Copper-diamond composite board with high thermal conductivity and low expansion coefficient and preparation method of copper-diamond composite board

Abstract

The invention discloses a copper-diamond composite board with high heat conductivity and low expansion coefficient and a preparation method thereof, and belongs to the technical field of preparation of heat-conducting packaging materials for electronic equipment. The preparation method comprises the following steps: grinding and cleaning a base copper plate, milling a rectangular groove to obtain a pretreated base copper plate, and performing electrochemical etching on the pretreated base copper plate to obtain an etched base copper plate; filling a rectangular groove in the etched base copper plate with the carbon nano tube and modified diamond, and compacting for 1-2 minutes under 20-30 MPa to obtain a mixed base copper plate; and the copper covering plate covers one side of the mixed base copper plate filled with the carbon nano tube modified diamond, and then the mixed base copper plate is placed in a graphite mold to be subjected to direct current hot pressing sintering to obtain the copper-diamond composite plate. The prepared copper-diamond composite board has good heat conduction performance and low thermal expansion performance, the bending strength is high, and the problem that the brittleness of the material is too high is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive packaging material preparation technology for electronic devices, specifically relating to a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion and its preparation method. Background Technology

[0002] In today's rapidly evolving global electronics and information industry, high-end fields such as 5G communication, artificial intelligence, new energy vehicles, and aerospace are placing unprecedentedly stringent demands on the performance of electronic devices. Among these, heat dissipation and electrical conductivity have become core bottlenecks restricting the development of electronic devices towards higher integration and higher power density. As device sizes continue to miniaturize and computing speeds increase, the heat generated per unit volume increases dramatically. If this heat cannot be dissipated in time, the operating temperature of the device will rise, not only reducing operating efficiency and shortening lifespan, but also potentially causing serious problems such as thermal failure. Against this backdrop, developing novel electronic packaging and heat dissipation materials that combine excellent thermal conductivity and good electrical conductivity with suitable mechanical properties has become a research hotspot in materials science and electronic engineering. Metal matrix composites have great potential in improving the heat dissipation of electronic devices, possessing higher thermal conductivity and meeting the requirements of ultra-high thermal conductivity in electronic equipment. Diamond, as the hardest material in nature, has extremely high thermal conductivity and extremely low coefficient of thermal expansion. Copper has good electrical conductivity, thermal conductivity and ductility, but its high coefficient of thermal expansion makes it poorly matched with silicon-based chips and prone to interface cracking due to thermal cycling, affecting its use. However, the copper-diamond composite material formed by combining the two can achieve both high thermal conductivity and low expansion characteristics through synergistic effect, making it an ideal choice for heat dissipation substrates for high-end chips. The current preparation technology of copper-diamond composite plates mainly faces the following bottlenecks: (1) Insufficient filling rate and thermal conductivity: Traditional powder metallurgy mixes copper powder and diamond particles, presses and sintersects them, which easily leads to uneven diamond dispersion and particle agglomeration, resulting in poor diamond filling effect. The thermal conductivity of the composite plate is mostly between 400 and 500 W / m·K, which cannot meet the requirements of high-power chips; (2) Poor interface bonding performance: The brazing method requires the addition of brazing filler metal (such as Ag-Cu-Ti alloy) to achieve the bonding between copper and diamond. However, the brazing filler metal will form brittle intermetallic compounds (such as TiC) at the interface, which not only hinders heat conduction but also reduces the mechanical stability of the composite plate, making it easy to delamination in subsequent processing or use; (3) Unreasonable process parameters: In order to pursue interface bonding, the existing hot pressing sintering technology often uses high temperature of 950~1050℃ and long-term heat preservation of 120~180min, which leads to abnormal growth of copper matrix grains. On the one hand, it reduces the thermal conductivity of copper, and on the other hand, it exacerbates the increase of the thermal expansion coefficient of copper, destroying the balance of "high thermal conductivity ~ low expansion".

[0003] Patent CN113210611A discloses a copper-diamond composite material with a surface metal coating, its preparation method, and its applications. The surface metal coating of this invention prevents the diamond particles in the copper-diamond core from being exposed, thereby reducing the machining difficulty of manufacturing parts and lowering the surface roughness of the copper-diamond composite material. The surface metal coating has high thermal conductivity and its coefficient of thermal expansion matches that of the copper-diamond core, resulting in low interfacial stress between the copper-diamond core and the surface metal coating, thus meeting the requirements of aerospace applications with high temperature cycling. Patent CN115138851A discloses a method for preparing a copper-diamond electronic packaging material with integrated heat pipe function. This invention first uses an integrated melt infiltration method to manufacture a copper-diamond / copper-chromium in-situ composite layered structure material. Then, a phase-selective dissolution method is used to dissolve and remove the chromium component in the copper-diamond / copper-chromium composite material in a strong alkaline solution, while the copper and diamond phases are not corroded by the alkaline solution, obtaining an in-situ composite layered structure of copper-diamond / porous copper. By using the copper-diamond side of this porous copper / copper-diamond layered structure as one end of the heat pipe shell and the porous copper side as the liquid wick of the heat pipe, and then performing liquid absorption and sealing of the end cap, a copper-diamond electronic packaging material with integrated heat pipe function can be manufactured.

[0004] By introducing alloying elements to coat the surface of diamond, a strong carbide transition layer is introduced to improve interfacial bonding, which can improve the hardness of the composite material. However, the carbide phase is brittle and its impact resistance is prone to decline over time. Furthermore, the doping of alloying elements can easily cause element segregation, which leads to poor interfacial bonding. As a result, this method has high requirements for the preparation process and is difficult to expand its application.

