Diamond copper composite material and preparation method thereof

Abstract

The invention discloses a diamond-copper composite material and a preparation method thereof, and belongs to the technical field of thermal management material preparation, the diamond-copper composite material comprises diamonds and copper covering the surfaces of the diamonds, the diamonds and the copper are connected through boron carbide, the particle size ranges of the diamonds are 1-10 microns and 100-1000 microns respectively, the volume fraction ratio of the two particle sizes is 1: (3-4), and the volume fraction ratio of the diamond to the copper is 1: (3-4). The weight content of the diamond is 60%-85%, the weight content of the boron is 0.1%-1%, the weight content of the copper is 14%-39.9%, the thickness of a boron carbide interface layer is smaller than 10 nm, and the heat conductivity of the diamond-copper composite material is 550-1000 W / m.K. According to the diamond-copper composite material, high density is guaranteed, and meanwhile the heat conductivity of the material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal management material preparation, and in particular to a diamond-copper composite material and a preparation method thereof. Background Art

[0002] With the continuous development of information technology, the transistor integration and operating speed of chips used in aerospace, high-end manufacturing, military electronic system equipment and other fields are constantly improving, and their heat flux density is constantly increasing. The heat flux density of some large-scale integrated circuits even exceeds 1kW / cm 2 Studies have shown that if the temperature of a single semiconductor component rises by 10K, the system reliability will decrease by 50%. Its thermal conductivity and the thermal expansion matching between it and the semiconductor chip directly determine the working stability and safety reliability of the electronic system. Currently, the commonly used SiC (thermal conductivity 70W / m·K, thermal expansion coefficient 3.8×10 -6 / K), GaAs (thermal conductivity 54W / m·K, thermal expansion coefficient 5.8×10 -6 / K), Kovar alloy (thermal conductivity 17W / m·K, thermal expansion coefficient 4.2×10 -6 / K), CuW (thermal conductivity 180~230W / m·K, thermal expansion coefficient 6.5×10 -6 ~9×10 -6 / K), CuMo (thermal conductivity 165~250W / m·K, thermal expansion coefficient 9.35×10 -6 ~10×10 -6 / K), SiC / Al (thermal conductivity 228W / m·K, thermal expansion coefficient 7.3×10 -6 / K) and other thermal management materials have been unable to meet the increasingly high heat dissipation requirements due to their low thermal conductivity. In order to solve the heat dissipation problem of highly integrated and high-speed chips and ensure the stability and reliability of chip operation, it is urgent to develop new heat dissipation materials with high thermal conductivity, good matching of thermal expansion coefficient with electronic components and excellent mechanical properties.

[0003] Diamond / copper composite materials have ultra-high thermal conductivity, low thermal expansion coefficient, low density and excellent mechanical properties. They can not only meet a large number of heat dissipation requirements, but also achieve good welding with chips. They can also be used to prepare various complex-shaped components through near-net forming without affecting thermal conductivity and mechanical properties. It is currently the most promising new generation of heat dissipation materials and has become a research hotspot for heat dissipation materials at home and abroad.

[0004] However, the diamond particle size and content, composite density, interface bonding strength, and interface layer thickness in diamond / copper composites all have a crucial impact on their thermal conductivity. Only by optimizing these factors simultaneously can ideal thermal conductivity be achieved. However, currently prepared diamond / copper composites only consider the influence of a single factor on thermal conductivity. For example, when the diamond content is fixed, larger diamond particle size leads to higher thermal conductivity; while maintaining high composite density, higher diamond content is more beneficial for improved thermal conductivity. Furthermore, the influence of interface carbide type on the composite is unknown. The effect of interface layer thickness on the thermal conductivity of diamond / copper composites has never been studied. Generally, a thicker interface layer increases the thermal resistance between diamond and copper. However, when the interface layer thickness is small, due to the thermal conductivity size effect, the proximity to the mean free path of phonons enhances phonon scattering at the interface, resulting in a decrease in thermal conductivity. Furthermore, a thin interface layer cannot withstand the interfacial stress generated during the sintering of the diamond / copper composite, causing the interface layer to detach from the diamond particle surface, resulting in poor interfacial bonding and reduced thermal conductivity and mechanical properties. Therefore, by comprehensively considering the above factors and giving full play to the thermal conductivity advantages of diamond, the thermal conductivity of diamond / copper composite materials can be greatly improved.

