A DBC ceramic copper clad laminate and its preparation process

Abstract

The present invention relates to the field of electronic packaging technology, and specifically to a DBC ceramic copper clad laminate and its preparation process. A preparation process of a DBC ceramic copper clad laminate includes the following steps: preparation of a highly thermally stable heat-conducting copper plate; pulsed laser deposition of a CuO transition layer on a ceramic substrate; and lamination of the highly thermally stable heat-conducting copper plate and the ceramic substrate coated with the CuO transition layer. In the process of pulsed laser deposition coating of CuO on a clean ceramic substrate in the present invention, by introducing oxygen plasma, not only can the organic impurities on the surface of CuO nanoparticles be effectively removed, enhancing their surface activity, reducing the wetting angle between the non-oxide ceramic and the metal and improving the adhesion, but also the high energy of the oxygen plasma can promote the surface rearrangement and crystallization of CuO nanoparticles, forming a more ordered crystal structure, enabling the prepared ceramic substrate coated with the CuO transition layer to better bond with the highly thermally stable heat-conducting copper plate, thereby improving the peel strength and thermal conductivity of the DBC ceramic copper clad laminate.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic packaging, and specifically relates to a DBC ceramic copper clad laminate and a preparation process thereof. Background Art

[0002] DBC (Direct Bonded Copper) ceramic copper clad laminate is an advanced composite material, which is widely used in fields such as high-power electronic devices, power modules, LED substrates, and automotive electronics. The DBC ceramic copper clad laminate combines the high thermal conductivity and electrical insulation of ceramic materials with the high electrical conductivity and high mechanical strength of copper by attaching a copper layer to a ceramic substrate, and has excellent thermal performance and mechanical stability, suitable for harsh working environments.

[0003] Currently, the most commonly used method for preparing ceramic copper clad laminates is the active metal brazing method. Usually, active elements such as Ti, Zr, and Cr are added to an alloy solder, and then plated on the ceramic surface as a transition layer. Although it can improve the bonding strength between the ceramic substrate and the conductive Cu layer, when wet etching the circuit, Ti and Cr are difficult to be corroded by general etching solutions and only react with strong acids and strong bases. Multiple etching methods are required during circuit preparation, and the process is too complex and the cost is high. However, if active elements are not added to the alloy solder, the bonding ability between the conductive Cu layer and the ceramic substrate will be greatly reduced, and the thermal stability and peel strength of the ceramic copper clad laminate will be reduced. Summary of the Invention

[0004] In order to solve the above technical defects, the present invention has developed a DBC ceramic copper clad laminate with high peel strength, strong heat conduction ability, excellent thermal stability, and easy etching, and a preparation method thereof.

[0005] A preparation process of a DBC ceramic copper clad laminate includes the following steps:

[0006] S1: Preparation of a highly thermally stable heat-conducting copper plate

[0007] Immerse nano-graphene in a fluotitanic acid solution and perform ultrasonic treatment, then immerse it in a 2-hydroxyethylenediaminetetraacetic acid solution, add triethoxysilane and then carry out heating and magnetic stirring, filter and dry to obtain modified nano-graphene. Mix NaBH 4 and an ethanol solution and place it in an ice-water bath for ultrasonic treatment to obtain a NaBH 4 solution. Mix CuCl 2 , modified nano-graphene and an ethanol solution evenly, add polyvinylpyrrolidone and then continuously introduce nitrogen, then place it in an ice-water bath for ultrasonic treatment, and while stirring in a sealed container, dropwise add NaBH 4The solution is left to stand in an ice-water bath and then centrifuged, filtered, and washed repeatedly. Finally, it is dried to obtain copper-coated graphene nanoparticles. The copper-coated graphene nanoparticles are mixed with oxygen-free pure copper powder and cold isostatically pressed. After sintering, a graphene-copper ingot is obtained. Then, horizontal continuous casting, annealing, milling to remove the oxide layer, rolling, and degreasing and cleaning are carried out in sequence to obtain a high-thermal-stability heat-conducting copper plate;

[0008] S2: Pulsed laser deposition of a CuO transition layer on a ceramic substrate

[0009] Copper acetate and an ethanol solution are mixed and placed in a container. After adjusting the pH of the solution, the container is sealed and shaken. After filtration, it is washed successively with deionized water and absolute ethanol, and dried to obtain CuO nanoparticles. After rinsing the ceramic substrate with deionized water, it is successively immersed in an acetone solution, a hydrofluoric acid solution, and deionized water for ultrasonic cleaning, and dried to obtain a clean ceramic substrate. The clean ceramic substrate is used as a substrate, and the CuO nanoparticles are used as a target and placed in the deposition chamber of a pulsed laser deposition system for deposition coating. While depositing the coating, oxygen plasma is introduced into the deposition chamber through a heated electric nozzle to obtain a ceramic substrate with a CuO transition layer;

[0010] S3: Lamination of the high-thermal-stability heat-conducting copper plate and the ceramic substrate with a CuO transition layer

[0011] The copper-clad laminate is assembled in a sandwich structure of high-thermal-stability heat-conducting copper plate - ceramic substrate with a CuO transition layer - high-thermal-stability heat-conducting copper plate and clamped with a quartz plate to obtain a pre-assembled copper-clad laminate. The pre-assembled copper-clad laminate is placed in a vacuum furnace for brazing. The vacuum degree in the vacuum furnace is adjusted, and then two-stage heating brazing is carried out. After cooling, a DBC ceramic copper-clad laminate is obtained.

