-0.01	ASTMD150
Density of	g/cm3	1.6-2.0	ASTMD792
				Coefficient of thermal diffusion	mm2/s	18-36	ASTME1461
Coefficient of thermal conductivity	W/(m·K)	30-80	ASTME1461

From the above table, compared with the heat-conducting membrane prepared by the traditional method, the heat-conducting membrane prepared by the invention has relatively low volume resistivity, simultaneously has the performances of low dielectric constant and dielectric loss, low ground and high heat conductivity coefficient, and the mechanical properties, especially the tensile strength, are different from those of the same type of products added with the reinforcing fibers by less than 1.7 percent through tests. The electrical property and the thermal conductivity among the embodiments 3, 4 and 5 do not generate a cliff type fault, the mechanical property of the diaphragm is not obviously influenced by the increase or decrease of the thickness of the diaphragm, and the preparation of the heat-conducting diaphragm with various required thicknesses can be realized. And each performance parameter of the membranes prepared in examples 6 and 7 is closest to that of example 5, but the mechanical performance and the membrane surface performance are both remarkably superior to those of example 5, and the performance of the heat-conducting membrane is optimized from another dimension. Therefore, the method provided by the invention can be used for stably producing the low-dielectric-constant heat-conducting membrane suitable for high-power high-frequency signal transmitting equipment/5G equipment and mobile terminals in a large scale.

While the preferred embodiments and examples of the present invention have been described in detail, the present invention is not limited to the embodiments and examples, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art.