[0005] Patent application publication number CN 110102758A discloses a Cu-X / C composite material and its preparation method, comprising the following steps: degreasing, roughening, sensitizing, and activating a carbon material in sequence; adding the activated carbon material to a Cu-X plating solution, adjusting the pH with an alkaline solution, then slowly adding a reducing agent until the solution becomes clear, rinsing with deionized water to a neutral pH, and drying to obtain a Cu-X-coated carbon material; adding the Cu-X-coated carbon material to a copper plating solution, adjusting the pH with an alkaline solution, then slowly adding a reducing agent, stirring until the solution becomes clear, rinsing with deionized water to a neutral pH, and drying to obtain a Cu-X / C composite material precursor; and sintering the precursor to obtain the Cu-X / C composite material. However, the thermal conductivity of the Cu-X / C composite material still does not meet the requirements. Summary of the Invention

[0006] The present invention aims to provide a diamond-copper composite material and a preparation method thereof, which can ensure high density while improving the thermal conductivity of the material.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a diamond-copper composite material comprising diamond and copper, the copper coating the diamond surface, the diamond and copper being connected by boron carbide. The diamond has two particle sizes, ranging from 1 to 10 μm and 100 to 1000 μm, respectively, with a volume fraction ratio of 1:3 to 4. The small-sized diamond particles fully fill the gaps formed by the stacked large-sized diamond particles, thereby improving the material's density and thermal conductivity. The diamond content by weight is 60% to 85%, the boron content by weight is 0.1% to 1%, and the copper content by weight is 14% to 39.9%. The boron carbide interface layer is less than 10 nm thick, and the thermal conductivity of the diamond-copper composite material is 550 to 1000 W / m·K.

[0008] Specifically, the two particle size ranges are preferably 5-10 μm and 400-600 μm, respectively, the weight content of the diamond is 70%-80%, the weight content of the boron is 0.3%-0.8%, and the weight content of the copper is 18%-30%.

[0009] A method for preparing the diamond-copper composite material is characterized by comprising the following steps:

[0010] Step 1: Degreasing, roughening, sensitizing and activating the diamond to obtain treated diamond;

[0011] Step 2: placing the treated diamond in a copper-boron plating solution for reaction to obtain a diamond-copper composite material precursor;

[0012] Step 3: Sintering the diamond copper composite material precursor to obtain the diamond copper composite material.

[0013] Specifically, the degreasing process involves adding diamonds to an alkali solution of 80 to 150 g / L to remove grease and dirt from the surface of the diamonds at a temperature of 85 to 100° C., and then washing with water until the diamonds are neutral. The alkali solution is at least one of potassium hydroxide and sodium hydroxide.

[0014] Specifically, the roughening refers to placing the deoiled diamond in an acidic solution containing dichromate for 1-3 hours. The acidic solution is nitric acid, sulfuric acid or hydrochloric acid solution. The concentration of dichromate in the acidic solution is 30-150 g / L. The temperature of the acidic solution is 60-80°C. After roughening, the diamond is washed with deionized water until it is neutral.

[0015] Specifically, the sensitizing solution used for sensitization is a mixed solution of 10-20 g / L stannous chloride and 20-40 ml / L hydrochloric acid. The temperature during sensitization is 20-40° C. and the time is 1-2 hours.

[0016] Specifically, the activation solution used for activation is a mixed solution of 0.05-0.15 g / L palladium chloride and 15%-25% hydrochloric acid, the temperature is 40-60° C., and the activation time is 1.5-3 hours. After activation treatment, it is washed with deionized water until neutral and vacuum dried.

[0017] Specifically, the copper-boron plating solution contains copper salt, a reducing agent, a complexing agent, a stabilizer and a dispersant, wherein the reducing agent is at least one of sodium borohydride, potassium borohydride, diborane and dimethylamine borane; the complexing agent is a mixture of disodium EDTA, potassium sodium tartrate and ethylenediamine; the stabilizer is potassium ferrocyanide; and the dispersant is polyethylene glycol.

[0018] Specifically, the concentration of the copper salt is 10-40 g / L, the concentration of the disodium EDTA is 20-80 g / L, the concentration of the potassium sodium tartrate is 15-60 g / L, the concentration ratio of the disodium EDTA to the potassium sodium tartrate is 1-1.5:1, the concentration of the ethylenediamine is 5-20 ml / L, the concentration of the stabilizer is 10-80 mg / L, and the concentration of the dispersant is 5-60 mg / L.

