CN113179611B

CN113179611B - Boron nitride heat dissipation film and preparation method and application thereof

Info

Publication number: CN113179611B
Application number: CN202110277139.0A
Authority: CN
Inventors: 丘陵; 刘闽苏; 成会明; 范维仁; 丁斯远
Original assignee: Foshan Shengpeng Technology Co ltd
Current assignee: Foshan Shengpeng Technology Co ltd
Priority date: 2021-03-15
Filing date: 2021-03-15
Publication date: 2023-03-24
Anticipated expiration: 2041-03-15
Also published as: CN113179611A; WO2022193572A1

Abstract

The invention discloses a boron nitride heat dissipation film and a preparation method and application thereof. A first aspect of the present application provides a method for preparing a boron nitride heat-dissipating film, comprising the steps of: mixing boron nitride powder, a polymer and a solvent to obtain first dispersion slurry; applying mechanical force to the first dispersed slurry for stripping to obtain a second dispersed slurry containing boron nitride nanosheets; coating the second dispersion slurry on a substrate to obtain a film; and compressing the film to obtain the boron nitride heat dissipation film. In the embodiment of the application, the dispersion slurry adopts a simple constitution system comprising boron nitride powder, polymer and solvent, and the cost and the processing difficulty are lower. In the stripping process, the polymer and the solvent can well protect the hexagonal boron nitride of the boron nitride powder from being broken, and part of impact force on the two-dimensional material is converted into shearing force, so that the two-dimensional sheet layer slides. Finally obtaining the two-dimensional boron nitride nanosheet with high relative quality, namely large size and small thickness.

Description

Boron nitride heat dissipation film and preparation method and application thereof

Technical Field

The application relates to the technical field of heat conduction materials, in particular to a boron nitride heat dissipation film and a preparation method and application thereof.

Background

The soaking film is also called as a heat dissipation film, and is a heat dissipation material commonly used in high-power communication equipment. The soaking film is generally prepared by using a material with lower thermal conductivity in a single axial direction compared with other dimensions, and the film generally has higher plane thermal conductivity and lower vertical thermal conductivity. The special heat conducting structure enables heat flow to quickly spread along a plane, and the heat flow is difficult to penetrate through the vertical direction of the heat dissipation film. A general soaking material is prepared based on a material having a two-dimensional layered structure, of which graphite is one of the most widely used materials. Graphite has excellent characteristics such as very high plane thermal conductivity, lower density, low coefficient of thermal expansion, and the like, and graphite heat dissipation films are widely used in various electronic devices with high heat dissipation requirements. However, graphite has excellent conductivity and is used only for insulating and encapsulating component parts in electronic devices. In addition, other problems may arise in electronic devices, such as die-cutting graphite heat spreading films that may generate small amounts of debris, potentially creating a short circuit risk, and such as graphite heat spreading films that may generate static electricity that may damage fragile electronic components. Graphite heat-dissipating films also have many problems in the field of communications. First, graphite, which is a good electromagnetic shielding material, hinders the transmission of communication signals, and therefore, it can be used only in a portion that does not affect the rf antenna in the communication device. Furthermore, graphite has a high dielectric coefficient, which results in a high signal delay, and is not favorable for the requirement of ultra-low delay of 5G in the future. In view of the problems of the graphite heat dissipation film in the 5G field, a heat dissipation material with high heat conductivity, insulation, low dielectric coefficient and low dielectric loss is urgently needed.

Hexagonal boron nitride as a two-dimensional layered material, and graphite possess similar crystal structures, also known as white graphite. The two-dimensional structure of hexagonal boron nitride is also called as boron nitride nanosheet, and has excellent properties such as thermal conductivity, mechanical strength and the like, and excellent insulating property, low dielectric coefficient and low dielectric loss. But the thermal conductivity of boron nitride is about 300Wm ^-1 K ^-1 Comparative graphite 2000Wm ^-1 K ^-1 The thermal conductivity of (a) is still at a lower level. Moreover, the thermal conductivity of the artificial graphite heat dissipation film can reach 1600Wm ^-1 K ^-1 The difference between the theoretical thermal conductivity of the boron nitride heat dissipation film and the theoretical thermal conductivity of graphite is small, the development of the preparation process of the boron nitride heat dissipation film is still in the primary stage, and the difference between the preparation process of the boron nitride heat dissipation film and the theoretical thermal conductivity of boron nitride is large. Therefore, it is necessary to provide a boron nitride heat dissipation film having a higher thermal conductivity.

Disclosure of Invention

The present application is directed to solving at least one of the problems in the prior art. Therefore, the application provides a boron nitride heat dissipation film with higher heat conductivity, and a preparation method and application thereof.

In a first aspect of the present application, a method for preparing a boron nitride heat dissipation film is provided, which includes the steps of:

s1: mixing boron nitride powder, a polymer and a solvent to obtain first dispersion slurry;

s2: applying mechanical force to the first dispersed slurry for stripping to obtain second dispersed slurry containing boron nitride nanosheets;

s3: coating the second dispersed slurry on a substrate to obtain a film;

s4: and compressing the film to obtain the boron nitride heat dissipation film.

According to the preparation method of the embodiment of the application, at least the following beneficial effects are achieved:

(1) In the embodiment of the application, the dispersion slurry adopts a simple constitution system comprising boron nitride powder, polymer and solvent, and the cost and the processing difficulty are lower. In the stripping process, the polymer and the solvent can well protect the hexagonal boron nitride of the boron nitride powder from being broken, and part of impact force on the two-dimensional material is converted into shearing force, so that the two-dimensional sheet layer slides. Finally obtaining the two-dimensional boron nitride nanosheet with high relative quality, namely large size and small thickness.

(2) In the compression process, two-dimensional materials in the thin film are effectively arranged through the interaction of the polymer and the two-dimensional boron nitride nanosheets, so that a highly ordered microstructure is obtained. The heat flow can be transmitted in the thin film with high directionality, so that the high plane heat conductivity is realized; moreover, high-density stacking of the heat dissipation film can be promoted, so that phonon scattering in the heat dissipation film is reduced, and the heat conductivity of the heat dissipation film is promoted to be improved; and finally, the highly ordered film structure can realize effective stacking of two-dimensional materials to form a pearl shell-like structure, so that the heat dissipation film has certain mechanical strength and flexibility under the interaction force between the two-dimensional boron nitride nanosheets.

