High-thermal-conductivity diamond / copper composite sheet and 3D printing preparation process thereof

Abstract

This invention discloses a high thermal conductivity diamond / copper composite sheet and its 3D printing preparation process. The diamond / copper composite sheet is obtained by 3D printing and sintering diamond particles, Cu-Cr alloy powder, and a binder. The preparation process combines 3D printing and powder metallurgy, resulting in a simple process with high production efficiency and automation. Furthermore, the resulting diamond / copper composite sheet exhibits a more compact and stable structure and higher thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the fields of thermally conductive materials technology and powder metallurgy, and relates to a high thermal conductivity diamond / copper composite sheet and its 3D printing preparation process. Background Technology

[0002] With the development of science and technology, electronic devices are being applied to industries, military, national production, high technology and other fields. Modern electronic devices are becoming smaller and miniaturized, with higher power density and integration. The increasingly concentrated electronic components make heat dissipation a prominent issue. Currently, the thermal conductivity of commonly used copper alloys and aluminum alloys is below 100W / m·K. This low thermal conductivity hinders the continued development of these industries.

[0003] Diamond has a thermal conductivity of approximately 2000 W / m·K, making it the most thermally conductive material in nature. However, diamond cannot be directly processed and sintered into the shape of a heat-conducting sheet. Therefore, other traditional thermally conductive materials are added to diamond to create a composite material with good thermal conductivity. Copper has a thermal conductivity of approximately 386 W / m·K and is inexpensive and easy to process. However, copper cannot directly meet the thermal conductivity requirements of current materials. Furthermore, diamond cannot be wetted by copper, making it difficult to obtain a good bonding interface during the composite material preparation process, and even resulting in voids. This leads to high interfacial thermal resistance, which significantly reduces the high thermal conductivity of diamond. In addition, traditional heat-conducting sheet production often involves producing a large heat-conducting sheet and then cutting it into smaller pieces according to needs before packaging. Some heat-conducting sheets with special structures are complex, time-consuming, and labor-intensive, making automated production impossible. Therefore, improving the thermal conductivity of diamond / copper composite materials and increasing their production efficiency is a current research focus. Summary of the Invention

[0004] To address the aforementioned challenges, the first objective of this invention is to provide a high thermal conductivity diamond / copper composite sheet. This composite sheet uses diamond, the material with the highest thermal conductivity found in nature, as its base material and embeds the diamond in copper, a metal with high thermal conductivity. The addition of a small amount of chromium enhances the interfacial bonding between the diamond and copper and reduces the thermal resistance of the composite material, resulting in a composite sheet with high thermal conductivity and strong interfacial bonding.

[0005] The second objective of this invention is to provide a method for preparing high thermal conductivity diamond / copper composite sheet. This method uses a special binder to tightly bond diamond particles and Cu-Cr alloy, and simultaneously employs 3D printing technology to overcome the problem of low density in products directly sintered by traditional powder metallurgy processes. This method has advantages such as high degree of automation, low cost, high production efficiency, and high precision.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a high thermal conductivity diamond / copper composite sheet, which is composed of diamond particles embedded in a Cu-Cr alloy sheet; the volume percentage composition of the diamond particles and the Cu-Cr alloy is (50-90%):(10-50%); the volume ratio of Cu to Cr in the Cu-Cr alloy is (10-90):(1-10).

[0007] In this invention, diamond particles are used as the reinforcement and Cu-Cr alloy powder is used as the matrix. This is because diamond has excellent comprehensive physical properties, high intrinsic thermal conductivity (700–2200 W / (mK) at room temperature), and a coefficient of thermal expansion of 0.8 × 10⁻⁶. -6 / K, as a reinforcement, is beneficial for improving the thermal conductivity of composite materials. Copper, as a metal with high thermal conductivity, can theoretically further enhance the thermal conductivity of composite materials when inlaid with diamond. However, the thermal conductivity of composite materials depends not only on the intrinsic thermal conductivity of the matrix and reinforcement, but also, and more importantly, on the composite interface. The non-wetting nature of the diamond-copper interface results in high interfacial thermal resistance, making direct processing difficult in existing technologies. In this invention, pre-alloyed Cu-Cr alloy powder is used. This not only ensures a more uniform element distribution, preventing element segregation in the final sintered product, but also reduces the energy required for the re-diffusion of other elements during sintering, lowering the sintering temperature and shortening the sintering time. Furthermore, the small amount of Cr doping effectively reduces the wetting angle between diamond and copper and generates a carbide layer that can dissolve in the copper matrix at the diamond / Cu interface after the reaction. This modifies and fills most of the gaps between the material interfaces, thereby improving the interfacial bonding between diamond and copper and the thermal conductivity of the composite material.