[0012] Furthermore, the preparation of the high-thermal-stability heat-conducting copper plate in step S1 includes the following steps:

[0013] S1.1: Immerse 2 - 3 parts of nano-graphene in a fluotitanic acid solution with a concentration of 60 - 70%, then use an ultrasonic generator to perform ultrasonic treatment at a frequency of 25 - 30 kHz for 8 - 10 minutes, and then immerse it in a 2-hydroxyethylenediaminetetraacetic acid solution with a concentration of 0.1 - 0.2 mol / L, add 10 - 15 wt% of triethoxysilane, heat to 45 - 60 °C, and then perform magnetic stirring for 3 - 4 hours. After filtration, it is dried to obtain modified nano-graphene;

[0014] S1.2: Mix NaBH 4 and an ethanol solution in a mass ratio of 1:(45 - 50) and place it in an ice-water bath at 0 - 4 °C. Then use an ultrasonic generator to ultrasonically treat for 10 - 15 minutes to obtain a NaBH 4 solution. Mix CuCl 2, the modified nano-graphene and ethanol solution are mixed in a mass ratio of 1:(0.8 - 1.2):(60 - 80) and placed in a container. After adding 0.5 - 0.8 wt% of polyvinylpyrrolidone, nitrogen is continuously introduced for 10 - 15 minutes, and then it is placed in an ice-water bath at 0 - 4 °C and ultrasonicated for 10 - 15 minutes. The container is sealed and 25 - 30 wt% of NaBH 4 solution is added dropwise through a catheter while stirring rapidly. When the addition of the NaBH 4 solution is completed, it is continued to be placed in an ice-water bath at 0 - 4 °C and allowed to stand for 45 - 50 minutes. Then, it is centrifuged at a speed of 10000 - 12000 rpm for 5 - 6 minutes using a centrifuge. After filtration, it is stirred in an ethanol solution for 6 - 8 minutes, and then centrifuged and filtered again. After repeating 2 - 3 times, it is placed in a drying oven and dried at a temperature of 60 - 65 °C for 4 - 6 hours to obtain copper-coated graphene nanoparticles;

[0015] S1.3: The copper-coated graphene nanoparticles and oxygen-free pure copper powder are mixed evenly in a mass ratio of 1:(10 - 12) and loaded into a mold, and cold isostatically pressed at 300 - 500 Mpa to form a shape. Then, it is put into a vacuum sintering furnace for sintering to obtain a graphene-copper ingot. Then, horizontal continuous casting, annealing, milling to remove the oxide layer, rolling, and degreasing and cleaning are carried out in sequence to obtain a high-thermal-stability heat-conducting copper plate.

[0016] Furthermore, the step of pulsed laser deposition of a CuO transition layer on the ceramic substrate in step S2 includes the following steps:

[0017] S2.1: Copper acetate and ethanol solution are mixed in a mass ratio of 1:(40 - 50) and placed in a container. The pH of the solution is adjusted to 10 - 12, and then the container is sealed and oscillated for 20 - 30 minutes. After filtration, it is washed 2 - 3 times with deionized water and absolute ethanol in sequence, and then placed in a vacuum drying oven and dried at a temperature of 60 - 65 °C for 6 - 8 hours to obtain CuO nanoparticles;

[0018] S2.2: The ceramic substrate is rinsed 2 - 3 times with deionized water, then immersed in an acetone solution and ultrasonically cleaned for 15 - 20 minutes, then immersed in a hydrofluoric acid solution with a concentration of 5 - 6% and ultrasonically cleaned for 5 - 6 minutes, and then immersed in deionized water and ultrasonically cleaned for 8 - 10 minutes and then put into a drying oven, and the temperature is adjusted to 100 - 120 °C and dried for 10 - 15 minutes to obtain a clean ceramic substrate;

[0019] S2.3: Introduce oxygen into the gas chamber of the radio frequency plasma generator. The gas chamber is equipped with an electrothermal nozzle, which is connected to the deposition chamber of the pulsed laser deposition system. First, close the electrothermal nozzle valve, set the power of the radio frequency plasma generator to 300 - 500 W, the radio frequency to 13 - 14 MHz. At the same time, use a clean ceramic substrate as the substrate and CuO nanoparticles with a purity of over 99% as the target, and transport them to the deposition chamber of the pulsed laser deposition system. Adjust the distance between the substrate and the target to 6 - 8 cm, pre-pump the pressure of the deposition chamber to 1×10 -4 -2×10 -4 Pa, and set the laser parameters to 180 - 200 mJ / Plus, the laser density to 4 - 5 J / cm 2 . First, turn on the plasma generator to continuously generate oxygen plasma, then heat the temperature of the electrothermal nozzle to 400 - 450 °C, the temperature of the deposition chamber to 500 - 550 °C. Then open the electrothermal nozzle valve, control the flow rate of the oxygen plasma introduced to be 15 - 20 sccm, control the deposition frequency of the pulsed laser deposition system to be 5 - 6 Hz, and control the thickness of the deposited CuO film to be within 50 - 100 μm to obtain a ceramic substrate with a CuO transition layer.