Among them, the boron nitride powder is preferably hexagonal boron nitride powder, which is in the form of a sheet, and the size thereof is preferably 0.5 to 100 micrometers, and more preferably 5 to 50 micrometers.

The polymer means a polymer or a mixture thereof that can be dissolved or dispersed by a polar solvent and/or a non-polar solvent, and non-limiting examples thereof include at least one of polyvinyl alcohol, polyamide, polyimide, epoxy resin, polyimide, polysulfone, polyester, polyether, polyethylene glycol, polyvinylpyrrolidone, polyethylene oxide, polymethacrylate, polyvinylidene fluoride, polyaramide, phenol resin, polycarbonate, polyethyleneimine, etc., nanocellulose, sodium carboxymethylcellulose, a silicone rubber precursor, etc.

The solvent means any solvent that can dissolve or disperse the aforementioned polymer, and non-limiting examples thereof include at least one of water, ethylene glycol, methanol, ethanol, isopropanol, N-butanol, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, N-methylpyrrolidone, benzene, toluene, xylene, and the like.

Applying mechanical force refers to providing mechanical force such that lateral slippage and peeling between adjacent sheets of boron nitride powder occurs, non-limiting examples of which include at least one of ball milling, sanding, grinding, sanding, rolling, mechanical agitation, high shear, sonication, high pressure homogenization, microfluidization, and the like.

The substrate refers to a material that provides a corresponding environmental background for the slurry to form the boron nitride film, and non-limiting examples thereof include glass, polymer films, silicon wafers, paper, and the like, preferably polymer films. The material source of the polymer film comprises polyimide, polyethylene terephthalate, polycarbonate, polyacrylate, silicon rubber, polytetrafluoroethylene and the like, and preferably polyethylene terephthalate. In addition, the selection of the substrate needs to take the problems of wettability and stability to the solvent and the like into consideration, and needs to have good affinity to the second dispersion slurry so as to promote the formation of a highly oriented liquid film on the surface of the substrate, and also needs to have certain thermal stability so as to withstand the temperature of the curing environment of the film without affecting the film-forming quality due to chemical corrosion. On the basis, the substrate can also be subjected to certain surface pretreatment (such as surface plasma etching, corona or coating of a corresponding compound layer) before the coating treatment so as to improve the surface property of the substrate.

Coating means that the second dispersed slurry is passed through a means to form a corresponding liquid layer on the substrate, non-limiting examples of which include casting, knife coating, roll-to-roll coating, spray coating, screen printing, dip coating, and the like, as are well known in the art.

The compression treatment is to apply a certain pressure to the formed thin film, so that the two-dimensional boron nitride nanosheets in the thin film layer are further oriented, laminated and stacked, and higher thermal conductivity and mechanical properties are obtained. Non-limiting examples of the compression treatment include room temperature rolling, heat rolling, flat pressing, flat plate hot pressing, and the like, which are well known in the art.

In some embodiments of the present application, the compression treatment pressure is 1 to 1000MPa and the treatment time is 10s to 24h. The pressure acting in the compression treatment process and the treatment time influence the arrangement effect of the two-dimensional boron nitride nanosheets in the process, when the pressure is controlled within the range, the compression effect is good, and the heat conductivity and other properties of the final heat dissipation film are excellent.

In some embodiments of the present application, the compression treatment pressure is 5 to 60MPa and the treatment time is 10s to 2h.

In some embodiments of the present application, the temperature of the compression treatment is 20 to 400 ℃.

In some embodiments of the present application, the temperature of the compression treatment is 20 to 300 ℃.

In some embodiments of the present application, S4 is: and compressing the film to obtain a boron nitride film layer loaded on the substrate, and transferring the boron nitride film layer to obtain the boron nitride heat dissipation film.

In some embodiments of the present application, the transferring is performed by contacting the double-sided adhesive tape with the release film with the boron nitride thin film layer, transferring the boron nitride thin film layer to the double-sided adhesive tape, and covering the single-sided adhesive tape on the side of the boron nitride thin film layer away from the double-sided adhesive tape to obtain the boron nitride heat dissipation film. And (3) the boron nitride film is pasted on the double-sided adhesive in a rotating way, so that the corresponding low-cost boron nitride composite heat dissipation film is prepared. Depending on the application scenario, different heat-dissipating film configurations may be developed. The multilayer heat dissipation film can well adhere the boron nitride film layer to an electronic element with heat dissipation requirements, and therefore efficient heat dissipation of the electronic element is achieved. The surface or the overall structure of the film is easily damaged in the transportation process, the release films on the two sides can well protect the film, and the effectiveness of the heat dissipation film is guaranteed in some extreme environments, such as high humidity environments.

In addition, the boron nitride heat dissipation film is used as a composite ceramic material, and the mechanical property of the boron nitride heat dissipation film also shows corresponding ceramic properties, namely the boron nitride heat dissipation film has higher strength but poorer toughness, and is easy to be damaged in the mounting process, so that the heat dissipation performance of the material is reduced. And a proper film layer is attached to one surface or two surfaces of the two-dimensional boron nitride film, so that the stress difference generated when the film is deformed can be well distributed, and the film is protected.

In some embodiments of the present application, the total thickness of the double-sided adhesive and the release film is 2 to 100 micrometers, preferably 5 to 15 micrometers.

In some embodiments of the present application, the double-sided adhesive tape has a thickness of 1 to 40 micrometers, preferably 2 to 10 micrometers; the thickness of the release film is 5 to 500 micrometers, preferably 10 to 100 micrometers.

In some embodiments of the present application, the transferring process further includes a step of removing the substrate, the substrate may be removed by rolling the composite double-sided adhesive tape, and the rolling process may be normal-temperature rolling, where the rolling pressure is 1 to 1000MPa, preferably 5 to 60MPa; the rolling speed is 0.2 to 100 m/min, preferably 0.2 to 50 m/min.

In some embodiments of the present application, the single-sided adhesive further has a release layer, and the total thickness is 2 to 100 micrometers, preferably 5 to 15 micrometers.

In some embodiments of the present application, the single-sided adhesive further has a release layer, and the thickness of the single-sided adhesive layer is 1 to 40 micrometers, preferably 2 to 10 micrometers; the thickness of the release layer is 5 to 500 micrometers, preferably 10 to 100 micrometers.