[0005] Therefore, by addressing the poor bonding between diamond and copper at the interface and reducing the formation of carbide phases from additional metal elements, the composite material exhibits excellent thermal conductivity and low thermal expansion, making it a promising candidate for various applications. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention modifies diamond to obtain carbon nanotube-modified diamond, then lays the carbon nanotube-modified diamond in grooves on a copper plate, and combines this with a low-temperature, short-time, direct current rapid hot pressing process to obtain a copper-diamond composite plate, thereby solving the technical problems mentioned in the background art. Specifically, the technical solution of this invention includes the following: One objective of this invention is to provide a method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, the method comprising the following steps: After grinding and cleaning, a rectangular groove is milled into the base copper plate to obtain a pretreated base copper plate. The pretreated base copper plate is then electrochemically etched to obtain an etched base copper plate. Carbon nanotubes@modified diamond are filled into rectangular grooves on an etched copper substrate and then compacted at 20MPa~30MPa for 1min~2min to obtain a hybrid copper substrate. A copper plate is placed over one side of a hybrid base copper plate filled with carbon nanotubes@modified diamond, and then placed in a graphite mold and sintered by DC hot pressing to obtain the copper-diamond composite plate.

[0007] Furthermore, the base copper plate is made of T2 copper plate, and its dimensions are 100mm long × 100mm wide × 5mm thick.

[0008] Furthermore, the rectangular groove on the pretreated copper base plate has a length of 95mm~99mm × width of 95mm~99mm × depth of 0.5mm~1mm.

[0009] Furthermore, the conditions for the electrochemical etching include a copper sulfate solution as the electrolyte, a pH of 4 to 4.5 as the electrolyte, a current density of 10 mA / cm² to 20 mA / cm² as the current density, and an etching time of 15 min to 20 min.

[0010] Furthermore, the preparation method of the carbon nanotube@modified diamond includes the following steps: Diamond, grinding balls, and dispersant are mixed and ground in a weight ratio of 1:5:0.3~0.4 to obtain pretreated diamond. The pretreated diamond is then etched by oxygen plasma to obtain modified diamond. One part by weight of modified diamond was impregnated in three to four parts by weight of precursor sol and ultrasonically dispersed, followed by drying and reduction treatment to obtain nano-metal particles@modified diamond; The carbon nanotubes@modified diamond were obtained by vapor deposition of nano-metal particles@modified diamond.

[0011] Furthermore, the diamond particles are obtained by screening through a 35-mesh sieve.

[0012] Furthermore, the grinding ball is made of aluminum oxide.

[0013] Furthermore, the dispersant includes anhydrous ethanol.

[0014] Furthermore, the conditions for the mixed grinding include a rotation speed of 400 r / min to 500 r / min and a grinding time of 1 h to 2 h.

[0015] Furthermore, the conditions for oxygen plasma etching include an oxygen pressure of 150 Pa, a power of 100 W to 150 W, and a processing time of 15 min to 30 min.

[0016] Furthermore, the preparation method of the precursor sol includes the following steps: Ferric nitrate nonahydrate, aluminum nitrate nonahydrate, silane coupling agent KH-560, ethanol, water, and chelating agent are mixed in a weight ratio of 2:1:0.3~0.5:12:3:0.5~0.7 and stirred at 60℃~70℃ for 50min~60min to form the precursor sol.

[0017] Furthermore, the chelating agent includes citric acid.

[0018] Furthermore, the conditions for mixing and dispersing include an ultrasonic power of 300W~400W and a dispersion time of 20min~30min.

[0019] Furthermore, the drying conditions include a drying temperature of 110°C and a drying time of 3 to 4 hours.

[0020] Furthermore, the conditions for the reduction treatment include a reducing gas consisting of hydrogen and argon in a volume ratio of 1:4, a gas flow rate of 200 mL / min to 250 mL / min, a reduction temperature of 400℃ to 450℃, and a reduction time of 40 min to 50 min.

[0021] Furthermore, the conditions for the vapor deposition include a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4, a mixed gas flow rate of 80 mL / min to 100 mL / min, a processing temperature of 750°C to 800°C, and a processing time of 1 h.

[0022] Furthermore, the copper cover plate is made of T2 copper plate, and its dimensions are 100mm long × 100mm wide × 3mm thick.

[0023] Furthermore, the conditions for DC hot pressing sintering include a temperature of 850℃~900℃, a pressure of 30MPa~40MPa, a holding time of 30min~60min, and a DC electric field strength of 5V / cm~8V / cm.

[0024] The second objective of this invention is to provide a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In this invention, the diamond surface is first mechanically ground and etched to increase the roughness and defect sites to obtain pretreated diamond. Then, the surface of the pretreated diamond is etched and activated by plasma to load oxygen-containing groups such as hydroxyl and carboxyl groups on its surface to obtain modified diamond. The introduction of oxygen-containing groups is beneficial to provide carbon network growth sites on the diamond surface in the future. Modified diamond is impregnated in a precursor sol and then dried to form a gel coating on its surface. Following this, a high-temperature reduction treatment is performed, reducing the metal ions in the precursor sol into reducible nano-metal particles. Simultaneously, the silane coupling agent in the precursor sol generates a high-temperature resistant silicon-oxygen network structure, anchoring the nanoparticles to the modified diamond surface and preventing them from detaching, thus obtaining nano-metal particles@modified diamond. Carbon nanotubes with a three-dimensional network porous structure are then grown in situ on the diamond using vapor deposition, resulting in carbon nanotubes@modified diamond. A copper plate is electrochemically etched to create rough etched channels on its surface, increasing interfacial wetting and bonding with the diamond. The network porous structure of the carbon nanotubes allows copper metal to diffuse and embed into the pores of the diamond surface after hot pressing, enhancing the interfacial bonding effect between copper and diamond through a mechanical interlocking effect, resulting in a copper-diamond composite plate. Furthermore, after the nano-metal particles catalyze the formation of carbon nanotubes, high-temperature treatment can form oxide crystalline phases, thereby refining the grains and inhibiting the growth of copper matrix grains. The synergistic combination of diamond surface activation, catalyst anchoring, and vapor deposition generates carbon nanotubes with a three-dimensional porous network structure in situ on the diamond surface. Through the synergistic effect of pore structure construction and interfacial chemical bonding, the wettability and bonding strength between diamond and metal materials are significantly improved, achieving high thermal conductivity and low thermal expansion.

