Preparation method of multilayer composite heat conducting material

Abstract

The application discloses a kind of multilayer composite heat conducting material preparation methods, it is related to heat conducting material technical field, the specific steps of the method are as follows: select metal powder as metal heat conducting gasket material, the metal powder is copper powder, the multilayer composite heat conducting material of the application has excellent heat conducting performance, by the compounding of metal heat conducting layer, inorganic non-metal heat conducting layer and high molecular polymer layer, the advantages of each layer material are fully exerted, copper powder in metal heat conducting layer has higher heat conductivity, can quickly transmit heat, boron nitride in inorganic non-metal heat conducting layer has good heat conductivity and high temperature resistance, can keep stable heat conducting performance under high temperature environment, high molecular polymer layer plays the role of protection and enhances material overall structure stability, the design of this multilayer structure makes heat can be efficiently transmitted inside material, greatly improves the heat conducting efficiency of material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-conducting materials, in particular to a preparation method of a multilayer composite heat-conducting material. BACKGROUND

[0002] In today's era of rapid development of science and technology, electronic equipment, new energy vehicles, aerospace and many other fields have made remarkable progress. With the continuous development of these fields, the performance requirements for materials are also increasing, especially in terms of thermal conductivity. High-performance heat-conducting materials are indispensable. Under such a background, it is of great significance to develop a composite heat-conducting material with excellent thermal conductivity, good stability and processability.

[0003] However, the existing preparation method of heat-conducting materials uses a single heat-conducting material, which limits its thermal conductivity. In addition, the existing composite heat-conducting material has problems in the bonding strength between layers. When used for a long time or subjected to certain external forces, the layers are prone to separation and delamination, which seriously affects the thermal conductivity and overall stability of the material.

[0004] In summary, the existing heat-conducting materials have certain limitations in performance, structure, preparation process and cost, and are difficult to meet the growing market demand. Therefore, it is necessary to develop a new type of multilayer composite heat-conducting material to overcome the shortcomings of existing technology, improve thermal conductivity, enhance the bonding strength between layers, simplify the preparation process and reduce costs. This has become a problem to be solved in the field of heat-conducting materials. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a preparation method of a multilayer composite heat-conducting material. The method can achieve the optimal combination and distribution of different heat-conducting coefficient materials. Copper powder is used as the bottom layer with high thermal conductivity, combined with the intermediate layer formed by boron nitride particles and the top layer composed of polyimide. This structure design not only takes full advantage of each material, but also greatly reduces the contact thermal resistance between layers through special surface treatment and bonding process.

[0006] To solve the above technical problems, the present application provides the following technical solution: a preparation method of a multilayer composite heat-conducting material, which comprises the following specific steps:

[0007] S100, selecting metal powder as a metal heat-conducting gasket material, the metal powder being copper powder with a particle size of 10-50 microns, and the copper powder being subjected to surface treatment to remove surface oxides and impurities;

[0008] The boron nitride is selected as the inorganic non-metallic heat-conducting material, the boron nitride is crushed and classified to obtain fine-grained boron nitride with a particle size of 1-10 microns and coarse-grained boron nitride with a particle size of 10-50 microns;

[0009] The polyimide is selected as the material of the high-molecular polymer layer, and the polyimide resin is a thermoplastic polyimide;

[0010] In S200, the copper powder after the surface treatment is mixed with a binder to form a copper powder slurry, the binder is an inorganic adhesive, and the amount of the binder is 3-8% of the mass of the copper powder;

[0011] The copper powder slurry is prepared into a metal heat-conducting layer by compression molding;

[0012] In S300, the fine-grained boron nitride with a particle size of 1-10 microns and the coarse-grained boron nitride with a particle size of 10-50 microns are mixed in a mass ratio of 1:1.5-1:2.5 to form a boron nitride mixed powder;

[0013] The boron nitride mixed powder is mixed with a binder and a solvent to form a boron nitride slurry;

