Diamond / copper composite heat-conducting material and preparation method thereof

Abstract

The present application belongs to the technical field of composite heat-conducting material, and particularly relates to a diamond / copper composite heat-conducting material and a preparation method thereof. The modified silane coupling agent is prepared by a two-step method, and then the modified silane coupling agent is used as a modifier to prepare a modified silica sol by taking tetraethyl orthosilicate as a reaction raw material. The mixed powder is surface-modified by the modified silica sol, so that the dispersibility of the diamond powder and the copper powder is improved, and a chemical bond is formed between the diamond powder and the copper powder, which greatly improves the interface bonding force between the diamond and the copper. Meanwhile, the interface bonding force between the diamond and the copper is further improved by process control of the vacuum sintering process, and the thermal conductivity, the density and the mechanical properties of the composite material are significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite heat-conducting materials, and particularly relates to a diamond / copper composite heat-conducting material and a preparation method thereof. BACKGROUND

[0002] In the current thriving microelectronics industry, the power density of electronic devices has significantly increased, and efficient heat dissipation has become one of the important conditions for the popularization and application of new-generation high-performance high-power electronic devices. Diamond / copper composite materials, which are composed of diamond with ultra-high thermal conductivity and low thermal expansion coefficient and copper with high thermal conductivity, are expected to become a new generation of efficient heat dissipation materials. However, the problems such as poor wettability and poor interface bonding between diamond and copper will result in a thermal conductivity of the composite material far lower than the theoretical value. Therefore, it is of great significance and technical value to realize the interface regulation and optimization of the diamond / copper composite material and to prepare a diamond / copper composite material with excellent performance.

[0003] The patent with the application number CN201610426906.9 provides a method for manufacturing diamond composite sheets with good heat conduction. First, diamond micro powder, copper powder and silver powder are uniformly mixed and stirred, and then are loaded into a metal cup and sintered under vacuum at high temperature and high pressure. The diamond composite sheets prepared by this process have good heat dissipation performance, long durability, and good hardness and wear resistance. However, the preparation process of the diamond composite sheets requires high equipment and has high energy consumption. The patent with the application number CN201711106615.2 provides a method for preparing a diamond / copper composite material with high thermal conductivity. First, tungsten powder is used to plate tungsten on diamond to obtain tungsten-plated diamond. Then, the tungsten-plated diamond is uniformly mixed with copper powder and sintered at high temperature. The invention uses a vacuum high-temperature blending reaction method to plate tungsten on diamond. The tungsten-plated diamond particle separation process is simple, the protection of diamond is high, and the intrinsic thermal conductivity of diamond is ensured. The method uses a spark plasma sintering method to shorten the sintering cycle and stabilize the performance of the product. However, when the invention uses a vacuum high-temperature blending method to plate tungsten on diamond, the plating temperature is as high as 1030℃, which can easily cause thermal damage to diamond and affect the performance of diamond. The above inventions use diamond powder and copper powder as raw materials to prepare high-thermal-conductivity composite materials. When the oxygen content of copper powder is high, it will reduce the sintering activity of the powder and have a great impact on the organization and performance of the sintered matrix.

[0004] According to the influencing factors of composite materials, after the matrix material and diamond particle reinforcement phase are selected, the design and optimization of the interface are the key factors to determine whether the composite material has excellent thermal performance. Therefore, in order to meet market demand, it is urgent to provide a composite heat-conducting material with good interface bonding and excellent comprehensive performance. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a diamond / copper composite thermal conductive material and a preparation method thereof, wherein the dispersibility and adhesion of the silica sol are improved by modifying the silica sol, the modified silica sol is mixed with raw materials such as diamond powder and copper powder, the raw materials interact with each other, and the prepared composite thermal conductive material has more excellent performance.

