Large-area copper-based diamond heat dissipation plate and normal-pressure continuous preparation process thereof

Abstract

A large-area copper-based diamond heat dissipation plate and a normal-pressure continuous preparation process thereof, relate to the field of metal-based composite material powder metallurgy manufacturing, the process comprises powder pretreatment, wet mixing ultrasonic slurry preparation, cold pressing forming, using 310S steel plate / graphite paper composite separation layer to separate green body and realize stack body stacking sealing packaging in double-layer staggered molybdenum foil package, stack body in three-section temperature zone nitrogen tunnel furnace normal-pressure continuous pre-burning, using pre-burning residual heat to segmentally hot-press the stack body in the hot press, pressure slow cooling, pressure relief and micro plane finishing of finished product post-processing. The porosity of the prepared plate is 0.072% to 0.087%, and the vertical thermal conductivity is 615 to 673 W / (m*K). The present application discards the large vacuum high-temperature cavity, realizes the flow line continuous solid phase preparation, solves the problems of limited size of traditional process forming, high energy consumption of intermittent production and large loss of subsequent processing, and the product is suitable for batch manufacturing of aviation thermal control components, computing server, new energy IGBT and military precision heat dissipation devices.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite powder metallurgy manufacturing, specifically relating to a large-area copper-based diamond heat dissipation plate and its continuous preparation process under normal pressure. Background Technology

[0002] With the rapid development of high power density in fields such as aerospace thermal control components, computing servers, new energy IGBTs, and military precision heat dissipation devices, heat dissipation substrate materials need to possess both excellent thermal conductivity and a controllable coefficient of thermal expansion. Copper-based diamond composite materials, due to their combination of diamond's ultra-high thermal conductivity and copper's good machinability, as well as their coefficient of thermal expansion being well-matched with chip materials, have become a core heat dissipation substrate for high heat flux density scenarios. However, the large-size, high-efficiency, and low-cost industrial fabrication of this material system still faces significant technical bottlenecks.

[0003] Currently, the industrial production of copper-based diamond composite panels mainly relies on the following three types of traditional batch processes: 1. Vacuum hot pressing: This process is limited by the size of the vacuum chamber and the pressure-bearing capacity of the mold, and the forming area of ​​a single sheet is only 1800 cm². 2 The current method is far from meeting the demand for large-area integrated heat dissipation substrates for high-power devices. Furthermore, the production process involves repeated heating and cooling, resulting in extremely high energy consumption. The resulting product is a thick blank, requiring subsequent wire cutting and extensive grinding, but diamond particles cause severe wear on the cutting tools, leading to high processing costs. After cutting, the substrate is prone to warping and deformation, necessitating an additional leveling process, further lengthening the process and increasing equipment investment. Therefore, this method is only suitable for the production of small-batch, small-to-medium-sized products.

[0004] 2. Spark Plasma Sintering: This method relies on pulsed current to achieve rapid densification, but it is limited to laboratory-scale small-sample preparation due to the constraints of electrode and mold size. More importantly, when the diamond volume filling exceeds 65%, the conductivity uniformity of the preform deteriorates sharply, resulting in a large number of residual internal micropores, making it difficult to obtain high-density large-area plates, and thus the feasibility of industrial mass production is extremely low.

[0005] 3. High-Temperature Melt Infiltration: This process typically involves molding temperatures exceeding 1100℃. At this temperature, the diamond surface is prone to graphitization, significantly increasing interfacial thermal resistance and weakening the thermal conductivity of the composite material. Furthermore, controlling the uniformity of molten copper wetting of the diamond preform is difficult, often resulting in localized material shortages and internal closed-cell defects. For large-size plates, microcracks easily develop in the corner areas due to thermal stress during cooling, leading to large fluctuations in product yield and poor stability. Therefore, this technology is currently only suitable for the production of low-end, small heat sink components.

[0006] To address the aforementioned issues, existing patents and literature do not provide effective systematic solutions. For example, patent CN104630527B discloses a process based on cladding hot isostatic pressing, with forming temperatures as high as 1100–1350°C. Densification is achieved through copper molten infiltration, but the cladding molybdenum foil softens easily at high temperatures, making it difficult to ensure structural stability during the forming process of large-size plates. Furthermore, other reports involving vacuum sintering or powder coating only disclose single steps and lack complete continuous preparation schemes for large-area plates. Meanwhile, research on atmospheric pressure sintering of aluminum-based composite materials or ceramic materials is incompatible with copper-based diamond systems in terms of processing objects and forming conditions, making it difficult to provide technical inspiration for the research of this invention.