[0014] The binder is an inorganic adhesive, the solvent is an organic solvent, the amount of the binder is 8-15% of the mass of the boron nitride powder, and the amount of the solvent is 40-60% of the mass of the boron nitride powder;

[0015] The boron nitride slurry is prepared into an inorganic non-metallic heat-conducting layer by flow casting;

[0016] In S400, the polyimide resin is mixed with an auxiliary agent, and then dried to form a polyimide mixture;

[0017] The polyimide mixture is prepared into a high-molecular polymer layer by extrusion molding;

[0018] In S500, the metal heat-conducting layer is placed at the bottom layer, the inorganic non-metallic heat-conducting layer is placed on the metal heat-conducting layer, and the high-molecular polymer layer is placed on the inorganic non-metallic heat-conducting layer, and the layers are tightly combined by hot pressing to form a multi-layer composite heat-conducting material.

[0019] Further, the surface treatment of the copper powder in S100 is specifically chemical treatment and physical treatment to remove the oxides and impurities on the surface of the copper powder, the chemical treatment is acid pickling, the copper powder is soaked in an acid solution, the acid reacts with the oxides on the surface of the copper powder to generate water-soluble salts, and the impurities and reaction products are removed by water washing; the physical treatment is mechanical grinding, and the oxides and impurities on the surface of the copper powder are removed by mechanical force.

[0020] Further, in the S200, the compression molding process is performed by placing the copper powder slurry into a mold and compressing it at a pressure of 8-12 MPa and a temperature of 140-160℃.

[0021] Further, in the S300, the flow casting process is performed by pouring the boron nitride slurry into a flow casting machine and casting it at a casting speed of 0.5-2.5 m / min and a temperature of 50-80℃.

[0022] Further, in the S400, the polyimide mixture is placed into an extruder and extruded at a temperature of 200-300℃ and a pressure of 2-5 MPa.

[0023] Further, in the S400, the polyimide mixture is pre-dried at a temperature of 80-120℃ for 2-4 hours to remove water and volatile substances.

[0024] Further, in the S400, the additives include 0.5% of an antioxidant, 1.5% of silicone oil, 15% of glass fibers, and 1% of a silane coupling agent.

[0025] Further, in the S500, the hot pressing process is performed at a temperature of 180-220℃ and a pressure of 4-6 MPa.

[0026] Compared with the prior art, the method for preparing the multi-layer composite heat-conducting material has the following advantages:

[0027] Firstly, the multi-layer composite heat-conducting material has excellent heat-conducting performance. The metal heat-conducting layer, the inorganic non-metal heat-conducting layer, and the high polymer layer are combined to fully utilize the advantages of each layer. The copper powder in the metal heat-conducting layer has a high heat-conducting coefficient and can quickly transfer heat. The boron nitride in the inorganic non-metal heat-conducting layer has good heat-conducting performance and high-temperature resistance and can maintain stable heat-conducting performance at high temperatures. The high polymer layer protects and enhances the stability of the overall structure of the material. The multi-layer structure design enables efficient heat transfer within the material, greatly improving the heat-conducting efficiency of the material.

[0028] Secondly, the ratio of fine and coarse particles of boron nitride is precisely controlled to improve the mechanical strength and high-temperature resistance of the inorganic non-metal heat-conducting layer. The use of thermoplastic polyimide as the outermost layer gives the entire composite system better flexibility and anti-aging ability, making the prepared heat-conducting material not only suitable for use in conventional environments but also capable of coping with more demanding and harsh working conditions.

[0029] Additional advantages, objects, and features of the application will be apparent to those skilled in the art upon examination of the following detailed description, it being understood that each embodiment can not represent an exhaustive listing of the application. Accordingly, the application will be described with particular reference to the examples described below. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings;

[0031] Figure 1 An operation flow chart of a preparation method of a multi-layer composite heat-conducting material. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0033] Embodiment one

[0034] This embodiment details the composite heat-conducting material prepared by a preparation method of a multi-layer composite heat-conducting material in the application of electronic equipment heat dissipation to improve the stability and service life of the equipment, and at the same time, ensure the safe operation of the electronic equipment.