[0020] Furthermore, the lamination of the high thermal stability heat conducting copper plate and the ceramic substrate with a CuO transition layer in step S3 includes the following steps:

[0021] S3.1: Assemble the copper clad laminate in the sandwich structure of high thermal stability heat conducting copper plate - ceramic substrate with a CuO transition layer - high thermal stability heat conducting copper plate, use a quartz plate to clamp it from above and below, and adjust the pressure to 5×10 -3 -7×10 - 3 MPa to obtain a pre-assembled copper clad laminate;

[0022] S3.2: Place the pre-assembled copper clad laminate in a vacuum furnace for brazing, adjust the vacuum degree in the vacuum furnace to 10 -4 -5×10 -4 Pa, then first heat it at a heating rate of 5 - 6 °C / min to 800 - 850 °C, keep it warm for 25 - 30 minutes, then heat it at a heating rate of 2 - 3 °C / min to 920 - 950 °C, and then cool it to room temperature with the furnace to obtain a DBC ceramic copper clad laminate.

[0023] Furthermore, the ethanol solution in step S1.2 is uniformly composed of ethanol and deionized water, and the volume fraction of ethanol is 50 - 60%.

[0024] Furthermore, the gas flow rate of nitrogen in step S1.2 is 40 - 45 mL / min.

[0025] Further, the thickness of the highly thermally stable copper plate prepared in step S1.3 is 0.5 - 1 mm.

[0026] Further, the method for adjusting the pH to 10 - 12 in step S2.1 is to gradually add sodium hydroxide dropwise while stirring.

[0027] Further, the material of the ceramic substrate in step S2.2 is Si 3 N 4 ceramics.

[0028] A DBC ceramic copper clad laminate is prepared by the preparation process of the above - mentioned DBC ceramic copper clad laminate.

[0029] The beneficial effects are as follows: 1. In the process of depositing CuO film on the cleaned ceramic substrate by pulsed laser deposition, oxygen plasma is introduced. Firstly, pure CuO is used to avoid introducing active elements such as Ti and Cr in the traditional process, so that the subsequent DBC ceramic copper clad laminate can be easily etched. Secondly, oxygen plasma is introduced into the deposition chamber. During the deposition process, CuO nanoparticles can collide with oxygen plasma at high speed. This can not only effectively remove the organic impurities on the surface of CuO nanoparticles, enhance their surface activity, reduce the wetting angle between non - oxide ceramics and metals and improve the adhesion, but also the high energy of oxygen plasma can promote the surface rearrangement and crystallization of CuO nanoparticles, forming a more ordered crystal structure. Thus, the defects and voids in the CuO film can be greatly reduced, and a uniform and dense CuO film can be formed, enabling the prepared CuO - coated transition - layer ceramic substrate to better combine with the highly thermally stable copper plate, thereby improving the peel strength and thermal conductivity of the DBC ceramic copper clad laminate.

[0030] 2. In the present invention, a NaBH 4 solution with strong reducibility is first prepared, and then the modified nano - graphene, CuCl 2 and ethanol solution are mixed. After adding polyvinylpyrrolidone, nitrogen is introduced to remove the oxygen in the solution, and then the reducing agent NaBH 4 solution is added dropwise to reduce Cu 2+Perform rapid reduction to grow a nano - copper layer on the surface of modified nano - graphene. The nano - copper layer obtained by this method has excellent adhesion on the surface of modified nano - graphene, which can greatly improve the interfacial compatibility between copper - coated graphene nanoparticles and oxygen - free pure copper powder. At the same time, after the nano - copper layer is grown, polyvinylpyrrolidone can quickly coat the formed copper - coated graphene nanoparticles, preventing their continuous growth and preventing the synthesized copper - coated graphene nanoparticles from being too large, resulting in a decrease in bonding strength. In summary, the components in the high - thermal - stability heat - conducting copper plate can be tightly combined, improving the heat - conducting ability of the subsequent DBC ceramic - coated copper plate. And graphene has a low coefficient of thermal expansion. In summary, it effectively reduces the risk of cracking and peeling of the copper layer at high temperatures, enabling the DBC ceramic - coated copper plate to maintain good peel strength after thermal cycling and having excellent thermal stability.

[0031] 3. In the present invention, nano - graphene is immersed in a fluotitanic acid solution for ultrasonic treatment. The fluotitanic acid reacts chemically with the surface of nano - graphene, introducing fluorine - and titanium - containing functional groups on the graphene surface, thereby providing multiple active sites on the graphene surface and improving its chemical activity. Then, 2 - hydroxyethylenediaminetetraacetic acid solution and triethoxysilane are used for treatment together. The obtained modified nano - graphene can better 2+ adsorb Cu, enabling a more uniform and dense nano - copper layer to grow better on the surface of the subsequent modified nano - graphene, improving the bonding ability between copper - coated graphene nanoparticles and oxygen - free pure copper powder, and thus enhancing the thermal stability of the DBC ceramic - coated copper plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a process flow diagram of the preparation of the DBC ceramic - coated copper plate adopted in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1

[0035] A DBC ceramic - coated copper plate and its preparation process, as Figure 1 shown, includes the following steps:

[0036] S1: Preparation of high - thermal - stability heat - conducting copper plate

[0037] S1.1: Immerse 2 parts of nano-graphene in a fluotitanic acid solution with a concentration of 60%, then use an ultrasonic generator to perform ultrasonic treatment for 8 minutes at a frequency of 25 kHz, and then immerse it in a 2-hydroxyethylenediaminetetraacetic acid solution with a concentration of 0.1 mol / L. Add 10 wt% of triethoxysilane, heat to 45 °C, and then perform magnetic stirring for 3 hours. After filtration and drying, modified nano-graphene is obtained;