[0007] In summary, existing copper-based diamond composite material sheet manufacturing technologies have significant shortcomings in three core dimensions: large-size integrated molding, continuous and efficient production, and low-energy operation. They have not yet formed a system capable of handling large areas (15,000–30,000 cm²). 2 There is a need for an industrial-scale process route that meets the requirements of high density, low interfacial thermal resistance, and high yield. Therefore, there is an urgent need to develop a new preparation method that can overcome the above-mentioned multiple limitations. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a large-area copper-based diamond heat dissipation plate and its continuous preparation process under normal pressure. This solves the problems of small forming size, low single-batch output, large cutting loss, high energy consumption in intermittent production, and expensive investment in large-scale vacuum equipment in traditional processes. It can produce plates of tens of thousands of square centimeters without the need for a sealed high-temperature vacuum chamber.

[0009] To achieve the above objectives, the technical solution adopted by this invention is: a continuous atmospheric pressure manufacturing process for large-area copper-based diamond heat dissipation plates, comprising the following steps: S1, Powder pretreatment: Diamond powder is acid-washed and chromium-plated, then mixed with oxygen-free copper powder to prepare composite powder; S2, Wet mixing: The prepared composite powder is dispersed in anhydrous ethanol and stirred to remove bubbles; S3, Fabrication and Cold Pressing: The degassed slurry is spread in a thin layer in the screw fabrication machine, and then the slurry is pressed layer by layer into a self-supporting green body using a segmented cold pressing process. The bending strength of the green body after molding is not less than 5MPa. S4, Stacking and Sealing of the Stack: 310S steel plates and graphite paper are placed between the obtained self-supporting green blanks to isolate the blanks, and the stacked stack is put into a double-layer staggered molybdenum foil sleeve. The corners and stress edges of the double-layer staggered molybdenum foil sleeve are thickened and rounded, and micro-beam plasma welding is used. After welding, vacuum sealing is performed and helium detection is completed. S5, Atmospheric Pressure Continuous Pre-firing: The stack body that passed the leak test in the previous step is sent into the tunnel furnace and subjected to atmospheric pressure continuous pre-firing in a nitrogen atmosphere. S6, Waste Heat Segmented Hot Pressing: The preset temperature range is 790~830℃; the high-temperature stacks after continuous pre-firing are transferred to the hot press, wherein the stacks with the billet temperature higher than the preset temperature range are transferred to the segmented pressing process, the stacks with the billet temperature within the preset temperature range are transferred to the tunnel furnace for reheating, and the billets with the billet temperature lower than the preset temperature range are scrapped; the segmented pressing process includes two stages: low-pressure pressing and high-pressure pressing. The purpose of low-pressure pressing is to stretch the stacks, and high-pressure pressing completes the densification of the billets. S7, pressurized slow cooling and depressurization: pressure is maintained and furnace cooling is performed throughout the pressing process. After the temperature drops to the preset temperature, additional pressure is maintained, and finally the pressure is slowly released. After cooling, a second helium test is performed. After passing the test, the molybdenum foil wrapping is removed to obtain the plate blank. S8, Post-processing of finished product: The surface of the blank plate is micro-grinded to remove the thin oxide layer on the surface, and the finished copper-based diamond heat dissipation plate is obtained.

[0010] Specifically, in step S1, the volume fraction of diamond powder in the composite powder is 68-75 vol%, and the diamond powder is tertiary graded diamond. The volume ratio of the particles inside the tertiary graded diamond is large particles: medium particles: small particles = 72:18:10, and the thickness of the chromium interface layer on the diamond surface is 0.15-0.35 μm.

[0011] Specifically, in step S2, ultrasonic stirring and degassing with a power of 300-320W is used for 40-50 minutes.

[0012] Specifically, in step S3, the thickness of a single layer of material is 2-5 mm; the cold pressing pressure is set to 210-230 MPa, and the single pressure holding time is 8-10 min.

[0013] Specifically, in step S4, the thickness of the 310S steel plate is 0.5-2mm, the thickness of the graphite paper is 0.1-0.5mm, and the interlayer spacing is 2-10mm; the thickness of a single layer of molybdenum foil in the double-layer staggered molybdenum foil sheath is 0.1-0.3mm, and the staggered overlap width is ≥10mm; when placing the green blanks, 3-6 green blanks are placed in a single stack, and when the diamond ratio in a single stack is 75 vol%, no more than 3 green blanks are placed, and when the diamond ratio is otherwise, a maximum of 6 green blanks are placed.

[0014] Specifically, in step S5, the nitrogen flow rate is 8-10 L / min, the pre-firing temperature is set to 850-870℃, and the holding time is 40-45 min; before pre-firing, the temperature rise curve in the tunnel furnace is calibrated.