[0035] First, raw materials are prepared, including metal powder: high-purity copper powder with an average particle size of 20 microns is selected, the copper powder is surface treated, first, the acid pickling method is used, the copper powder is soaked in a dilute nitric acid solution for 25 minutes, then washed with water, and then mechanically ground, using a ball mill to grind the copper powder at a speed of 450 revolutions per minute for 1.5 hours; inorganic non-metallic material: boron nitride is selected as the inorganic non-metallic heat-conducting material, the boron nitride is crushed and classified to obtain fine-grained boron nitride with an average particle size of 3 microns and coarse-grained boron nitride with an average particle size of 20 microns, the mass ratio of fine-grained and coarse-grained is 1:1.6; high molecular polymer material: thermoplastic polyimide is used as the material of the high molecular polymer layer, a suitable polyimide resin is selected, and 0.4% of antioxidant, 1.2% of silicone oil, 13% of glass fiber and 0.8% of silane coupling agent are added.

[0036] Then, the metal heat-conducting layer is prepared by mixing the pretreated copper powder with an appropriate amount of inorganic adhesive to form a copper powder slurry. The amount of the binder is 4% of the mass of the copper powder. The copper powder slurry is placed in a mold and is subjected to compression molding under the conditions of a pressure of 9 MPa and a temperature of 145℃. The gaps between the copper powder particles are reduced, the binder is softened and filled between the copper powder particles, and a dense metal heat-conducting layer is formed. As the pressure increases, the contact area between the copper powder particles increases, the heat-conducting performance is improved, the solidification of the binder is promoted, and the strength and stability of the metal heat-conducting layer are improved. The compression time is 1.2 hours, and the metal heat-conducting layer with a thickness of 0.45 mm is obtained.

[0037] Subsequently, the inorganic non-metal heat-conducting layer is prepared by mixing the boron nitride mixed powder with an appropriate amount of inorganic adhesive and organic solvent to form a boron nitride slurry. The amount of the binder is 10% of the mass of the boron nitride powder, and the amount of the solvent is 50% of the mass of the boron nitride powder. The boron nitride slurry is poured into a casting machine and is uniformly spread on the base band of the casting machine. The casting is performed under the conditions of a casting speed of 1.2 m / min and a temperature of 60℃. The casting time is 35 minutes. As the solvent volatilizes and the slurry solidifies, the inorganic non-metal heat-conducting layer with a certain thickness of 0.28 mm is formed.

[0038] Next, the high molecular polymer layer is prepared by uniformly mixing the polyimide resin with the auxiliary agent and drying the polyimide mixture at a temperature of 95℃ for 2.5 hours. The polyimide mixture is placed in an extruder and is subjected to extrusion under the conditions of a temperature of 260℃ and a pressure of 3.5 MPa. The high molecular polymer layer with a thickness of 0.18 mm is obtained.

[0039] Finally, the composite molding is performed by placing the metal heat-conducting layer at the bottom layer, placing the inorganic non-metal heat-conducting layer on the metal heat-conducting layer, and placing the high molecular polymer layer on the inorganic non-metal heat-conducting layer. The hot pressing process is performed under the conditions of a temperature of 195℃ and a pressure of 4.5 MPa for 1.5 hours. The materials of the layers are tightly combined to form the multilayer composite heat-conducting material.

[0040] Performance test: The thermal conductivity coefficient of the composite heat-conducting material is 75 W / (m·K), the heat-resistant temperature reaches 340℃, and the deformation rate under pressure is 1.5%. The material can effectively reduce the equipment temperature by 15℃. The bending strength of the material is 140 MPa, which has good mechanical strength and can withstand external force without damage.