In some embodiments of the present application, the mass ratio of the boron nitride powder in the first dispersion slurry is 1 to 50%, preferably 2 to 35%; the mass ratio of the polymer is 1 to 50%, preferably 1 to 30%.

In some embodiments of the present application, the mass of boron nitride in the boron nitride thin film layer is 50 to 99wt%.

In some embodiments herein, the mixing of the boron nitride powder, the polymer, and the solvent to obtain the first dispersed slurry is by blending and stirring.

In some embodiments herein, the blending agitation speed is from 50 to 30000rpm, preferably from 100 to 4000rpm; the blending and stirring time is 5 minutes to 72 hours, preferably 10 minutes to 36 hours; the temperature of the blending and stirring is 20 ℃ to the boiling point of the solvent, and the particularly preferred temperature depends on the dissolution or dispersion of the specific polymer compound in the specific solvent.

In some embodiments of the present application, the mechanical force is applied for a period of time in the range of 1 to 144 hours, preferably 2 to 48 hours.

In some embodiments of the present application, the second dispersion slurry is adjusted to have a viscosity of 200 to 10000mPa · s before coating. The solvent used for adjusting the viscosity is the solvent in S1, and the solvent needs to be fully stirred after dilution, wherein the stirring speed is 100-1000 rpm. Preferably 200 to 800rpm; the stirring time is 10 minutes to 24 hours, preferably 20 minutes to 2 hours.

In some embodiments of the present application, the second dispersion slurry is adjusted to a viscosity of 500 to 5000mPa · s before coating.

In some embodiments of the present application, the manner of applying mechanical force in S2 is ball milling.

Compared with the traditional process, the preparation method is simplified, and the high-quality two-dimensional hexagonal boron nitride dispersion can be obtained through one-step treatment of the first dispersion slurry and used for preparing the two-dimensional boron nitride composite heat dissipation film. The traditional process needs to involve a series of complex processes while screening and cleaning the two-dimensional boron nitride nanosheets, increases the cost, also causes the generation of waste water, waste gas and dust, and has certain influence on environmental protection and production safety.

The simple ball-milling process adopted in the application can promote the interaction force of the polymer and the two-dimensional hexagonal boron nitride, can realize the effect of similar gelatinization of the dispersed slurry while promoting the stripping efficiency of the two-dimensional boron nitride, and can rivet the two-dimensional boron nitride nanosheets through the molecular chain of the polymer. The mutual riveting and crosslinking can promote the two-dimensional hexagonal boron nitride to have stronger interaction force during coating, and further improve the ordered arrangement effect.

In some embodiments of the present application, the stripping in S2 is followed by a sieving treatment to remove non-stripped boron nitride powder, thereby obtaining a second dispersion slurry comprising the boron nitride nanoplates.

In some embodiments of the present application, the manner of performing the sieving treatment after the stripping in S2 includes, but is not limited to, natural sedimentation, centrifugal sieving, and the like, and natural sedimentation is preferred. The time for natural settling is 12 to 144 hours, preferably 12 to 48 hours. Wherein, the un-stripped hexagonal boron nitride can be recycled in the next production to improve the utilization efficiency of the raw materials. And the peeled boron nitride is distinguished from the non-peeled boron nitride by adopting a natural sedimentation method, and the slurry which is obtained by sedimentation and mainly contains the non-peeled boron nitride at the lower layer can be returned to the S2 for re-applying mechanical force for peeling, so that the slurry is recycled, the screening step is avoided, the process is simplified, and the production cost is reduced.

In some embodiments of the present application, the film has a thickness of 1 to 10000 microns, preferably 5 to 500 microns.

In some embodiments of the present application, drying is also required after coating is completed, so that the coated wet film is converted into a dry film. The drying temperature is 20 to 200 ℃, preferably 40 to 150 ℃. In addition, the drying temperature also needs to take into account the thermal stability of the polymer in the substrate and film, as well as the boiling point and volatilization rate of the solvent. The drying time is 2 minutes to 24 hours, preferably 5 minutes to 2 hours.

In a second aspect of the present application, a boron nitride heat dissipation film is provided, which is prepared by the above preparation method.

In a third aspect of the present application, there is provided an electronic device provided with the above-described boron nitride heat dissipation film. Non-limiting examples of such electronic devices include printed circuit boards, radio frequency devices, and the like. The heat dissipation film utilizes the boron nitride material to replace the traditional graphite heat dissipation film in partial application scenes, and on the basis of ensuring certain heat dissipation capability, the two-dimensional boron nitride material has high insulativity, low dielectric loss, low dielectric coefficient, wave permeability and white appearance, so that a plurality of pain points of the graphite heat dissipation film in practical application can be well solved, particularly in the heat dissipation scenes of related electronic components such as 5G communication equipment, radio frequency devices, high-speed communication devices and the like. In addition, the appearance of the two-dimensional boron nitride composite heat dissipation film can better change the design idea of the existing electronic equipment, and is beneficial to the miniaturization and compact development of the electronic equipment. In addition, the heat dissipation film has potential development space and application value in the fields of flexible printed circuit boards, insulating films, flexible electronic packaging and the like.

In a fourth aspect of the present application, an electronic device is provided, which includes the above-described boron nitride heat dissipation film.

Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.

Drawings

Fig. 1 is a scanning electron microscope image of two-dimensional boron nitride nanosheets in experimental example 1 of the present application.

Fig. 2 is a transmission electron microscope image of two-dimensional boron nitride nanosheets in experimental example 1 of the present application.

Fig. 3 is a statistical graph of the size of the two-dimensional boron nitride nanosheets in experimental example 1 of the present application.

Fig. 4 is an atomic force microscope schematic diagram of two-dimensional boron nitride nanosheets in experimental example 1 of the present application.

Fig. 5 is a statistical schematic diagram of the thickness of the two-dimensional boron nitride nanosheet in experimental example 1 of the present application.

FIG. 6 is a digital photograph of a boron nitride heat-dissipating film as a finished product in Experimental example 1 of this application.

FIG. 7 is a digital photograph of a boron nitride heat-dissipating film as a finished product in Experimental example 1 of the present application.

FIG. 8 is a scanning electron microscope image of a cross section of a heat-dissipating boron nitride film in Experimental example 1 of the present application.