[0015] Specifically, in the segmented pressing of step S6, the pressure of low-pressure pressing is 35-45 MPa and held for 15-25 seconds; the pressure of high-pressure pressing is the target pressure, and the target pressure of the stack with a diamond ratio of 72 vol% is 80-88 MPa, and the target pressure of the stack with a diamond ratio of 75 vol% is 90-95 MPa.

[0016] Specifically, in step S7, the cooling rate is 5-15℃ / min, and after the temperature drops to 750℃, the pressure is maintained for an additional 20 seconds before slowly depressurizing.

[0017] Specifically, ceramic brackets are used for transporting the stacks during the manufacturing process.

[0018] This invention further proposes a large-area copper-based diamond heat dissipation plate, prepared by the above-described atmospheric pressure continuous manufacturing process. The plate has a porosity of 0.072%–0.087%, a vertical thermal conductivity of 615–673 W / (m·K), and a total forming area of ​​15,000–30,000 cm² per stack in a single pressing. 2 The coefficient of thermal expansion of the plate can be adjusted by the diamond volume fraction to meet the requirements of chip packaging.

[0019] This invention develops a continuous solid-state molding process for heat dissipation substrates of high-power devices, which differs from the three traditional intermittent processes of vacuum hot pressing, SPS, and melt infiltration. The molding area of ​​a single substrate is 5000 cm². 2 The total forming area of ​​a single stack in a single pressing can reach 15,000 to 30,000 cm². 2 The products are suitable for mass production of aerospace thermal control components, computing server heat dissipation substrates, new energy IGBTs, and military precision heat dissipation devices.

[0020] This invention can solve the following problems: 1. Based on the idea of ​​copper-based diamond solid-phase molding, this invention solves the problems of small molding size, low single batch output, large cutting loss, high energy consumption of intermittent production, and expensive investment in large vacuum equipment in traditional processes. It can produce tens of thousands of square centimeters of plates without the need for a sealed high-temperature vacuum chamber.

[0021] 2. Limitations of Traditional Processes: In existing technologies, 75 vol% high diamond ratio blanks have relatively weak rigidity, and the number of blanks stacked in a single pile should not be too large; if the forming area of ​​a single sheet exceeds 5000 cm²... 2 Or the total forming area of ​​a single stack exceeds 30,000 cm². 2 At this time, it is necessary to widen the hot press workbench and modify the supporting tooling.

[0022] The technical principle involved in this invention is analyzed as follows: 1. This invention employs a double-layer staggered molybdenum foil with nitrogen solid-phase pre-firing at 850-870℃ under normal pressure to form a double airtight barrier. The molybdenum foil sheath is thickened at the corners and rounded with an R8 radius to eliminate stress concentration. The molybdenum foil maintains suitable plasticity within the 830-870℃ range, remaining below the melting point of copper throughout the process, thus eliminating the need for continuous operation of a vacuum system. The high-temperature melting and infiltration environment above 1100℃ described in patent CN104630527B easily leads to softening of the molybdenum foil, making it unable to maintain its sealed shape; therefore, this sealing structure cannot be applied using the melting and infiltration process approach. In this invention, "normal pressure" specifically refers to the tunnel furnace cavity being a nitrogen atmosphere at normal pressure. The workpiece relies on the pre-evacuation of the molybdenum foil sheath to isolate the atmosphere, eliminating the need to place the entire workpiece in a large, sealed vacuum chamber.

[0023] 2. In this invention, the 310S stainless steel plate combined with graphite paper provides layered isolation for the green body. The 310S stainless steel has strong high-temperature creep resistance, allowing pressure to be evenly transmitted to each green body. The graphite paper acts as a buffer, preventing the hard edges of the green body from piercing the molybdenum foil. Only the combination of these two materials can achieve simultaneous pressing of multiple pieces. Using graphite paper alone can easily lead to high-temperature pressure loss, while using ordinary steel plate alone can easily lead to high-temperature deformation. Only the combination of the two can ensure uniform stress distribution throughout the stack and prevent the molybdenum foil from being scratched by the edges of the plate.

[0024] 3. Traditional sintering and pressurization are carried out simultaneously in a vacuum furnace, consuming a large amount of energy for each heating and cooling cycle. This invention uses a tunnel furnace with uninterrupted feeding, allowing the billet to be hot-pressed directly using residual heat while still carrying its high temperature. Molybdenum foil exhibits a significant decrease in plasticity below 790℃, and low-temperature pressing easily produces minute air leakage cracks. Therefore, a graded temperature control standard is established to prevent oxidation and porosity defects from the source: billets below 790℃ are scrapped, reheated in the furnace between 790 and 830℃, and pressed only above 830℃. Simultaneously, a segmented gradient hot-pressing process is employed: first, low-pressure stretching to release thermal stress, followed by high-pressure densification, reducing energy loss from repeated heating and forming an assembly line operation. Simply using low temperature or direct high pressure will cause cladding cracking and internal porosity concentration.

