A copper-diamond composite material and a method for producing the same

Abstract

The application discloses a copper-diamond composite material. The application provides a copper-diamond composite material and a preparation method thereof. The copper-diamond composite material provided by the application has a thermal conductivity of 580-660 W / mK, and after 1000 times of thermal cycle at-55 DEG C to 150 DEG C, the thermal conductivity attenuation rate of the copper-diamond composite material is less than 6%. The copper-diamond composite material has important application value in the technical fields of high-power electronic devices, aerospace thermal management systems and the like.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a copper-diamond composite material and its preparation method. Background Technology

[0002] With the continuous increase in power density of electronic devices and the rapid development of aerospace, new energy and other fields, the demand for high-efficiency thermal management materials is becoming increasingly urgent. Thermal management materials need to maintain excellent thermal conductivity under extreme environments such as high temperature and high frequency thermal cycling to ensure stable operation of equipment.

[0003] Traditional metal-based materials (such as pure copper and aluminum) used as thermal management materials, despite their high thermal conductivity, are prone to interfacial delamination or structural failure under long-term thermal stress, leading to a decrease in thermal conductivity and affecting the stable operation of equipment. Furthermore, traditional metal materials often experience significant decreases in thermal conductivity due to grain boundary slip or oxidation during repeated thermal cycling, making them unsuitable for high-standard application scenarios.

[0004] In recent years, diamond has been considered an ideal reinforcement for thermal management due to its ultra-high thermal conductivity (approximately 2000 W / mK). Researchers have subsequently developed various thermal management composite materials that combine diamond as a reinforcement with traditional metal matrix materials. However, in existing thermal management composite materials, the poor wettability between metal and diamond leads to high interfacial thermal resistance when directly composited, weakening the interfacial bond strength and resulting in poor thermal cycling performance. Therefore, the interfacial bonding problem between diamond and metal matrix materials remains a significant constraint on the development of this industry.

[0005] To address the aforementioned issues, improving the interface of diamond to enable it to be combined with metallic materials to obtain a metal composite material that possesses both high thermal conductivity and excellent thermal cycling stability has significant industry implications and commercial value. Summary of the Invention

[0006] To address the shortcomings of existing thermal management metal composite materials in terms of thermal conductivity and thermal cycling stability caused by interfacial bonding issues between diamond and the metal matrix, this invention provides a copper-diamond composite material and its preparation method. The copper-diamond composite material provided by this invention achieves a thermal conductivity of 580-660 W / mK, and its thermal conductivity decay rate is less than 6% after 1000 thermal cycles from -55℃ to 150℃; it has significant application value in high-power electronic devices and aerospace thermal management systems.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0008] This invention provides a method for preparing a copper-diamond composite material, which includes the following steps:

[0009] S1, diamond particles and nickel powder are mixed evenly and then placed in a vacuum furnace for high-temperature treatment to obtain diamond containing a nickel metal film; mixed steam is passed into the diamond containing the nickel metal film for annealing treatment; then acid treatment is used to remove the nickel metal film on the surface of the diamond to obtain etched diamond; wherein, the mixed steam contains N2, H2O, O2 and H2O2.

[0010] S2, copper powder, nickel powder and tin powder are mixed evenly in a horizontal mixer to obtain a mixture, and the mixture is pressed by a four-column hydraulic forming machine to obtain an alloy blank. Then, the alloy blank is placed in a frequency induction furnace for sintering to obtain a Cu / Ni / Sn alloy.

[0011] S3, using a magnetron sputtering coating device, the Cu / Ni / Sn alloy is deposited on the surface of the etched diamond to obtain a diamond with an alloy coating;

[0012] S4, copper-diamond composite material is prepared by vacuum hot pressing of diamond with alloy coating.

[0013] In this invention, in step S1, the mixed steam is prepared by bubbling nitrogen gas into hydrogen peroxide; preferably, it is prepared by bubbling nitrogen gas into 10%-30% hydrogen peroxide; more preferably, it is prepared by bubbling nitrogen gas into 10% hydrogen peroxide.

[0014] In this invention, in step S1, the mass ratio of the diamond particles to the nickel powder is (2-4):1; preferably 3:1.

[0015] In this invention, in step S1, the acid is one or more of hydrochloric acid, phosphoric acid, sulfuric acid and nitric acid, preferably sulfuric acid and / or nitric acid; more preferably, the volume ratio of sulfuric acid and nitric acid is 3:1.

