Diamond metal composite surface high precision coating method

Abstract

The application discloses a high-precision coating method for a diamond metal composite material surface, polishes the surface of a diamond metal composite material core body to expose array-distributed diamond particles, and carves out a reticular groove avoiding the array-distributed diamond particles; polishes the surface of a block-shaped coating layer material to carve out a reticular groove which is a mirror image of the upper and lower surfaces of the obtained diamond metal composite material core body; and stacks the block-shaped coating layer material, a brazing material, the diamond metal composite material core body, the brazing material and the block-shaped coating layer material in sequence, and carries out vacuum brazing after being fixed by a clamp to obtain a diamond metal composite material with a surface coated with metal; the obtained product has the characteristics of a neat coating interface, controllable shape, size and dimension of the coating layer, adjustable coating material and the like, so as to solve the problems of diamond metal composite material processing difficulty, easy exposure of diamond particles on the surface and the like.

Description

Technical Field

[0001] This invention belongs to the field of metal-based diamond composite materials technology, specifically relating to a high-precision coating method for the surface of diamond metal composite materials. Background Technology

[0002] With the rapid advancement of electronic information technology, electronic components such as chips are becoming increasingly integrated and miniaturized, resulting in higher heat flux densities and significant temperature rises. Research shows that for every 10°C increase in temperature, the reliability of semiconductor components decreases by 50%; approximately 55% of failures in modern microelectronic circuits are caused by thermal damage. Therefore, improving heat dissipation efficiency is crucial to ensuring the stable and reliable operation of electronic components.

[0003] Diamond-aluminum / copper composites possess advantages such as high thermal conductivity and adjustable coefficient of thermal expansion, making them highly promising heat sink materials. However, the presence of diamond in the composite results in extremely high hardness and poor wettability with metals, leading to difficulties in machining and surface plating. Conventional machining methods such as turning, milling, grinding, and planing are largely ineffective when processing diamond-aluminum / copper; electroplating often results in incomplete plating in the diamond areas. Furthermore, heat sink structures are often not limited to simple shapes and frequently require Ni or Au plating to support subsequent processes. These challenges in machining and surface plating significantly limit the application of diamond-aluminum / copper in the heat sink field.

[0004] Coating the surface of diamond-aluminum / copper with easily machinable and plating materials is a good technical approach to solve the above problems. Currently, the main methods for preparing diamond-aluminum / copper materials are liquid phase infiltration and powder metallurgy. While liquid phase infiltration can coat the surface with a metal layer, the interface uniformity between the metal layer and the diamond-aluminum / copper layer, as well as the thickness of the metal layer, are often difficult to control precisely, making it difficult to obtain a thin metal layer. Furthermore, the surface coating layer prepared by liquid phase infiltration is generally only the same metal used for infiltration, making it difficult to achieve coating with dissimilar materials, such as copper or aluminum-silicon composites on the surface of diamond-aluminum. In addition, the cost of preparing composite materials by liquid phase infiltration is relatively high. Powder metallurgy typically requires high temperature and high pressure conditions. If a coating layer is pre-placed on the surface of the preform, the metal layer is prone to loss, resulting in uneven interfaces and difficulty in controlling the size of the coating layer. During further surface processing, diamond leakage may occur. In summary, the preparation of diamond aluminum / copper with a uniform coating interface, controllable coating layer shape and size, and adjustable coating material is an urgent technical problem to be solved to realize the widespread application of diamond aluminum / copper. Summary of the Invention

[0005] The purpose of this invention is to provide a method for coating a diamond metal composite material with a metal / metal matrix composite material. The resulting product has the characteristics of a neat coating interface, controllable shape and size of the coating layer, and adjustable coating material, so as to solve the problems of difficult processing of diamond metal composite materials and easy exposure of diamond particles on the surface.

[0006] To achieve the above objectives, the following technical solution is adopted: A high-precision coating method for diamond metal composite surfaces includes the following steps: (1) Polish the surface of the diamond metal composite core to expose the array of diamond particles, and carve a mesh groove to avoid the array of diamond particles. (2) Polish the surface of the block coating material and carve out mesh grooves that are mirror images of the upper and lower surfaces of the diamond metal composite core obtained in step (1). (3) The block coating material, brazing material, diamond metal composite core, brazing material and block coating material are stacked in sequence, and vacuum brazing is performed after the fixture is fixed to obtain a diamond metal composite material with metal coating on the surface.