[0008] The inventors discovered that controlling the volume ratio of diamond micropowder to Cu-Cr alloy powder within the aforementioned range results in excellent product performance. Too much diamond micropowder leads to excessive voids that cannot be completely filled by the Cu-Cr alloy powder, while too little diamond micropowder diminishes the thermal conductivity advantage of diamond. More preferably, the volume percentage composition of the diamond particles and Cu-Cr alloy is (50-85%):(15-50%).

[0009] The inventors discovered that the volume ratio of Cu to Cr in the Cu-Cr alloy directly affects the thermal conductivity of the finished product. Excessive Cr results in an overly thick transition layer at the interface, hindering the thermal conductivity of the finished product. Conversely, insufficient Cr leads to inadequate carbide formation at the diamond / Cu interface, resulting in insufficient bonding between Cu and diamond and consequently reduced thermal conductivity. More preferably, the volume ratio of Cu to Cr in the Cu-Cr alloy is (18–90):(1–10).

[0010] As a preferred embodiment, the diamond particles have a particle size of 10–400 mesh; the Cu-Cr alloy powder has a particle size of 200–800 mesh. The inventors have discovered that controlling the particle size of the diamond particles and Cu-Cr alloy powder within the above-mentioned ranges results in optimal printing accuracy and finished product performance.

[0011] This invention also provides a process for preparing high thermal conductivity diamond / copper composite sheet. The method involves mixing diamond particles, Cu-Cr alloy powder and binder, followed by mixing, granulation and drawing to obtain a filament material. The filament material is then 3D printed to form a green blank, which is then degreased and sintered to obtain the final product.

[0012] This invention combines 3D printing technology with powder metallurgy processes and uses a special binder to achieve a tight bond between diamond particles and Cu-Cr alloy powder.

[0013] As a preferred embodiment, the granules produced in the granulation step need to be sieved through a screen, leaving a 4-mesh sieve for finer granulation.

[0014] As a preferred embodiment, the adhesive comprises, by weight percentage: 50-60% thermoplastic polyester elastomer, 30-40% acrylonitrile-butadiene-styrene copolymer, 1-3% plasticizer, 2-5% dispersant, and 1-3% surfactant.

[0015] Another key aspect of this invention lies in the use of a special binder, the working principle of which is as follows: Thermoplastic polyester elastomer, as the skeleton component of the binder, possesses advantages such as high hardness, high tensile strength, and excellent flexural properties. During use, its good melt flowability and stable melt state allow for the production of a stable mixture during internal mixing, suitable for granulation and fiber drawing. Its excellent melt flowability ensures the mixture maintains good fluidity even under shearing and high-temperature conditions in the internal mixer rotor and extrusion screw, preventing jamming and ensuring more thorough mixing. Simultaneously, it also imparts a certain strength to the drawn filaments, improving their printability and allowing them to be smoothly extruded from the printer's extrusion gears and fed to the nozzle for printing. This prevents the material from sticking to the screw during the fiber drawing process, resulting in smoother filament output. More importantly, both the thermoplastic polyester elastomer and the acrylonitrile-butadiene-styrene copolymer exhibit excellent adhesion; when used together, their properties complement each other, resulting in superior bonding performance. Furthermore, the acrylonitrile-butadiene-styrene copolymer is characterized by its hardness, high strength, and high toughness, resulting in filaments with good flexibility and the ability to bond with various resins and organic solvents. Plasticizers effectively prevent filament breakage during printing and facilitate the coiling and collection of filaments required for 3D printing. Small amounts of surfactants and dispersants effectively regulate particle surface properties and interparticle interactions, improving the compatibility of diamond particles with other polymers.