FIG. 9 is a scanning electron microscope image of the surface of a heat-dissipating boron nitride film in Experimental example 1 of the present application.

Fig. 10 is a scanning electron microscope image of two-dimensional boron nitride nanosheets in experimental example 2 of the present application.

Fig. 11 is a transmission electron microscope image of two-dimensional boron nitride nanosheets in experimental example 2 of the present application.

FIG. 12 is a digital photograph of a boron nitride heat-dissipating film as a finished product in Experimental example 2 of the present application.

FIG. 13 is a photograph showing a heat sink film of boron nitride in Experimental example 3 of the present application.

FIG. 14 is a digital photograph of a boron nitride heat-dissipating film as a finished product in Experimental example 9 of the present application.

FIG. 15 is a schematic view of a structure of a boron nitride heat dissipation film according to an embodiment of the present application.

FIG. 16 is a schematic view showing another structure of a boron nitride heat dissipating film according to an embodiment of the present invention.

FIG. 17 is a schematic diagram showing the heat dissipating capability of a boron nitride heat dissipating film product in Experimental example 10 of the present application.

FIG. 18 is a comparison of the effect of the boron nitride heat-dissipating film of the experimental example 10 of the present application in a simulated experimental environment with other conventional thermal interface materials.

Reference numerals are as follows: the first release film layer 151, the double-sided adhesive film layer 152, the boron nitride film layer 153, the second release film layer 154 and the single-sided adhesive layer 161.

Detailed Description

The conception and the resulting technical effects of the present application will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive efforts based on the embodiments of the present application belong to the protection scope of the present application.

The following detailed description of embodiments of the present application is provided for the purpose of illustration only and is not intended to be construed as a limitation of the application.

In the description of the present application, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the above, below, exceeding, etc. are understood as excluding the present number, and the above, below, within, etc. are understood as including the present number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present application, unless otherwise expressly limited, terms such as set, mounted, connected and the like should be construed broadly, and those skilled in the art can reasonably determine the specific meaning of the terms in the present application by combining the detailed contents of the technical solutions.

In the description of the present application, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example" or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Example 1

The embodiment provides a heat dissipation film and a preparation method thereof, wherein the preparation method comprises the following steps:

s1: 1800g of hexagonal boron nitride powder, 200g of sodium carboxymethylcellulose and 8000ml of deionized water are mixed, mixed at the temperature of 80 ℃, stirred at the rotating speed of 1000rpm for 2 hours and then cooled to room temperature, and first dispersion slurry is obtained.

S2: the first dispersion slurry was fed to a large jacketed reactor connected at a suitable flow rate with circulating water at a temperature of 5 ℃. And inserting a high-speed shearing cutter with a proper size and shape into the slurry to a proper position, carrying out high-speed stirring treatment at the speed of 10000rpm for 1 hour after sealing is completed, stopping for 20 minutes, and repeating the operation. After the high-speed shearing treatment is carried out for 12 hours, the obtained two-dimensional boron nitride dispersed slurry is taken out from the jacket reactor and stands still. After the two-dimensional boron nitride dispersion slurry is kept stand for 24 hours, the dispersion slurry of 90% of the upper layer of the total height of the liquid level is taken as the upper layer dispersion slurry, and the lower layer dispersion slurry of 10% of the lower layer is added into the first dispersion slurry produced in the next batch after proper concentration calibration for high-speed shearing and stripping treatment again.

In this step, the initial concentration of boron nitride was 18% of the total mass of the slurry, and the concentration in the upper layer dispersed slurry after standing and settling was about 17.8%, and the concentration in the lower layer dispersed slurry was about 19.7%. The mass of the two-dimensional boron nitride in the upper-layer dispersion slurry accounts for 89.9% of the total mass of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the second dispersion slurry, and the specific gravity difference of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the upper-layer dispersion slurry is smaller than that of the 90% of the initial dispersion liquid.

The viscosity of the obtained upper layer dispersion slurry was characterized by using a rotary viscometer and was 4123mPa · s. An additional 875ml of deionized water was added to the upper dispersion slurry, stirred at 1000rpm for 30 minutes at a temperature of 80 ℃ and then stopped and cooled to room temperature. The diluted dispersion was used as a second dispersion slurry, and the viscosity of the dispersion was 1020 mPas.

S3: taking a polyimide film with the thickness of 30 microns as a substrate, firstly confirming the cleanness degree of the surface of the substrate, and cleaning the substrate by wiping corresponding parts with acetone; the substrate is then subjected to uv-ozone treatment to further clean the substrate surface and promote wettability of the substrate surface. And (3) carrying out vacuum stirring and defoaming treatment on the second dispersed slurry, and then extruding the second dispersed slurry into a precise roll coating system for coating treatment to obtain a wet film loaded on the substrate. The wet film thickness was about 500 microns during the roll coating process. And (3) drying the wet film at the temperature of 60-80 ℃ for 20 minutes in a gradient manner to obtain the boron nitride film layer attached to the bottom surface of the polyimide base.

S4: attaching a double-sided adhesive film with a release film on one side of the boron nitride film layer far away from the bottom surface of the polyimide, contacting the double-sided adhesive film with the boron nitride film layer, and carrying out static pressure on the double-sided adhesive film for 20 minutes by using a normal-temperature flat plate with the pressure of 10MPa to obtain the final product, namely the boron nitride heat dissipation film.

And (3) centrifuging a small amount of upper-layer dispersed slurry at 10000rpm for 3 minutes, dispersing the precipitate by deionized water, and repeating the centrifuging-dispersing step for 5 times to obtain the aqueous dispersion of the two-dimensional boron nitride nanosheet. Fig. 1 is a scanning electron microscope image of a two-dimensional boron nitride nanosheet, and it can be seen from the image that the two-dimensional boron nitride nanosheet peeled off by mechanical force has an obvious two-dimensional layered structure, is efficiently peeled off, and has a small thickness. Fig. 2 is a transmission electron microscope image of a two-dimensional boron nitride nanosheet, from which it can be seen that the thickness of the two-dimensional boron nitride nanosheet is small and the lamella size is still in the micron range. Through statistical analysis of the image of the transmission electron microscope, the result is shown in fig. 3, and it can be seen that the average lamella size of the peeled nanosheet is about 1 micron, and the nanosheet belongs to a high-quality large-piece two-dimensional material. Fig. 4 is an atomic force microscope image of the prepared two-dimensional boron nitride nanosheet, and it can be seen from the figure that the thickness of the two-dimensional boron nitride nanosheet is within the interval of 1-10 nanometers, and the average thickness is relatively low and uniform. The statistical analysis result of the atomic force microscope image is shown in fig. 5, and it can be seen from fig. 5 that the average thickness of the two-dimensional boron nitride nanosheet is about 5 nm, which is less than about 20 atomic layers. In conclusion, the experimental example scheme can efficiently prepare high-quality, large-sheet and thin-layer two-dimensional boron nitride materials with extremely high yield.