[0006] The technical scheme adopted by the present application to achieve the above-mentioned purpose is as follows:

[0007] A preparation method of a diamond / copper composite thermal conductive material, comprising the following steps:

[0008] S1, under stirring, 5,6-epoxyhexyl triethoxysilane and phenylacetic acid are dispersed in 2-methyltetrahydrofuran, then chromium acetate is added, the temperature is raised to 60-70 DEG C, and the reaction is carried out for 5-7 h, then filtration is carried out, the filtrate is taken, and the filtrate is subjected to vacuum distillation and drying to obtain an intermediate;

[0009] S2, under stirring, the intermediate obtained in step S1 and 4-(tetramethyl-1,3,2-dioxaborolan-2-yl) butyric acid are dispersed in 2-methyltetrahydrofuran, then p-toluenesulfonic acid is added, the temperature is raised to 75-85 DEG C, and the reaction is carried out for 4-6 h, then filtration is carried out, the filtrate is taken, and the filtrate is subjected to vacuum distillation, extraction, concentration and drying to obtain a modified silane coupling agent;

[0010] S3, under stirring, tetraethyl orthosilicate is uniformly mixed with anhydrous ethanol, the modified silane coupling agent obtained in step S2 is added, the reaction is carried out for 10-20 min, then deionized water is added, the pH is adjusted to 4-5, the reaction is carried out for 10-20 min, then the temperature is raised to 50-60 DEG C, the reflux reaction is continued for 0.5-1.5 h, the temperature is cooled to room temperature, and the mixture is left to stand for 15-20 h to obtain a modified silica sol;

[0011] S4, diamond powder and copper powder are dispersed in a sodium hydroxide aqueous solution, the temperature is raised to 80-100 DEG C, the stirring reaction is carried out for 3-5 h, the temperature is cooled to room temperature, solid-liquid separation is carried out, the solid is washed and dried to obtain a mixed powder; under stirring, the mixed powder is dispersed in the modified silica sol obtained in step S3, the temperature is raised to 75-85 DEG C, the reaction is carried out for 3-5 h, the temperature is cooled to room temperature, solid-liquid separation is carried out, the solid is washed and dried, and after ball milling and sieving, a surface-modified mixed powder is obtained;

[0012] S5, the surface-modified mixed powder obtained in step S4 is placed in a graphite mold, the powder is compacted, and the compacted powder is placed in a vacuum hot pressing furnace for vacuum hot pressing sintering; after the sintering is completed, the pressure in the vacuum hot pressing furnace is reduced to below 5 MPa, the temperature in the furnace is reduced to room temperature, and the compacted powder is demolded to obtain a diamond / copper composite thermal conductive material.

[0013] The synthesis route of the modified silane coupling agent is as follows:

[0014]

[0015] The silica sol is a good inorganic binder, which has the advantages of high temperature resistance, large specific surface area, strong adsorption and low thermal expansion coefficient, but also has the disadvantages of poor dispersibility and adhesion. The intermediate is obtained by ring-opening reaction of the epoxy compound under the action of chromium acetate, using 5,6-epoxyhexyl triethoxysilane and phenylacetic acid as raw materials; then the modified silane coupling agent is obtained by esterification reaction under the action of p-toluenesulfonic acid, using the intermediate and 4-(tetramethyl-1,3,2-dioxaborinanyl-2-yl) butyric acid as raw materials; finally, the modified silica sol is prepared by hydrolysis and polycondensation reaction, using tetraethyl orthosilicate as a raw material and the modified silane coupling agent as a modifier.

[0016] In order to obtain the modified silica sol and improve its dispersibility and adhesion, the molar ratio of 5,6-epoxyhexyl triethoxysilane, phenylacetic acid and chromium acetate in step S1 is 1:0.6-0.9:0.012-0.017, and the addition amount of 5,6-epoxyhexyl triethoxysilane in 2-methyltetrahydrofuran is 0.12-0.18 g / mL; the molar ratio of the intermediate, 4-(tetramethyl-1,3,2-dioxaborinanyl-2-yl) butyric acid and p-toluenesulfonic acid in step S2 is 1:0.8-1.0:0.01-0.02, and the addition amount of 4-(tetramethyl-1,3,2-dioxaborinanyl-2-yl) butyric acid in 2-methyltetrahydrofuran is 0.1-0.3 g / mL; the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent and deionized water in step S3 is 35-40:60-70:6-8:20.