[0019] Specifically, the sintering is SPS sintering, the sintering temperature is 800-950°C, the heating rate is 50-100°C / min, the vacuum degree is lower than 10-2Pa, the sintering pressure is 40-50MPa, and the holding time is 5-20min.

[0020] The principle and beneficial effects of this technical solution:

[0021] The present invention treats diamond particles through surface degreasing, coarsening, sensitization and activation, making their surfaces rough and rich in palladium ions, thereby improving the catalytic efficiency of palladium ions, enhancing the bonding force between the chemically plated metal deposition layer and the surface of the diamond particles, ensuring better metal deposition on the diamond surface during the chemical plating process, and improving the mechanical properties and thermal conductivity of the composite material.

[0022] The present invention uses boron-containing salts as reducing agents to co-deposit copper and boron ions, forming a Cu-B coating. The boron ion concentration in this coating is approximately 0.1 to 0.8 wt.%, and it is evenly distributed on the surface of the diamond particles. After sintering, a boron carbide transition layer less than 10 nm thick forms between the copper and diamond, enhancing the interfacial bonding strength between the copper and diamond and improving the thermal conductivity of the composite material.

[0023] The present invention summarizes a preferred sintering temperature and pressure, thereby avoiding the problems that, due to low sintering temperature and pressure, copper atoms obtain low activation energy and poor fluidity, and boron atoms and carbon atoms in the Cu-B coating cannot fully react to form a boron carbide intermediate modified layer, resulting in poor interface bonding ability between copper and diamond, high interface defect density, and unsatisfactory thermal conductivity. At the same time, the present invention avoids the problems that high sintering temperature and pressure may cause diamond carbonization, seriously affecting the thermal conductivity of diamond, and when the sintering temperature is too high, a large amount of copper in the coating is melted into a liquid phase. Due to the large difference in thermal expansion coefficients between copper and diamond, interfacial separation of copper and diamond is likely to occur during the cooling process, reducing the density and comprehensive performance of the diamond / copper composite material. At the same time, excessively high sintering temperature or pressure may also lead to problems such as high energy consumption and high equipment maintenance costs.

[0024] The present invention concludes that when the volume ratio of diamond particles with a particle size range of 1 to 10 μm to diamond particles with a particle size range of 100 to 1000 μm in the diamond-copper composite material is 1:3 to 4, the composite material has a higher thermal conductivity.

[0025] Reducing the interface thickness is an effective way to improve thermal conductivity. The composite material prepared by the present invention has a boron content of 0.1-1.0 wt.%, and the boron carbide interface layer formed after sintering is uniform and thin, which further reduces the interface thermal resistance and improves thermal conductivity.

[0026] The present invention prepares diamond copper composite materials through SPS sintering, which features simple process, convenient operation, short production cycle and low cost. The prepared composite materials have excellent mechanical properties, high density and thermal conductivity, with a density of ≥97% and a thermal conductivity of ≥550W / m·K, which can meet the demand for heat dissipation materials in fields such as large-scale integrated circuits, aviation, aerospace, high-power electronic devices, and high-end CNC machining. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an SEM image of copper-boron-plated diamond surface in Example 2;

[0028] Figure 2 is a SEM image of the diamond / copper composite material in Example 2;

[0029] Figure 3 This is the SEM image of copper-boron plating on the diamond surface in Comparative Example 2. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the embodiments:

[0031] Example 1:

[0032] 1. Material preparation

[0033] 10 g of diamond particles with a particle size of 5 μm and 10 g of diamond particles with a particle size of 100 μm produced by Changsha Moben New Materials Co., Ltd. were selected.

[0034] 2 Preprocessing

[0035] Degreasing: Immerse the two diamond particles mentioned above in 1L of 100g / L NaOH solution respectively, boil and stir for 1h to remove grease and dirt on the surface, and rinse repeatedly with deionized water until neutral.

[0036] Roughening: Diamond particles that have been free of grease and dirt are added to a 1L mixed solution containing 70g of potassium dichromate and 100ml of concentrated sulfuric acid (mass concentration of concentrated sulfuric acid is 98.3%), and stirred at 70°C for 3h to roughen the surface of the diamond particles. The particles are then repeatedly rinsed with deionized water until they are neutral.

[0037] Sensitization: Add the roughened diamond particles into 1L of a sensitizing solution containing 15g / L stannous chloride and 30ml of hydrochloric acid, stir at room temperature for 1h, and rinse repeatedly with deionized water until neutral.