[0016] As a preferred embodiment, the plasticizer is dibutyl phthalate; the dispersant is stearic acid; and the surfactant is polyethyleneimine.

[0017] As a preferred embodiment, the operating temperature of the wire drawing machine is set to 170–210°C, and the diameter of the drawn filamentous printing material is 1.6–2.2 mm, more preferably 1.7–2.0 mm.

[0018] As a preferred embodiment, the volume ratio of the total volume of the diamond particles and Cu-Cr alloy powder to the binder is (3-4):(3-4). The inventors have found that controlling the volume ratio of diamond particles and Cu-Cr alloy powder to the binder within this range yields a better mixture suitable for wire drawing and printing.

[0019] As a preferred embodiment, the mixing conditions are: temperature of 170–210°C and time of 30–120 min.

[0020] As a preferred embodiment, the 3D printing parameters are: printing layer thickness 0.05~0.4mm, nozzle temperature 180~250℃, and platform temperature 70~110℃.

[0021] As a preferred embodiment, the degreasing process employs a stepped heating and holding method in a degreasing furnace purged with hydrogen, with the following steps: heating from room temperature to 170–250°C for 15–45 minutes, holding for 10–30 minutes; heating from 170–250°C to 270–350°C for 30–90 minutes, holding for 15–60 minutes; heating from 270–350°C to 370–450°C for 30–90 minutes, holding for 15–60 minutes; heating from 370–450°C to 470–550°C for 10–60 minutes, holding for 1–2 hours; and then cooling in the furnace. The purpose of the degreasing treatment in this invention is to remove the adhesive from the sheet. The advantages of using stepped heating and heat preservation degreasing compared to direct heating and heat preservation degreasing are as follows: Direct heating and heat preservation degreasing causes multiple binders to decompose into gases simultaneously and be discharged from the green body. Excessive gas discharge can lead to a large number of bubbles or cracks on the surface of the green body after degreasing, which has a negative impact on the thermal conductivity of the final composite sheet product. Stepped heating and heat preservation degreasing allows multiple binders to be discharged slowly and sequentially, prolonging the degreasing time and effectively avoiding the disadvantages of direct heating and heat preservation degreasing. It also makes the degreasing more thorough and complete.

[0022] As a preferred embodiment, the sintering process uses a hydrogen atmosphere and a sintering pressure of 20–60 MPa. The temperature setting steps are as follows: from room temperature to 680–730°C, heating time 1–10 min, holding at 680–730°C for 1–5 min; from 680–730°C to 980–1180°C, heating time 1–10 min, holding at 980–1180°C for 1–10 min; then cooling in the furnace. This invention, by employing a two-stage heating and holding sintering process, can effectively reduce the internal and external temperature difference of the composite material, reduce the internal stress of the material, and avoid warping and cracking of the sintered product.

[0023] The present invention provides a process for preparing a high thermal conductivity diamond / copper composite sheet, comprising the following specific steps:

[0024] 1) Internal mixing: Weigh a certain amount of Cu-Cr alloy powder, diamond particles and binder according to the design ratio, mix them and put the mixture into an internal mixer for internal mixing. Set the internal mixing temperature to 170-210℃. When the temperature reaches the set temperature, add materials and start timing. The total internal mixing time is 30-120 minutes.

[0025] 2) Granulation: Take out the intensively mixed material and put it into a granulator for granulation. The granules need to be screened and sorted to select particles finer than 4 mesh for wire drawing.

[0026] 3) Fiber drawing: The produced granules are poured into the feed port of the fiber drawing machine, and the material is squeezed into the heating zone by the rotation of the screw and heated into a viscous state. Then, it is extruded from the discharge port to form 1.6-2.2mm filament-like printing material.

[0027] 4) Printing green blanks: Create a 3D model of the high thermal conductivity diamond copper / composite material sheet in the computer, save the model file in STL format, import the model file into the slicing software to set the printing parameters, then export the slicing file for printing, and finally import the slicing file into the 3D printer and print according to the set printing parameters to obtain the high thermal conductivity diamond / copper composite material sheet green blank.

[0028] 5) Degreasing: Place the obtained green body into a degreasing mold and use a degreasing furnace to remove the special binder from the green body through high-temperature degreasing.