[0041] Example Two

[0042] Firstly, raw materials are prepared, including metal powder: high-purity copper powder with an average particle size of 25 microns is selected, the copper powder is surface treated, an acid pickling method is adopted, the copper powder is soaked in a dilute sulfuric acid solution for 30 minutes, then washed with water, and then the copper powder is ground with a grinder at a speed of 480 revolutions per minute for 1.8 hours; inorganic non-metallic material: boron nitride is selected as the inorganic non-metallic heat-conducting material, the boron nitride is crushed and classified to obtain fine-grained boron nitride with an average particle size of 4 microns and coarse-grained boron nitride with an average particle size of 25 microns, the mass ratio of the fine-grained and coarse-grained boron nitride is 1:1.8; high-molecular polymer material: thermoplastic polyimide is used as the material of the high-molecular polymer layer, a suitable polyimide resin is selected, and 0.45% of antioxidant, 1.3% of silicon oil, 14% of glass fiber and 0.9% of silane coupling agent are added.

[0043] Then, the metal heat-conducting layer is prepared, the pre-processed copper powder is uniformly mixed with an appropriate amount of inorganic adhesive to form a copper powder slurry. The amount of adhesive is 5% of the mass of copper powder, the copper powder slurry is placed in a mold, and is pressed and formed under the conditions of a pressure of 10 MPa and a temperature of 150°C. In this process, the gap between copper powder particles gradually decreases, the adhesive softens and fills between the particles. As the pressure increases, the contact area of the copper powder particles increases, the heat-conducting performance is improved, and at the same time, the adhesive solidifies, enhancing the strength and stability of the metal heat-conducting layer. The pressing time is 1.3 hours, and a metal heat-conducting layer with a thickness of 0.48 mm is obtained.

[0044] Subsequently, the inorganic non-metallic heat-conducting layer is prepared, the mixed boron nitride powder is mixed with an appropriate amount of inorganic adhesive and organic solvent to form a boron nitride slurry, the amount of adhesive is 11% of the mass of boron nitride powder, and the amount of solvent is 52% of the mass of boron nitride powder. The boron nitride slurry is poured into a casting machine and cast under the conditions of a casting speed of 1.4 m / min and a temperature of 65°C. The casting time is 40 minutes. As the solvent volatilizes and the slurry solidifies, an inorganic non-metallic heat-conducting layer with a thickness of 0.3 mm is formed.

[0045] Next, the high-molecular polymer layer is prepared. The polyimide resin is uniformly mixed with additives, then dried at a temperature of 100°C for 2.8 hours to form a polyimide mixture. The polyimide mixture is placed in an extruder and extruded under the conditions of a temperature of 270°C and a pressure of 4 MPa. A high-molecular polymer layer with a thickness of 0.19 mm is obtained.

[0046] Finally, the composite molding is performed. The metal heat-conducting layer is placed at the bottom layer, the inorganic non-metallic heat-conducting layer is placed on the metal heat-conducting layer, and the high-molecular polymer layer is placed on the inorganic non-metallic heat-conducting layer. A hot pressing process is adopted, and the hot pressing is performed under the conditions of a temperature of 200°C and a pressure of 5 MPa for 1.6 hours. The materials of each layer are tightly combined to form a multi-layer composite heat-conducting material.

[0047] Performance test: the thermal conductivity of the composite heat-conducting material is 80 W / (m·K), the heat-resistant temperature reaches 350℃, the deformation rate under pressure is 1.4%, the material can effectively reduce the equipment temperature by 16℃, the bending strength of the material is 145 MPa, and the material has good mechanical strength and can withstand external force without damage.