The final product of the boron nitride heat dissipation film obtained by the final preparation is shown in fig. 6 and 7 after the surface release film is uncovered, and it can be seen from the drawings that one surface of the boron nitride heat dissipation film is attached with a double-sided adhesive layer, so that the boron nitride heat dissipation film can be well attached to the surface of a corresponding electronic component to realize tight attachment and has certain flexibility. Moreover, the film has certain strength, can realize self-supporting and presents obvious ceramic texture.

Fig. 8 and 9 are scanning electron microscope images of the interface and the surface of the boron nitride heat dissipation film, respectively, showing highly ordered planar arrangement inside the visible film, and the visible film is tightly connected with each other, and the surface of the visible film also shows highly compact appearance, so that the original powder structure is difficult to observe, and the potential risk of short circuit of the electronic component is avoided. And measuring each film layer of the boron nitride heat dissipation film by a screw micrometer to obtain that the thickness of the boron nitride film layer is 55 micrometers, the total thickness of the two release films is 60 micrometers, the thickness of the double-sided adhesive layer is 5 micrometers, and the total thickness is 120 micrometers.

Example 2

s1: 1800g of hexagonal boron nitride powder, 200g of polyethyleneimine and 8000ml of deionized water are mixed, mixed at the temperature of 80 ℃, stirred at the speed of 1000rpm for 2 hours and then cooled to room temperature, and first dispersion slurry is obtained.

S2: the first dispersion slurry was fed to a large jacketed reactor connected at a suitable flow rate with circulating water at a temperature of 5 ℃. Inserting a high-speed shearing cutter with proper size and shape into the slurry to a proper position, carrying out high-speed stirring treatment at the speed of 10000rpm for 1 hour after sealing is completed, stopping for 20 minutes, and repeating the operation. After the high-speed shearing treatment is carried out for 12 hours, the obtained two-dimensional boron nitride dispersed slurry is taken out from the jacket reactor and stands still. After the two-dimensional boron nitride dispersion slurry is kept stand for 24 hours, the dispersion slurry of 90% of the upper layer of the total height of the liquid level is taken as the upper layer dispersion slurry, and the lower layer dispersion slurry of 10% of the lower layer is added into the first dispersion slurry produced in the next batch after proper concentration calibration for high-speed shearing and stripping treatment again.

In this step, the initial concentration of boron nitride was 18% of the total mass of the slurry, and the concentration in the upper layer dispersed slurry after standing and precipitation was about 17.7%, and the concentration in the lower layer dispersed slurry was about 20.5%. The mass of the two-dimensional boron nitride in the upper-layer dispersed slurry accounts for 89.8% of the total mass of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the second dispersed slurry, and the specific gravity difference of 90% compared with that of the initial dispersed solution is smaller.

The viscosity of the obtained upper layer dispersion slurry was characterized by using a rotary viscometer and was 3220mPa · s. An additional 550ml of deionized water was added to the upper dispersion slurry, stirred at 1000rpm for 30 minutes at a temperature of 80 ℃ and then stopped and cooled to room temperature. The diluted dispersion had a viscosity of 1070 mPas as a second dispersion slurry.

S3: taking a polyimide film with the thickness of 30 microns as a substrate, firstly confirming the cleanness degree of the surface of the substrate, and cleaning the substrate by wiping corresponding parts with acetone; the substrate is then subjected to an ultraviolet-ozone treatment to further clean the substrate surface and promote the wettability of the substrate surface. And (3) carrying out vacuum stirring and defoaming treatment on the second dispersed slurry, and then extruding the second dispersed slurry into a precise roll coating system for coating treatment to obtain a wet film loaded on the substrate. During the roll coating process, the wet film thickness was about 600 microns. And (3) drying the wet film at the temperature of 60-80 ℃ for 20 minutes in a gradient manner to obtain the boron nitride film layer attached to the bottom surface of the polyimide base.

The two-dimensional boron nitride nanosheet prepared in S2 is detected according to the method in example 1, and a scanning electron microscope image is shown in fig. 10, from which it can be seen that the two-dimensional boron nitride nanosheet presents an obvious two-dimensional layered structure, is efficiently peeled, and has a small thickness. Fig. 11 is a transmission electron microscope image of a two-dimensional boron nitride nanosheet, and it can be seen from the image that the thickness of the two-dimensional boron nitride nanosheet is small, the average lamella size of the two-dimensional boron nitride nanosheet is about 1 micrometer, and the two-dimensional boron nitride nanosheet belongs to a high-quality large-piece two-dimensional material. The final product of the boron nitride heat dissipation film obtained after the surface release film is uncovered is shown in fig. 12, and it can be seen from the figure that one surface of the boron nitride heat dissipation film is attached with a double-sided adhesive layer, so that the boron nitride heat dissipation film can be well attached to the surface of a corresponding electronic component to realize tight attachment and has certain flexibility. And (3) measuring each film layer of the boron nitride heat dissipation film by a screw micrometer, wherein the thickness of the measured boron nitride film layer is 65 micrometers, the total thickness of the two release film layers is 60 micrometers, the thickness of the double-sided adhesive layer is 5 micrometers, and the total thickness is 130 micrometers.

Example 3

s1: 1800g of hexagonal boron nitride powder, 200g of polyimide and 8000ml of dimethylacetamide are blended, mixed at the temperature of 130 ℃, stirred at the speed of 1000rpm for 2 hours and then cooled to room temperature to obtain first dispersion slurry.

