Preparation and processing method of large-size diamond functional structural member

Abstract

The application relates to a preparation and processing method of a large-size diamond functional structural part, and belongs to the field of diamond materials and processing. A large-size diamond material meeting functional and structural application is formed by welding and laser engraving of multiple pieces of diamond, and the process steps are as follows: 1. a diamond film is prepared by adopting a chemical vapor deposition method, and the diamond film meeting mechanical and thermal performance requirements is cut, annealed, ground, polished and cleaned; the surface roughness of the diamond film after being ground and polished is 0.1-1.5 mu; 2. a transition layer and a welding metal layer are deposited on the surface of the pretreated diamond; 3. the diamond film after being metallized on the surface is assembled and welded by adopting a welding technology, and a large-size diamond composite material is obtained by welding; 4. a method combining three-dimensional structure modeling and laser processing forming is adopted to process the above diamond composite material into a complex structure, three-dimensional structure engraving is realized, and assembly requirements of the functional structural part are met.

Description

Technical Field

[0001] This invention relates to a method for preparing and processing diamond functional structural components, which can obtain large-size, high thermal conductivity diamond functional structural materials to meet the needs of multiple technical fields such as electronics, power, aerospace and nuclear reactors. Background Technology

[0002] Diamond possesses excellent properties such as high thermal conductivity, high carrier mobility, wide bandgap, high optical transmittance, low dielectric constant, low optical absorption, and high chemical stability, making it widely used in high-power devices, semiconductors, aerospace, nuclear reactors, and other fields. Based on the quality of diamond films, they can be classified into tool-grade, heat sink-grade, optical-grade, and electronic-grade. Therefore, diamond's numerous superior properties have led to a wide range of application demands.

[0003] Traditional heat dissipation materials suffer from drawbacks such as low thermal conductivity and high density, failing to meet the requirements of electronic packaging applications. Diamond, however, boasts the highest thermal conductivity in nature, with a theoretical value reaching 2200 W / mK, several times that of commonly used metallic thermal conductive materials. Diamond also exhibits a low coefficient of thermal expansion and specific heat capacity, demonstrating excellent thermal conductivity and good chemical stability at high temperatures. While DC arc jet CVD and microwave plasma CVD equipment are primarily used for growing large-area heat-dissipating diamond films, the currently produced diamond films remain limited in size, with a maximum area of ​​6 inches and a maximum thickness of approximately 1-2 mm after grinding. Neither size nor thickness meets the requirements for most heat dissipation applications. For example, some satellites and other equipment require diamond heat dissipation areas greater than 200 mm². Direct CVD deposition of diamond films is too slow, hindering the fabrication of large-size diamond films. Therefore, large-size diamond films not only require overcoming issues related to uniformity, integrity, and internal defects inherent in the growth process, but also necessitate careful consideration of equipment structure and plasma distribution. Therefore, due to the limited size of synthetic diamonds, which cannot meet the size and functional requirements of designs, researchers have begun to focus on the preparation of diamond composite materials. Currently, many scholars use sintering technology to reinforce high thermal conductivity metal matrices (such as Al and Cu) with diamond particles to prepare composite materials with high thermal conductivity and low coefficient of expansion, becoming a new generation of high-performance packaging and heat dissipation materials. This composite material can solve the problem of large size, but due to the poor surface wettability of diamond and metal alloys and low interfacial bonding strength, the thermal conductivity of the composite material is reduced, and the surface finish of the processed material is affected. Therefore, in response to this situation, it is necessary to develop a method for preparing large-size, high thermal conductivity diamond materials to meet practical application needs. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a method for preparing and processing large-size diamond functional structural components. This method employs welding technology to connect multiple diamond films and uses laser processing technology to fabricate a three-dimensional structure, thereby constructing a large-size, high thermal conductivity diamond three-dimensional structure that meets the application requirements of equipment for functional structural components.

[0005] A method for preparing and processing large-size diamond functional structural components, characterized by connecting small-size diamonds into large-size diamonds and forming large-size diamond functional structural components through laser three-dimensional structural engraving, includes the following steps:

[0006] Step 1: Prepare a diamond film using chemical vapor deposition, and then cut, anneal, grind, polish and clean the diamond film that meets the requirements. The diamond film is ground and polished to a surface roughness of 0.1-1.5 μm.

[0007] Step 2: Using magnetron sputtering, a transition layer is first deposited on the pretreated diamond surface, and then a metal layer is deposited on the surface of the transition layer. This is beneficial to improving the subsequent welding strength. The thickness of the transition layer is 10-500 nm, and the thickness of the metal layer is 100-5000 nm.