[0048] Example three

[0049] First, raw material preparation is performed, including metal powder: high-purity copper powder with an average particle size of 30 microns is selected, the copper powder is surface treated, the copper powder is first soaked in a hydrochloric acid solution for 35 minutes, then washed with water, and then the copper powder is ground with a ball mill at a speed of 500 revolutions per minute for 2 hours; inorganic non-metallic material: boron nitride is selected as the inorganic non-metallic heat-conducting material, the boron nitride is crushed and classified to obtain fine-grained boron nitride with an average particle size of 5 microns and coarse-grained boron nitride with an average particle size of 30 microns, and the mass ratio of fine-grained and coarse-grained boron nitride is 1:2; high molecular polymer material: thermoplastic polyimide is used as the material of the high molecular polymer layer, a suitable polyimide resin is selected, and 0.5% of an antioxidant, 1.4% of silicon oil, 15% of glass fiber, and 1% of silane coupling agent are added.

[0050] Then, the metal heat-conducting layer is prepared, the pre-processed copper powder is uniformly mixed with an appropriate amount of inorganic adhesive to form a copper powder slurry. The amount of adhesive is 6% of the mass of copper powder, the copper powder slurry is placed in a mold, and the copper powder particles are tightly combined under the conditions of a pressure of 11 MPa and a temperature of 155℃, the adhesive fully plays a role, and the strength and stability of the heat-conducting layer are improved. The pressing time is 1.4 hours, and a metal heat-conducting layer with a thickness of 0.5 mm is obtained.

[0051] Subsequently, the inorganic non-metallic heat-conducting layer is prepared, the boron nitride mixed powder is mixed with an appropriate amount of inorganic adhesive and organic solvent to form a boron nitride slurry, the amount of adhesive is 12% of the mass of boron nitride powder, and the amount of solvent is 55% of the mass of boron nitride powder, the boron nitride slurry is poured into a casting machine, and the inorganic non-metallic heat-conducting layer with a thickness of 0.32 mm is formed under the conditions of a casting speed of 1.6 m / min and a temperature of 70℃.

[0052] Next, the high molecular polymer layer is prepared, the polyimide resin is uniformly mixed with additives, and then dried at a temperature of 105℃ for 3 hours to form a polyimide mixture, the polyimide mixture is placed in an extruder, and the high molecular polymer layer with a thickness of 0.2 mm is obtained under the conditions of a temperature of 280℃ and a pressure of 4.5 MPa.

[0053] Finally, the composite is formed by placing the metal heat-conducting layer at the bottom, the inorganic non-metal heat-conducting layer on the metal heat-conducting layer, and the high polymer layer on the inorganic non-metal heat-conducting layer. The heat pressing process is performed at a temperature of 205°C and a pressure of 5.5 MPa for 1.8 hours to tightly combine the layers and form a multi-layer composite heat-conducting material.

[0054] Performance test: the thermal conductivity of the composite heat-conducting material is 85 W / (m·K), the heat resistance temperature reaches 360°C, the deformation rate under pressure is 1.3%, the material can effectively reduce the equipment temperature to 17°C, the bending strength of the material is 150 MPa, and the material has good mechanical strength and can withstand external force without damage.

[0055] Example Four

[0056] First, the raw materials are prepared, including metal powder: high-purity copper powder with an average particle size of 35 microns is selected, the copper powder is surface treated, acid washing method is adopted, the copper powder is soaked in dilute sulfuric acid solution for 40 minutes, then washed with water, and then ground with a grinder at a speed of 520 revolutions per minute for 2.2 hours; inorganic non-metallic material: boron nitride is selected as the inorganic non-metallic heat-conducting material, the boron nitride is crushed and classified to obtain fine particles of boron nitride with an average particle size of 6 microns and coarse particles of boron nitride with an average particle size of 35 microns, the mass ratio of fine particles to coarse particles is 1:2.2; high molecular polymer material: thermoplastic polyimide is used as the material of the high molecular polymer layer, appropriate polyimide resin is selected, and 0.55% of antioxidant, 1.5% of silicon oil, 16% of glass fiber and 1.1% of silane coupling agent are added.