[0026] (2) In the process of combining carbon nanotubes@modified diamond with metallic copper, the present invention abandons the traditional powder mixing metallurgy method and innovatively adopts the method of opening grooves on the copper plate for positioning. The carbon nanotubes@modified diamond are laid in the grooves on the copper plate, and then combined with a low temperature and short time hot pressing process. On the one hand, it avoids the easy agglomeration of particles during mixing, which will generate gaps and affect the interface bonding between diamond and metallic copper. On the other hand, it reduces the temperature and time required for sintering, and overcomes the defects of poor interface bonding and brittle phase caused by grain growth due to excessive temperature and time, which affect the thermal conductivity and thermal expansion properties of copper diamond composite plate. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0029] Preparation Example 1 The preparation method of the precursor sol is as follows: Weigh 2 parts by weight of ferric nitrate nonahydrate, 1 part by weight of aluminum nitrate nonahydrate and 3 parts by weight of deionized water and mix and stir until completely dissolved. Then add 0.3 parts by weight of silane coupling agent KH-560, 10 parts by weight of ethanol and 0.5 parts by weight of citric acid, mix and place in a water bath at 60°C and stir at 200 r / min for 50 min to obtain the precursor sol.

[0030] Preparation Example 2 The preparation method of the precursor sol is as follows: Weigh 2 parts by weight of ferric nitrate nonahydrate, 1 part by weight of aluminum nitrate nonahydrate and 3 parts by weight of deionized water and mix and stir until completely dissolved. Then add 0.3 parts by weight of silane coupling agent KH-560, 10 parts by weight of ethanol and 0.6 parts by weight of citric acid, mix and place in a water bath at 60°C and stir at 200 r / min for 55 min to obtain the precursor sol.

[0031] Preparation Example 3 The preparation method of the precursor sol is as follows: Weigh 2 parts by weight of ferric nitrate nonahydrate, 1 part by weight of aluminum nitrate nonahydrate and 3 parts by weight of deionized water and mix until completely dissolved. Then add 0.4 parts by weight of silane coupling agent KH-560, 10 parts by weight of ethanol and 0.6 parts by weight of citric acid, mix and place in a water bath at 65°C and stir at 200 r / min for 55 min to obtain the precursor sol.

[0032] Preparation Example 4 The preparation method of the precursor sol is as follows: Weigh 2 parts by weight of ferric nitrate nonahydrate, 1 part by weight of aluminum nitrate nonahydrate and 3 parts by weight of deionized water and mix until completely dissolved. Then add 0.5 parts by weight of silane coupling agent KH-560, 10 parts by weight of ethanol and 0.7 parts by weight of citric acid, mix and place in a water bath at 70°C and stir at 200 r / min for 60 min to obtain the precursor sol.

[0033] Preparation Example 5 The preparation method of the precursor sol is as follows: Weigh 2 parts by weight of ferric nitrate nonahydrate, 1 part by weight of aluminum nitrate nonahydrate and 3 parts by weight of deionized water and mix and stir until completely dissolved. Then add 10 parts by weight of ethanol and 0.7 parts by weight of citric acid and mix. Place in a water bath at 70°C and stir at 200 r / min for 60 min to obtain the precursor sol.

[0034] Preparation Example 6 The preparation method of the precursor sol is as follows: Weigh 2 parts by weight of ferric nitrate nonahydrate, 1 part by weight of aluminum nitrate nonahydrate and 3 parts by weight of deionized water and mix until completely dissolved. Then add 1 part by weight of silane coupling agent KH-560, 10 parts by weight of ethanol and 0.7 parts by weight of citric acid, mix and place in a water bath at 70°C and stir at 200 r / min for 60 min to obtain the precursor sol.

[0035] Preparation Example 7 The preparation method of the precursor sol is as follows: Weigh 2 parts by weight of ferric nitrate nonahydrate, 1 part by weight of aluminum nitrate nonahydrate, and 3 parts by weight of deionized water, mix and stir until completely dissolved. Then add 0.5 parts by weight of silane coupling agent KH-560, 10 parts by weight of ethanol, and 0.7 parts by weight of ethylenediaminetetraacetic acid, mix and place in a water bath at 70°C, stir at 200 r / min for 60 min. It was found that the gel solidified and the sol preparation failed. This may be because the chelating ability of ethylenediaminetetraacetic acid is stronger than that of citric acid, which may lead to the overall gel solidification due to excessive chelation during sol preparation.