[0017] Further, the mass ratio of the diamond powder and the copper powder in step S4 is 2:2-4, the mass concentration of the sodium hydroxide aqueous solution is 0.10-0.13 g / mL, the addition amount of the diamond powder in the sodium hydroxide aqueous solution is 0.07-0.12 g / mL, the mass ratio of the mixed powder and the modified silica sol is 4:140-180, the dry ball milling is adopted in the ball milling, the ball milling speed is 130-170 r / min, the ball milling time is 20-40 min, and the ball to material ratio is 3-5:1; the specific steps of the vacuum hot-pressing sintering in step S5 are as follows: first, heating to 200-250 ℃ at a heating rate of 1-5 ℃ / min, and keeping the temperature for 20-40 min; then, heating to 850-950 ℃ at a heating rate of 5-10 ℃ / min, and keeping the temperature for 20-40 min; the pressure in the vacuum hot-pressing furnace is 30-50 MPa.

[0018] The diamond / copper composite thermal conductive material is prepared by the above method.

[0019] Diamond and copper have great difference in structure and performance, and the problems of mutual non-wetting and poor interface bonding will seriously affect the actual thermal conductivity of diamond / copper composite material. Meanwhile, the great difference in thermal expansion coefficient between diamond and copper will introduce thermal stress at the interface of the composite material, which is tensile stress during the cooling process. If the interface bonding strength is insufficient, it will increase the risk of interface debonding during the preparation and service of the composite material, and thus directly threaten the performance reliability of the composite material. In addition, the specific surface energy of fine particle diamond powder and copper powder is large, and the surface active groups are more, so the agglomeration is easy to occur during processing and use, and thus the use performance of the composite material is affected. In order to improve the use performance of diamond powder, copper powder and their products, the mixed powder is surface modified by modified silica sol in the application, the chemical properties of the surface of diamond and copper are changed, and the dispersibility and interface bonding force of diamond powder and copper powder are greatly improved.

[0020] The application has the following beneficial effects:

[0021] The modified silica sol is prepared by using tetraethyl orthosilicate as a raw material and the modified silane coupling agent as a modifier, and boron heterocycle, benzene ring and siloxane are introduced into the structure of the silica sol. The introduction of siloxane can form chemical bonding between the raw material components and improve the bonding performance of the silica sol. The introduction of boron heterocycle and benzene ring can improve the dispersibility of the silica sol and avoid agglomeration. The mixed powder of diamond powder and copper powder is surface modified by the modified silica sol, which can not only improve the dispersibility of the diamond powder and the copper powder, but also form chemical bonding between the diamond powder and the copper powder, so that a more firm combination between the diamond and the copper is formed.

[0022] The vacuum sintering process of the application is divided into two stages. A slow heating rate is adopted in the low-temperature stage, so that sufficient chemical bonding is formed between the raw material components, which can effectively improve the assembly uniformity and interface bonding force of diamond and copper, and can keep the deformation as small as possible during the subsequent sintering process, so as to realize the uniform and controllable high-temperature densification of the material.

[0023] The modified silica sol is used as a modifier in the application. The carbon produced in the high-temperature pyrolysis process of the modified silica sol not only can react with the oxides in the copper powder to effectively reduce the oxygen content of the copper powder and improve the sintering structure performance of the copper powder, and thus improve the thermal conductivity of the composite material, but also can fill the pores and micro defects in the material, increase the contact area between the particles and increase the heat conduction path, so as to enhance the heat conduction effect of the material. In the hot-pressing sintering process, the simultaneous existence of boron element, diamond and copper can further form chemical bonding between the diamond and the copper, significantly improve the interface bonding strength of the diamond and the copper, and improve the thermal conductivity, density and mechanical properties of the composite material. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application. The raw materials used in the following embodiments are all commercially available products.