In this step, the initial concentration of boron nitride was 18% of the total mass of the slurry, and the concentration in the upper layer dispersed slurry after standing still for precipitation was about 17.7%, and the concentration in the lower layer dispersed slurry was about 20.6%. The mass of the two-dimensional boron nitride in the upper-layer dispersed slurry accounts for 89.8% of the total mass of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the second dispersed slurry, and the specific gravity difference of 90% compared with that of the initial dispersed solution is smaller.

The viscosity of the obtained upper layer dispersion slurry was characterized by using a rotary viscometer and was 2175mPa · s. An additional 250ml of dimethylacetamide was added to the upper dispersion slurry, and after stirring at 1000rpm for 30 minutes at a temperature of 130 ℃ the stirring was stopped and cooled to room temperature. The diluted dispersion had a viscosity of 978 mPas as a second dispersion slurry.

S3: taking a polyimide film with the thickness of 30 microns as a substrate, firstly confirming the cleanness degree of the surface of the substrate, and cleaning the substrate by wiping corresponding parts with acetone; the substrate is then subjected to uv-ozone treatment to further clean the substrate surface and promote wettability of the substrate surface. And (3) carrying out vacuum stirring and defoaming treatment on the second dispersed slurry, and then extruding the second dispersed slurry into a precise roll coating system for coating treatment to obtain a wet film loaded on the substrate. The wet film thickness was about 375 μm during the roll coating process. And (3) drying the wet film at the temperature of 60-120 ℃ for 20 minutes in a gradient manner to obtain the boron nitride film layer attached to the bottom surface of the polyimide base.

S4: attaching a double-sided adhesive film with a release film on one side to one side of the boron nitride film layer away from the bottom surface of the polyimide base, contacting the double-sided adhesive film with the boron nitride film layer, and carrying out static pressure on the double-sided adhesive film for 20 minutes by a normal-temperature flat plate with the pressure of 10MPa to obtain the final product, namely the boron nitride heat dissipation film.

The boron nitride heat-dissipating film thus produced is shown in FIG. 13, and it can be seen that it has excellent flexibility. And (3) measuring each film layer of the boron nitride heat dissipation film by a screw micrometer, wherein the thickness of the measured boron nitride film layer is 55 micrometers, the total thickness of the two release film layers is 60 micrometers, the thickness of the double-sided adhesive layer is 5 micrometers, and the total thickness is 120 micrometers.

Example 4

s1: 1800g of hexagonal boron nitride powder, 200g of polyvinylidene fluoride and 8000ml of dimethylacetamide are blended, mixed at the temperature of 130 ℃, stirred at the speed of 1000rpm for 2 hours and then cooled to room temperature to obtain first dispersion slurry.

In this step, the initial concentration of boron nitride was 18% of the total mass of the slurry, and the concentration in the upper layer dispersed slurry after standing and precipitation was about 17.7%, and the concentration in the lower layer dispersed slurry was about 20.7%. The mass of the two-dimensional boron nitride in the upper-layer dispersed slurry accounts for 89.8% of the total mass of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the second dispersed slurry, and the specific gravity difference of 90% compared with that of the initial dispersed solution is smaller.

The viscosity of the obtained upper layer dispersion slurry was characterized by using a rotary viscometer and was 2340mPa · s. An additional 280ml of dimethylacetamide was added to the upper dispersion slurry, and after stirring at 1000rpm for 30 minutes at a temperature of 130 ℃ the stirring was stopped and cooled to room temperature. The diluted dispersion was used as a second dispersion slurry, and the viscosity of the dispersion was 1025 mPas.

And (3) measuring each film layer of the boron nitride heat dissipation film by a screw micrometer, wherein the thickness of the measured boron nitride film layer is 55 micrometers, the total thickness of the two release film layers is 60 micrometers, the thickness of the double-sided adhesive layer is 5 micrometers, and the total thickness is 120 micrometers.

Example 5

s1: 1800g of hexagonal boron nitride powder, 200g of polyvinylidene fluoride and 8000ml of dimethylacetamide are blended, mixed at the temperature of 130 ℃, stirred at the speed of 1000rpm for 2 hours and then cooled to room temperature to obtain a first dispersion slurry.

S2: the first dispersion slurry was fed to a large jacketed reactor connected at a suitable flow rate with circulating water at a temperature of 5 ℃. Inserting a high-power ultrasonic probe into the slurry to a proper position, carrying out ultrasonic treatment for 6 seconds at the power of 800W after sealing is completed, stopping for 20 seconds, and setting a program to repeat the operation. After the ultrasonic treatment for 72 hours, the obtained two-dimensional boron nitride dispersed slurry was taken out from the jacketed reactor and left to stand. After the two-dimensional boron nitride dispersion slurry is kept stand for 24 hours, the dispersion slurry of 90% of the upper layer of the total height of the liquid level is taken as the upper layer dispersion slurry, and the lower layer dispersion slurry of 10% of the lower layer is added into the first dispersion slurry produced in the next batch after proper concentration calibration for high-speed shearing and stripping treatment again.

In this step, the initial concentration of boron nitride was 18% of the total mass of the slurry, and the concentration in the upper layer dispersed slurry after standing and precipitation was about 17.1%, and the concentration in the lower layer dispersed slurry was about 25.2%. The mass of the two-dimensional boron nitride in the upper-layer dispersed slurry accounts for 89.5% of the total mass of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the second dispersed slurry, and the specific gravity difference of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the upper-layer dispersed slurry is smaller than that of 90% of the initial dispersed solution.

The viscosity of the obtained upper layer dispersion slurry was characterized by using a rotary viscometer and was 1940mPa · s. An additional 195ml of dimethylacetamide was added to the upper dispersion slurry, and after stirring at 1000rpm for 30 minutes at a temperature of 130 ℃ the stirring was stopped and cooled to room temperature. The diluted dispersion had a viscosity of 925 mPas as a second dispersion slurry.

S3: taking a polyimide film with the thickness of 30 microns as a substrate, firstly, confirming the cleanliness degree of the surface of the substrate, and cleaning the substrate by wiping a corresponding part with acetone; the substrate is then subjected to uv-ozone treatment to further clean the substrate surface and promote wettability of the substrate surface. And (3) carrying out vacuum stirring and defoaming treatment on the second dispersed slurry, and then extruding the second dispersed slurry into a precise roll coating system for coating treatment to obtain a wet film loaded on the substrate. The wet film thickness was about 300 microns during the roll coating process. And (3) drying the wet film at the temperature of 60-120 ℃ for 20 minutes in a gradient manner to obtain the boron nitride film layer attached to the bottom surface of the polyimide base.