[0008] Step 3: Weld multiple diamond films using welding technology. Welding is carried out in a multi-functional heating furnace or tube furnace. Welding parameters such as temperature, pressure and time are set. After welding, large-sized diamond / diamond composite material is obtained.

[0009] Step 4: The diamond composite material is processed with a combination of three-dimensional structural modeling and laser processing. The laser processing program is implemented by software modeling, and then laser processing is used to carve the three-dimensional structure on the diamond surface.

[0010] Furthermore, the diamond film deposited in step 1 is prepared using two methods: DC arc plasma jet CVD and microwave plasma CVD. Both methods are suitable for the preparation of large-area heat-dissipating diamond films. The size of a single diamond film is greater than 70mm×70mm, the thickness is greater than 1mm, the flatness and warpage are both less than 20μm, the thermal conductivity of the diamond is greater than 1200W / mK, and the strength is greater than 200MPa.

[0011] Furthermore, after the deposited diamond film described in step 1 is ground and polished, it needs to undergo vacuum annealing post-treatment at a temperature of 800-1500℃ for 1-12 hours.

[0012] Furthermore, the metal layer film in step 2 is made of metals such as Au, Ag, Cu, Al and Ni, and the transition layer is made of metals such as Cr, Ti and Ti / Pt, which helps to improve the bonding strength between diamond and solder layer.

[0013] Furthermore, the welding method selects welding processes based on the application scenario, using Au / Sn, Sn / Ag / Cu, nano-silver, etc. as solder. Specifically, nano-silver solder is used for low-temperature welding below 300℃, with a welding time exceeding 2 hours; Au / Sn or Sn / Ag / Cu high-temperature solder is used for welding above 300℃, with a pressure greater than 5MPa and a heating rate of 10-20℃ / min; the welding strength is greater than 15MPa.

[0014] Furthermore, the processing of the three-dimensional structure in step 4 includes drilling and grooving processes, wherein the laser processing parameters are: processing current of 60-80A, laser frequency of 200-300Hz, laser pulse width of 450-500ms, and processing speed of 100-300mm / min.

[0015] Furthermore, the engraving of the three-dimensional structure on the diamond surface is performed using a microsecond laser, nanosecond laser, or picosecond laser.

[0016] The key to the implementation of this invention lies in:

[0017] 1. The diamond wafers used in diamond functional structural components are larger than 70mm × 70mm in size and thicker than 1mm. For diamonds smaller than this size, single-wafer deposition is usually sufficient. Only for diamonds larger than this size does single-wafer deposition become difficult, requiring multi-wafer bonding. Especially for achieving structural properties, the thickness of a single wafer is often insufficient, thus necessitating multi-wafer welding.

[0018] 2. Controlling the surface roughness of the diamond film to 0.1-1.5 μm is beneficial for improving the welding quality of diamond functional structural components. To ensure good weldability of diamond functional structural components and meet post-weld dimensional accuracy requirements, the flatness and warpage of large-size diamonds are typically required to be less than 20 μm. Furthermore, to meet final heat dissipation and strength requirements, the thermal conductivity of the diamond must reach above 1200 W / mK, and the strength must reach above 200 MPa.

[0019] 3. Before depositing the metal thin film, the diamond film needs to be subjected to high-temperature annealing to eliminate the internal stress within the film and improve the bonding strength during welding. To eliminate the internal stress caused by point defects such as vacancies and line defects such as dislocations inside the diamond, and to improve the surface condition, the annealing temperature is usually 800-1500℃, and the annealing time is 1-12 hours.

[0020] 4. When performing low-temperature welding on diamond films, nano-silver solder is typically used. To obtain sufficient weld strength, the diamond / diamond composite structure needs to be pre-dried to prevent the interlayer from peeling off due to excessively rapid heating. Additionally, a suitable temperature must be selected, not exceeding 300℃, and the welding time must be ensured to exceed 2 hours to facilitate a tight bond between the diamonds.

[0021] 5. When using high-temperature solder for welding, ensure that a sufficiently high welding pressure is applied, usually above 5 MPa, and that the heating rate is fast enough, usually 10-20℃ / min.

[0022] 6. During the fabrication of complex microstructures, ensuring the machining current is controlled within 60-80A and minimizing the machining speed helps reduce the error between the model dimensions and the actual dimensions. Furthermore, the dimensional machining parameters can be adjusted according to specific dimensional accuracy requirements.

[0023] 7. Diamond three-dimensional structures can be processed not only using microsecond lasers, but also using nanosecond and picosecond lasers.

[0024] The advantages of this invention are:

[0025] 1. The welding method can obtain composite materials with large-size diamond films, which solves the problems of size limitation and long preparation time of thick diamond films that exist when using the CVD method for direct growth.