[0025] Embodiment 1

[0026] A preparation method of a diamond / copper composite thermal conductive material, comprising the following steps:

[0027] S1, under the condition of stirring at 180 rpm, dispersing 5,6-epoxyhexyl triethoxysilane and phenylacetic acid in 2-methyltetrahydrofuran, then adding chromium acetate, heating to 65 DEG C, reacting for 6 h, filtering, taking the filtrate, removing 2-methyltetrahydrofuran by distillation under reduced pressure, and vacuum drying at 55 DEG C for 12 h to obtain an intermediate; wherein the molar ratio of 5,6-epoxyhexyl triethoxysilane, phenylacetic acid and chromium acetate is 1:0.8:0.014, and the addition amount of 5,6-epoxyhexyl triethoxysilane in 2-methyltetrahydrofuran is 0.16 g / mL;

[0028] S2, under the condition of stirring at 180 rpm, dispersing the intermediate obtained in step S1 and 4-(tetramethyl-1,3,2-dioxaborinanyl-2-yl) butyric acid in 2-methyltetrahydrofuran, then adding p-toluenesulfonic acid, heating to 80 DEG C, reacting for 5 h, filtering, taking the filtrate, removing 2-methyltetrahydrofuran by distillation under reduced pressure, extracting with ethyl acetate and water, concentrating the organic phase, and vacuum drying at 60 DEG C for 12 h to obtain a modified silane coupling agent; wherein the molar ratio of the intermediate, 4-(tetramethyl-1,3,2-dioxaborinanyl-2-yl) butyric acid and p-toluenesulfonic acid is 1:0.9:0.014, and the addition amount of 4-(tetramethyl-1,3,2-dioxaborinanyl-2-yl) butyric acid in 2-methyltetrahydrofuran is 0.2 g / mL;

[0029] S3, under the condition of stirring at 200 rpm, the tetraethyl orthosilicate is uniformly mixed with anhydrous ethanol, the modified silane coupling agent obtained in step S2 is added, and the reaction is carried out for 15 min, deionized water is added, the pH is adjusted to 4-5 with 30% hydrochloric acid, the reaction is carried out for 15 min, then the temperature is raised to 55°C, the reflux reaction is continued for 1 h, and then the temperature is cooled to room temperature, and the mixture is left to stand for 17 h to obtain a modified silica sol, which is used in the next step within 30 min; wherein the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent and deionized water is 37:65:7:20, the viscosity of the modified silica sol is 12 mPa·S, the solid content (calculated as SiO2) is 20%, the particle size and particle size distribution of the sample are tested by using a Brookhaven multi-angle particle size analyzer 173Pl, the results show that the particle size of the modified silica sol is 17-22 nm, the particle size distribution is 0.114, the particle size distribution of the modified silica sol is relatively uniform, and the dispersibility of the modified silica sol is good, which overcomes the problem of easy agglomeration of SiO2 in the prior art;

[0030] S4, the diamond powder (particle size 5-10 μm, purity ≥98 wt%) and the copper powder (particle size 1-5 μm, purity ≥99 wt%) are dispersed in a sodium hydroxide aqueous solution, the temperature is raised to 90°C, the stirring reaction is carried out for 4 h, the temperature is cooled to room temperature, the solid-liquid separation is carried out, the solid is taken out, washed with deionized water until neutral, and dried at 120°C to obtain a mixed powder; under the condition of stirring at 200 rpm, the mixed powder is dispersed in the modified silica sol obtained in step S3, the temperature is raised to 80°C, the reaction is carried out for 4 h, the temperature is cooled to room temperature, the solid-liquid separation is carried out, the solid is taken out, washed with anhydrous ethanol for 3-4 times, vacuum dried at 50°C for 24 h, ball milled, and sieved through a 400 mesh sieve to obtain a surface-modified mixed powder; wherein the mass ratio of the diamond powder and the copper powder is 2:3, the mass concentration of the sodium hydroxide aqueous solution is 0.11 g / mL, the addition amount of the diamond powder in the sodium hydroxide aqueous solution is 0.1 g / mL, and the mass ratio of the mixed powder and the modified silica sol is 4:160; the ball milling is dry ball milling, the ball milling speed is 150 r / min, the ball milling time is 30 min, the ball-to-material ratio is 4:1, and the ball material is zirconia, and the ball is 1 mm and 3 mm balls distributed according to a weight ratio of 1:1;