[0038] S1.2: Mix NaBH 4 and an ethanol solution at a mass ratio of 1:45 and place it in an ice-water bath at 0 °C. Then use an ultrasonic generator to ultrasonically treat for 10 minutes to obtain a NaBH 4 solution. Mix CuCl 2 , modified nano-graphene and an ethanol solution at a mass ratio of 1:0.8:60 and place them in a container. After adding 0.5 wt% of polyvinylpyrrolidone, continuously introduce nitrogen for 10 minutes, and the gas flow rate of nitrogen is 40 mL / min. Then place it in an ice-water bath at 0 °C and ultrasonically treat for 10 minutes. Seal the container and dropwise add a 25 wt% NaBH 4 solution while quickly stirring. After the NaBH 4 solution is added dropwise, continue to place it in an ice-water bath at 0 °C and let it stand for 45 minutes. Then use a centrifuge to centrifuge at a speed of 10000 rpm for 5 minutes. After filtration, stir it in an ethanol solution for 6 minutes. All the above ethanol solutions are mixed by ethanol and deionized water, and the volume fraction of ethanol is 50%. Then perform centrifugal filtration again. After repeating 2 times, place it in a drying oven and dry at a temperature of 60 °C for 4 hours to obtain copper-coated graphene nanoparticles;

[0039] S1.3: Mix the copper-coated graphene nanoparticles and oxygen-free pure copper powder evenly at a mass ratio of 1:10, load them into a mold and press them into shape by cold isostatic pressing at 300 Mpa. Then put them into a vacuum sintering furnace for sintering to obtain a graphene-copper ingot. Then successively perform horizontal continuous casting, annealing, milling to remove the oxide layer, rolling and degreasing and cleaning to obtain a high-thermal-stability heat-conducting copper plate with a thickness of 0.5 mm.

[0040] S2: Pulse laser deposition of a CuO transition layer on a ceramic substrate

[0041] S2.1: Mix copper acetate and an ethanol solution at a mass ratio of 1:40 and place them in a container. While stirring, gradually add sodium hydroxide to adjust the pH of the solution to 10. Then seal the container and oscillate for 20 minutes. After filtration, wash it 2 times with deionized water and anhydrous ethanol successively, and then place it in a vacuum drying oven and dry at a temperature of 60 °C for 6 hours to obtain CuO nanoparticles;

[0042] S2.2: Rinse the ceramic substrate 2 times with deionized water. The material of the ceramic substrate is Si 3 N4 The ceramic was then immersed in an acetone solution for ultrasonic cleaning for 15 minutes, then immersed in a 5% hydrofluoric acid solution for ultrasonic cleaning for 5 minutes, then immersed in deionized water for ultrasonic cleaning for 8 minutes and then placed in a drying oven, and the temperature was adjusted to 100 °C for drying for 10 minutes to obtain a clean ceramic substrate;

[0043] S2.3: Oxygen was introduced into the gas chamber of the radio frequency plasma generator. The gas chamber was equipped with an electrothermal nozzle, and the electrothermal nozzle was connected to the deposition chamber of the pulsed laser deposition system. First, the electrothermal nozzle valve was closed, the power of the radio frequency plasma generator was set to 300 W, and the radio frequency was set to 13 MHz. At the same time, the clean ceramic substrate was used as the substrate, and CuO nanoparticles with a purity of more than 99% were used as the target and transported into the deposition chamber of the pulsed laser deposition system. The distance between the substrate and the target was adjusted to 6 cm, and the pressure in the deposition chamber was pre-pumped to 1×10 -4 Pa and the laser parameters were set to 180 mJ / Plus, and the laser density was 4 J / cm 2 , First, the plasma generator was turned on to continuously generate oxygen plasma, then the temperature of the electrothermal nozzle was heated to 400 °C, the temperature of the deposition chamber was 500 °C, then the electrothermal nozzle valve was opened, the flow rate of the oxygen plasma was controlled to be 15 sccm, the deposition frequency of the pulsed laser deposition system was controlled to be 5 Hz, and the thickness of the deposited CuO film was controlled to be 50 μm to obtain a ceramic substrate with a CuO transition layer.

[0044] S3: Composite of the high thermal stability heat conducting copper plate and the ceramic substrate with a CuO transition layer

[0045] S3.1: The copper clad laminate was assembled in a sandwich structure of high thermal stability heat conducting copper plate - ceramic substrate with a CuO transition layer - high thermal stability heat conducting copper plate, and the upper and lower parts were clamped with a quartz plate, and the pressure was adjusted to 5×10 -3 MPa to obtain a pre-assembled copper clad laminate;

[0046] S3.2: The pre-assembled copper clad laminate was placed in a vacuum furnace for brazing, and the vacuum degree in the vacuum furnace was adjusted to 10 -4 Pa, then it was first heated at a heating rate of 5 °C / min to 800 °C and held for 25 minutes, then heated at a heating rate of 2 °C / min to 920 °C, and then cooled to room temperature with the furnace to obtain a DBC ceramic copper clad laminate.