[0029] 6) Sintering: The degreased green blank is placed into a sintering mold for high-temperature and high-pressure sintering. After sintering, it is taken out to obtain a thin sheet of high thermal conductivity diamond / copper composite material.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1) This invention provides a high thermal conductivity diamond / copper composite sheet, which uses diamond, the natural material with the highest thermal conductivity, as the basic raw material, and uses copper, a metal with high thermal conductivity, to inlay diamond. The addition of chromium overcomes the problem that diamond and copper are difficult to bond well, resulting in high thermal resistance, and meets the current market demand for high thermal conductivity materials.

[0032] 2) This invention combines emerging 3D printing technology with powder metallurgy processes and successfully applies this process to the manufacture of high thermal conductivity diamond / copper composite sheet. Compared with traditional processes, 3D printing technology has the advantages of higher density, lower cost, higher production efficiency and better performance, requires less manpower and has a higher degree of automation, providing a new direction for the manufacture and production of thermal conductive sheets.

[0033] 3) The diamond / copper composite sheet provided by this invention has a thermal conductivity greater than 530 W / m·K, which can meet the needs of high-tech fields.

[0034] 4) The binder provided by the present invention has high viscosity and can improve the printability of diamond composite materials and the flexibility of filaments through the synergistic effect between the components. When used in combination with the components of the composite material of the present invention, it can further improve the thermal conductivity and structural stability of the material. Detailed Implementation

[0035] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the protection scope of this invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] The acrylonitrile-butadiene-styrene copolymer used in the embodiments and comparative examples of this invention is of type PA-758r; the molecular weight of polyethyleneimine is 70,000.

[0038] Example 1

[0039] This example provides a high thermal conductivity diamond / copper composite sheet with dimensions of 20mm × 20mm and a thickness of 0.8mm. The sheet contains 60% diamond particles by volume, 37% copper by volume, and 3% chromium by volume. The Cu-Cr alloy powder is 230–270 mesh, and the diamond particles have a particle size of 120–140 mesh. The special binder contains the following components by mass percentage: 50% thermoplastic polyester elastomer, 40% acrylonitrile-butadiene-styrene copolymer, 2% dibutyl phthalate, 5% stearic acid, and 3% polyethyleneimine.

[0040] This example provides a manufacturing process for high thermal conductivity diamond / copper composite sheet, including the following steps:

[0041] (1) Take a certain amount of Cu-Cr alloy powder, diamond particles and special binder according to the design ratio and mix them (the total volume ratio of diamond particles and Cu-Cr alloy powder to the volume ratio of binder is 3:4).

[0042] (2) Turn on the internal mixer and set the mixing temperature to 185℃. When the internal mixer temperature reaches 185℃, put the mixture into the internal mixer for internal mixing and start timing. The total mixing time is 70 minutes. Then, granulate the mixture sequentially. Put the granulated granules into an extruder for extrusion and drawing into fibers. Set the working temperature of the extruder to 185℃. Obtain filaments with a diameter of 1.75mm and complete the traction and winding on the traction machine.

[0043] (3) Build a 3D model of a high thermal conductivity diamond copper / composite material sheet in the computer, save the model file in STL format, and then use slicing software to set the slicing, printing parameters and printing support. Import the final slicing file into the 3D printer, set the printing parameters to a printing layer thickness of 0.2 mm, nozzle temperature of 220°C and platform temperature of 90°C, and start printing to obtain a green blank of a high thermal conductivity diamond / copper composite material sheet.

[0044] (4) Place the green billet in a degreasing furnace for degreasing. Degreasing is carried out in a degreasing machine with a protective atmosphere of hydrogen by step heating and holding. The steps are as follows: heat up from room temperature to 190°C for 25 minutes and hold for 15 minutes; heat up from 190°C to 290°C for 50 minutes and hold for 30 minutes; heat up from 290°C to 400°C for 50 minutes and hold for 30 minutes; heat up from 400°C to 520°C for 30 minutes and hold for 1 hour; then cool with the furnace.