[0057] Then, the metal heat-conducting layer is prepared, the pre-treated copper powder is mixed with an appropriate amount of inorganic adhesive to form a copper powder slurry. The amount of adhesive is 7% of the mass of copper powder, the copper powder slurry is placed in a mold, and the copper powder particles are formed into a dense structure under the conditions of a pressure of 12 MPa and a temperature of 160°C to improve the heat-conducting performance, the pressing time is 1.5 hours, and a metal heat-conducting layer with a thickness of 0.55 mm is obtained.

[0058] Subsequently, the inorganic non-metal heat-conducting layer is prepared, the boron nitride mixed powder is mixed with an appropriate amount of inorganic adhesive and organic solvent to form a boron nitride slurry, the amount of adhesive is 13% of the mass of boron nitride powder, and the amount of solvent is 58% of the mass of boron nitride powder, the boron nitride slurry is poured into a casting machine, and the boron nitride slurry is cast under the conditions of a casting speed of 1.8 m / min and a temperature of 75°C to form an inorganic non-metal heat-conducting layer with a thickness of 0.35 mm.

[0059] Next, the high polymer layer is prepared by mixing the polyimide resin with the additives uniformly, drying for 3.2 hours at a temperature of 110°C to form a polyimide mixture, and extruding the polyimide mixture in an extruder at a temperature of 290°C and a pressure of 5 MPa to obtain a high polymer layer with a thickness of 0.22 mm.

[0060] Finally, the composite molding is performed by placing the metal heat-conducting layer at the bottom, placing the inorganic non-metal heat-conducting layer on the metal heat-conducting layer, and placing the high polymer layer on the inorganic non-metal heat-conducting layer, and then performing hot pressing at a temperature of 210°C and a pressure of 6 MPa for 2 hours to tightly combine the layers and form a multilayer composite heat-conducting material.

[0061] Performance test: the thermal conductivity of the composite heat-conducting material is 90 W / (m·K), the heat resistance temperature reaches 370°C, the deformation rate under pressure is 1.2%, the material can effectively reduce the equipment temperature by 18°C, the bending strength of the material is 155 MPa, and the material has good mechanical strength and can withstand external force without damage.

[0062] Example Five

[0063] First, the raw materials are prepared, including metal powder: high-purity copper powder with an average particle size of 40 microns is selected, and the copper powder is surface treated by immersing it in a hydrochloric acid solution for 45 minutes, then washing with water, and then grinding the copper powder with a ball mill at a speed of 550 revolutions per minute for 2.5 hours; inorganic non-metallic material: boron nitride is selected as the inorganic non-metallic heat-conducting material, and the boron nitride is crushed and classified to obtain fine particles of boron nitride with an average particle size of 7 microns and coarse particles of boron nitride with an average particle size of 40 microns, with a mass ratio of fine particles to coarse particles of 1:2.5; high polymer material: thermoplastic polyimide is used as the material for the high polymer layer, and appropriate polyimide resin is selected, with the addition of 0.6% antioxidant, 1.6% silicone oil, 17% glass fiber, and 1.2% silane coupling agent.

[0064] Then, the metal heat-conducting layer is prepared by mixing the pre-treated copper powder with an appropriate amount of inorganic adhesive uniformly to form a copper powder slurry. The amount of adhesive is 8% of the mass of copper powder, and the copper powder slurry is placed in a mold and pressed at a pressure of 13 MPa and a temperature of 165°C to form a high-strength heat-conducting layer, with the copper powder particles tightly combined. The pressing time is 1.6 hours, and the metal heat-conducting layer obtained has a thickness of 0.6 mm.