[0031] S5, the surface-modified mixed powder obtained in step S4 is placed in a graphite mold, the powder is tamped with a tamping hammer, and then vacuum hot pressing sintering is carried out in a vacuum hot pressing furnace, after the sintering is completed, the pressure in the vacuum hot pressing furnace is reduced to below 5 MPa, the temperature in the furnace is naturally cooled to room temperature, and then the mold is demolded to obtain the product; wherein the specific steps of vacuum hot pressing sintering are as follows: first, the temperature is raised to 220°C at a rate of 5°C / min, and then the temperature is kept for 30 min, then the temperature is raised to 900°C at a rate of 10°C / min, and then the temperature is kept for 30 min, the pressure in the vacuum hot pressing furnace is 40 MPa, and the pressure reduction rate of the pressure in the vacuum hot pressing furnace is 10 kPa / min.

[0032] The NMR result of the modified silane coupling agent is as follows: 1 H NMR (300 MHz, DMSO-d6) δ 7.24-7.27 (m, 5H), 5.14-5.18 (m, 1H), 4.13-4.16 (m, 1H), 4.40-4.45 (m, 1H), 3.80-3.84 (m, 6H), 3.71 (s, 2H), 2.35 (t, 2H), 1.71-1.74 (m, 2H), 1.45-1.49 (m, 2H), 1.20-1.25 (m, 25H), 0.54-0.58 (m, 4H).

[0033] Example 2

[0034] The preparation method of the diamond / copper composite thermal conductive material is prepared according to the method described in Example 1, and the difference lies in that the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent and deionized water in step S3 is 35:60:6:20.

[0035] Example 3

[0036] The preparation method of the diamond / copper composite thermal conductive material is prepared according to the method described in Example 1, and the difference lies in that the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent and deionized water in step S3 is 40:70:8:20.

[0037] Example 4

[0038] The preparation method of the diamond / copper composite thermal conductive material is prepared according to the method described in Example 1, and the difference lies in that the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent and deionized water in step S3 is 40:70:8:20.

[0039] Example 5

[0040] The preparation method of the diamond / copper composite thermal conductive material is prepared according to the method described in Example 1, and the difference lies in that the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent and deionized water in step S3 is 40:70:8:20.

[0041] Comparative Example 1

[0042] The preparation method of the diamond / copper composite thermal conductive material is prepared according to the method described in Example 1, and the difference lies in that the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent and deionized water in step S3 is 40:70:8:20.

[0043] Comparative Example 2

[0044] The preparation method of the diamond / copper composite thermal conductive material comprises the following steps:

[0045] S1, under the condition of stirring at 200 rpm, tetraethyl orthosilicate is uniformly mixed with anhydrous ethanol, 5,6-epoxyhexyl triethoxysilane is added, and the reaction is carried out for 15 min, deionized water is added, the pH is adjusted to 4-5 with 30% hydrochloric acid, the reaction is carried out for 15 min, then the temperature is raised to 55°C, and the reflux reaction is continued for 1 h, and then the temperature is cooled to room temperature, and the mixture is left to stand for 17 h to obtain a modified silica sol, which is used in the next step within 30 min; wherein the mass ratio of tetraethyl orthosilicate, anhydrous ethanol, 5,6-epoxyhexyl triethoxysilane, and deionized water is 37:65:7:20;