[0025] 4. After cooling to 750℃, the pressure is released after a delay. Combined with the whole process of cold preservation, the overall density of the board is stabilized. This process works in conjunction with molybdenum foil sealing and gradient pressurization.

[0026] Therefore, the beneficial effects of this invention are: 1. Significantly breaking through the size bottleneck and achieving ultra-large-scale integrated molding. This invention breaks through the size limitations of traditional molds and vacuum chambers, achieving a single sheet molding area of ​​5000 cm². 2 A single stack can simultaneously produce 3 to 6 boards, with a total formed area of ​​15,000 to 30,000 cm². 2 The molding area is increased by 8 to 16 times compared with the traditional process, which can meet the needs of ultra-large heat dissipation substrates.

[0027] 2. Enables continuous assembly line operation, significantly boosting production efficiency. This invention employs continuous assembly line production, allowing multiple blanks to be processed simultaneously in a single stack, greatly improving equipment utilization and significantly increasing production efficiency.

[0028] 3. Significantly reduced energy consumption and outstanding low-carbon advantages. This invention eliminates the need for long-term operation of high-power vacuum units. Tests show that, under the same production capacity conditions, the overall energy consumption of this process can be reduced by more than 35% compared to the traditional intermittent vacuum hot pressing process (this data comes from pilot-scale simulation and experimental results, and may fluctuate due to equipment operating conditions), significantly reducing carbon emissions and electricity costs per unit product, aligning with the trend of green manufacturing development.

[0029] 4. Near-net-shape forming significantly reduces subsequent processing and internal stress issues. Product thickness can be precisely controlled to achieve near-net-shape forming, eliminating the traditional cutting process for thick blanks. This avoids rapid wear of the diamond tool and eliminates warping deformation caused by internal stress during cutting. No additional leveling treatment is required, greatly shortening the process flow and reducing processing costs.

[0030] 5. Excellent density and uniform and stable thermal conductivity. The porosity inside the board is stably controlled below 0.09%, resulting in a high-density composite material structure. For large-area boards, the spatial uniformity of its thermal conductivity is superior to that of traditional intermittent processes, effectively ensuring the heat dissipation consistency of large-size heat dissipation substrates across the entire area. The coefficient of thermal expansion of the board can be adjusted with the diamond content to meet the matching requirements of chip packaging.

[0031] 6. Low equipment requirements and significantly reduced industrialization barriers. The entire process only requires an atmospheric pressure tunnel furnace and a conventional hot press, eliminating the need for expensive high-temperature vacuum sintering equipment or high-power pulse power supplies. This greatly reduces equipment investment and maintenance costs, enabling small and medium-sized enterprises to achieve large-scale production and facilitating technology promotion and industrial expansion.

[0032] 7. The entire process consists of four parts: double-layer molybdenum foil sealing, 310S / graphite composite separator, continuous pre-firing at atmospheric pressure, and graded temperature control and gradient pressurization. The absence of any one of these parts will result in product scrap, and the same effect cannot be achieved by simply adjusting conventional process parameters. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of the atmospheric pressure continuous preparation process of the large-area copper-based diamond heat dissipation plate described in this invention. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the embodiments, but this should not be construed as limiting the invention in any way.

[0035] The atmospheric pressure continuous manufacturing process of the large-area copper-based diamond heat dissipation plate of the present invention includes the following steps: Step 1: Powder pretreatment Three-stage graded diamond is selected, wherein the volume ratio of internal particles of the three-stage graded diamond is large particles: medium particles: small particles = 72:18:10. After acid pickling and impurity removal, diamond is deposited with a 0.15-0.35 μm chromium layer by magnetron sputtering, and then mixed with bimodal particle size oxygen-free copper powder to obtain composite powder, wherein the volume fraction of diamond is 68-75 vol%; Step 2: Wet mixing Disperse the prepared composite powder in absolute ethanol, perform ultrasonic stirring and degassing at a power of 300-320 W for a total duration of 40-50 min to eliminate air bubbles inside the slurry. In summer with high temperature, the degassing time can be shortened by 10 min; in winter with low temperature, the degassing time can be extended by 15 min; Step 3: Cloth laying and cold press molding Lay the degassed slurry obtained in the previous step in thin layers in a screw fabric laying machine, with a single laying thickness of 2-5 mm. Then, a segmented cold press molding process is adopted to press the laid slurry layer by layer into self-supporting green bodies. The cold pressing pressure is set to 210-230 MPa, and the single pressure holding time is 8-10 min. The bending strength of the green body after molding is not less than 5 MPa, which can be independently supported and stacked, and the molding area of a single green body is 5000 cm 2 .