[0038] Activation: Finally, add the sensitized diamond particles into 1L of activation solution, which is a mixed solution of 0.1g / L palladium chloride and 20% hydrochloric acid. Stir at 50°C for 2h to evenly distribute the catalytic centers of palladium ions on the surface of the diamond particles. Rinse repeatedly with deionized water until neutral.

[0039] 3. Chemical copper boron plating

[0040] The activated diamond particles are chemically plated with Cu-B alloy, wherein the ratio of the volume of the plated Cu to the volume of the diamond is 3:7.

[0041] The specific operation is as follows: first, a Cu-B plating solution is prepared, and the composition and concentration of the Cu-B plating solution are: 10g / L copper sulfate, 20g / L disodium EDTA, 15g / L potassium sodium tartrate, 10ml / L ethylenediamine, 20mg / L potassium ferrocyanide, and 10mg / L polyethylene glycol. The pH value is adjusted with potassium hydroxide solution, and the pH value is ≥13; after the Cu-B plating solution is heated to 40°C, diamond particles to be plated are added and continuously stirred, and at the same time, a sodium borohydride alkaline solution with a concentration of 2g / L is slowly added until the plating solution becomes clear. During the stirring process, the pH value needs to be continuously adjusted with potassium hydroxide solution so that the pH value of the plating solution is always greater than 13. Then, the solution is repeatedly washed with deionized water until it is neutral; finally, diamond particles with a surface coated with Cu-B alloy are obtained by vacuum drying.

[0042] 4 Sintering treatment

[0043] The diamond particles coated with Cu-B alloy were placed in a graphite mold for SPS sintering, and the vacuum degree was controlled below 10 -2Pa, sintering temperature 850 °C, heating rate 100 °C min, sintering pressure 50 MPa, holding time 10 min, to obtain diamond / copper composite material.

[0044] 5 Performance Testing

[0045] Transmission electron microscopy (TEM) microstructural characterization of the diamond / copper composite material prepared in this example revealed an average thickness of 8.2 nm for the boron-carbon interface layer between the diamond and copper. Testing also revealed a density of 97.62% and a thermal conductivity of 561 W / m·K.

[0046] Example 2:

[0047] 1. Material preparation

[0048] 5 g of diamond particles with a particle size of 10 μm and 10 g of diamond particles with a particle size of 500 μm produced by Changsha Moben New Materials Co., Ltd. were selected.

[0049] 2 Preprocessing

[0050] Degreasing: Immerse the two diamond particles mentioned above in 1L of 100g / L NaOH solution respectively, boil and stir for 1h to remove grease and dirt on the surface, and rinse repeatedly with deionized water until neutral.

[0051] Roughening: Add the diamond particles that have been free of grease and dirt to 1L of a mixed solution containing 50g of potassium dichromate and 150mL of concentrated sulfuric acid (mass concentration of concentrated sulfuric acid is 98.3%), boil and stir for 3h to roughen the surface of the diamond particles, and then rinse repeatedly with deionized water until neutral.

[0052] Sensitization: Add the roughened diamond particles into 1L of sensitizing solution containing 20g / L stannous chloride and 40ml of hydrochloric acid, stir at room temperature for 1.5h, and rinse repeatedly with deionized water until neutral.

[0053] Activation: Finally, add the sensitized diamond particles into 1L of activation solution, which is a mixed solution of 0.15g / L palladium chloride and 20% hydrochloric acid. Stir at 60°C for 3h to evenly distribute the catalytic centers of palladium ions on the surface of the diamond particles. Rinse repeatedly with deionized water until neutral.

[0054] 3. Chemical copper boron plating

[0055] The surface of the activated diamond particles is chemically plated with Cu-B alloy, wherein the ratio of the volume of the plated Cu to the volume of the diamond is 2:8.

[0056] The specific operation is as follows: first, a Cu-B plating solution is prepared, and the composition and concentration of the Cu-B plating solution are 20g / L copper sulfate, 30g / L disodium EDTA, 20g / L potassium sodium tartrate, 10ml / L ethylenediamine, 20mg / L potassium ferrocyanide, and 10mg / L polyethylene glycol. The pH value is adjusted with potassium hydroxide solution, and the pH value is ≥13; after the Cu-B plating solution is heated to 40°C, diamond particles to be plated are added and continuously stirred, and at the same time, a sodium borohydride alkaline solution with a concentration of 2g / L is slowly added until the plating solution becomes clear. During the stirring process, the pH value needs to be continuously adjusted with potassium hydroxide solution so that the pH value of the plating solution is always greater than 13. Then, the solution is repeatedly washed with deionized water until it is neutral; finally, diamond particles with a surface coated with Cu-B alloy are obtained by vacuum drying.