[0046] S2, the diamond powder and copper powder are dispersed in a sodium hydroxide aqueous solution, the temperature is raised to 90°C, and the mixture is stirred for 4 h, then the temperature is cooled to room temperature, the solid-liquid separation is performed, the solid is washed with deionized water until it is neutral, and then the solid is dried at 120°C to obtain a mixed powder; under the condition of stirring at 200 rpm, the mixed powder is dispersed in the modified silica sol obtained in step S1, the temperature is raised to 80°C, and the reaction is carried out for 4 h, then the temperature is cooled to room temperature, the solid-liquid separation is performed, the solid is washed with anhydrous ethanol for 3-4 times, and then the solid is vacuum dried at 50°C for 24 h, ball milled, and sieved through a 500-mesh sieve to obtain a surface-modified mixed powder; wherein the mass ratio of the diamond powder and the copper powder is 2:3, the mass concentration of the sodium hydroxide aqueous solution is 0.11 g / mL, the addition amount of the diamond powder in the sodium hydroxide aqueous solution is 0.1 g / mL, and the mass ratio of the mixed powder and the modified silica sol is 4:160; the ball milling is dry ball milling, the ball milling speed is 150 r / min, the ball milling time is 30 min, the ball-to-material ratio is 4:1, and the ball material is zirconia, and the ball is 1 mm and 3 mm balls in a weight ratio of 1:1;

[0047] S3, the surface-modified mixed powder is placed in a graphite mold, the powder is tamped with a tamping hammer, and then the mixture is placed in a vacuum hot pressing furnace for vacuum hot pressing sintering; after the sintering is completed, the pressure in the vacuum hot pressing furnace is reduced to below 5 MPa, and then the temperature in the furnace is naturally cooled to room temperature, and the mixture is demolded to obtain the product; wherein the specific steps of vacuum hot pressing sintering are as follows: first, the temperature is raised to 220°C at a rate of 5°C / min, and then the temperature is maintained for 30 min; then, the temperature is raised to 900°C at a rate of 10°C / min, and then the temperature is maintained for 30 min; the pressure in the vacuum hot pressing furnace is 40 MPa, and the pressure reduction rate of the vacuum hot pressing furnace is 10 kPa / min.

[0048] The diamond / copper composite heat-conducting materials prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to relevant performance tests. The thermal diffusivity and thermal conductivity tests were performed according to GB / T22588-2008 "Flash Method for Measuring Thermal Diffusivity or Thermal Conductivity"; the density tests were performed using the drainage method; the bending strength tests were performed according to GB / T6569-2006 "Fine Ceramic Bending Strength Test Method"; the above tests were repeated three times and the average values were taken, and the test results are shown in Table 1. As can be seen from Table 1, the thermal diffusivity, thermal conductivity, density and bending strength of the composite heat-conducting materials prepared in Examples 1-5 are significantly better than those of Comparative Examples 1-2, wherein the thermal conductivities of the composite heat-conducting materials prepared in Examples 1-5 are all above 680 W / (m·K), and the densities of the materials are all above 99%; as can be seen from the effect data of Example 1 and Comparative Example 1, the modified silane coupling agent is prepared by a two-step method, and the silica sol is modified using the modified silane coupling agent to obtain a modified silica sol, which is compounded with diamond powder and copper powder, thereby significantly improving the thermal conductivity, mechanical properties and density of the composite material.

[0049] Table 1: Relevant performance test results of diamond / copper composite heat-conducting materials

[0050] Test item Thermal diffusivity (mm 2 / s) Thermal conductivity (W / (m·K)) Densification (%) Bending strength (MPa) Example 1 273.4 712.8 99.8 580 Example 2 270.7 708.3 99.6 572 Example 3 272.9 710.4 99.7 585 Example 4 267.0 702.1 99.4 566 Example 5 269.5 706.7 99.6 571 Comparative Example 1 241.2 637.9 91.3 519 Comparative Example 2 201.6 529.0 84.1 428