[0026] 2. Laser engraving technology can perform fine processing on large-sized diamond films after welding based on three-dimensional model structure diagrams, including engraving microstructures of various complex shapes such as surface micropores, micropillars, and microchannels, to meet the needs of different application fields. At the same time, it solves the problem that conventional laser processing cannot achieve complex structure processing based on the adjustment of the worktable.

[0027] 3. This method can be used to obtain large-size diamond functional structural components with various structures, and their thermal conductivity is significantly higher than that of diamond / metal composite materials. Attached Figure Description

[0028] Figure 1 The original diamond sample is shown;

[0029] Figure 2 This shows a thin metal film deposited on the surface of a diamond.

[0030] Figure 3 The large-size diamond composite structure after welding is shown.

[0031] Figure 4 The front and side views of a large-sized diamond functional structural component are shown. Detailed Implementation

[0032] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] 1) Preparation of diamond film

[0035] Diamond films were deposited using a DC arc jet CVD system. Specific process parameters were as follows: a 100mm diameter graphite substrate was dried and placed into the CVD system; the system was evacuated to a vacuum of 0.5Pa, and the following parameters were set: power approximately 23kW, substrate temperature 870℃, methane flow rate 120sccm, hydrogen flow rate 7.5slm, and argon flow rate 3.6slm; after deposition, the diamond film on the substrate was circumferentially cut to obtain a uniform and dense diamond film.

[0036] 2) Grinding, polishing and cutting of diamond films

[0037] The diamond surface was ground and polished using a grinding and polishing machine, resulting in a surface roughness of 1.5 μm. Specific process parameters were as follows: a 200# diamond grinding wheel was used for rough polishing at 40 rpm, followed by a W40# diamond grinding wheel for fine polishing at 25 rpm, with powder and water dripping frequency of 5 seconds per cycle. Finally, the polished diamond film underwent acid washing and ultrasonic cleaning. First, the diamond film was placed in a beaker, and a mixture of concentrated sulfuric acid and concentrated nitric acid in a 3:1 ratio was poured into the beaker. The beaker was then fixed on a heating furnace, boiled, and heated for approximately 30 minutes. After removal, it was ultrasonically cleaned with acetone for 15 minutes, then transferred to anhydrous ethanol for 10 minutes, and finally transferred to deionized water for 10 minutes. It was then removed and dried. After cutting, the dimensions were 70 mm × 70 mm, with a thickness of 1.1 mm after grinding and polishing, a flatness of 15 μm, a warpage of 18 μm, a thermal conductivity of 1250 W / mK, and a strength of 330 MPa.

[0038] 3) Post-annealing treatment of diamond film

[0039] The diamond film from the above steps was annealed in a vacuum annealing furnace at a temperature of approximately 1200℃ for 2 hours.

[0040] 4) Diamond surface metallization treatment

[0041] Two identical diamond films were used, and 50 nm Ti and 500 nm Ag thin films were deposited on their surfaces using magnetron sputtering. The diamond films were placed in a sputtering apparatus and deposited under identical conditions, with the apparatus evacuated to a vacuum of 5 × 10⁻⁶. -4Below Pa; firstly, the target material is pre-sputtered, with a sputtering power of 100W, an argon flow rate of 50 sccm, and a pre-sputtering time of 15 min; then, Ti film deposition is performed, with the argon flow rate adjusted to 23.5 sccm and the sputtering power set to 100W, completing the Ti deposition process; finally, Ag layer deposition is performed, with a sputtering power of 100W and an argon flow rate of 23.5 sccm, completing the Ag deposition process. This yields a diamond film with a metallized layer;

[0042] 5) Welding of large-area diamond composite samples

[0043] The two diamond films from step 4) above were welded using nano-silver welding technology. The welding process involved fixing one diamond film, uniformly applying solder to the diamond surface using screen printing, placing the other diamond film on top of the solder, and finally welding in a heating furnace. Specific process parameters were as follows: first, a pre-drying treatment was performed, i.e., the temperature was raised to 130℃ and held for 30 minutes. After the holding period, a pressure of 0.2 MPa was applied to the diamond / diamond composite sample. Then, the temperature was raised to 300℃ to begin welding, and the holding period continued for 2 hours until welding was completed. After returning to room temperature, the sample was removed. The weld strength was 18.3 MPa.