[0036] Preparation Example 8 The preparation method of carbon nanotube@modified diamond is as follows: Diamond was crushed using a crusher and then sieved through a 35-mesh sieve to obtain diamond particles. One part by weight of diamond particles and five parts by weight of alumina grinding balls were weighed and placed in a ball mill. 0.3 parts by weight of anhydrous ethanol were added, and the grinding speed was set to 400 r / min for 1 hour. After grinding, the solid particles were collected by filtration and rinsed with deionized water. The particles were then dried in an oven at 80°C until constant weight to obtain pretreated diamond. The pretreated diamond was placed in the reaction chamber of a plasma device, and a vacuum was drawn to 0.01 MPa. Oxygen was then introduced, and the working pressure of the oxygen was adjusted to 150 Pa. The discharge power was adjusted to 100 W, and the diamond was etched for 15 minutes at this discharge power to obtain modified diamond. One part by weight of the modified diamond was completely impregnated in three parts by weight of the precursor sol obtained in Preparation Example 1, and then transferred to an ultrasonic disperser. The ultrasonic power was adjusted to 300 W, and the diamond was dispersed for 20 minutes at this power. After dispersion treatment, the impregnated modified diamond was removed and dried in a vacuum drying oven at 110℃ for 3 hours. The dried modified diamond was then transferred to the reaction chamber of a plasma device, and argon gas was introduced to purge the air from the reaction chamber. The volume ratio of hydrogen to argon was then adjusted to 1:4, and the gas flow rate was controlled at 200 mL / min. The temperature was increased to 400℃ at a rate of 5℃ / min, and the reduction treatment was carried out at this temperature for 40 minutes. After the reduction treatment, the hydrogen gas supply was stopped, and the mixture was allowed to cool naturally to room temperature in an argon atmosphere to obtain nano-metal particles@modified diamond. The nano-metal particles@modified diamond were then transferred to a CVD device, and a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4 was introduced. The flow rate of the mixed gas was adjusted to 80 mL / min, and the temperature was increased to 700℃ at a rate of 5℃ / min. The mixture was then held at this temperature for deposition treatment for 1 hour. Finally, the mixture was cooled to room temperature in an argon atmosphere to obtain carbon nanotubes@modified diamond.

[0037] Preparation Example 9 The preparation method of carbon nanotube@modified diamond is as follows: Diamond was crushed using a crusher and then screened through a 35-mesh sieve to obtain diamond particles. One part by weight of diamond particles and five parts by weight of alumina grinding balls were weighed and placed in a ball mill. 0.35 parts by weight of anhydrous ethanol were added, and the grinding speed was set to 400 r / min for 1 hour. After grinding, the solid particles were collected by filtration and rinsed with deionized water. The particles were then dried in an oven at 80°C until constant weight to obtain pretreated diamond. The pretreated diamond was placed in the reaction chamber of a plasma device, and a vacuum of 0.01 MPa was created. Oxygen was then introduced, and the working pressure was adjusted to 150 Pa. The discharge power was adjusted to 100 W, and the diamond was etched for 20 minutes at this discharge power to obtain modified diamond. One part by weight of the modified diamond was completely impregnated in 3.5 parts by weight of the precursor sol obtained in Preparation Example 2, and then transferred to an ultrasonic disperser. The ultrasonic power was adjusted to 300 W, and the diamond was dispersed for 25 minutes at this power. After dispersion treatment, the impregnated modified diamond was removed and dried in a vacuum drying oven at 110℃ for 3 hours. The dried modified diamond was then transferred to the reaction chamber of a plasma device, and argon gas was introduced to purge the air from the reaction chamber. The volume ratio of hydrogen to argon was then adjusted to 1:4, and the gas flow rate was controlled at 230 mL / min. The temperature was increased to 420℃ at a rate of 5℃ / min, and the reduction treatment was performed at this temperature for 40 minutes. After the reduction treatment, the hydrogen gas supply was stopped, and the diamond was allowed to cool naturally to room temperature in an argon atmosphere to obtain nano-metal particles@modified diamond. The nano-metal particles@modified diamond were then transferred to a CVD device, and a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4 was introduced. The flow rate of the mixed gas was adjusted to 80 mL / min, and the temperature was increased to 720℃ at a rate of 5℃ / min. The deposition treatment was performed at this temperature for 1 hour. The diamond was then cooled to room temperature in an argon atmosphere to obtain carbon nanotubes@modified diamond.

[0038] Preparation Example 10 The preparation method of carbon nanotube@modified diamond is as follows: Diamond was crushed using a crusher and then sieved through a 35-mesh screen to obtain diamond particles. One part by weight of diamond particles and five parts by weight of alumina grinding balls were weighed and placed in a ball mill. 0.35 parts by weight of anhydrous ethanol were added, and the grinding speed was set to 500 r / min for 1.5 h. After grinding, the solid particles were collected by filtration and rinsed with deionized water. The particles were then dried in an oven at 80°C until constant weight to obtain pretreated diamond. The pretreated diamond was placed in the reaction chamber of a plasma device, and a vacuum was drawn to 0.01 MPa. Oxygen was then introduced, and the working pressure of the oxygen was adjusted to 150 Pa. The discharge power was adjusted to 120 W, and the diamond was etched for 25 min at this discharge power to obtain modified diamond. One part by weight of the modified diamond was completely impregnated in 3.5 parts by weight of the precursor sol obtained in Preparation Example 3, and then transferred to an ultrasonic disperser. The ultrasonic power was adjusted to 400 W, and the diamond was dispersed for 30 min at this power. After dispersion treatment, the impregnated modified diamond was removed and dried in a vacuum drying oven at 110℃ for 4 hours. The dried modified diamond was then transferred to the reaction chamber of a plasma device, and argon gas was introduced to purge the air from the reaction chamber. The volume ratio of hydrogen to argon was then adjusted to 1:4, and the gas flow rate was controlled at 250 mL / min. The temperature was increased to 440℃ at a rate of 5℃ / min, and the reduction treatment was performed at this temperature for 45 minutes. After the reduction treatment, the hydrogen gas supply was stopped, and the mixture was allowed to cool naturally to room temperature in an argon atmosphere to obtain nano-metal particles@modified diamond. The nano-metal particles@modified diamond were then transferred to a CVD device, and a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4 was introduced. The flow rate of the mixed gas was adjusted to 90 mL / min, and the temperature was increased to 750℃ at a rate of 5℃ / min. The mixture was then held at this temperature for deposition treatment for 1 hour. Finally, the mixture was cooled to room temperature in an argon atmosphere to obtain carbon nanotubes@modified diamond.