[0036] Step 4: Stacking, sealing and packaging of the stack Between the green bodies, 310S steel plates and graphite paper are alternately placed, wherein the thickness of the 310S steel plate is 0.5-2 mm, the thickness of the graphite paper is 0.1-0.5 mm, the interlayer spacing is 2-10 mm, and backing plates with warpage greater than 0.2 mm are prohibited from reuse. The whole stack is loaded into a double-layer staggered molybdenum foil mantle, the thickness of a single molybdenum foil layer is 0.1-0.3 mm, and the staggered lapping width is ≥10 mm. The corners and stressed edges of the mantle are thickened and stamped with R8 rounded corners. Microbeam plasma welding is adopted, after welding, vacuum is pumped to 5×10 -3 Pa, then seal welding is performed and helium inspection is completed. The qualified criterion is that the helium leak detection rate is ≤1×10 -9 Pa·m 3 / s. 3-6 green bodies are placed in a single stack, and the molding area of a single green body is 5000 cm 2 ; when the diamond ratio in a single stack is 75 vol%, the rigidity of the green body is relatively weak. If the number of green bodies in a single stack is more than 3, defects such as green body compression deformation, mantle damage, finished product warpage, and uneven density are prone to occur, so no more than 3 green bodies are placed; when the diamond ratio is other values, up to 6 green bodies can be placed. Ceramic brackets are used for stack transfer. The ceramic brackets are high temperature resistant, do not react with molybdenum foil and stack materials under high temperature conditions, and avoid abrasion of the bottom molybdenum foil.

[0037] Step 5: Continuous pre-sintering at atmospheric pressure Leak-tested stacks are sent to a three-zone nitrogen tunnel furnace for continuous pre-firing at atmospheric pressure. Nitrogen is continuously introduced into the tunnel furnace as a protective atmosphere at a flow rate of 8–10 L / min. The pre-firing temperature is set at 850–870℃, and the holding time is 40–45 min to complete the solid-phase pre-firing. Before production, thermocouples are pre-embedded in the tunnel furnace to calibrate the furnace temperature rise curve and reduce the adverse effects of temperature differences between the two ends and the middle of the furnace on product performance consistency. In this step, "atmospheric pressure" refers to the atmospheric pressure of nitrogen in the tunnel furnace cavity, and the workpiece relies on the pre-vacuuming of the molybdenum foil sheath to isolate the atmosphere.

[0038] Step 6: Segmented hot pressing using waste heat After continuous pre-firing, the high-temperature stacks are transferred to the hot press. First, an infrared thermometer is used to measure the temperature of the stacks to confirm whether the billet temperature is within the suitable pressing temperature range. For those that meet the temperature standard (billet temperature ≥ 830℃), they immediately proceed to the segmented pressing process; for those that do not meet the standard temperature range (billet temperature 790~830℃), they are promptly sent back to the tunnel furnace for reheating; and for those that are too cold (billet temperature below 790℃), they are directly scrapped.

[0039] During segmented pressing, a two-stage pressurization process is employed: first, a low pressure of 35–45 MPa is applied and held for 15–25 seconds to allow the bulk material to expand; then, the pressure is increased to the target value and maintained at that temperature and pressure to allow the billet to achieve final densification with the assistance of residual heat. For bulk materials with a diamond content of 72 vol%, a target pressure of 80–88 MPa is used; for bulk materials with a diamond content of 75 vol%, a target pressure of 90–95 MPa is used.

[0040] The entire hot pressing process relies on the residual heat from preheating, eliminating the need for additional heating and effectively reducing energy consumption and time costs in the hot pressing stage.

[0041] Step 7: Slowly cool and depressurize under pressure Throughout the pressing process, pressure is maintained while the furnace is cooled, with a cooling rate of 5–15℃ / min. After the temperature drops to 750℃, an additional 20 seconds of pressure is maintained before slow depressurization. A second helium leak test is then performed after cooling to screen for high-temperature, easily leaking workpieces. The helium leak rate is ≤1×10⁻⁶. -9 Pa・m 3 / s is deemed qualified. After passing the qualification, the molybdenum foil wrapping is removed to obtain the plate blank.

[0042] Step 8: Post-processing of finished products The surface of the blank plate is micro-grinded to remove the thin oxide layer on the surface, resulting in the finished copper-based diamond heat dissipation plate.