[0044] 6) Modeling, programming, and laser processing

[0045] First, a large-sized diamond was modeled using SOLIDWORKS software, and graphic features, including micropores, micropillars, and microchannels, were constructed on the diamond surface. Then, the model was post-processed to obtain the machining G-code. Finally, a laser was used for machining, with the following parameters: current of 68A, frequency of 200Hz, pulse width of 450ms, and speed of 100mm / min. The machined diamond had dimensions of 70mm×70mm, a thickness of 2.2mm, and a composite thermal conductivity of 1080W / mK.

[0046] Example 2

[0047] 1) Preparation of diamond film

[0048] Diamond films were deposited using a microwave plasma CVD system. The specific process parameters were as follows: a silicon substrate with a diameter of 110 mm was placed in the microwave plasma CVD system, the system was evacuated to a vacuum of 0.5 Pa, and the parameters were set as follows: power of approximately 4800 W, substrate temperature of 890 °C, methane flow rate of 18 sccm, and hydrogen flow rate of 300 sccm. After deposition, the diamond film on the substrate was circumferentially cut to obtain a uniform and dense diamond film.

[0049] 2) Grinding, polishing and cutting of diamond films

[0050] The diamond surface was ground and polished using a grinding and polishing machine, resulting in a surface roughness of 1 μm. Specific process parameters were as follows: a W40# diamond grinding wheel was used at a speed of 40 rpm, with powder and water droplets applied every 5 seconds. Finally, the polished diamond film underwent acid washing and ultrasonic treatment. First, the diamond film was placed in a beaker, and a mixture of concentrated sulfuric acid and concentrated nitric acid in a 3:1 ratio was poured into the beaker. The beaker was then fixed on a heating furnace, boiled, and heated for approximately 30 minutes. After removal, it was ultrasonically cleaned with acetone for 15 minutes, then transferred to anhydrous ethanol for 10 minutes, and finally transferred to deionized water for 10 minutes. The film was then removed and dried for later use. After cutting, the dimensions were 75 mm × 75 mm, with a polished thickness of 1.0 mm, a flatness of 18 μm, a warpage of 18 μm, a thermal conductivity of 1680 W / mK, and a strength of 250 MPa.

[0051] 3) Post-annealing treatment of diamond film

[0052] The diamond film from the above steps was annealed in a vacuum annealing furnace at a temperature of approximately 900°C for 5 hours.

[0053] 4) Diamond surface metallization treatment

[0054] Three identical diamond films were used, and 100 nm Cr and 1 μm Au thin films were deposited on their surfaces using magnetron sputtering. The diamond films were placed in a sputtering apparatus and deposited under identical conditions, with the apparatus evacuated to a vacuum of 5 × 10⁻⁶. -4 Below Pa; firstly, the target material is pre-sputtered, with a sputtering power of 100W, an argon flow rate of 50 sccm, and a pre-sputtering time of 15 min; then, a Ti film is deposited, with the argon flow rate adjusted to 23.5 sccm and the sputtering power set to 100W, completing the Cr deposition process; finally, an Au layer is deposited, with a sputtering power of 100W and an argon flow rate of 23.5 sccm, completing the Au deposition process. This yields a diamond film with a metallized layer.

[0055] 5) Welding of diamond / diamond composite samples

[0056] Au / Sn was used to weld the diamond films from step 4) above. The welding process involved laying two diamond films flat and fixing them in place. Solder was then evenly applied to the joint area of ​​the diamond surface using screen printing. Another diamond film was then placed on top of the solder at the joint area. Finally, welding was performed in a vacuum tube furnace. The specific process parameters were: welding pressure of 5 MPa, heating rate of 20℃ / min, welding temperature of 800℃, welding time of 30 min, and the sample was removed after being allowed to return to room temperature. The weld strength was 25.6 MPa.

[0057] 6) Modeling, programming, and laser processing

[0058] First, a large-sized diamond was modeled using SOLIDWORKS software, and graphical features were constructed on the diamond surface, mainly including shapes such as micropores, micropillars, and microchannels. Then, the model was post-processed to obtain the machining G-code. Finally, laser machining was performed with the following parameters: current 72A, frequency 300Hz, pulse width 500ms, and speed 200mm / min. The machined diamond measured 150mm × 150mm and had a thickness of 1.0mm (2.0mm in the central welding area, e.g., ...). Figures 1-4 As shown in the figure, the transverse composite thermal conductivity is 1350 W / mK.

[0059] Comparative Example 1

[0060] Currently, the largest diamond film that can be produced by DC arc jet CVD is 150mm in diameter, equivalent to cutting a 106mm × 106mm diamond film. However, the growth rate is very slow, typically not exceeding 3 micrometers per hour. To obtain a 2mm polished diamond film, at least 4mm needs to be grown, resulting in a growth time of over 1000 hours and a high risk of cracking. This invention enables the deposition of diamond films by welding two diamond sheets, achieving a deposition rate of 15 micrometers per hour for a single 75mm × 75mm diamond sheet. The overall rate is twice that of DC arc jet CVD diamond films.