[0016] In this invention, in step S1, the mass fraction of the sulfuric acid is 40%-98%; preferably 50%-70%; and most preferably 50%.

[0017] In this invention, in step S1, the mass fraction of the nitric acid is 50%-70%; preferably 65%.

[0018] In this invention, in step S2, the mass ratio of copper powder, nickel powder and tin powder is 1:(2-6):(2-7); more preferably 1:4:(2-7), for example 1:4:4 or 1:4:6.

[0019] In this invention, in step S2, the copper powder particle size is 20-40 μm; preferably 30 μm.

[0020] In this invention, in step S2, the nickel powder particle size is 20-40 μm; preferably 30 μm.

[0021] In this invention, in step S2, the tin powder particle size is 20-40 μm; preferably 30 μm.

[0022] In this invention, in step S2, the process parameters for pressing and mixing materials by the four-column hydraulic molding machine are as follows: pressure is 10-40 MPa, preferably 25 MPa.

[0023] In this invention, in step S2, the sintering process parameters in the frequency induction furnace are: sintering at 600-1300℃ for 2-10 hours under a vacuum of less than 1000Pa; more preferably: sintering at 600-1300℃ for 2-10 hours under a vacuum of less than 500Pa; and most preferably: heating to 800℃ at a rate of 5℃ / min under a vacuum of 100Pa, pre-firing for 2 hours, and then heating to 1200℃ at a rate of 5℃ / min and holding for 5 hours.

[0024] In this invention, in step S3, the thickness of the alloy coating on the diamond containing the alloy coating is 100-300 nm; preferably 150-250 nm; more preferably 200 nm.

[0025] In this invention, step S4, the vacuum hot pressing process is as follows: chromium powder and diamond with an alloy coating are mixed at a mass ratio of 1:(80-120) to obtain a mixed powder. The mixed powder is then placed between two copper foils to form a copper foil-mixed powder-copper foil structure. Hot pressing is then performed at a temperature of 900-1300℃ (preferably 1000-1100℃; more preferably 1050℃) and a pressure of 10-50 MPa (preferably 25-35 MPa; more preferably 30 MPa) to obtain the copper-diamond composite material.

[0026] The present invention also provides a copper-diamond composite material prepared by the above-described method for preparing copper-diamond composite materials.

[0027] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0028] The reagents and raw materials used in this invention are all commercially available.

[0029] The positive and progressive effects of this invention are as follows: the thermal conductivity of the copper-diamond composite material provided by this invention reaches 580-660 W / mK, and after 1000 thermal cycles from -55℃ to 150℃, the thermal conductivity decay rate is less than 6%; it has important application value in the fields of high-power electronic devices and aerospace thermal management systems. Attached Figure Description

[0030] Figure 1 The image shown is an electron microscope image of the diamond after surface etching obtained in step one of Example 1.

[0031] Figure 2 The image shows an electron microscope (EM) image of the diamond in the alloy coating obtained in step three of Example 1.

[0032] Figure 3 The graph shows the change in thermal conductivity of copper-diamond composite material with thermal cycling.

[0033] Figure 4 The graph shows the change in thermal conductivity attenuation rate of copper-diamond composite material with thermal cycling. Detailed Implementation

[0034] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0035] Example 1

[0036] Copper-diamond composite materials are prepared by the following method

[0037] Step 1: Diamond surface etching

[0038] Diamond particles with a diameter of approximately 0.5 mm were immersed in a 30% (w / w) dilute sulfuric acid aqueous solution and heated to 90°C for 30 minutes to remove surface contaminants. They were then washed with ethanol and dried at 100°C. The dried diamond particles were mixed with electrolytic nickel powder with a diameter of approximately 30 μm at a mass ratio of 3:1. The mixture was placed in a quartz boat within a quartz tube and transferred to a vacuum furnace at 5 × 10⁻⁶ °C. -3 Under a vacuum of Pa, the diamond was heated to 1000°C at a heating rate of 10°C / min and held for 30 minutes to obtain a diamond containing a nickel metal film. Subsequently, a mixed vapor prepared by bubbling 10% hydrogen peroxide through a ceramic conduit was introduced into the diamond containing the nickel metal film for annealing. After 10 minutes, it was cooled to room temperature. It was then transferred to a mixed solution of sulfuric acid (50% by mass) and nitric acid (65% by mass) in a volume ratio of 3:1 and immersed in the solution, heated to 60°C to remove the surface metal film. After washing three times with distilled water, it was dried at 120°C to obtain the etched diamond. The etched diamond was then subjected to scanning electron microscopy (SEM). The SEM results are shown in [Figure number missing]. Figure 1 As shown, after etching, obvious etching marks appear on the surface of the diamond, making the diamond surface rough.