[0047] Example 2

[0048] A preparation process of a DBC ceramic copper clad laminate, as Figure 1 shown, includes the following steps:

[0049] S1: Preparation of the high thermal stability heat conducting copper plate

[0050] S1.1: Immerse 3 parts of nano-graphene in a fluotitanic acid solution with a concentration of 60%, then use an ultrasonic generator to perform ultrasonic treatment for 8 minutes at a frequency of 25 kHz, and then immerse it in a 2-hydroxyethylenediaminetetraacetic acid solution with a concentration of 0.1 mol / L. Add 15 wt% of triethoxysilane, heat to 45 °C, and then perform magnetic stirring for 3 hours. After filtration and drying, modified nano-graphene is obtained;

[0051] S1.2: Mix NaBH 4 and an ethanol solution in a mass ratio of 1:50 and place it in an ice-water bath at 0 °C. Then use an ultrasonic generator to ultrasonicate for 10 minutes to obtain a NaBH 4 solution. Mix CuCl 2 , modified nano-graphene and an ethanol solution in a mass ratio of 1:1.2:80 and place them in a container. After adding 0.8 wt% of polyvinylpyrrolidone, continuously introduce nitrogen for 10 minutes, and the gas flow rate of nitrogen is 40 mL / min. Then place it in an ice-water bath at 0 °C and ultrasonicate for 10 minutes. Seal the container and dropwise add a 30 wt% NaBH 4 solution while quickly stirring. After the NaBH 4 solution is added dropwise, continue to place it in an ice-water bath at 0 °C and let it stand for 45 minutes. Then use a centrifuge to centrifuge at a speed of 10000 rpm for 5 minutes. After filtration, stir it in an ethanol solution for 6 minutes. All the above ethanol solutions are mixed with ethanol and deionized water, and the volume fraction of ethanol is 50%. Then perform centrifugal filtration again. After repeating 2 times, place it in a drying oven and dry at 60 °C for 4 hours to obtain copper-coated graphene nanoparticles;

[0052] S1.3: Mix the copper-coated graphene nanoparticles and oxygen-free pure copper powder in a mass ratio of 1:12, load them into a mold and press them into shape by cold isostatic pressing at 300 Mpa, and then put them into a vacuum sintering furnace for sintering to obtain a graphene-copper ingot. Then successively perform horizontal continuous casting, annealing, milling to remove the oxide layer, rolling and degreasing and cleaning to obtain a high-thermal-stability heat-conducting copper plate with a thickness of 0.5 mm.

[0053] S2: Pulsed laser deposition of a CuO transition layer on a ceramic substrate

[0054] S2.1: Mix copper acetate and an ethanol solution in a mass ratio of 1:50 and place them in a container. While stirring, gradually add sodium hydroxide dropwise to adjust the pH of the solution to 10. Then seal the container and shake it for 20 minutes. After filtration, wash it with deionized water and absolute ethanol twice in sequence, and then place it in a vacuum drying oven and dry at 60 °C for 6 hours to obtain CuO nanoparticles;

[0055] S2.2: Rinse the ceramic substrate twice with deionized water. The material of the ceramic substrate is Si 3 N4 The ceramic was then immersed in an acetone solution for ultrasonic cleaning for 15 minutes, then immersed in a 5% hydrofluoric acid solution for ultrasonic cleaning for 5 minutes, then immersed in deionized water for ultrasonic cleaning for 8 minutes and then placed in a drying oven. The temperature was adjusted to 100 °C and dried for 10 minutes to obtain a clean ceramic substrate;

[0056] S2.3: Oxygen was introduced into the gas chamber of the radio frequency plasma generator. The gas chamber was equipped with an electrothermal nozzle, and the electrothermal nozzle was connected to the deposition chamber of the pulsed laser deposition system. First, the electrothermal nozzle valve was closed, the power of the radio frequency plasma generator was set to 300 W, and the radio frequency was set to 13 MHz. At the same time, the clean ceramic substrate was used as the substrate, and CuO nanoparticles with a purity of over 99% were used as the target and transported into the deposition chamber of the pulsed laser deposition system. The distance between the substrate and the target was adjusted to 6 cm, and the pressure in the deposition chamber was pre-pumped to 1×10 -4 Pa and the laser parameters were set to 180 mJ / Plus, and the laser density was 4 J / cm 2 . First, the plasma generator was turned on to continuously generate oxygen plasma, then the temperature of the electrothermal nozzle was heated to 400 °C, the temperature of the deposition chamber was 500 °C, then the electrothermal nozzle valve was opened, the flow rate of the oxygen plasma introduced was controlled to 15 sccm, the deposition frequency of the pulsed laser deposition system was controlled to 5 Hz, and the thickness of the deposited CuO film was controlled to 50 μm to obtain a ceramic substrate with a CuO transition layer.

[0057] S3: Lamination of the high thermal stability heat-conducting copper plate and the ceramic substrate with a CuO transition layer

[0058] S3.1: The copper-clad laminate was assembled in the sandwich structure of high thermal stability heat-conducting copper plate - ceramic substrate with a CuO transition layer - high thermal stability heat-conducting copper plate, and the upper and lower parts were clamped with a quartz plate, and the pressure was adjusted to 5×10 -3 MPa to obtain a pre-assembled copper-clad laminate;

[0059] S3.2: The pre-assembled copper-clad laminate was placed in a vacuum furnace for brazing. The vacuum degree in the vacuum furnace was adjusted to 10 -4 Pa, then it was first heated at a heating rate of 5 °C / min to 800 °C and held for 25 minutes, then heated at a heating rate of 2 °C / min to 920 °C, and then cooled to room temperature with the furnace to obtain a DBC ceramic copper-clad laminate.