[0061] Comparative Example 2

[0062] Microwave plasma CVD equipment can prepare thin film coatings with a maximum diameter of 200 mm, equivalent to cutting films up to 141 mm × 141 mm. The deposition rate is less than 1 micrometer / hour, and to obtain a 2 mm polished diamond film, the growth time requires more than 2000 hours. This invention can obtain diamond functional structural materials of 150 mm × 75 mm, with a deposition rate of 15 micrometers / hour for a single 75 mm × 75 mm diamond film. The overall rate is four times that of preparing large-size diamond films using microwave plasma CVD equipment.

[0063] Comparative Example 3

[0064] A diamond / Cu composite material with a size of 150mm×150mm was obtained by powder sintering of diamond powder and Cu powder. The thermal conductivity of this composite material reached a maximum of 589W / mK. In comparison, the transverse composite thermal conductivity of the large-size diamond material obtained by this invention is 1350W / mK, which is 2.3 times that of the composite material.

Claims

1. A method for preparing and processing large-size diamond functional structural components, characterized in that... The process involves depositing a transition layer and a metal layer on the surface of a small diamond, then soldering them together to form a large diamond. Finally, a large-sized diamond functional structural component is formed by laser 3D structural engraving. The steps include: Step 1: Prepare a diamond film using chemical vapor deposition, and then cut, anneal, grind, polish and clean the diamond film that meets the requirements. The diamond film is ground and polished to a surface roughness of 0.1-1.5 μm. Step 2: Using magnetron sputtering, a transition layer is first deposited on the pretreated diamond film surface, and then a metal layer is deposited on the transition layer surface. This is beneficial to improving the subsequent welding strength. The thickness of the transition layer is 10-500 nm, and the thickness of the metal layer is 100-5000 nm. The metal layer is selected from Au, Ag, Cu, Al and Ni metals, and the transition layer is selected from Cr, Ti and Ti / Pt metals. Step 3: Welding multiple diamond films using welding technology. The welding process is selected according to the application scenario, using Au / Sn, Sn / Ag / Cu, or nano-silver as solder. Welding is carried out in a multi-functional heating furnace or tube furnace. The solder is evenly applied to the diamond surface by screen printing. Then, another diamond film is placed on top of the solder. Welding temperature, pressure, and time parameters are set. After welding, a large-sized diamond composite material is obtained. Step 4: The diamond composite material is processed with a combination of three-dimensional structural modeling and laser processing. The laser processing program is implemented by software modeling, and then laser processing is used to carve the three-dimensional structure on the diamond surface. The three-dimensional structure carving includes drilling and grooving processes.

2. The method for preparing and processing large-size diamond functional structural components according to claim 1, characterized in that, The diamond film deposition in step 1 is carried out using either DC arc plasma jet CVD or microwave plasma CVD. Both methods are suitable for the preparation of large-area heat-dissipating diamond films with a single diamond size greater than 70mm×70mm, a thickness greater than 1mm, a flatness and warpage of less than 20μm, a thermal conductivity of greater than 1200W / mK, and a strength greater than 200MPa.

3. The method for preparing and processing large-size diamond functional structural components according to claim 1, characterized in that, After the diamond film described in step 1 is ground and polished, it needs to undergo vacuum annealing post-treatment. The annealing temperature is 800-1500℃ and the annealing time is 1-12 hours.

4. The method for preparing and processing large-size diamond functional structural components according to claim 1, characterized in that, The welding process is selected according to the application scenario, using Au / Sn, Sn / Ag / Cu, or nano-silver as solder. Specifically, nano-silver solder is used for low-temperature welding below 300℃, with a welding time exceeding 2 hours; Au / Sn or Sn / Ag / Cu high-temperature solder is used for welding above 300℃, with a pressure greater than 5MPa and a heating rate of 10-20℃ / min; the welding strength is greater than 15MPa.

5. The method for preparing and processing large-size diamond functional structural components according to claim 1, characterized in that, Step 4 describes the processing of the three-dimensional structure, which includes drilling and grooving processes. The laser processing parameters are: processing current of 60-80A, laser frequency of 200-300Hz, laser pulse width of 450-500ms, and processing speed of 100-300mm / min.

6. The method for preparing and processing large-size diamond functional structural components according to claim 1, characterized in that, The engraving of the three-dimensional structure on the diamond surface is performed using a microsecond laser, nanosecond laser, or picosecond laser.

Images