[0007] According to the above scheme, the diamond volume fraction of the diamond metal composite core is distributed in a gradient from the middle to the top and bottom, with a higher volume fraction in the middle and a lower volume fraction on the surface; the diamond particles on the upper and lower surfaces are distributed in an array.

[0008] According to the above scheme, the preparation method of the diamond metal composite core includes the following steps: a. Use a centrifugal mixer to mix the coated diamond particles with metal powder and binder evenly; use a cold press to cold press the blank in a cold press mold to obtain the first diamond metal composite blank; b. Use a punching machine to punch an array of through holes on a metal foil with the same shape as the upper and lower surfaces of the diamond metal composite blank. Use a single-sided metal foil tape of the same shape to adhere to any side of the punched metal foil. Sprinkle the coated diamond particles on the other side of the metal foil so that they adhere to the holes to form a diamond composite metal foil. c. Place several metal foils on the upper and lower surfaces of the diamond metal composite blank, then place the diamond composite metal foil corresponding to step b, and then place several metal foils on the upper and lower surfaces to obtain the second diamond metal composite blank. d. The second diamond metal composite material blank is placed in a mold and vacuum hot-pressed to obtain a diamond metal composite material core.

[0009] According to the above scheme, the surface coating of the coated diamond particles is one of Ti, Cr, Ni, B, and Si.

[0010] According to the above scheme, the metal powder is one of aluminum, aluminum alloy, copper, and copper alloy, and the particle size is 10-200μm.

[0011] According to the above scheme, the metal foil, the single-sided metal foil tape and the metal powder are made of the same material; the thickness of the metal foil is 10-100μm, and the thickness of the metal foil layer in the single-sided metal foil tape is 10-30μm.

[0012] According to the above scheme, the array of through holes is a square or rhomboid array with a hole diameter of 60-350μm and a hole spacing of 1-6mm; the diameter of the coated diamond particles is 50-300μm, which is 10-50μm smaller than the hole diameter of the array of through holes.

[0013] According to the above scheme, the number of layers of the plurality of metal foils is 1-3.

[0014] According to the above scheme, the cold pressing pressure is 40-80MPa; in the vacuum hot pressing forming process, the vacuum degree is <10Pa, the hot pressing temperature is 500-680℃, and the pressure is 10-40MPa.

[0015] According to the above scheme, the mesh grooves are engraved using a CNC milling machine or a multi-wire saw; the width of the mesh grooves is 0.1-1.5mm and the depth is 0.1-0.3mm.

[0016] According to the above scheme, the block coating material is one of aluminum, aluminum alloy, copper, copper alloy, molybdenum, aluminum-silicon composite material, and aluminum-silicon carbide composite material; the coating thickness is determined according to the processing requirements.

[0017] According to the above scheme, the alternative to step 3 is as follows: Scrape brazing slurry into the mesh grooves on the upper and lower surfaces of the diamond metal composite core obtained in step (1); place a metal wire mesh corresponding to the shape of the mesh grooves above the mesh grooves on the upper and lower surfaces, and then scrape brazing slurry into the mesh holes; scrape brazing slurry into the mesh grooves of the blocky coating material obtained in step (2), and then align it on the metal wire mesh on the upper and lower surfaces; after fixing the fixture, perform vacuum brazing or vacuum brazing followed by diffusion welding to obtain a diamond metal composite material with a metal coating on the surface.

[0018] According to the above scheme, the metal wire mesh material is the same metal material used in the diamond metal composite material.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention can precisely coat the surface of diamond aluminum / copper composite material with various metals (such as aluminum, copper, molybdenum) and metal matrix composites (such as aluminum silicon composite material, aluminum silicon carbide) by welding.

[0020] 2. The surface coating layer of the diamond metal composite material of this invention has a neat interface and strong bonding force, and the size and shape of the coating layer are controllable (almost identical to that before welding). The surface coating layer can be processed using conventional precision machining methods such as CNC milling machines and CNC grinding machines to obtain diamond aluminum / copper composite materials with complex surface shapes or ultra-thin uniform coating layers, where the coating layer thickness can be as low as 0.03 mm.