[0039] Step 2: Preparation of Cu / Ni / Sn alloy

[0040] Electrolytic copper powder (≥99.9% purity), electrolytic nickel powder (≥99.9% purity), and electrolytic tin powder (≥99.8% purity) with a particle size of approximately 30 μm were mixed in a horizontal mixer at a mass ratio of 1:4:4, with a total feed amount of 1000 g, a mixing speed of 1000 r / min, and a mixing time of 2 h. After uniform mixing, the mixture was pressed into shape in a four-column hydraulic forming machine at a pressure of 25 MPa for 1 minute to obtain an alloy blank. The blank was then transferred to a medium-frequency induction furnace and pre-fired at 800 °C at a rate of 5 °C / min under a vacuum of 100 Pa for 2 h. Next, the temperature was increased to 1200 °C at a rate of 5 °C / min and held for 5 h. After cooling, a Cu / Ni / Sn alloy was obtained.

[0041] Step 3: Coating the diamond surface with an alloy

[0042] The etched diamond was placed on the sample stage of the magnetron sputtering coating equipment. The chamber temperature was 25°C, and the chamber vacuum was 5×10⁻⁶. -3 Under Pa conditions, ultrasonic vibration was initiated at a frequency of 40 kHz. The temperature was raised to 200 °C, and the sputtering power was set to 130 W for 15 min. Using the Cu / Ni / Sn alloy obtained in step two as the target material, the target current was 0.5 A, the working vacuum was 0.5 Pa, and the sputtering time was 15 min. Three-dimensional uniform deposition was achieved using a planetary rotating sample holder. A Cu / Ni / Sn alloy coating with a thickness of approximately 200 nm was deposited on the etched diamond surface, resulting in a diamond with an alloy coating. Samples were taken for scanning electron microscopy (SEM) analysis, and the results are shown below. Figure 2 As shown, after an alloy layer is coated on the surface of the diamond, the original etching marks are covered by the alloy layer and cannot be observed.

[0043] Step 4: Preparation of copper-diamond composite material by hot pressing process

[0044] The diamond with alloy coating obtained in step three was used to prepare a copper-diamond composite material via vacuum hot pressing. The hot pressing process involved mixing chromium powder with copper alloy-coated diamond particles at a mass ratio of 1:100. 6g of this mixed powder was placed on a 100mm × 100mm copper foil with a thickness of 0.2mm. Two copper foils covered with the copper alloy coating were stacked, and then another copper foil of the same size was added as a covering layer. The hot pressing process was carried out at 1050℃ and 30MPa for 120 minutes. After hot pressing, a composite material sheet with a thickness of approximately 1.4mm was obtained. This was then laser-cut into 10mm × 10mm square sheets, yielding copper-diamond composite material A.

[0045] Example 2

[0046] The process is basically the same as in Example 1, except that the formulation for preparing the Cu / Ni / Sn alloy is different. In Example 2, electrolytic copper powder, electrolytic nickel powder and pure tin powder are mixed in a mass ratio of 1:4:6 to prepare an alloy sample, and finally, copper diamond composite material B is obtained.

[0047] Example 3

[0048] The process is basically the same as in Example 1, except that the formulation for preparing the Cu / Ni / Sn alloy is different. In Example 3, electrolytic copper powder, electrolytic nickel powder and pure tin powder are mixed in a mass ratio of 1:4:8 to prepare the alloy sample, and finally the copper diamond composite material C is obtained.

[0049] Example 4

[0050] The process is basically the same as in Example 1, except that unetched diamond particles are used instead of the etched diamond in step one of Example 1 to prepare copper-diamond composite material D.