[0051] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a diamond / copper composite thermally conductive material, characterized in that, Includes the following steps: S1. Under stirring conditions, 5,6-epoxyhexyltriethoxysilane and phenylacetic acid are dispersed in 2-methyltetrahydrofuran, then chromium acetate is added, the temperature is raised to 60-70℃, and the reaction is carried out for 5-7 hours. The mixture is filtered, and the filtrate is collected, distilled under reduced pressure, and dried to obtain the intermediate. The molar ratio of 5,6-epoxyhexyltriethoxysilane, phenylacetic acid, and chromium acetate is 1:0.6-0.9:0.012-0.017, and the amount of 5,6-epoxyhexyltriethoxysilane added to 2-methyltetrahydrofuran is 0.12-0.18 g / mL. The structural formula of the intermediate is: ； S2. Under stirring conditions, the intermediate obtained in step S1 and 4-(tetramethyl-1,3,2-dioxaborcyclopentan-2-yl)butyric acid are dispersed in 2-methyltetrahydrofuran, and then p-toluenesulfonic acid is added. The mixture is heated to 75-85℃ and reacted for 4-6 hours. After filtration, the filtrate is collected, and then subjected to vacuum distillation, extraction, concentration, and drying to obtain the modified silane coupling agent. The molar ratio of the intermediate, 4-(tetramethyl-1,3,2-dioxaborcyclopentan-2-yl)butyric acid, and p-toluenesulfonic acid is 1:0.8-1.0:0.01-0.02, and the amount of 4-(tetramethyl-1,3,2-dioxaborcyclopentan-2-yl)butyric acid added to 2-methyltetrahydrofuran is 0.1-0.3 g / mL. The structural formula of the modified silane coupling agent is: ； The synthetic route for modified silane coupling agents is as follows: S3. Under stirring conditions, tetraethyl orthosilicate and anhydrous ethanol are mixed evenly, and the modified silane coupling agent obtained in step S2 is added. The reaction is carried out for 10-20 minutes, then deionized water is added to adjust the pH to 4-5, and the reaction is carried out for 10-20 minutes. Then the temperature is raised to 50-60℃, and the reaction is continued under reflux for 0.5-1.5 hours. The mixture is then cooled to room temperature and allowed to stand for 15-20 hours to obtain the modified silica sol. The mass ratio of tetraethyl orthosilicate, anhydrous ethanol, modified silane coupling agent, and deionized water is 35-40:60-70:6-8:

20. S4. Disperse diamond powder and copper powder in an aqueous sodium hydroxide solution, heat to 80-100℃, stir and react for 3-5 hours, cool to room temperature, separate the solid and liquid, take the solid, wash and dry it to obtain a mixed powder; under stirring conditions, disperse the mixed powder in the modified silica sol obtained in step S3, heat to 75-85℃, react for 3-5 hours, cool to room temperature, separate the solid and liquid, take the solid, wash and dry it, and after ball milling and sieving, obtain a surface-modified mixed powder; S5. Place the surface-modified mixed powder obtained in step S4 into a graphite mold, compact the powder, and place it in a vacuum hot press furnace for vacuum hot pressing sintering. After sintering, reduce the pressure inside the vacuum hot press furnace to below 5 MPa, and then reduce the temperature inside the furnace to room temperature. Demold to obtain the product. The specific steps of the vacuum hot pressing sintering are as follows: first, heat the powder to 200-250℃ at a heating rate of 1-5℃ / min and hold for 20-40 min; then, heat the powder to 850-950℃ at a heating rate of 5-10℃ / min and hold for 20-40 min. The pressure inside the vacuum hot press furnace is 30-50 MPa.

2. The method for preparing a diamond / copper composite thermally conductive material according to claim 1, characterized in that, In step S4, the mass ratio of diamond powder to copper powder is 2:2-4, the mass concentration of sodium hydroxide aqueous solution is 0.10-0.13 g / mL, and the amount of diamond powder added to the sodium hydroxide aqueous solution is 0.07-0.12 g / mL.

3. The method for preparing a diamond / copper composite thermally conductive material according to claim 1, characterized in that, In step S4, the mass ratio of the mixed powder to the modified silica sol is 4:140-180. The ball milling is a dry ball milling process with a milling speed of 130-170 r / min, a milling time of 20-40 min, and a ball-to-material ratio of 3-5:

1.

4. A diamond / copper composite thermal conductive material prepared by any one of the methods described in claims 1-3.

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