[0060] Example 3

[0061] A preparation process of a DBC ceramic copper-clad laminate, as Figure 1 shown, includes the following steps:

[0062] S1: Preparation of the high thermal stability heat-conducting copper plate

[0063] S1.1: Immerse 2 parts of nano-graphene in a fluotitanic acid solution with a concentration of 70%, then use an ultrasonic generator to perform ultrasonic treatment for 10 minutes at a frequency of 30 kHz, and then immerse it in a 2-hydroxyethylenediaminetetraacetic acid solution with a concentration of 0.2 mol / L. Add 10 wt% of triethoxysilane, heat to 60 °C, and then perform magnetic stirring for 4 hours. After filtration and drying, modified nano-graphene is obtained;

[0064] S1.2: Mix NaBH 4 and an ethanol solution in a mass ratio of 1:45 and place it in an ice-water bath at 4 °C. Then use an ultrasonic generator to ultrasonicate for 15 minutes to obtain a NaBH 4 solution. Mix CuCl 2 , modified nano-graphene and an ethanol solution in a mass ratio of 1:0.8:60 and place them in a container. After adding 0.5 wt% of polyvinylpyrrolidone, continuously introduce nitrogen for 15 minutes, and the gas flow rate of nitrogen is 45 mL / min. Then place it in an ice-water bath at 4 °C and ultrasonicate for 15 minutes. Seal the container and drip a 25 wt% NaBH 4 solution drop by drop while stirring rapidly. When the NaBH 4 solution is completely dropped, continue to place it in an ice-water bath at 4 °C and let it stand for 60 minutes. Then use a centrifuge to centrifuge at a speed of 12000 rpm for 6 minutes. After filtration, stir in an ethanol solution for 8 minutes. All the above ethanol solutions are composed of ethanol and deionized water, and the volume fraction of ethanol is 60%. Then perform centrifugal filtration again. After repeating 3 times, place it in a drying oven and dry at 65 °C for 6 hours to obtain copper-coated graphene nanoparticles;

[0065] S1.3: Mix the copper-coated graphene nanoparticles and oxygen-free pure copper powder evenly in a mass ratio of 1:10, load them into a mold, and press them into shape by cold isostatic pressing at 500 Mpa. Then put them into a vacuum sintering furnace for sintering to obtain a graphene-copper ingot. Then successively perform horizontal continuous casting, annealing, milling to remove the oxide layer, rolling and degreasing and cleaning to obtain a high-thermal-stability heat-conducting copper plate with a thickness of 1 mm.

[0066] S2: Pulsed laser deposition of a CuO transition layer on a ceramic substrate

[0067] S2.1: Mix copper acetate and an ethanol solution in a mass ratio of 1:40 and place them in a container. While stirring, gradually add sodium hydroxide to adjust the pH of the solution to 12. Then seal the container and shake it for 30 minutes. After filtration, wash it 3 times with deionized water and anhydrous ethanol successively, and then place it in a vacuum drying oven and dry at 65 °C for 8 hours to obtain CuO nanoparticles;

[0068] S2.2: Rinse the ceramic substrate 3 times with deionized water. The material of the ceramic substrate is Si 3 N4 The ceramic was then immersed in an acetone solution for ultrasonic cleaning for 20 minutes, then immersed in a 5% hydrofluoric acid solution for ultrasonic cleaning for 6 minutes, then immersed in deionized water for ultrasonic cleaning for 10 minutes and then placed in a drying oven, and the temperature was adjusted to 120 °C for drying for 15 minutes to obtain a clean ceramic substrate;

[0069] S2.3: Oxygen was introduced into the gas chamber of the radio frequency plasma generator. The gas chamber was equipped with an electrothermal nozzle, and the electrothermal nozzle was connected to the deposition chamber of the pulsed laser deposition system. First, the electrothermal nozzle valve was closed, the power of the radio frequency plasma generator was set to 500 W, and the radio frequency was set to 14 MHz. At the same time, the clean ceramic substrate was used as the substrate, and CuO nanoparticles with a purity of over 99% were used as the target and transported into the deposition chamber of the pulsed laser deposition system. The distance between the substrate and the target was adjusted to 8 cm, and the pressure in the deposition chamber was pre-pumped to 2×10 -4 Pa and the laser parameters were set to 200 mJ / Plus, and the laser density was 5 J / cm 2 . First, the plasma generator was turned on to continuously generate oxygen plasma, then the temperature of the electrothermal nozzle was heated to 450 °C, and the temperature of the deposition chamber was 550 °C. Then, the electrothermal nozzle valve was opened, the flow rate of the oxygen plasma introduced was controlled to 20 sccm, the deposition frequency of the pulsed laser deposition system was controlled to 6 Hz, and the thickness of the deposited CuO film was controlled to 100 μm to obtain a ceramic substrate with a CuO transition layer.