[0051] Example 5

[0052] The process is essentially the same as in Example 1, except that the diamond surface etching steps are different. Specifically, diamond particles with a diameter of approximately 0.5 mm are immersed in a 30% (w / w) dilute sulfuric acid aqueous solution, heated to 90°C, and held for 30 minutes to remove surface contaminants. They are then cleaned with ethanol and dried at 100°C. The dried diamond particles are mixed with electrolytic nickel powder with a diameter of approximately 30 μm at a mass ratio of 3:1. The mixture is placed in a quartz boat within a quartz tube and transferred to a vacuum furnace at 5 × 10⁻⁶ °C. -3 Under a vacuum of Pa, the sample was heated to 1000°C at a heating rate of 10°C / min and held for 30 minutes. Subsequently, nitrogen / water vapor generated by bubbling distilled water with nitrogen was introduced into the sample for annealing, followed by cooling to room temperature after 10 minutes. The mixed sample was then transferred to a 3:1 mixture of sulfuric acid (50% by mass) and nitric acid (65% by mass) and immersed in the solution, heated to 200°C to remove the surface metal film. After washing three times with distilled water and drying at 120°C, surface-etched diamond was obtained. Finally, copper-diamond composite material E was prepared.

[0053] Example 6

[0054] This embodiment describes the thermal conductivity test. The measurement was performed using a laser flash method (LFA467, Netzsch) at a temperature of 25°C. The thermal conductivity (λ) of the copper-diamond composite material was calculated based on the average value of four flash points.

[0055] The calculation formula is λ=α×Cp×ρ.

[0056] Where λ is the thermal diffusivity of the composite material, ρ is the density of the composite material, and Cp is the specific heat capacity of the composite material. The density of the composite material is measured by the specific gravity bottle method, and the specific heat capacity of the composite material is based on its constituent diamond, copper, and surface alloy Cp values ​​are estimated by the mixing rule.

[0057] Example 7

[0058] This embodiment demonstrates the thermal cycling test of a copper-diamond composite material. The copper-diamond composite material was placed in a quartz tube and then placed in a thermal shock test chamber (Novite, LR3-49LA). A nitrogen atmosphere was used to prevent sample oxidation. The test temperature was divided into two levels: a low temperature (-55℃) and a high temperature (150℃). The sample was held in each of the high and low temperature chambers for 10 minutes. The switching time from the high to the low temperature chamber was less than 10 seconds, and the cycling rate was 3 cycles per hour. After every 200 thermal cycles, the thermal conductivity of the sample was measured at 25℃, and a total of 6 tests were performed, including the initial thermal conductivity. The thermal cycling test results of the copper-diamond composite material AE are shown in Table 1. The thermal conductivity of the copper-diamond composite material AE during thermal cycling is shown in Table 1. Figure 3 As shown; and the thermal decay rate of the copper-diamond composite material AE during thermal cycling is as follows: Figure 4 As shown.

[0059] Table 1

[0060] Copper-diamond composite materials Initial thermal conductivity (W / mK) Final thermal conductivity (W / mK) Thermal conductivity attenuation rate (%) Sample A 652.3 633.4 2.89 Sample B 640.7 608.2 5.07 Sample C 598.9 533.6 10.91 Sample D 446.5 376.4 15.69 Sample E 610.3 564.9 7.43

[0061] Comparing samples AE and D, it is evident that sample D, using unetched diamond particles, exhibits a significantly lower initial thermal conductivity (446.5 W / mK) compared to samples AC and E (approximately 580-660 W / mK), and a higher thermal conductivity decay rate of 15.69%, far exceeding that of other samples (which have a thermal decay rate below 11%). This indicates that diamond surface etching is a crucial step in enhancing interfacial bonding strength. The reason for this may be that the etching and acid washing process during high-temperature annealing removes surface contaminants and creates a micro-rough structure, thereby increasing the contact area between the metal coating and the diamond. Furthermore, the etched surface exposes more active sites, promoting chemical bonding of metal atoms and reducing interfacial thermal resistance, resulting in superior thermal conductivity and thermal decay rate in the copper-diamond composite material. However, the unetched sample D suffers from numerous interfacial defects, hindering heat conduction paths and leading to relatively poor initial performance and thermal cycling stability in the copper-diamond composite material.