[0039] Preparation Example 11 The preparation method of carbon nanotube@modified diamond is as follows: Diamond was crushed using a crusher and then sieved through a 35-mesh sieve to obtain diamond particles. One part by weight of diamond particles and five parts by weight of alumina grinding balls were weighed and placed in a ball mill. 0.4 parts by weight of anhydrous ethanol were added, and the grinding speed was set to 500 r / min for 2 hours. After grinding, the solid particles were collected by filtration and rinsed with deionized water. The particles were then dried in an oven at 80°C until constant weight to obtain pretreated diamond. The pretreated diamond was placed in the reaction chamber of a plasma device, and a vacuum was drawn to 0.01 MPa. Oxygen was then introduced, and the working pressure of the oxygen was adjusted to 150 Pa. The discharge power was adjusted to 150 W, and the diamond was etched at this discharge power for 30 minutes to obtain modified diamond. One part by weight of the modified diamond was completely impregnated in four parts by weight of the precursor sol obtained in Preparation Example 4, and then transferred to an ultrasonic disperser. The ultrasonic power was adjusted to 400 W, and the diamond was dispersed at this power for 30 minutes. After dispersion treatment, the impregnated modified diamond was removed and dried in a vacuum drying oven at 110℃ for 4 hours. The dried modified diamond was then transferred to the reaction chamber of a plasma device, and argon gas was introduced to purge the air from the reaction chamber. The volume ratio of hydrogen to argon was then adjusted to 1:4, and the gas flow rate was controlled at 250 mL / min. The temperature was increased to 450℃ at a rate of 5℃ / min, and the reduction treatment was carried out at this temperature for 50 minutes. After the reduction treatment, the hydrogen gas supply was stopped, and the mixture was allowed to cool naturally to room temperature in an argon atmosphere to obtain nano-metal particles@modified diamond. The nano-metal particles@modified diamond were then transferred to a CVD device, and a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4 was introduced. The flow rate of the mixed gas was adjusted to 100 mL / min, and the temperature was increased to 750℃ at a rate of 5℃ / min. The deposition treatment was carried out at this temperature for 1 hour. The mixture was then cooled to room temperature in an argon atmosphere to obtain carbon nanotubes@modified diamond.

[0040] Preparation Example 12 The preparation method of carbon nanotube@modified diamond is as follows: The precursor sol in Preparation Example 11 was replaced with the precursor sol obtained in Preparation Example 5, and the rest of the preparation process was the same as in Preparation Example 11.

[0041] Preparation Example 13 The preparation method of carbon nanotube@modified diamond is as follows: The precursor sol in Preparation Example 11 was replaced with the precursor sol obtained in Preparation Example 6, and the rest of the preparation process was the same as in Preparation Example 11.

[0042] Preparation Example 14 The preparation method of carbon nanotube@modified diamond is as follows: The modified diamond obtained in Preparation Example 11 was transferred to a CVD apparatus, and a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4 was introduced. The flow rate of the mixed gas was adjusted to 100 mL / min, and the temperature was increased to 750 °C at a heating rate of 5 °C / min. The deposition process was carried out at this temperature for 1 h. Subsequently, it was cooled to room temperature in an argon atmosphere to obtain carbon nanotube@modified diamond.

[0043] Preparation Example 15 The preparation method of carbon nanotube@modified diamond is as follows: Diamond was crushed using a crusher and then sieved through a 35-mesh sieve to obtain diamond particles. One part by weight of diamond particles and five parts by weight of alumina grinding balls were weighed and placed in a ball mill. 0.4 parts by weight of anhydrous ethanol were added, and the grinding speed was set to 500 r / min for 2 hours. After grinding, the solid particles were collected by filtration and rinsed with deionized water. The particles were then dried in an oven at 80°C until constant weight to obtain pretreated diamond. The pretreated diamond was placed in the reaction chamber of a plasma device, and a vacuum was drawn to 0.01 MPa. Oxygen was then introduced, and the working pressure of the oxygen was adjusted to 300 Pa. The discharge power was adjusted to 200 W, and etching was performed at this discharge power for 40 minutes to obtain modified diamond. The remaining preparation process was consistent with Preparation Example 11.

[0044] Preparation Example 16 The preparation method of carbon nanotube@modified diamond is as follows: The nano-metal particles@modified diamond obtained in Preparation Example 11 were transferred to a CVD apparatus, and a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4 was introduced. The flow rate of the mixed gas was adjusted to 150 mL / min, and the temperature was increased to 800 °C at a heating rate of 5 °C / min. The deposition process was carried out at this temperature for 1.5 h. Subsequently, the mixture was cooled to room temperature in an argon atmosphere to obtain carbon nanotubes@modified diamond. Example 1

[0045] A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: T2 copper plates were selected and cut into base copper plates (100mm x 100mm x 5mm) and cover copper plates (100mm x 100mm x 3mm). The surfaces of the base copper plates and cover copper plates were polished with 800# sandpaper to remove the oxide layer. They were then placed in an ultrasonic cleaner with anhydrous ethanol as the cleaning medium and cleaned at 200W for 20 minutes. After cleaning, they were rinsed with deionized water and dried to constant weight. A rectangular groove (95mm x 95mm x 1mm) was milled on one side of the base copper plate using a CNC milling machine to obtain a pretreated base copper plate. The pretreated base copper plate was placed in an electrolytic cell and connected to the positive terminal of the power supply as the anode. A graphite rod was used as the cathode. A 0.1mol / L copper sulfate solution was adjusted to pH 4 and poured into the electrolytic cell as the electrolyte. The current density was controlled at 10mA / cm2, and then etching was performed for 20 minutes. After etching, the power supply was stopped, the plate was removed, rinsed with deionized water, and dried to obtain an etched base copper plate. The carbon nanotubes@modified diamond obtained in Preparation Example 8 were filled into the rectangular grooves on the etched base copper plate. After being gently pressed flat with a scraper, the plate was transferred to a press and compacted at 20 MPa for 2 minutes to obtain a hybrid base copper plate. A cover copper plate was placed over one side of the hybrid base copper plate filled with carbon nanotubes@modified diamond, aligned and tightly attached. It was then placed in a graphite mold, and the mold was transferred to a DC rapid hot press furnace. The furnace door was closed, and a vacuum of 5 × 10⁻³ Pa was applied to remove oxygen and prevent copper oxidation. The temperature was increased to 850°C at a rate of 25°C / min, with a DC electric field strength of 5 V / cm. An initial pressure of 15 MPa was applied simultaneously until the target temperature was reached, at which point the pressure reached 30 MPa. The plate was then hot-pressed and sintered in this environment for 60 minutes. The heating system was then turned off, and the pressure was maintained until the furnace temperature dropped to 400°C. The plate was then allowed to cool naturally to room temperature to obtain a copper-diamond composite plate. Example 2