[0070] S3: Lamination of the high thermal stability heat conducting copper plate and the ceramic substrate with a CuO transition layer

[0071] S3.1: The copper clad laminate was assembled in a sandwich structure of high thermal stability heat conducting copper plate - ceramic substrate with a CuO transition layer - high thermal stability heat conducting copper plate, and the upper and lower parts were clamped with a quartz plate, and the pressure was adjusted to 7×10 -3 MPa to obtain a pre-assembled copper clad laminate;

[0072] S3.2: The pre-assembled copper clad laminate was placed in a vacuum furnace for brazing. The vacuum degree in the vacuum furnace was adjusted to 5×10 -4 Pa, then it was first heated to 850 °C at a heating rate of 6 °C / min and held for 30 minutes, then heated to 950 °C at a heating rate of 3 °C / min, and then cooled to room temperature with the furnace to obtain a DBC ceramic copper clad laminate.

[0073] Comparative Example 1

[0074] Compared with Example 1, the difference in Comparative Example 1 was that oxygen plasma was not introduced into the deposition chamber of the pulsed laser deposition system in step S2.3, and the other steps were the same as those in Example 1. The obtained DBC ceramic copper clad laminate was designated as Comparative Example 1.

[0075] Comparative Example 2

[0076] Compared with Example 1, the difference in Comparative Example 2 is that step S1 is removed, and the subsequent highly thermally stable copper clad plate is replaced with a pure copper clad plate with a thickness of 0.5 mm. The remaining steps are the same as those in Example 1. The prepared DBC ceramic clad plate is denoted as Comparative Example 2.

[0077] Comparative Example 3

[0078] Compared with Example 1, the difference in Comparative Example 3 is that step S1.1 is removed, and the subsequent modified nano-graphene is replaced with nano-graphene. The remaining steps are the same as those in Example 1. The prepared DBC ceramic clad plate is denoted as Comparative Example 3.

[0079] Experiment 1

[0080] Respectively take the DBC ceramic clad plates prepared in the examples and Comparative Example 1, and use a Shimadzu tensile machine to measure the peel strength of their copper clad layers three times. Record the data and make a table as shown in Table 1. It can be seen that the peel strength of the DBC ceramic clad plates prepared in the examples is better than that of Comparative Example 1, which can prove that introducing oxygen plasma during the CuO pulsed laser deposition coating process on the clean ceramic substrate can improve the peel strength of the DBC ceramic clad plate.

[0081] Table 1: Peel Strength of DBC Ceramic Clad Plates

[0082]

[0083] Experiment 2

[0084] Take the DBC ceramic clad plates prepared in the examples, Comparative Example 1 and Comparative Example 2, and cut them into three circular specimens with a diameter of 6 mm respectively. According to GB / T22588-2008 "Flash Method for Measuring Thermal Diffusivity or Thermal Conductivity", measure their thermal conductivity. The experimental temperature is 350±1K. Record the data and make a table as shown in Table 2. It can be seen that the thermal conductivity of the DBC ceramic clad plates prepared in the examples is greater than that of Comparative Example 1 and Comparative Example 2, which can prove that introducing oxygen plasma during the CuO pulsed laser deposition coating process on the clean ceramic substrate can improve the thermal conductivity of the DBC ceramic clad plate, and can also prove that the prepared highly thermally stable copper clad plate can improve the thermal conductivity of the DBC ceramic clad plate.

[0085] Table 2: Thermal Conductivity of DBC Ceramic Clad Plates

[0086]

[0087] Experiment 3

[0088] Take two samples of the DBC ceramic copper clad laminates prepared in the examples, Comparative Example 2 and Comparative Example 3 respectively, and adopt the high and low temperature cycle number test method: set the temperature to be maintained at -50 °C for 15 min, then raise the temperature to 150 °C, and then maintain it at 150 °C for 15 min, and then cool it down to -50 °C. Do N cycles in sequence until the ceramic cracks or the copper layer peels off. Record the number of cycles and make a table as shown in Table 3. It can be seen that the high and low temperature cycle numbers of the DBC ceramic copper clad laminates prepared in the examples are both greater than those of Comparative Example 2 and Comparative Example 3, indicating that the thermal stability of the DBC ceramic copper clad laminates prepared in the examples is better than that of Comparative Example 2 and Comparative Example 3. It can be proved that adding polyvinylpyrrolidone to grow a nano copper layer on the surface of the modified nano graphene can improve the thermal stability of the DBC ceramic copper clad laminate, and it can also be proved that modifying the nano graphene can also improve the thermal stability of the DBC ceramic copper clad laminate.

[0089] Table 3: High and low temperature cycle numbers of DBC ceramic copper clad laminates

[0090]