[0057] 4 Sintering treatment

[0058] The surface coated Cu-B alloy coated diamond particles were placed into a graphite mold for SPS sintering, and the vacuum degree was controlled below 10 -2 Pa, sintering temperature 930℃, heating rate 100℃ / min, sintering pressure 50MPa, and holding time 10min to obtain diamond / copper composite material.

[0059] 5 Performance Testing

[0060] Transmission electron microscopy (TEM) microstructural characterization of the diamond / copper composite material prepared in this example revealed an average thickness of 5.1 nm for the boron-carbon interface layer between the diamond and copper. Testing also revealed a density of 98.11% and a thermal conductivity of 748 W / m·K.

[0061] Comparative Example 1:

[0062] In the material preparation step, 15 g of diamond particles with a particle size of 10 μm were selected, and the other steps were the same as those in Example 1. According to the test, the diamond / copper composite material prepared in this comparative example had a density of 88.2% and a thermal conductivity of 321 W / m·K.

[0063] Comparative Example 2

[0064] In the roughening step, the diamond particles, cleaned of grease and dirt, were added to 1 L of a mixed solution containing 150 mL of concentrated sulfuric acid (98.3% by mass), boiled and stirred for 3 hours to roughen the surface of the diamond particles. The particles were then repeatedly rinsed with deionized water until neutral. The other steps were the same as in Example 1. Testing showed that the diamond / copper composite prepared in this comparative example had a density of 70.5% and a thermal conductivity of 161 W / m·K.

[0065] Comparative Example 3

[0066] In the electroless copper-boron plating step, the 2 g / L sodium borohydride alkaline solution was replaced with a 2 g / L glyoxylic acid alkaline solution, and the other steps were the same as in Example 1. Testing showed that the diamond / copper composite material prepared in this comparative example had a density of 95.3% and a thermal conductivity of 485 W / m·K.

[0067] Comparative Example 4

[0068] In the sintering step, the sintering pressure was 35 MPa, and the other steps were the same as those in Example 1. According to the test, the diamond / copper composite material prepared in this comparative example had a density of 91.6% and a thermal conductivity of 393 W / m·K.

[0069] In the embodiment, two diamond particles with different particle size ranges (1-10 μm and 100-1000 μm) are used, and their volume fraction ratio is controlled to be 1:3-4, so that the small-size diamond particles are fully filled into the gaps formed by the stacking of large-size diamond particles, which significantly improves the density and thermal conductivity of the material. However, Comparative Example 1 only uses diamond particles of a single particle size, resulting in its density and thermal conductivity being significantly lower than those of the embodiment. The degreasing, coarsening, sensitization and activation treatments performed on the diamond particles in the embodiment can effectively improve the catalytic efficiency of palladium ions, enhance the bonding force between the chemically plated metal deposition layer and the surface of the diamond particles, thereby ensuring that the metal is better deposited on the diamond surface during the chemical plating process, and improving the mechanical properties and thermal conductivity of the composite material. Comparative Example 2 does not add dichromate in the coarsening step, resulting in a significant decrease in the density and thermal conductivity of the composite material prepared therefrom. In the examples, a copper-boron plating solution containing a boron salt as a reducing agent was used, and parameters such as sintering temperature, heating rate, vacuum level, sintering pressure, and holding time were strictly controlled. This resulted in a boron carbide transition layer less than 10 nm thick between the copper and diamond, enhancing the interfacial bonding strength between the copper and diamond while avoiding problems such as diamond carbonization and interfacial separation caused by inappropriate sintering temperature and pressure. In Comparative Example 3, the sodium borohydride alkaline solution was replaced with a glyoxylic acid alkaline solution, and in Comparative Example 4, the sintering pressure was lower than that in the examples, resulting in unsatisfactory composite material performance.