[0046] A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: T2 copper plates were selected and cut into base copper plates (100mm x 100mm x 5mm) and cover copper plates (100mm x 100mm x 3mm). The surfaces of the base copper plates and cover copper plates were polished with 800# sandpaper to remove the oxide layer. They were then placed in an ultrasonic cleaner with anhydrous ethanol as the cleaning medium and cleaned at 200W for 20 minutes. After cleaning, they were rinsed with deionized water and dried to constant weight. A rectangular groove (95mm x 95mm x 1mm) was milled on one side of the base copper plate using a CNC milling machine to obtain a pretreated base copper plate. The pretreated base copper plate was placed in an electrolytic cell and connected to the positive terminal of the power supply as the anode. A graphite rod was used as the cathode. A 0.1mol / L copper sulfate solution was adjusted to pH 4 and poured into the electrolytic cell as the electrolyte. The current density was controlled at 15mA / cm2, and then etching was performed for 18 minutes. After etching, the power supply was stopped, the plate was removed, rinsed with deionized water, and dried to obtain an etched base copper plate. The carbon nanotubes@modified diamond obtained in Preparation Example 9 were filled into the rectangular grooves on the etched base copper plate. After being gently pressed flat with a scraper, the plate was transferred to a press and compacted at 25 MPa for 2 minutes to obtain a hybrid base copper plate. A cover copper plate was placed over one side of the hybrid base copper plate filled with carbon nanotubes@modified diamond, aligned and tightly attached. It was then placed in a graphite mold, and the mold was transferred to a DC rapid hot press furnace. The furnace door was closed, and a vacuum of 5 × 10⁻³ Pa was applied to remove oxygen and prevent copper oxidation. The temperature was increased to 850°C at a rate of 25°C / min, with a DC electric field strength of 7 V / cm. An initial pressure of 15 MPa was applied simultaneously until the target temperature was reached, at which point the pressure reached 35 MPa. The plate was then hot-pressed and sintered in this environment for 50 minutes. The heating system was then turned off, and the pressure was maintained until the furnace temperature dropped to 400°C. The plate was then allowed to cool naturally to room temperature to obtain a copper-diamond composite plate. Example 3

[0047] A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: T2 copper plates were selected and cut into base copper plates (100mm x 100mm x 5mm) and cover copper plates (100mm x 100mm x 3mm). The surfaces of both plates were polished with 800# sandpaper to remove the oxide layer. They were then placed in an ultrasonic cleaner containing anhydrous ethanol and cleaned at 200W for 20 minutes. After cleaning, they were rinsed with deionized water and dried to constant weight. A rectangular groove (99mm x 99mm x 0.5mm) was milled on one side of the base copper plate using a CNC milling machine to obtain a pretreated base copper plate. This pretreated base copper plate was placed in an electrolytic cell and connected to the positive terminal of the power supply as the anode. A graphite rod was used as the cathode. A 0.1mol / L copper sulfate solution was added to the electrolytic cell, adjusted to pH 4.5, as the electrolyte. The current density was controlled at 15mA / cm², and etching was performed for 17 minutes. After etching, the power supply was stopped, the plate was removed, rinsed with deionized water, and dried to obtain an etched base copper plate. The carbon nanotubes@modified diamond obtained in Preparation Example 10 were filled into the rectangular grooves on the etched base copper plate, and then gently pressed flat with a scraper. The plate was then transferred to a press and compacted at 25 MPa for 1 min to obtain a hybrid base copper plate. A cover copper plate was placed over one side of the hybrid base copper plate filled with carbon nanotubes@modified diamond, aligned and tightly attached. The plate was then placed in a graphite mold, and the mold was transferred to a DC rapid hot press furnace. After closing the furnace door, a vacuum of 5 × 10⁻³ Pa was drawn to remove oxygen from the furnace and prevent copper oxidation. The temperature was increased to 900 °C at a rate of 25 °C / min, the DC electric field strength was set to 7 V / cm, and an initial pressure of 15 MPa was applied simultaneously until the target temperature was reached and the pressure reached 35 MPa. The plate was then hot-pressed and sintered in this environment for 40 min. The heating system was then turned off, and the pressure was maintained until the temperature inside the furnace dropped to 400°C. After that, the pressure was stopped, and the furnace was allowed to cool naturally to room temperature. The copper-diamond composite plate was then removed. Example 4