[0043] In the above preparation process, ceramic brackets are used for the transfer stack to avoid wear on the bottom molybdenum foil.

[0044] The copper-based diamond heat sink plate prepared by the above method has a porosity of 0.072%–0.087%, a vertical thermal conductivity of 615–673 W / (m·K), and a single plate forming area of ​​5000 cm². 2 A single stack can form 3 to 6 boards at a time, with a total forming area of ​​15,000 to 30,000 cm². 2 The coefficient of thermal expansion of the sheet material is adjustable with the volume fraction of diamond, making it suitable for chip packaging.

[0045] Examples 1-3 below describe the preparation of copper-based diamond heat dissipation plates according to the above preparation method, and Comparative Examples 1-5 further illustrate the preparation of copper-based diamond heat dissipation plates using conventional processes. Through performance comparison of the experimental examples and comparative examples, the superiority of the process described in this invention is further explained.

[0046] Example 1: Preparation of diamond with a volume fraction of 72 vol%, a single stack of 4 diamonds with an area of ​​5000 cm² 2 The board material.

[0047] Its process parameters are as follows: (1) In the powder pretreatment, the thickness of the diamond chromium layer is 0.22 μm; (2) In wet mixing, the ultrasonic power is 300W and the mixture is stirred for 45 minutes; (3) During cold pressing, the pressure is 220 MPa and the holding pressure is 8 min; (4) During continuous pre-firing at atmospheric pressure, the nitrogen flow rate is 8L / min and the pre-firing temperature is 860℃; (5) During the residual heat segmented hot pressing, the billet temperature is 842℃, and the pressure is increased to 85MPa after 20s at a low pressure of 40MPa. (6) During the pressurized slow cooling and depressurization process, the pressure is maintained at 750℃ for 20 seconds before depressurization; (7) The porosity of the finished product is 0.072% and the thermal conductivity is 650 W / (m·K).

[0048] Example 2: Preparation of diamond with a volume fraction of 68 vol%, with a single stack of 6 diamonds having an area of ​​5000 cm². 2 The board material.

[0049] The process parameters differ from those in Example 1 as follows: (1) In the powder pretreatment, the thickness of the diamond chromium layer is 0.18 μm; (2) In wet mixing, stir at room temperature for 40 minutes; (3) During cold pressing, the pressure is 210 MPa and the pressure is held for 8 minutes; (4) During continuous pre-firing at atmospheric pressure, the pre-firing temperature is 850℃; (5) During the residual heat segmented hot pressing, the billet temperature is 836℃ and the low pressure is 38MPa; (6) The porosity of the finished product is 0.078% and the thermal conductivity is 615 W / (m·K).

[0050] Example 2: Preparation of diamond with a volume fraction of 75 vol%, with a single stack of 3 diamonds having an area of ​​5000 cm². 2 The board material.

[0051] The process parameters differ from those in Example 1 as follows: (1) In the powder pretreatment, the thickness of the diamond chromium layer is 0.28 μm; (2) In wet mixing, the ultrasonic power is 320W and the mixture is stirred for 50 minutes; (3) During cold pressing, the pressure is 230 MPa and the pressure is held for 10 min; (4) During continuous pre-firing at atmospheric pressure, the nitrogen flow rate is 10 L / min and the pre-firing temperature is 870 °C; (5) During the residual heat segmented hot pressing, the billet temperature is 845℃, and the pressure is increased from 42MPa to 92MPa after the low pressure. (6) The porosity of the finished product is 0.087% and the thermal conductivity is 673 W / (m·K).

[0052] Five comparative examples are set up below.

[0053] Comparative Example 1: Standard sample prepared using conventional vacuum hot pressing The raw materials and coating parameters are the same as in Example 1. The mixed powder is loaded into a mold, and a single piece with an area of ​​1800 cm² is prepared by single-mold single-step molding. 2 The blank is formed by intermittent vacuum hot pressing and sintering, and then cut and ground to obtain the finished product. The porosity of the obtained finished sheet is 0.061%, and the thermal conductivity is 648 W / (m·K). This process has high overall energy consumption, cannot be produced continuously, and the sheet is prone to warping and deformation after cutting, requiring additional leveling treatment. The product yield and production efficiency are significantly limited.

[0054] Comparative Example 2: Eliminating gradient pressure and directly high-pressure molding This comparative example mainly adopts the basic steps and parameters of Example 1, but the difference is that in the sixth step of residual heat segmented hot pressing, gradient pressurization is no longer used, the step of low-pressure stretching of the stack is cancelled, and a higher target pressure is directly used for pressing. The porosity of the final obtained plate is 0.213%, and the internal pore distribution is uneven, with a thermal conductivity of only 576 W / (m・K), which cannot meet the actual requirements.