[0070] In summary, the diamond-copper composite material prepared by the present invention exhibits excellent mechanical properties, high density, and thermal conductivity. Its density is ≥97%, and its thermal conductivity is ≥550 W / m·K. It can meet the high demands for heat dissipation materials in fields such as large-scale integrated circuits, aviation, aerospace, high-power electronic devices, and high-end CNC machining, and has broad application prospects. The preparation method of the present invention features simple process, convenient operation, short production cycle, and low cost, making it easy to industrialize and manufacture, providing new ideas and methods for the research and development and application of high-performance heat dissipation materials.

[0071] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. For those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A diamond copper composite material, characterized in that: The diamond-copper composite material comprises diamond and copper, wherein the copper covers the surface of the diamond, and the diamond and copper are connected by boron carbide. The diamond has two particle sizes, which range from 1 to 10 μm and 100 to 1000 μm, respectively, and the volume fraction ratio of the two particle sizes is 1:3 to 4. The weight content of the diamond is 60% to 85%, the weight content of the boron is 0.1% to 1%, and the weight content of the copper is 14% to 39.9%. The thickness of the boron carbide interface layer is less than 10 nm, and the thermal conductivity of the diamond-copper composite material is 550 to 1000 W / m·K.

2. The diamond-copper composite material according to claim 1, characterized in that: The two particle size ranges are preferably 5-10 μm and 400-600 μm respectively, the weight content of the diamond is 70%-80%, the weight content of the boron is 0.3%-0.8%, and the weight content of the copper is 18%-30%.

3. A method for preparing the diamond-copper composite material according to claim 1 or 2, characterized in that: The steps include: Step 1: Degreasing, roughening, sensitizing and activating the diamond to obtain treated diamond; Step 2: placing the treated diamond in a copper-boron plating solution for reaction to obtain a diamond-copper composite material precursor; Step 3: Sintering the diamond copper composite material precursor to obtain the diamond copper composite material.

4. The method for preparing the diamond-copper composite material according to claim 3, wherein: The degreasing process comprises adding the diamond into an alkali solution of 80 to 150 g / L to remove grease and dirt on the surface of the diamond at a temperature of 85 to 100° C., and then washing with water until the diamond is neutral. The alkali solution is at least one of potassium hydroxide and sodium hydroxide.

5. The method for preparing the diamond-copper composite material according to claim 3, wherein: The roughening process involves placing the deoiled diamond in an acidic solution containing dichromate for 1-3 hours. The acidic solution is a nitric acid, sulfuric acid or hydrochloric acid solution. The concentration of dichromate in the acidic solution is 30-150 g / L and the temperature of the acidic solution is 60-80°C. After roughening, the diamond is washed with deionized water until it becomes neutral.

6. The method for preparing the diamond-copper composite material according to claim 3, wherein: The sensitizing solution used for sensitization is a mixed solution of 10-20 g / L stannous chloride and 20-40 ml / L hydrochloric acid. The temperature during sensitization is 20-40° C. and the time is 1-2 hours.

7. The method for preparing the diamond-copper composite material according to claim 3, wherein: The activation solution used for activation is a mixed solution of 0.05-0.15 g / L palladium chloride and 15%-25% hydrochloric acid, the temperature is 40-60° C., the time is 1.5-3 hours, and after activation treatment, it is washed with deionized water until neutral and vacuum dried.

8. The method for preparing the diamond-copper composite material according to claim 3, wherein: The copper-boron plating solution contains a copper salt, a reducing agent, a complexing agent, a stabilizer and a dispersant, wherein the reducing agent is at least one of sodium borohydride, potassium borohydride, diborane and dimethylamine borane; the complexing agent is a mixture of disodium EDTA, sodium potassium tartrate and ethylenediamine; the stabilizer is potassium ferrocyanide; and the dispersant is polyethylene glycol.

9. The method for preparing the diamond-copper composite material according to claim 8, wherein: The concentration of the copper salt is 10-40 g / L, the concentration of the disodium EDTA is 20-80 g / L, the concentration of the potassium sodium tartrate is 15-60 g / L, the concentration ratio of the disodium EDTA to the potassium sodium tartrate is 1-1.5:1, the concentration of the ethylenediamine is 5-20 ml / L, the concentration of the stabilizer is 10-80 mg / L, and the concentration of the dispersant is 5-60 mg / L.

10. The method for preparing the diamond-copper composite material according to claim 3, wherein: The sintering is SPS sintering, with a sintering temperature of 850-1000° C., a heating rate of 50-100° C. / min, a vacuum degree lower than 10-2 Pa, a sintering pressure of 40-50 MPa, and a holding time of 5-20 min.

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