[0045] (5) Then place it in a sintering furnace for sintering. Sinter in a sintering furnace with a protective atmosphere of hydrogen at a pressure of 30 MPa. The heating steps are as follows: from room temperature to 680°C, heating time is 5 minutes, and at 680°C, hold for 2 minutes; from 680°C to 1050°C, heating time is 4 minutes, and at 1050°C, hold for 4 minutes; then cool with the furnace to obtain a high thermal conductivity diamond / copper composite sheet.

[0046] After obtaining the high thermal conductivity diamond / copper composite sheet, its thermal conductivity was tested using the laser scintillation method. The thermal conductivity was measured to be 687 W / m·K using an LFA467 laser diffractometer, and its density was found to be 97.6%. Its coefficient of thermal expansion was measured to be 7.8 × 10⁻⁶ using a DIL402E pusher-type thermal dilatometer. -6 / K indicates that the high thermal conductivity diamond / copper composite sheet prepared using the present invention has good thermal conductivity.

[0047] Example 2

[0048] This example provides a high thermal conductivity diamond / copper composite sheet with dimensions of 30mm × 30mm and a thickness of 1.2mm. The diamond particle content is 70% by volume, copper is 28% by volume, and chromium is 2% by volume. The Cu-Cr alloy powder is 325–400 mesh, and the diamond particle size is 170–200 mesh. The binder contains the following components in the following mass ratios: thermoplastic polyester elastomer 55%, acrylonitrile-butadiene-styrene copolymer 38%, dibutyl phthalate 1%, stearic acid 4%, and polyethyleneimine 2%.

[0049] This example provides a manufacturing process for high thermal conductivity diamond / copper composite sheet, including the following steps:

[0050] (1) Take a certain amount of Cu-Cr alloy powder, diamond particles and special binder according to the design ratio and mix them (the total volume of diamond particles and Cu-Cr alloy powder and the volume ratio of binder are 3:3).

[0051] (2) Turn on the internal mixer and set the mixing temperature to 190℃. When the internal mixer temperature reaches 190℃, put the mixture into the internal mixer for internal mixing and start timing. The total mixing time is 90 minutes. Then, granulate the mixture sequentially. Put the granulated granules into an extruder for extrusion and drawing. Set the working temperature of the extruder to 190℃. Obtain filaments with a diameter of 1.80mm and complete the traction and winding on the traction machine.

[0052] (3) Build a 3D model of a high thermal conductivity diamond copper / composite material sheet in the computer, save the model file in STL format, and then use slicing software to set the slicing, printing parameters and printing bracket. Import the final slicing file into the 3D printer, set the printing parameters to a printing layer thickness of 0.3 mm, nozzle temperature of 230°C and platform temperature of 95°C, and start printing to obtain a green blank of a high thermal conductivity diamond / copper composite material sheet.

[0053] (4) Place the green billet in a degreasing furnace for degreasing. Degreasing is carried out in a degreasing machine with a protective atmosphere of hydrogen by step heating and holding. The steps are as follows: heat up from room temperature to 200°C for 30 minutes and hold for 20 minutes; heat up from 200°C to 320°C for 60 minutes and hold for 40 minutes; heat up from 320°C to 430°C for 60 minutes and hold for 40 minutes; heat up from 430°C to 530°C for 35 minutes and hold for 1 hour; then cool with the furnace.

[0054] (5) Then place it in a sintering furnace for sintering. Sinter in a sintering furnace with a protective atmosphere of hydrogen at a pressure of 40 MPa. The heating steps are as follows: from room temperature to 700°C, heating time is 6 minutes, and at 700°C, hold for 3 minutes; from 700°C to 1100°C, heating time is 5 minutes, and at 1100°C, hold for 5 minutes; then cool with the furnace to obtain a high thermal conductivity diamond / copper composite sheet.

[0055] After obtaining the high thermal conductivity diamond / copper composite sheet, its thermal conductivity was tested using the laser scintillation method. The thermal conductivity was measured to be 609 W / m·K using an LFA467 laser diffractometer, and its density was 98.5%. Its coefficient of thermal expansion was measured to be 8.2 × 10⁻⁶ using a DIL402E pusher-type thermal dilatometer. -6 / K indicates that the high thermal conductivity diamond / copper composite sheet prepared using the present invention has good thermal conductivity.