[0021] 3. The present invention prepares a diamond aluminum / copper composite material with a surface diamond monolayer array. The core of the material has a high diamond volume fraction, high thermal conductivity and low coefficient of thermal expansion. The surface diamond monolayer array is distributed and has a relatively low volume fraction. The surface monolayer array of diamond can prevent excessive loss of surface metal, thereby significantly improving the weldability of the material surface compared to the core.

[0022] 4. Based on the characteristics of the diamond single-layer array on the surface of the diamond aluminum / copper composite core, the present invention can further groove the surface to improve the welding contact surface and obtain a high-precision diamond aluminum / copper composite material with better welding bonding force. Attached Figure Description

[0023] Figure 1 : A schematic diagram of the structure of the diamond composite metal foil of the present invention.

[0024] Figure 2 : Schematic diagram of the structure of the second diamond metal composite material blank of the present invention.

[0025] Figure 3 : Schematic diagram of the diamond metal composite core structure with engraved mesh grooves according to the present invention. Detailed Implementation

[0026] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0027] A specific embodiment discloses a method for preparing a diamond metal composite core, including the following steps: a. Use a centrifugal mixer to mix the coated diamond particles with metal powder and binder evenly; use a cold press to cold press the blank in a cold press mold to obtain the first diamond metal composite blank; b. Using a drilling machine, drill an array of through holes on a metal foil with the same shape as the upper and lower surfaces of the diamond metal composite blank. Adhere single-sided metal foil tape of the same shape to either side of the drilled metal foil. Sprinkle coated diamond particles onto the other side of the metal foil, allowing them to adhere into the holes, thus forming a diamond composite metal foil. (See attached diagram) Figure 1 As shown; c. Place several metal foils on the upper and lower surfaces of the diamond metal composite blank, then place the diamond composite metal foil corresponding to step b, and then place several more metal foils on the upper and lower surfaces to obtain the second diamond metal composite blank, see appendix. Figure 2 As shown; d. The second diamond metal composite material blank is placed in a mold and vacuum hot-pressed to obtain a diamond metal composite material core.

[0028] Specifically, the surface coating of the coated diamond particles is one of Ti, Cr, Ni, B, and Si.

[0029] Specifically, the metal powder is one of aluminum, aluminum alloy, copper, or copper alloy, with a particle size of 10-200 μm.

[0030] Specifically, the metal foil, the single-sided metal foil tape, and the metal powder are made of the same material; the thickness of the metal foil is 10-100μm, and the thickness of the metal foil layer in the single-sided metal foil tape is 10-30μm.

[0031] Specifically, the array of through holes is a square or rhomboid array with a hole diameter of 60-350μm and a hole spacing of 2-6mm; the coated diamond particles have a particle size of 50-300μm, which is 10-50μm smaller than the hole diameter of the array of through holes.

[0032] Specifically, the number of layers of the plurality of metal foils is 1-3.

[0033] Specifically, the cold pressing pressure is 40-80 MPa; in the vacuum hot pressing process, the vacuum degree is <10 Pa, the hot pressing temperature is 500-680℃, and the pressure is 10-40 MPa.

[0034] The diamond metal composite core obtained by the above method is used in the embodiments.

[0035] The specific implementation also provides a method for high-precision coating of diamond metal composite material surfaces, including the following steps: (1) Polish the surface of the diamond metal composite core to expose the array of diamond particles, and carve a mesh groove to avoid the array of diamond particles. (2) Polish the surface of the block coating material and carve out mesh grooves that are mirror images of the upper and lower surfaces of the diamond metal composite core obtained in step (1). (3) The block coating material, brazing material, diamond metal composite core, brazing material and block coating material are stacked in sequence, and vacuum brazing is performed after the fixture is fixed to obtain a diamond metal composite material with metal coating on the surface.

[0036] Specifically, the diamond volume fraction of the diamond metal composite core is distributed in a gradient from the middle to the top and bottom, with a higher volume fraction in the middle and a lower volume fraction on the surface; the diamond particles on the upper and lower surfaces are distributed in an array.