[0091] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A preparation process of a DBC ceramic copper-clad laminate, characterized in that: The following steps are involved: S1: Preparation of high thermal stability thermal conductive copper plate S1.1: immerse 2-3 portions of nanographene in a 60-70% fluorotitanic acid solution, then perform ultrasonic treatment for 8-10 minutes at a frequency of 25-30kHz using an ultrasonic generator, then immerse in a 0.1-0.2 mol / L 2-hydroxyethylenediaminetetraacetic acid solution, add 10-15wt% triethoxysilane, heat to 45-60°C, then perform magnetic stirring for 3-4 hours, filter and dry to obtain modified nanographene; S1.2: NaBH4 and ethanol solution were mixed in a mass ratio of 1: (45-50) and placed in an ice water bath at 0-4°C, and then ultrasonicated for 10-15 minutes using an ultrasonic generator to obtain a NaBH4 solution. CuCl2, modified nanographene and ethanol solution were mixed in a mass ratio of 1: (0.8-1.2): (60-80) and placed in a container. 0.5-0.8wt% polyvinyl pyrrolidone was added and nitrogen was continuously introduced for 10-15 minutes, and then placed in an ice water bath at 0-4°C and ultrasonicated for 10-15 minutes. minutes, dripping 25-30wt% NaBH4 solution through a catheter in a sealed container, stirring rapidly while dripping, and after the NaBH4 solution is dripped, continue to stand in an ice water bath at 0-4°C for 45-50 minutes, and then centrifuge at a speed of 10000-12000rpm for 5-6 minutes, and then immerse in an ethanol solution and stir for 6-8 minutes after filtering, and then centrifuge and filter again, repeat 2-3 times, and then place in a drying oven at a temperature of 60-65°C for 4-6 hours to obtain copper-coated graphene nanoparticles; S1.3: The copper-coated graphene nanoparticles and oxygen-free pure copper powder are mixed uniformly in a mass ratio of 1: (10-12) and loaded into a mold for cold isostatic pressing at 300-500 MPa, and then placed in a vacuum sintering furnace for sintering to obtain a graphene-copper ingot, and then horizontal continuous casting, annealing, milling to remove the oxide layer, rolling and degreasing and cleaning are carried out in sequence to obtain a high thermal stability thermal conductive copper plate; S2: Pulsed laser deposition of CuO transition layer on ceramic substrate S2.1: copper acetate and ethanol solution are mixed in a container at a mass ratio of 1: (40-50), the pH of the solution is adjusted to 10-12, and then the sealed container is shaken for 20-30 minutes, filtered, washed with deionized water and anhydrous ethanol 2-3 times in sequence, and then placed in a vacuum drying oven at a temperature of 60-65°C for 6-8 hours to obtain CuO nanoparticles; S2.2: Rinse the ceramic substrate with deionized water for 2-3 times, then immerse it in an acetone solution for ultrasonic cleaning for 15-20 minutes, then immerse it in a 5-6% hydrofluoric acid solution for ultrasonic cleaning for 5-6 minutes, then immerse it in deionized water for ultrasonic cleaning for 8-10 minutes, then put it in a drying oven, adjust the temperature to 100-120°C and dry it for 10-15 minutes to obtain a clean ceramic substrate; S2.3: Oxygen is introduced into the gas chamber of the RF plasma generator. The gas chamber is equipped with an electrothermal nozzle, which is connected to the deposition chamber of the pulsed laser deposition system. First, the valve of the electrothermal nozzle is closed, and the power of the RF plasma generator is set to 300-500W and the RF frequency is set to 13-14MHz. At the same time, a clean ceramic substrate is used as a substrate, and CuO nanoparticles with a purity of more than 99% are used as a target material. The distance between the substrate and the target material is adjusted to 6-8cm, and the pressure of the deposition chamber is pre-pumped to 1×10 -4 -2×10 -4 Pa and set the laser parameters to 180-200mJ / Plus and the laser density to 4-5J / cm 2 , first turn on the plasma generator to continuously generate oxygen plasma, then heat the electric heating nozzle to 400-450°C, the deposition chamber temperature to 500-550°C, then open the electric heating nozzle valve, control the oxygen plasma flow rate to 15-20sccm, control the deposition frequency of the pulsed laser deposition system to 5-6Hz, and control the thickness of the deposited CuO film to 50-100μm, to obtain a CuO transition layer-plated ceramic substrate; S3: Composite of high thermal stability thermal conductive copper plate and CuO transition layer ceramic substrate S3.1: The copper clad laminate is assembled in a sandwich structure of high thermal stability thermal conductive copper plate-CuO-plated transition layer ceramic substrate-high thermal stability thermal conductive copper plate. Quartz plates are used to clamp the upper and lower parts, and the pressure is adjusted to 5×10 -3 -7×10 -3 MPa, and a pre-assembled copper clad laminate is obtained; S3.2: Place the pre-assembled copper clad laminate in a vacuum furnace for brazing, and adjust the vacuum degree in the vacuum furnace to 10 -4 -5×10 -4 Pa, then heat it to 800-850°C at a heating rate of 5-6°C / min, keep it warm for 25-30 minutes, then heat it to 920-950°C at a heating rate of 2-3°C / min, and then cool it to room temperature with the furnace to obtain a DBC ceramic copper clad laminate.

2. The preparation process of a DBC ceramic copper-clad laminate according to claim 1, characterized in that: The ethanol solution in step S1.2 is a mixture of ethanol and deionized water, wherein the volume fraction of ethanol is 50-60%.

3. The preparation process of a DBC ceramic copper-clad laminate according to claim 1, characterized in that: The nitrogen gas flow rate in step S1.2 is 40-45 mL / min.

4. The preparation process of a DBC ceramic copper-clad laminate according to claim 1, characterized in that: The thickness of the high thermal stability thermal conductive copper plate prepared in step S1.3 is 0.5-1 mm.

5. The preparation process of a DBC ceramic copper-clad laminate according to claim 1, characterized in that: Step S2.1: The pH value is adjusted to 10-12 by adding sodium hydroxide dropwise while stirring.

6. The preparation process of a DBC ceramic copper-clad laminate according to claim 1, characterized in that: The material of the ceramic substrate in step S2.2 is Si3N4 ceramic.

7. A DBC ceramic copper-clad laminate, characterized in that: The DBC ceramic copper-clad plate is prepared by the preparation process of any one of claims 1 to 6.

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