[0056] Example 3

[0057] This example provides a high thermal conductivity diamond / copper composite sheet with dimensions of 40mm × 40mm and a thickness of 1.2mm. It consists of two parts: a mixed powder (including diamond particles and Cu-Cr alloy powder) and a special binder, with a volume ratio of 4:3. The mixed powder contains 80% diamond particles by volume, 17% copper by volume, and 3% chromium by volume. The Cu-Cr alloy powder is of 460–540 mesh; the diamond particles have a particle size of 230–270 mesh. The binder contains the following components by mass ratio: 65% thermoplastic polyester elastomer, 30% acrylonitrile-butadiene-styrene copolymer, 1% dibutyl phthalate, 2% stearic acid, and 2% polyethyleneimine.

[0058] This example provides a manufacturing process for high thermal conductivity diamond / copper composite sheet, including the following steps:

[0059] (1) Take a certain amount of Cu-Cr alloy powder, diamond micro powder and special binder according to the design ratio and mix them (the total volume ratio of diamond particles and Cu-Cr alloy powder to the volume ratio of binder is 4:3).

[0060] (2) Turn on the internal mixer and set the mixing temperature to 200℃. When the mixing temperature reaches 200℃, put the mixture into the internal mixer for internal mixing and start timing. The total mixing time is 120 minutes. Then, granulate the mixture sequentially. Put the granulated granules into an extruder for extrusion and drawing into fibers. Set the working temperature of the extruder to 200℃. Obtain filaments with a diameter of 1.85mm and complete the traction and winding on the traction machine.

[0061] (3) Build a 3D model of a high thermal conductivity diamond copper / composite material sheet in the computer, save the model file in STL format, and then use slicing software to set the slicing, printing parameters and printing support. Import the final slicing file into the 3D printer, set the printing parameters to a printing layer thickness of 0.4 mm, nozzle temperature of 240℃, and platform temperature of 100℃, and start printing to obtain a green blank of a high thermal conductivity diamond / copper composite material sheet.

[0062] (4) Place the green billet in a degreasing furnace for degreasing. Degreasing is carried out in a degreasing machine with a protective atmosphere of hydrogen by step heating and holding. The steps are as follows: heat up from room temperature to 220°C for 35 minutes and hold for 25 minutes; heat up from 220°C to 350°C for 70 minutes and hold for 50 minutes; heat up from 350°C to 450°C for 60 minutes and hold for 50 minutes; heat up from 400°C to 550°C for 40 minutes and hold for 2 hours; then cool with the furnace.

[0063] (5) Then place it in a sintering furnace for sintering. Sinter in a sintering furnace with a protective atmosphere of hydrogen at a pressure of 50 MPa. The heating steps are as follows: from room temperature to 730°C, heating time is 7 minutes, and at 730°C, hold for 4 minutes; from 730°C to 1150°C, heating time is 6 minutes, and at 1150°C, hold for 6 minutes; then cool with the furnace to obtain a high thermal conductivity diamond / copper composite sheet.

[0064] After obtaining the high thermal conductivity diamond / copper composite sheet, its thermal conductivity was tested using the laser scintillation method. The thermal conductivity was measured to be 547 W / m·K using an LFA467 laser diffractometer, and its density was 97.3%. Its coefficient of thermal expansion was measured to be 8.4 × 10⁻⁶ using a DIL402E pusher-type thermal dilatometer. -6 / K indicates that the high thermal conductivity diamond / copper composite sheet prepared using the present invention has good thermal conductivity.

[0065] Comparative Example 1

[0066] The comparative example had the same conditions as Example 1, except that the volume ratio of diamond powder was changed to 30%, copper to 65%, and chromium to 5%. The resulting diamond / copper composite sheet had a thermal conductivity of only 353 W / m·K, which was lower than that of dense pure copper, because it contained too little diamond reinforcing phase.

[0067] Comparative Example 2

[0068] The comparative example was conducted under the same conditions as Example 2, except that a direct one-time heating method was used during sintering (i.e., the temperature was directly increased from room temperature to 1100°C over 11 minutes). The final product sheet warped due to excessive internal stress, and flattening it resulted in direct cracking.