And measuring each film layer of the boron nitride heat dissipation film by a screw micrometer, wherein the thickness of the measured boron nitride film layer is 45 micrometers, the total thickness of the two release film layers is 60 micrometers, the thickness of the double-sided adhesive layer is 5 micrometers, and the total thickness is 110 micrometers.

Example 6

S3: taking a polyimide film with the thickness of 30 microns as a substrate, firstly confirming the cleanness degree of the surface of the substrate, and cleaning the substrate by wiping corresponding parts with acetone; the substrate is then subjected to uv-ozone treatment to further clean the substrate surface and promote wettability of the substrate surface. And (3) carrying out vacuum stirring and defoaming treatment on the second dispersed slurry, and then extruding the second dispersed slurry into a precise roll coating system for coating treatment to obtain a wet film loaded on the substrate. During the roll coating, the wet film thickness was about 200 microns. And (3) drying the wet film at the temperature of 60-120 ℃ for 20 minutes in a gradient manner to obtain the boron nitride film layer attached to the bottom surface of the polyimide base.

The spiral micrometer measures each rete of boron nitride heat dissipation membrane, and the thickness of surveying the boron nitride film layer is 30 microns, and the total thickness of two-layer type rete is 60 microns, and the thickness of two-sided adhesive layer is 5 microns, and the total thickness is 95 microns.

Example 7

S2: adding the first dispersed slurry into a ball milling tank, and adding a proper amount of zirconia grinding balls with different sizes, wherein the ball milling speed is 300rpm. And after ball milling treatment is carried out for 24 hours, taking the obtained two-dimensional boron nitride dispersed slurry out of the ball milling tank, filtering to remove grinding balls, and standing. After the two-dimensional boron nitride dispersion slurry is stood for 24 hours, the dispersion slurry of which the total height of the liquid surface is 90 percent of that of the upper layer is taken as the upper layer dispersion slurry, and the lower layer dispersion slurry of which the total height of the lower layer is 10 percent of that of the lower layer is calibrated by proper concentration and then added into the first dispersion slurry produced in the next batch for high-speed shearing and stripping treatment again.

In this step, the initial concentration of boron nitride was 18% of the total mass of the slurry, and the concentration in the upper layer dispersed slurry after standing and settling was about 17.8%, and the concentration in the lower layer dispersed slurry was about 29.7%. The mass of the two-dimensional boron nitride in the upper-layer dispersed slurry accounts for 89.8% of the total mass of the two-dimensional boron nitride and the sodium carboxymethyl cellulose in the second dispersed slurry, and the specific gravity difference of 90% compared with that of the initial dispersed solution is smaller.

The viscosity of the obtained upper layer dispersion slurry was characterized by using a rotary viscometer, and it was 2050mPa · s. An additional 200ml of dimethylacetamide was added to the upper dispersion slurry, and after stirring at 1000rpm for 30 minutes at a temperature of 130 ℃ the stirring was stopped and cooled to room temperature. The diluted dispersion had a viscosity of 1000 mPas as a second dispersion slurry.

S3: taking a polyimide film with the thickness of 30 microns as a substrate, firstly confirming the cleanness degree of the surface of the substrate, and cleaning the substrate by wiping corresponding parts with acetone; the substrate is then subjected to uv-ozone treatment to further clean the substrate surface and promote wettability of the substrate surface. And (3) carrying out vacuum stirring and defoaming treatment on the second dispersed slurry, and then extruding the second dispersed slurry into a precise roll coating system for coating treatment to obtain a wet film loaded on the substrate. The wet film thickness was about 750 microns during the roll coating process. And (3) drying the wet film at the temperature of 60-120 ℃ for 20 minutes in a gradient manner to obtain the boron nitride film layer attached to the bottom surface of the polyimide base.

And (3) measuring each film layer of the boron nitride heat dissipation film by a screw micrometer, wherein the thickness of the measured boron nitride film layer is 100 micrometers, the total thickness of the two release film layers is 60 micrometers, the thickness of the double-sided adhesive layer is 5 micrometers, and the total thickness is 165 micrometers.

Example 8

S2: adding the first dispersed slurry into a ball milling tank, and adding a proper amount of zirconia grinding balls with different sizes, wherein the ball milling speed is 300rpm. And after ball milling treatment is carried out for 24 hours, taking the obtained two-dimensional boron nitride dispersed slurry out of the ball milling tank, filtering to remove grinding balls, and standing. After the two-dimensional boron nitride dispersion slurry is kept stand for 24 hours, the dispersion slurry of 90% of the upper layer of the total height of the liquid level is taken as the upper layer dispersion slurry, and the lower layer dispersion slurry of 10% of the lower layer is added into the first dispersion slurry produced in the next batch after proper concentration calibration for high-speed shearing and stripping treatment again.

The viscosity of the obtained upper layer dispersion slurry was characterized by using a rotary viscometer and was 2050mPa · s. An additional 200ml of dimethylacetamide was added to the upper dispersion slurry, and after stirring at 1000rpm for 30 minutes at a temperature of 130 ℃ the stirring was stopped and cooled to room temperature. The diluted dispersion had a viscosity of 1000 mPas as a second dispersion slurry.

S3: taking a polyimide film with the thickness of 30 microns as a substrate, firstly, confirming the cleanliness degree of the surface of the substrate, and cleaning the substrate by wiping a corresponding part with acetone; the substrate is then subjected to uv-ozone treatment to further clean the substrate surface and promote wettability of the substrate surface. And (3) carrying out vacuum stirring and defoaming treatment on the second dispersed slurry, and then extruding the second dispersed slurry into a precise roll coating system for coating treatment to obtain a wet film loaded on the substrate. The wet film thickness during roll coating was approximately 2250 microns. And (3) drying the wet film at the temperature of 60-120 ℃ for 20 minutes in a gradient manner to obtain the boron nitride film layer attached to the bottom surface of the polyimide base.

And (3) measuring each film layer of the boron nitride heat dissipation film by a screw micrometer, wherein the thickness of the measured boron nitride film layer is 300 micrometers, the total thickness of the two release film layers is 60 micrometers, the thickness of the double-sided adhesive layer is 5 micrometers, and the total thickness is 365 micrometers.