[0065] Subsequently, the inorganic non-metallic heat-conducting layer is prepared by mixing the boron nitride mixed powder with an appropriate amount of inorganic adhesive and organic solvent to form a boron nitride slurry, the amount of adhesive is 14% of the mass of boron nitride powder, and the amount of solvent is 60% of the mass of boron nitride powder, the boron nitride slurry is poured into a casting machine, and the casting is carried out at a casting speed of 2 m / min and a temperature of 80℃, the casting time is 55 minutes, and the inorganic non-metallic heat-conducting layer with a thickness of 0.38 mm is formed.

[0066] Next, the high molecular polymer layer is prepared by uniformly mixing the polyimide resin with the auxiliary agent, drying at a temperature of 115℃ for 3.5 hours to form a polyimide mixture, and then placing the polyimide mixture into an extruder and extruding at a temperature of 300℃ and a pressure of 5.5 MPa to obtain a high molecular polymer layer with a thickness of 0.25 mm.

[0067] Finally, the composite molding is carried out by placing the metal heat-conducting layer at the bottom, placing the inorganic non-metallic heat-conducting layer on the metal heat-conducting layer, and placing the high molecular polymer layer on the inorganic non-metallic heat-conducting layer, and then hot pressing at a temperature of 215℃ and a pressure of 6.5 MPa for 2.2 hours to tightly bond the layers and form a multi-layer composite heat-conducting material.

[0068] Performance test: the thermal conductivity of the composite heat-conducting material is 95 W / (m·K), the heat resistance temperature reaches 380℃, the deformation rate under pressure is 1.1%, the material can effectively reduce the equipment temperature by 19℃, the bending strength of the material is 160 MPa, and the mechanical strength is good, which can withstand external force without damage.

[0069] Comparative example

[0070] A single copper sheet is used as the heat-conducting material without multi-layer composite treatment.

[0071] Performance test: the thermal conductivity of the single copper sheet heat-conducting material is 60 W / (m·K), the heat resistance temperature reaches 300℃, the deformation rate under pressure is 2.5%, the material can effectively reduce the equipment temperature by 10℃, the bending strength of the material is 120 MPa, and the mechanical strength is relatively weak, which is easily damaged when subjected to external force.

[0072] In summary, by testing the performance of the examples and comparative examples of the multilayer composite heat-conducting material, from the heat conductivity, examples 1-5 gradually improve with the change of parameters, indicating that the multilayer composite structure has a significant improvement in the heat-conducting performance; in terms of heat resistance temperature, the examples are also significantly higher than the comparative examples, indicating that the material can work stably in a high-temperature environment; in terms of deformation rate, the examples are controlled at a low level, reflecting good structural stability; in terms of reducing the temperature of the equipment and the bending strength, the examples can effectively reduce the temperature of the equipment and have high bending strength, and can withstand external force; the comparative examples are inferior in various performances, and the multilayer composite heat-conducting material of the present application has excellent performance. The performance test results of examples 1-5 and comparative examples are shown in the following table:

[0073] Examples Thermal conductivity (W / (m・K)) Heat resistance temperature (℃) Deformation rate (%) Lowering equipment temperature (℃) Bending strength (MPa) Overall test evaluation Example 1 75 340 1.5 15 140 Good Example 2 80 350 1.4 16 145 Good Example 3 85 360 1.3 17 150 Excellent Example 4 90 370 1.2 18 155 Excellent Example 5 95 380 1.1 19 160 Excellent Comparative example 60 300 2.5 10 120 Poor

[0074] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the application being defined by the appended claims rather than the above description, and it is intended that all changes which come within the meaning and range of equivalency of the claims are embraced therein. Any reference signs in the claims should not be construed as limiting the claims concerned.