[0048] A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: T2 copper plates were selected and cut into base copper plates (100mm x 100mm x 5mm) and cover copper plates (100mm x 100mm x 3mm). The surfaces of both plates were polished with 800# sandpaper to remove the oxide layer. They were then placed in an ultrasonic cleaner containing anhydrous ethanol and cleaned at 200W for 20 minutes. After cleaning, they were rinsed with deionized water and dried to constant weight. A rectangular groove (99mm x 99mm x 0.5mm) was milled on one side of the base copper plate using a CNC milling machine to obtain a pretreated base copper plate. This pretreated base copper plate was placed in an electrolytic cell and connected to the positive terminal of the power supply as the anode. A graphite rod was used as the cathode. A 0.1mol / L copper sulfate solution was added to the electrolytic cell, adjusted to pH 4.5, as the electrolyte. The current density was controlled at 20mA / cm², and etching was performed for 15 minutes. After etching, the power supply was stopped, the plate was removed, rinsed with deionized water, and dried to obtain an etched base copper plate. The carbon nanotubes@modified diamond obtained in Preparation Example 11 were filled into the rectangular grooves on the etched base copper plate, and then gently pressed flat with a scraper. The plate was then transferred to a press and compacted at 30 MPa for 1 min to obtain a hybrid base copper plate. A cover copper plate was placed over one side of the hybrid base copper plate filled with carbon nanotubes@modified diamond, aligned and tightly attached. The plate was then placed in a graphite mold, and the mold was transferred to a DC rapid hot press furnace. After closing the furnace door, a vacuum of 5 × 10⁻³ Pa was drawn to remove oxygen from the furnace and prevent copper oxidation. The temperature was increased to 900 °C at a rate of 25 °C / min, the DC electric field strength was set to 8 V / cm, and an initial pressure of 15 MPa was applied simultaneously until the target temperature was reached and the pressure reached 40 MPa. The plate was then hot-pressed and sintered in this environment for 30 min. The heating system was then turned off, and the pressure was maintained until the temperature inside the furnace dropped to 400°C. After that, the pressure was stopped, and the furnace was allowed to cool naturally to room temperature. The copper-diamond composite plate was then removed.

[0049] Comparative Example 1 A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: The carbon nanotubes@modified diamond in Example 4 were replaced with the carbon nanotubes@modified diamond obtained in Preparation Example 12, and the rest of the preparation process was the same as in Example 4.

[0050] Comparative Example 2 A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: The carbon nanotubes@modified diamond in Example 4 were replaced with the carbon nanotubes@modified diamond obtained in Preparation Example 13, and the rest of the preparation process was the same as in Example 4.

[0051] Comparative Example 3 A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: The carbon nanotubes@modified diamond in Example 4 were replaced with the carbon nanotubes@modified diamond obtained in Preparation Example 14, and the rest of the preparation process was the same as in Example 4.

[0052] Comparative Example 4 A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: The carbon nanotubes@modified diamond in Example 4 were replaced with the carbon nanotubes@modified diamond obtained in Preparation Example 15, and the rest of the preparation process was the same as in Example 4.

[0053] Comparative Example 5 A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: The carbon nanotubes@modified diamond in Example 4 were replaced with the carbon nanotubes@modified diamond obtained in Preparation Example 16, and the rest of the preparation process was the same as in Example 4.

[0054] Comparative Example 6 A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: A T2 copper plate was selected and cut into a base copper plate (100mm long × 100mm wide × 5mm thick) and a cover copper plate (100mm long × 100mm wide × 3mm thick). The surfaces of the base copper plate and the cover copper plate were polished with 800# sandpaper to remove the oxide layer. Then, they were placed in an ultrasonic cleaner with anhydrous ethanol as the cleaning medium and cleaned at 200W for 20 minutes. After cleaning, they were taken out, rinsed with deionized water, and then dried to constant weight. A rectangular groove (99mm long × 99mm wide × 2mm deep) was milled on one side of the base copper plate using a CNC milling machine to obtain a pretreated base copper plate. The rest of the preparation process was the same as in Example 4. It was found that burn-through occurred on the other side of the base copper plate where the rectangular groove was located during DC sintering.

[0055] Comparative Example 7 A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, specifically including the following steps: A T2 copper plate was selected and cut into a base copper plate (100mm long × 100mm wide × 5mm thick) and a cover copper plate (100mm long × 100mm wide × 3mm thick). The surfaces of the base copper plate and the cover copper plate were polished with 800# sandpaper to remove the oxide layer. Then, they were placed in an ultrasonic cleaner with anhydrous ethanol as the cleaning medium and cleaned at 200W for 20 minutes. After cleaning, they were taken out, rinsed with deionized water, and then dried to constant weight. A rectangular groove (99mm long × 99mm wide × 0.5mm deep) was milled on one side of the base copper plate using a CNC milling machine to obtain a pretreated base copper plate. The carbon nanotubes@modified diamond obtained in Preparation Example 11 were filled into the rectangular groove on the pretreated base copper plate. The rest of the preparation process was the same as in Example 4.

[0056] The thermal conductivity of the copper-diamond composite plates obtained in Examples 1-4 and Comparative Examples 1-7 was measured using a laser thermal conductivity meter. The results are shown in Table 1 below.

[0057] The coefficients of thermal expansion of the copper-diamond composite plates obtained in Examples 1-4 and Comparative Examples 1-7 were measured using a dilatometer, and the results are shown in Table 2 below. The bending strength of the copper-diamond composite plates obtained in Examples 1-4 and Comparative Examples 1-7 was measured using an electronic universal testing machine. The results are shown in Table 3 below. The following conclusions can be drawn from Tables 1-3 above: (1) As can be seen from Examples 1 to 4, the copper-diamond composite plate prepared by the present invention has good thermal conductivity and low thermal expansion properties, and high bending strength, which effectively reduces the problem of excessive brittleness of the material.

[0058] (2) Comparative Example 1 shows that when no silane coupling agent is used in the precursor sol, the nanoparticles generated by the reduction of iron and aluminum may have poor adhesion stability on the modified diamond surface during subsequent high-temperature treatment, and are easy to fall off, which affects the surface modification of diamond. As a result, the final copper-diamond composite plate has low thermal conductivity and high coefficient of thermal expansion, which is not conducive to use.