[0055] Comparative Example 3: Single-layer right-angled molybdenum foil, without double-layer or rounded corner thickening. This comparative example mainly adopts the basic steps and parameters of Example 1, but the difference is that in the fourth step of stacking and sealing the packaging, a single-layer right-angle molybdenum foil sleeve is used. The corners and stress edges of the sleeve are no longer thickened and rounded, which leads to tearing of the molybdenum foil corners during the pressing process, and air intrusion and oxidation. The final prepared plate has a porosity of 0.568% and a thermal conductivity of 520W / (m・K), and the product is unusable.

[0056] Comparative Example 4: Vacuum Intermittent Pre-firing This comparative example mainly adopts the basic steps and parameters of Example 1, but the difference is that in the fifth step of continuous pre-firing at atmospheric pressure, the atmospheric pressure tunnel furnace is eliminated and replaced with vacuum intermittent pre-firing. Therefore, continuous production capacity is lost, the cycle time per batch is extended by 112%, and energy consumption increases by 38%.

[0057] Comparative Example 5: Temperature interlock removed, low-temperature pressing at 770℃ This comparative example mainly adopts the basic steps and parameters of Example 1, but the difference is that in the residual heat segmented hot pressing in the sixth step, the blank at a temperature of 770°C is pressed. Due to the insufficient plasticity of the molybdenum foil at low temperature, micro-leakage occurs, resulting in a final plate porosity of 0.336% and a thermal conductivity of 552 W / (m・K). The yield rate of a single batch is less than 40%.

[0058] Table 1 shows a comparison of the product performance and production indicators of Examples 1-3 and Comparative Examples 1-5.

[0059] Table 1. Comparison of performance and production indicators between the examples and comparative examples.

[0060] As can be seen from the comparison results in Table 1, compared with the traditional vacuum hot pressing process, the present invention has obvious advantages in terms of molding size, production capacity, and energy consumption. Furthermore, the removal of some core processes in the process of the present invention will lead to a significant deterioration in product performance. Therefore, it is proven that the processes involved in the entire process of the present invention cannot be separated in order to solve the problems of small molding size, low single-batch output, large cutting loss, high energy consumption of intermittent production, and expensive investment in large vacuum equipment in the traditional process.

[0061] Based on the above description and analysis, the overall process of the atmospheric pressure continuous manufacturing process of the large-area copper-based diamond heat dissipation plate involved in this invention is as follows: Figure 1 As shown, and summarized as follows: Diamond pickling and chromium plating followed by mixing with bimodal copper powder → ultrasonic slurry preparation and degassing with anhydrous ethanol → screw-driven thin-layer cold pressing to form a single 5000cm block. 2Green billet → 310S steel plate and graphite paper are stacked in layers, then wrapped with double-layered staggered R8 rounded corner molybdenum foil and welded with helium detection seal → the stack is sent into a normal pressure nitrogen tunnel for continuous pre-firing → high-temperature billet transfer press, low-pressure expansion + high-pressure segmented hot pressing with corresponding billet temperature grade control → pressure is maintained throughout the process and slowly cooled to 750℃ with a delayed pressure release, the molybdenum foil is removed to obtain the blank → micro-surface grinding to obtain a single 5000cm block 2 Integrated high thermal conductivity copper-based steel plate, a single stack can produce 3 to 6 plates of this specification at the same time.

[0062] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the specific implementation of the present invention with reference to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the pending claims.

Claims

1. A continuous atmospheric pressure manufacturing process for large-area copper-based diamond heat dissipation plates, characterized in that, Includes the following steps: S1, Powder pretreatment: Diamond powder is acid-washed and chromium-plated, then mixed with oxygen-free copper powder to prepare composite powder; S2, Wet mixing: The prepared composite powder is dispersed in anhydrous ethanol and stirred to remove bubbles; S3, Fabrication and Cold Pressing: The degassed slurry is spread in a thin layer in the screw fabrication machine, and then the slurry is pressed layer by layer into a self-supporting green body using a segmented cold pressing process. The bending strength of the green body after molding is not less than 5MPa. S4, Stacking and Sealing of the Stack: 310S steel plates and graphite paper are placed between the obtained self-supporting green blanks to isolate the blanks, and the stacked stack is put into a double-layer staggered molybdenum foil sleeve. The corners and stress edges of the double-layer staggered molybdenum foil sleeve are thickened and rounded, and micro-beam plasma welding is used. After welding, vacuum sealing is performed and helium detection is completed. S5, Atmospheric Pressure Continuous Pre-firing: The stack that passed the leak test in the previous step is sent into the tunnel furnace and subjected to atmospheric pressure continuous pre-firing in a nitrogen atmosphere. S6, Waste Heat Segmented Hot Pressing: The high-temperature stacks after continuous pre-firing are transferred to a hot press with a preset temperature range of 790-830℃; stacks with a billet temperature higher than the preset temperature range are transferred to the segmented pressing process, stacks with a billet temperature within the preset temperature range are transferred to a tunnel furnace for reheating, and billets with a billet temperature lower than the preset temperature range are scrapped; the segmented pressing process includes two stages: low-pressure pressing and high-pressure pressing. The purpose of low-pressure pressing is to stretch the stacks, and high-pressure pressing completes the densification of the billets. S7, pressurized slow cooling and depressurization: pressure is maintained and furnace cooling is performed throughout the pressing process. After the temperature drops to the preset temperature, additional pressure is maintained, and finally the pressure is slowly released. After cooling, a second helium test is performed. After passing the test, the molybdenum foil wrapping is removed to obtain the plate blank. S8, Post-processing of finished product: The surface of the blank plate is micro-grinded to remove the thin oxide layer on the surface, and the finished copper-based diamond heat dissipation plate is obtained.