[0069] Comparative Example 3

[0070] The comparative example was conducted under the same conditions as Example 3, except that the volume ratio of the diamond micron powder and Cu-Cr alloy powder mixture to the proprietary binder was changed to 3:1. During the mixing process, due to insufficient binder, not all the powders could be bonded together, leaving a large amount of powder remaining, thus preventing wire drawing and printing.

[0071] Comparative Example 4

[0072] The only difference between this comparative example and Example 1 is the absence of an acrylonitrile-butadiene-styrene copolymer. During the mixing process, the binder's adhesion was insufficient, preventing all the powders from being bonded together and hindering subsequent processes.

[0073] Comparative Example 5

[0074] The only difference between this comparative example and Example 1 is that the binder composition was changed as follows: the amount of thermoplastic polyester elastomer was changed to 70%, the amount of acrylonitrile-butadiene-styrene copolymer was changed to 20%, dibutyl phthalate 2%, stearic acid 5%, and polyethyleneimine 3%. During the mixing process, due to the insufficient amount of acrylonitrile-butadiene-styrene copolymer, the mixed material after mixing lacked toughness and broke during the drawing process.

Claims

1. A process for preparing a high thermal conductivity diamond / copper composite sheet, characterized in that: Diamond particles, Cu-Cr alloy powder and binder are mixed and then kneaded, granulated and drawn to obtain filamentous material; The filamentous material is 3D printed to form a green body, which is then degreased and sintered to obtain the final product. The binder comprises, by weight percentage: 50-60% thermoplastic polyester elastomer, 30-40% acrylonitrile-butadiene-styrene copolymer, 1-3% plasticizer, 2-5% dispersant and 1-3% surfactant; the total volume ratio of the diamond particles and Cu-Cr alloy powder to the binder is (3-4):(3-4). The degreasing process is carried out in a degreasing furnace purged with hydrogen using a stepped heating and holding method, with the following steps: heating from room temperature to 170–250°C for 15–45 minutes, holding for 10–30 minutes; heating from 170–250°C to 270–350°C for 30–90 minutes, holding for 15–60 minutes; heating from 270–350°C to 370–450°C for 30–90 minutes, holding for 15–60 minutes; heating from 370–450°C to 370–450°C for 30–90 minutes, holding for 15–60 minutes; and heating from 370–450°C... The temperature is raised to 470–550℃ for 10–60 minutes, and held at 470–550℃ for 1–2 hours; then cooled in the furnace. The sintering process uses hydrogen atmosphere and a sintering pressure of 20–60 MPa. The temperature setting steps are as follows: from room temperature to 680–730℃, the temperature is raised for 1–10 minutes, and held at 680–730℃ for 1–5 minutes; from 680–730℃ to 980–1180℃, the temperature is raised for 1–10 minutes, and held at 980–1180℃ for 1–10 minutes; then cooled in the furnace. The composite material sheet is composed of diamond particles embedded in a Cu-Cr alloy sheet; the volume percentage composition of the diamond particles and the Cu-Cr alloy is (50~90%):(10~50%); the volume ratio of Cu to Cr in the Cu-Cr alloy is (10~90):(1~10).

2. The preparation process of a high thermal conductivity diamond / copper composite sheet according to claim 1, characterized in that: The diamond particles have a particle size of 10~400 mesh; The powder particle size of the Cu-Cr alloy is 200~800 mesh.

3. The preparation process of a high thermal conductivity diamond / copper composite sheet according to claim 1, characterized in that: The plasticizer is dibutyl phthalate; The dispersant is stearic acid; The surfactant is polyethyleneimine.

4. The preparation process of a high thermal conductivity diamond / copper composite sheet according to claim 3, characterized in that: The conditions for the intensive mixing are: temperature 170~210℃, time 30~120min; During the drawing process, the working temperature of the drawing machine is set at 170-210℃, and the diameter of the drawn filament-shaped printing material is 1.6-2.2mm.

5. The preparation process of a high thermal conductivity diamond / copper composite sheet according to claim 3, characterized in that: The parameters for the 3D printing are: layer thickness 0.05-0.4 mm, nozzle temperature 180-250℃, and platform temperature 70-110℃.