[0059] (3) Comparative Example 2 shows that when too much silane coupling agent is used in the current driving sol, the excessive silane coupling agent may produce a thicker silicon-oxygen network structure, resulting in fewer nanoparticles generated by the reduction of iron and aluminum. This is not conducive to the carbon nanotube structure constructed on the diamond surface by high-temperature vapor deposition, thus affecting the interfacial bonding between diamond and copper. As a result, the thermal conductivity of the copper-diamond composite plate prepared in the end is low and the coefficient of thermal expansion is high, which is not conducive to its use.

[0060] (4) Comparative Example 3 shows that if nano-metal particles are not loaded on the surface of modified diamond through precursor sol, it may be difficult to form carbon nanotubes on the modified diamond in situ by vapor deposition alone, which affects the interfacial bonding between diamond and copper. As a result, the copper-diamond composite plate prepared in the end has low thermal conductivity and high coefficient of thermal expansion, which is not conducive to use.

[0061] (5) Comparative Example 4 shows that if the intensity of oxygen plasma etching is further increased, although it is beneficial to increase the oxygen-containing groups on the surface, the structure of diamond may be greatly damaged due to excessive etching, which weakens the performance improvement of diamond on copper plate. As a result, the thermal conductivity of the copper-diamond composite plate is low and the coefficient of thermal expansion is high, which is not conducive to use.

[0062] (6) Comparative Example 5 shows that although vapor deposition is beneficial for preparing carbon nanotubes, if the gas flow is too large, the temperature is too high, or the processing time is too long, on the one hand, carbon atoms may not be stably adsorbed on the diamond surface and are easily swept away by the gas flow, resulting in poor deposition effect. On the other hand, excessively high temperature and excessively long processing time may cause the deposited carbon atoms to grow excessively, agglomerate and entangle when forming carbon nanotubes, which will damage the porous network structure of carbon nanotubes, affect the mechanical interlocking effect of copper diffusion and embedding, and result in the copper-diamond composite plate with low thermal conductivity and high thermal expansion coefficient, which is not conducive to use.

[0063] (7) Comparative Example 6 shows that if the rectangular groove is milled too deep, the burn-through phenomenon during sintering affects the structural integrity of the copper-diamond composite plate, and may cause some carbon nanotubes@modified diamond to fall off and not be able to combine with copper, resulting in a lower thermal conductivity and a higher coefficient of thermal expansion of the final copper-diamond composite plate, which is not conducive to use.

[0064] (8) Comparative Example 7 shows that if the pretreated base copper plate is not subjected to electrochemical etching treatment and relies solely on the surface modification of diamond, although the performance of the copper-diamond composite plate can be improved, the improvement effect is poor.

[0065] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of thermal expansion, characterized in that, The preparation method includes the following steps: After grinding and cleaning, a rectangular groove is milled into the base copper plate to obtain a pretreated base copper plate. The pretreated base copper plate is then electrochemically etched to obtain an etched base copper plate. Carbon nanotubes@modified diamond are filled into rectangular grooves on an etched copper substrate and then compacted at 20MPa~30MPa for 1min~2min to obtain a hybrid copper substrate. A copper plate is placed over one side of a hybrid base copper plate filled with carbon nanotubes@modified diamond, and then placed in a graphite mold and sintered by DC hot pressing to obtain the copper-diamond composite plate.

2. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 1, characterized in that, The electrochemical etching conditions include a copper sulfate solution as the electrolyte, a pH of 4-4.5, and a current density of 10 mA / cm². 2 ~20mA / cm 2 Etching time is 15-20 minutes.

3. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 1, characterized in that, The preparation method of the carbon nanotube@modified diamond includes the following steps: Diamond particles, grinding balls, and dispersant are mixed and ground in a weight ratio of 1:5:0.3~0.4 to obtain pretreated diamond. The pretreated diamond is then etched by oxygen plasma to obtain modified diamond. One part by weight of modified diamond was impregnated in three to four parts by weight of precursor sol and ultrasonically dispersed, followed by drying and reduction treatment to obtain nano-metal particles@modified diamond; The carbon nanotubes@modified diamond were obtained by vapor deposition of nano-metal particles@modified diamond.

4. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 3, characterized in that, The conditions for oxygen plasma etching include an oxygen pressure of 150 Pa, a power of 100 W to 150 W, and a processing time of 15 min to 30 min.

5. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 3, characterized in that, The preparation method of the precursor sol includes the following steps: Ferric nitrate nonahydrate, aluminum nitrate nonahydrate, silane coupling agent KH-560, ethanol, water, and chelating agent are mixed in a weight ratio of 2:1:0.3~0.5:12:3:0.5~0.7 and stirred at 60℃~70℃ for 50min~60min to form the precursor sol.

6. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 5, characterized in that, The chelating agent includes citric acid.

7. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 3, characterized in that, The conditions for the reduction treatment include a reducing gas consisting of hydrogen and argon in a volume ratio of 1:4, a gas flow rate of 200 mL / min to 250 mL / min, a reduction temperature of 400℃ to 450℃, and a reduction time of 40 min to 50 min.

8. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 3, characterized in that, The conditions for vapor deposition include a mixed gas consisting of methane, hydrogen, and nitrogen in a volume ratio of 1:1:4, a mixed gas flow rate of 80 mL / min to 100 mL / min, a processing temperature of 750℃ to 800℃, and a processing time of 1 h.

9. The method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion according to claim 1, characterized in that, The conditions for DC hot pressing sintering include a temperature of 850℃~900℃, a pressure of 30MPa~40MPa, a holding time of 30min~60min, and a DC electric field strength of 5V / cm~8V / cm.

10. A copper-diamond composite plate prepared by the method for preparing a copper-diamond composite plate with high thermal conductivity and low coefficient of expansion as described in any one of claims 1 to 9.

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