Claims

1. A method for preparing a multilayer composite thermal conductive material, characterized in that: The specific steps of this method are: S100, selecting metal powder as a material for the metal thermal pad, wherein the metal powder is copper powder with a particle size of 10 μm to 50 μm, and performing surface treatment on the copper powder to remove surface oxides and impurities; Boron nitride is selected as the inorganic non-metallic thermal conductive material, and the boron nitride is crushed and classified to obtain fine boron nitride particles with a particle size of 1 μm-10 μm and coarse boron nitride particles with a particle size of 10 μm-50 μm; Polyimide is selected as the material of the high molecular polymer layer, and the polyimide resin is thermoplastic polyimide; S200, uniformly mixing the surface-treated copper powder with a binder to form a copper powder slurry, wherein the binder is an inorganic adhesive, and the amount of the binder is 3%-8% of the mass of the copper powder; The copper powder slurry is pressed to prepare a metal heat-conducting layer; S300, fine boron nitride particles with a particle size of 1 μm to 10 μm and coarse boron nitride particles with a particle size of 10 μm to 50 μm are uniformly mixed in a mass ratio of 1:1.5 to 1:2.5 to form a boron nitride mixed powder; and mixing the boron nitride mixed powder with a binder and a solvent to form a boron nitride slurry; The binder is an inorganic adhesive, the solvent is an organic solvent, the amount of the binder is 8%-15% of the mass of the boron nitride powder, and the amount of the solvent is 40%-60% of the mass of the boron nitride powder; The boron nitride slurry is used to prepare an inorganic non-metallic heat conductive layer by tape casting; S400, uniformly mixing the polyimide resin and the additives and drying them to form a polyimide mixture; The polyimide mixture is extruded to prepare a high molecular polymer layer; S500: placing a metal thermal conductive layer at the bottom layer, placing an inorganic non-metallic thermal conductive layer on the metal thermal conductive layer, and placing a high molecular polymer layer on the inorganic non-metallic thermal conductive layer, and using a hot pressing method to tightly combine the layers to form a multi-layer composite thermal conductive material.

2. The method for preparing a multilayer composite thermal conductive material according to claim 1, characterized in that: The surface treatment of the copper powder in S100 specifically adopts chemical treatment and physical treatment methods to remove oxides and impurities on the surface of the copper powder. The chemical treatment adopts an acid pickling method, in which the copper powder is immersed in an acid solution. The acid reacts with the oxides on the surface of the copper powder to generate water-soluble salts, and the impurities and reaction products are removed by water washing; the physical treatment adopts a mechanical grinding method, in which the oxides and impurities on the surface of the copper powder are removed by the action of mechanical force.

3. The method for preparing a multilayer composite thermal conductive material according to claim 1, characterized in that: In the pressing and forming process in S200 , the copper powder slurry is placed in a mold and pressed under the conditions of a pressure of 8 MPa-12 MPa and a temperature of 140° C.-160° C.

4. The method for preparing a multilayer composite thermally conductive material according to claim 1, wherein: In the tape casting process in S300, the boron nitride slurry is poured into a tape casting machine and tape casting is performed at a casting speed of 0.5 m / min-2.5 m / min and a temperature of 50-80°C.

5. The method for preparing a multi-layer composite thermal conductive material according to claim 1, characterized in that: In the extrusion molding process in S400 , the polyimide mixture is placed in an extruder and the process is carried out at a temperature of 200° C. to 300° C. and a pressure of 2 MPa to 5 MPa.

6. The method for preparing a multi-layer composite thermal conductive material according to claim 1, characterized in that: In the step S400 , the polyimide mixture is pre-dried at a temperature of 80° C. to 120° C. for 2 to 4 hours to remove moisture and volatile substances from the polyimide mixture.

7. The method for preparing a multi-layer composite thermal conductive material according to claim 1, characterized in that: The additives in the S400 are 0.5% by mass of an antioxidant, 1.5% by mass of silicone oil, 15% by mass of glass fiber, and 1% by mass of a silane coupling agent.

8. The method for preparing a multi-layer composite thermal conductive material according to claim 1, characterized in that: The hot pressing process in S500 is performed at a temperature of 180° C. to 220° C. and a pressure of 4 MPa to 6 MPa.

Images