Example 9

S4: attaching a double-sided adhesive film with a release film on one side to one side of the boron nitride film layer away from the bottom surface of the polyimide, contacting the double-sided adhesive film with the boron nitride film layer, removing the original polyimide substrate, attaching a single-sided adhesive protective film layer to the side of the boron nitride film layer again, and performing static pressure on a normal-temperature flat plate at the pressure of 10MPa for 20 minutes to obtain the final product, namely the boron nitride heat dissipation film.

FIG. 14 is a photograph of a boron nitride heat-dissipating film product produced in this example. The spiral micrometer measures each membranous layer of boron nitride heat dissipation membrane, and the thickness of measuring boron nitride film layer is 55 microns, and the total thickness of two-layer from type membranous layer is 60 microns, and the thickness of two-sided glue film is 5 microns, and the thickness of single face glue film is 5 microns, and the total thickness is 125 microns.

Fig. 15 and fig. 16 are schematic structural diagrams of the boron nitride heat dissipation films prepared in embodiments 1 to 9, respectively, and one of the structures is shown in fig. 15, and includes, from bottom to top, a first release film layer 151, a double-sided adhesive film layer 152, a boron nitride thin film layer 153, and a second release film layer 154. Another structure is shown in fig. 16, which includes, from bottom to top, a first release film layer 151, a double-sided adhesive film layer 152, a boron nitride film layer 153, a single-sided adhesive layer 161, and a second release film layer 154.

Example 10

Performance testing of heat-dissipating films

The heat diffusion coefficients of the heat-dissipating films obtained in examples 1 to 9 were measured by a flash method thermal diffusivity measuring instrument (LFA-467), the specific heat capacities of the heat-dissipating films were measured by differential scanning calorimetry, and the densities of the heat-dissipating films were measured by the drainage method, respectively, and the results are shown in table 1.

TABLE 1 test results of the Performance of the Heat-dissipating film

As can be seen from the figure, the thermal diffusivity and the thermal conductivity of the boron nitride heat dissipation film prepared by the embodiment of the application are greatly improved and can reach 24.53mm at most ² S and 50.17Wm ^-1 K ^-1 。

Example 11

Heat dissipation capability verification experiment

The effect of the two-dimensional boron nitride heat dissipation film in the actual use environment is measured by adopting a simulation experiment method for carrying out steady-state heat dissipation on a single heating source. The basic principle is as shown in fig. 17, the heat dissipation film is heated mainly by a constant temperature heating plate, an aluminum block and a heat insulation space are arranged between the constant temperature heating plate and the heat dissipation film, and the hot spot temperature on the surface of the heat dissipation film is observed after the steady state is reached. The result of a simulation experiment comparing the heat-dissipating film of boron nitride prepared in example 6 with the same thickness as conventional high-performance heat-conductive films such as aluminum oxide and aluminum nitride is shown in fig. 18, where a is the heat-dissipating film of boron nitride provided in the examples of the present application, and B and C are the heat-dissipating films of aluminum oxide and aluminum nitride, respectively. As can be seen from the figure, the Average Value (AVG) and the maximum value (MAX) of the hot spot temperatures of the surface of the heat dissipation film provided by the embodiment of the present application are significantly lower than those of the other two types of heat conductive films, and the temperature reduction is significant, which indicates that the heat dissipation film of boron nitride provided by the embodiment of the present application has excellent heat dissipation performance.

The present application has been described in detail with reference to the embodiments, but the present application is not limited to the embodiments described above, and various changes can be made within the knowledge of those skilled in the art without departing from the gist of the present application. Furthermore, the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

Claims

1. The preparation method of the boron nitride heat dissipation film is characterized by comprising the following steps of:

s1: mixing boron nitride powder, a polymer and a solvent to obtain first dispersion slurry, wherein the mass percent of the boron nitride powder in the first dispersion slurry is 2-35%, and the mass percent of the polymer is 1-30%;

s2: applying mechanical force to the first dispersed slurry for stripping to obtain second dispersed slurry containing boron nitride nanosheets, wherein the manner of applying the mechanical force is ball milling;

s3: coating the second dispersion slurry on a substrate to obtain a film;

s4: and compressing the film to obtain the boron nitride heat dissipation film, wherein the mass of the boron nitride in the boron nitride heat dissipation film is 50-99 wt%.

2. The method according to claim 1, wherein the pressure of the compression treatment is 1 to 1000MPa, and the treatment time is 10s to 24h.

3. The method according to claim 2, wherein the pressure of the compression treatment is 5 to 60MPa, and the treatment time is 10s to 2h.

4. The production method according to claim 2, wherein the temperature of the compression treatment is 20 to 400 ℃.

5. The method according to claim 1, wherein S4 is: compressing the film to obtain a boron nitride film layer loaded on the substrate, and transferring the boron nitride film layer to obtain the boron nitride heat dissipation film.

6. The preparation method according to claim 5, wherein the transferring is performed by contacting a double-sided adhesive tape with a release film with the boron nitride thin film layer, and transferring the boron nitride thin film layer to the double-sided adhesive tape to obtain the boron nitride heat dissipation film.

7. The preparation method of claim 6, further comprising covering a single-sided adhesive on a side of the boron nitride film layer away from the double-sided adhesive after transferring to the double-sided adhesive.

8. The production method according to claim 1, characterized in that the second dispersion slurry is adjusted to a viscosity of 200 to 10000 mPa-s, preferably 500 to 5000 mPa-s, before coating.

9. The production method according to any one of claims 1 to 8, wherein the polymer is at least one selected from the group consisting of polyvinyl alcohol, polyamide, polyimide, epoxy resin, polysulfone, polyester, polyether, polyethylene glycol, polyvinylpyrrolidone, polyethylene oxide, polymethacrylate, polyvinylidene fluoride, polyaramide, phenol resin, polycarbonate, polyethyleneimine, nanocellulose, sodium carboxymethylcellulose, and a silicone rubber precursor.

10. A boron nitride heat-dissipating film produced by the production method according to any one of claims 1 to 9.

11. An electronic device, characterized in that the boron nitride heat-dissipating film according to claim 10 is provided.

12. An electronic device comprising the boron nitride heat spreading film of claim 10.