[0037] Specifically, the mesh grooves are cut using a CNC milling machine or a multi-wire saw; the width of the mesh grooves is 0.1-1.5mm and the depth is 0.1-0.3mm.

[0038] Specifically, the blocky coating material is one of aluminum, aluminum alloy, copper, copper alloy, aluminum-silicon composite material, and aluminum-silicon carbide composite material; the coating thickness is determined according to the processing requirements.

[0039] Specifically, the alternative to step 3 is as follows: Scrape brazing slurry into the mesh grooves on the upper and lower surfaces of the diamond metal composite core obtained in step (1); place a metal wire mesh corresponding to the shape of the mesh grooves above the mesh grooves on the upper and lower surfaces, and then scrape brazing slurry into the mesh holes; scrape brazing slurry into the mesh grooves of the blocky coating material obtained in step (2), and then align it on the metal wire mesh on the upper and lower surfaces; after fixing the fixture, perform vacuum brazing or vacuum brazing followed by diffusion welding to obtain a diamond metal composite material with a metal coating on the surface.

[0040] The metal wire mesh is made of the same metal material as that used in the diamond metal composite material.

[0041] Example 1 (1) Ti-plated diamond particles and pure aluminum powder were mixed using a centrifugal mixer. The volume fraction of the diamond particles was 65% and the particle size was 200 μm. The particle size of the pure aluminum powder was 10 μm. Paraffin wax was added during the mixing process, and the mixture was prepared for use after being mixed evenly. The mixture was then cold-pressed into a blank with a diameter of φ50 mm in a cold-pressing mold using a cold press at a pressure of 50 MPa, forming diamond aluminum blank 1.

[0042] (2) Cut aluminum foil and single-sided aluminum foil tape with a diameter of φ50mm using a cutting machine. The aluminum foil is 100μm thick, and the aluminum foil layer in the single-sided aluminum foil tape is 20μm thick. Use a punching machine to punch an array of through holes on the surface of the aluminum foil. The hole diameter is 350μm, and the array is in the form of 3*3mm. Then, the aluminum foil tape is adhered to one side of the punched aluminum foil to form a composite aluminum foil. Sprinkle 300μm Ti-plated diamond particles on the side of the composite aluminum foil that is not adhered to the metal foil tape, so that the diamonds adhere to the holes. Then, pour out the excess diamonds to form a diamond composite aluminum foil.

[0043] (3) In step (1), place one layer of 100μm aluminum foil on each of the upper and lower sides of the diamond aluminum blank 1, then place diamond composite aluminum foil on the upper and lower sides in sequence, and then place two layers of 100μm aluminum foil on the outermost side to form diamond aluminum blank 2.

[0044] (4) Place the diamond aluminum billet 2 in a mold and perform vacuum hot pressing in a vacuum hot press furnace. The hot pressing temperature is 650℃, the pressure is 40MPa, and the holding time is 2h. After hot pressing, demold the billet, grind the upper and lower surfaces flat, and completely expose the surface array diamond layer to form a diamond aluminum core.

[0045] (5) Polish the surface of the diamond aluminum core; use a 2mm thick pure aluminum sheet as a cladding material and polish the surface of the pure aluminum sheet; clean the surfaces of the resulting 2mm aluminum sheet, Al-Si12 brazed sheet, diamond aluminum core, Al-Si12 brazed sheet, and 2mm aluminum sheet, stack them sequentially, fix them with a fixture, place them in a vacuum furnace, and then perform vacuum soldering. The brazing vacuum degree is less than 10. -3 Pa is heated at 595-605℃ for 5 minutes and then rapidly cooled. After welding, a diamond-aluminum composite material with a surface aluminum coating thickness of 2mm is obtained. After milling off 1.9mm of the surface aluminum layer, a diamond-aluminum composite material with a surface aluminum coating of 0.1mm can be obtained.

[0046] In this embodiment, no diamond particles are leaked from the surface of the 0.1mm aluminum-coated diamond-aluminum core; the thermal conductivity of the diamond-aluminum core is 450W / mK, and the coefficient of thermal expansion is 7.40*10. -6 / K; The thermal conductivity of diamond-coated aluminum with a 0.1mm aluminum coating is 435W / mK, and the coefficient of thermal expansion is 7.45*10. -6 / K; The interfacial shear strength between the aluminum coating and the diamond aluminum core is 20MPa.