2. The atmospheric pressure continuous manufacturing process for the large-area copper-based diamond heat dissipation plate according to claim 1, characterized in that, In step S1, the volume fraction of diamond powder in the composite powder is 68-75 vol%, and the diamond powder is tertiary graded diamond. The volume ratio of the particles inside the tertiary graded diamond is large particles: medium particles: small particles = 72:18:10, and the thickness of the chromium interface layer on the diamond surface is 0.15-0.35 μm.

3. The atmospheric pressure continuous manufacturing process for the large-area copper-based diamond heat dissipation plate according to claim 1, characterized in that, In step S2, ultrasonic stirring and degassing with a power of 300-320W is used for 40-50 minutes.

4. The atmospheric pressure continuous manufacturing process for the large-area copper-based diamond heat dissipation plate according to claim 1, characterized in that, In step S3, the thickness of a single layer of material is 2-5 mm; the cold pressing pressure is set to 210-230 MPa, and the single pressure holding time is 8-10 min.

5. The atmospheric pressure continuous manufacturing process for large-area copper-based diamond heat dissipation plates according to claim 1, characterized in that, In step S4, the thickness of the 310S steel plate is 0.5-2mm, the thickness of the graphite paper is 0.1-0.5mm, and the interlayer spacing is 2-10mm; the thickness of a single layer of molybdenum foil in the double-layer staggered molybdenum foil sheath is 0.1-0.3mm, and the overlap width of the staggered joint is ≥10mm; when placing the green blanks, 3-6 green blanks are placed in a single stack, and when the diamond ratio in a single stack is 75 vol%, no more than 3 green blanks are placed, and when the diamond ratio is otherwise, a maximum of 6 green blanks are placed.

6. The atmospheric pressure continuous manufacturing process for large-area copper-based diamond heat dissipation plates according to claim 1, characterized in that, In step S5, the nitrogen flow rate is 8-10 L / min, the pre-firing temperature is set to 850-870℃, and the holding time is 40-45 min; before pre-firing, the heating curve in the tunnel furnace is calibrated.

7. The atmospheric pressure continuous manufacturing process for large-area copper-based diamond heat dissipation plates according to claim 1, characterized in that, In the segmented pressing of step S6, the pressure of low-pressure pressing is 35-45 MPa and held for 15-25 seconds; the pressure of high-pressure pressing is the target pressure, and the target pressure of stack with a diamond ratio of 72 vol% is 80-88 MPa, and the target pressure of stack with a diamond ratio of 75 vol% is 90-95 MPa.

8. The atmospheric pressure continuous manufacturing process for large-area copper-based diamond heat dissipation plates according to claim 1, characterized in that, In step S7, the cooling rate is 5-15℃ / min, and after the temperature drops to 750℃, the pressure is maintained for an additional 20 seconds before slowly depressurizing.

9. The atmospheric pressure continuous manufacturing process for large-area copper-based diamond heat dissipation plates according to claim 1, characterized in that, Ceramic brackets are used for transporting the stacks during the manufacturing process.

10. A large-area copper-based diamond heat dissipation plate, characterized in that, The sheet material prepared by the atmospheric pressure continuous preparation process according to any one of claims 1 to 9 has a porosity of 0.072% to 0.087%, a vertical thermal conductivity of 615 to 673 W / (m·K), and a total forming area of ​​15,000 to 30,000 cm² per stack in a single pressing. 2 The coefficient of thermal expansion of the sheet material can be controlled by adjusting the diamond volume fraction.

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