[0062] Comparing samples A and E, it can be seen that the initial thermal conductivity and thermal cycling stability of sample E, which was treated with steam annealing, are inferior to those of sample A. This may be because hydrogen peroxide decomposes into water vapor and oxygen during high-temperature annealing. Since hydrogen peroxide and its decomposed oxygen can react with the nickel metal film, the etching effect on the diamond surface is better than that of annealing with steam alone.

[0063] Samples A and C, with different metal coating ratios, exhibited thermal conductivity attenuation rates of 2.89%, 5.07%, and 10.91% respectively after 1000 thermal cycles. Sample A, with an alloy coating using a copper:nickel:tin ratio of 1:4:4, demonstrated the best stability, with a thermal conductivity attenuation rate of only 2.89%. This may be because nickel's high melting point and oxidation resistance help maintain the integrity of the coating structure during high-temperature hot pressing; tin's low melting point promotes coating uniformity; and copper, as the main material, ensures good compatibility between the metal coating and the copper substrate. Therefore, the synergistic effect of these specific metal alloy ratios results in unexpectedly low thermal conductivity attenuation rates and low thermal conductivity in the copper-diamond composite material.

[0064] In addition, the ratio of copper powder: nickel powder: tin powder = 1:4:8 in sample C, the higher tin content led to an increase in the decay rate to 10.91%, which may be because as the proportion of tin increases and the proportion of nickel decreases, the overall melting point of the coating decreases and the high-temperature strength is insufficient, making the interface deterioration easy to occur during thermal cycling; thus, the thermal conductivity decay performance of the copper diamond composite material decreases significantly.

[0065] In summary, the copper-diamond composite material of this invention, through interface engineering and process innovation, meets the requirements of high thermal conductivity and stability in extreme temperature applications for thermal management materials, providing a reliable solution for high-performance thermal management applications.

Claims

1. A method for preparing a copper-diamond composite material, characterized in that, It includes the following steps: S1, diamond particles and nickel powder are mixed evenly and then placed in a vacuum furnace for high-temperature treatment to obtain diamond containing a nickel metal film; mixed steam is passed into the diamond containing the nickel metal film for annealing treatment; then acid treatment is used to remove the nickel metal film on the surface of the diamond to obtain etched diamond; wherein, the mixed steam contains N2, H2O, O2 and H2O2. S2, copper powder, nickel powder and tin powder are mixed evenly in a horizontal mixer to obtain a mixture, and the mixture is pressed by a four-column hydraulic forming machine to obtain an alloy blank. Then, the alloy blank is placed in a frequency induction furnace for sintering to obtain a Cu / Ni / Sn alloy; the mass ratio of copper powder, nickel powder and tin powder is 1:(2-6):(2-7). S3, using a magnetron sputtering coating device, deposit the Cu / Ni / Sn alloy on the surface of the etched diamond to obtain a diamond with an alloy coating, wherein the thickness of the alloy coating on the diamond with the alloy coating is 100-300nm. S4, A copper-diamond composite material is prepared by vacuum hot pressing of diamond with alloy coating. The steps of the vacuum hot pressing process are as follows: Chromium powder and diamond with alloy coating are mixed at a mass ratio of 1:(80-120) to obtain mixed powder. The mixed powder is then placed between two copper foils to form a copper foil-mixed powder-copper foil structure. The mixture is then hot pressed at a temperature of 900-1300℃ and a pressure of 10-50 MPa to obtain the copper-diamond composite material.

2. The method for preparing the copper-diamond composite material as described in claim 1, characterized in that, In step S1, the mixed steam is prepared by bubbling nitrogen gas through hydrogen peroxide.

3. The method for preparing the copper-diamond composite material as described in claim 1, characterized in that, In step S1, the mass ratio of the diamond particles to the nickel powder is (2-4):

1.

4. The method for preparing the copper-diamond composite material as described in claim 1, characterized in that, In step S1, the acid is one or more of hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid.

5. The method for preparing the copper-diamond composite material as described in claim 1, characterized in that, In step S2, the mass ratio of copper powder, nickel powder and tin powder is 1:4:(2-7).

6. The method for preparing the copper-diamond composite material as described in claim 1, characterized in that, In step S2, the sintering process parameters in the frequency induction furnace are: sintering at 600-1300℃ for 2-10 hours under a vacuum of less than 1000Pa.

7. A copper-diamond composite material prepared by the method for preparing copper-diamond composite materials as described in any one of claims 1-6.

Images