[0047] Example 2 Repeat Example 1, but replace step (5) with the following solution: (a) Polish the surface of the diamond aluminum core to expose the array of diamond particles, and carve a mesh groove to avoid the array of diamond particles. The mesh groove has a spacing of 3 mm, a width of 0.2 mm, and a depth of 0.2 mm. (b) Polish the surface of a 2mm thick pure aluminum sheet and carve out mesh grooves that are mirror images of the upper and lower surfaces of the diamond aluminum core obtained in step (1). (c) The 2mm thick pure aluminum sheet, Al-Si12 brazed sheet, diamond aluminum core, Al-Si12 brazed sheet and 2mm thick pure aluminum sheet are stacked in sequence, fixed by a fixture and vacuum welding is performed. After welding, a diamond aluminum composite material with a surface aluminum coating thickness of 2mm is obtained. 1.9mm of the surface aluminum layer is milled off to obtain a diamond aluminum composite material with a surface aluminum coating of 0.1mm.

[0048] In this embodiment, no diamond particles leaked from the surface of the 0.1mm aluminum-coated diamond-aluminum core; the thermal conductivity of the diamond-aluminum core was 443W / mK, and the coefficient of thermal expansion was 7.41*10. -6 / K; The thermal conductivity of diamond aluminum after being coated with 0.1mm aluminum is 437W / mK, and the coefficient of thermal expansion is 7.46*10. -6 / K; The interfacial shear strength between the aluminum coating and the diamond aluminum core reaches 45MPa, demonstrating excellent bonding performance.

[0049] Example 3 Repeat Example 1, but replace step (5) with the following solution: (a) Polish the surface of the diamond aluminum core to expose the array of diamond particles, and carve a mesh groove to avoid the array of diamond particles. The mesh groove has a spacing of 3 mm, a width of 0.2 mm, and a depth of 0.2 mm. (b) Polish the surface of a 2mm thick pure aluminum sheet and carve out mesh grooves that are mirror images of the upper and lower surfaces of the diamond aluminum core obtained in step (1). (c) Scrape Al-Si12 brazing slurry into the mesh grooves on the upper and lower surfaces of the diamond aluminum core obtained in step (1); place an aluminum wire mesh corresponding to the shape of the mesh grooves above the mesh grooves on the upper and lower surfaces, and then scrape Al-Si12 brazing slurry into the holes of the aluminum wire mesh; scrape Al-Si12 brazing slurry into the mesh grooves of the 2mm thick pure aluminum sheet obtained in step (2), and then align the aluminum wire mesh placed on the upper and lower surfaces; after fixing the fixture, perform vacuum brazing, and after welding, a diamond aluminum composite material with a surface aluminum coating thickness of 2mm is obtained. Mill off 1.9mm of the surface aluminum layer to obtain a diamond aluminum composite material with a surface aluminum coating of 0.1mm.

[0050] In this embodiment, no diamond particles leaked from the surface of the 0.1mm aluminum-coated diamond-aluminum core; the thermal conductivity of the diamond-aluminum core was 447 W / mK, and the coefficient of thermal expansion was 7.43 × 10⁻⁶. -6 / K; The thermal conductivity of diamond aluminum after being coated with 0.1mm aluminum is 434W / mK, and the coefficient of thermal expansion is 7.41*10. -6 / K; The interfacial shear strength between the aluminum coating and the diamond aluminum core reaches 58MPa, indicating good bonding performance.

[0051] Repeat Example 3, but change the aperture of the array through holes, the square array form and the size of the diamond particles in the holes in step (2) of Example 3. Under the condition that other conditions remain unchanged, the thermal conductivity and thermal expansion coefficient of the obtained diamond aluminum composite material do not change much, but have a great impact on the shear strength of the welding interface. The specific results are shown in Table 1.

[0052] Table 1

[0053] Repeat Example 3, but change the type of surface coating material. Under the condition that other conditions remain unchanged, the material properties obtained are shown in Table 2.

[0054] Table 2

[0055] Repeat Example 3, but change the surface condition of the diamond aluminum core and the aluminum-coated sheet. Use a CNC milling machine to carve mesh grooves with a spacing of 3 mm, a depth of 0.2 mm, and different widths on the surface. After fixing with a fixture, place in a vacuum furnace and then perform vacuum brazing. The material properties obtained are shown in Table 3, keeping other conditions unchanged.

[0056] Table 3

Claims

1. A method for high-precision coating of diamond metal composite material surfaces, characterized in that... Includes the following steps: (1) Polish the surface of the diamond metal composite core to expose the array of diamond particles, and carve a mesh groove to avoid the array of diamond particles. (2) Polish the surface of the block coating material and carve out mesh grooves that are mirror images of the upper and lower surfaces of the diamond metal composite core obtained in step (1). (3) The block coating material, brazing material, diamond metal composite core, brazing material and block coating material are stacked in sequence, fixed by a fixture and then vacuum brazed to obtain a diamond metal composite material with metal coating on the surface. The method for preparing the diamond metal composite core includes the following steps: a. Use a centrifugal mixer to mix the coated diamond particles with metal powder and binder evenly; use a cold press to cold press the mixture into a blank in a cold press mold to obtain a first diamond metal composite material blank; the metal powder is one of aluminum, aluminum alloy, copper, and copper alloy, with a particle size of 10-200μm; the cold pressing pressure is 40-80MPa; b. Using a punching machine, drill arrayed through holes on a metal foil with the same shape as the upper and lower surfaces of the diamond metal composite material blank. Adhere a single-sided metal foil tape of the same shape to either side of the drilled metal foil. Sprinkle coated diamond particles onto the other side of the metal foil, allowing them to adhere into the holes, thus forming a diamond composite metal foil. The metal foil layer in the metal foil and the single-sided metal foil tape is made of the same material as the metal powder. The metal foil thickness is 10-100 μm, and the metal foil layer thickness in the single-sided metal foil tape is 10-30 μm. The arrayed through holes are square or rhomboid arrays with a diameter of 60-350 μm and a spacing of 1-6 mm. The coated diamond particles have a particle size of 50-300 μm, which is 10-50 μm smaller than the diameter of the arrayed through holes. c. Place several metal foils on the upper and lower surfaces of the diamond metal composite blank, then place the diamond composite metal foil corresponding to step b, and then place several metal foils on the upper and lower surfaces to obtain the second diamond metal composite blank. d. The second diamond metal composite material blank is placed in a mold and vacuum hot-pressed to obtain a diamond metal composite material core; the vacuum degree in the vacuum hot-pressing process is <10Pa, the hot-pressing temperature is 500-680℃, and the pressure is 10-40MPa.

2. The high-precision coating method for diamond metal composite material surface as described in claim 1, characterized in that... The diamond volume fraction of the diamond metal composite core is distributed in a gradient from the middle to the top and bottom, with a higher volume fraction in the middle and a lower volume fraction on the surface; the diamond particles on the upper and lower surfaces are distributed in an array.

3. The high-precision coating method for diamond metal composite material surface as described in claim 1, characterized in that... The mesh grooves are cut using a CNC milling machine or a multi-wire saw; the width of the mesh grooves is 0.1-1.5mm and the depth is 0.1-0.3mm.

4. The high-precision coating method for diamond metal composite material surface as described in claim 1, characterized in that... The blocky coating material is one of aluminum, aluminum alloy, copper, copper alloy, molybdenum, aluminum-silicon composite material, and aluminum-silicon carbide composite material; the coating thickness is determined according to processing requirements.

5. The high-precision coating method for diamond metal composite material surface as described in claim 1, characterized in that... The alternative to step 3 is as follows: Scrape brazing slurry into the mesh grooves on the upper and lower surfaces of the diamond metal composite core obtained in step (1); place a metal wire mesh corresponding to the shape of the mesh grooves above the mesh grooves on the upper and lower surfaces, and then scrape brazing slurry into the holes of the metal wire mesh; scrape brazing slurry into the mesh grooves of the blocky coating material obtained in step (2), and then align it on the metal wire mesh on the upper and lower surfaces; after fixing the fixture, perform vacuum brazing or vacuum brazing followed by diffusion welding to obtain a diamond metal composite material with a metal coating on the surface; the metal wire mesh material is the same metal material as that in the diamond metal composite material.

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