Vapor chamber with surface coated with diamond coating and preparation method of vapor chamber

Abstract

The invention discloses a vapor chamber coated with a diamond coating on the surface and a preparation method of the vapor chamber, metal is plated on the surface of diamond powder to obtain diamond powder containing a metal coating, the diamond powder containing the metal coating and the metal powder are mixed to obtain mixed powder, then the mixed powder is sprayed on the surface of a vapor chamber base plate through cold gas power, and the vapor chamber is prepared. The vapor chamber substrate containing the composite coating is obtained, the composite coating on the surface of the vapor chamber substrate is subjected to laser remelting to obtain the vapor chamber substrate containing the laser remelting coating, and then the vapor chamber substrate is subjected to annealing heat treatment to obtain the vapor chamber substrate with the surface coated with the diamond coating. The preparation method is simple, the process is stable and reliable, the preparation speed is high, the material size is not limited by the size of a cavity of a high-temperature and high-pressure synthesis press, and the prepared vapor chamber has the performance advantages of high thermal conductivity, low thermal expansion coefficient, excellent thermal cycle performance and high bending strength and has wide market application prospects.

Description

Technical Field

[0001] The invention belongs to the application in the technical field of electronic chip heat dissipation, and specifically relates to a heat spreader with a diamond coating on the surface and a preparation method thereof. Background Art

[0002] Miniaturization, integration, and high heat flux density are the development trends of various electronic components today. At the same time, the problem of heat accumulation in electronic devices caused by high heat flux density, which leads to performance degradation, is gradually emerging. The problem of how to efficiently transfer and dissipate heat in electronic devices is becoming more and more severe. As an efficient phase change heat transfer device, the heat spreader has been widely used in the field of heat dissipation technology of electronic equipment due to its high thermal conductivity, high cooling capacity, high stability and long life, and has gradually become the mainstream heat dissipation method for high-end central processing units (CPUs), graphics cards, storage, and laptops.

[0003] With the rapid development of microelectronics technology, the packaging density of semiconductor integrated circuits is getting higher and higher, and higher requirements are placed on the thermal conductivity, thermal expansion coefficient and mechanical properties of the heat spreader. At present, the materials used for the heat spreader are mainly metal materials such as copper and aluminum, which have low thermal conductivity and a large difference in thermal expansion coefficient from the chip. During use, the metal heat spreader expands due to heat, and the metal heat spreader may fall off the circuit board, resulting in the heat dissipation of electronic devices being blocked, and the product reliability and service life being reduced. Therefore, it is urgent to find a method to improve the performance of the heat spreader. The methods to improve the performance of the heat spreader mainly include: improving the liquid wick structure of the substrate under the heat spreader, improving the liquid working fluid, and improving the thermal properties of the heat spreader material.

[0004] At present, the materials on the market to improve the performance of heat spreader substrates are mainly diamond metal-based composite materials. However, the gas pressure-assisted infiltration or powder metallurgy preparation technology currently used has high costs and long preparation time. In addition, the prepared diamond metal-based composite materials need to be further processed through post-treatment processes such as electroplating of metal nickel and gold before they can be bonded with the heat spreader. The application process is complicated, the preparation cost is high, the material stability is poor, and the practical value is low. Summary of the invention

[0005] In view of the defects of the existing preparation technology, which has complicated process and high preparation cost, the first purpose of the present invention is to provide a preparation method of a heat spreader with a diamond coating on the surface. The present invention directly sprays the surface-treated diamond and metal powder onto the heat spreader substrate by cold spraying, and then treats the coating by laser remelting process. The preparation method of the present invention has simple process, low preparation cost, short production time, is suitable for large-scale production application, and has broad market application prospects.

[0006] The second object of the present invention is to provide a heat spreader with a diamond coating on the surface prepared by the above preparation method. The heat spreader substrate provided by the present invention has a thermal conductivity of 400 to 800 W / mK and a thermal expansion coefficient of 3.1 to 6.5×10 - 6 K -1 The flexural strength is between 50 and 400 MPa, which meets the market's higher performance requirements for heat spreaders and has broad market application prospects.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention discloses a method for preparing a heat spreader with a diamond coating on its surface, comprising the steps of plating a diamond powder surface with metal to obtain a diamond powder containing a metal coating, mixing the diamond powder containing the coating with a metal powder to obtain a mixed powder, then spraying the mixed powder on the surface of a heat spreader substrate by cold air power to obtain a heat spreader substrate containing a composite coating, laser remelting the composite coating on the surface of the heat spreader substrate to obtain a heat spreader substrate containing a laser remelted coating, and then annealing the heat spreader substrate to obtain a heat spreader substrate with a diamond coating on its surface.

[0009] The preparation method of the present invention is to first plate a layer of metal on the surface of diamond powder to improve the wettability of diamond powder and metal powder, then use cold air power spraying to mix the surface treated diamond and metal powder and spray them onto the substrate of the heat spreader, use cold spraying technology to impact the substrate at high speed to cause severe plastic deformation and form a coating, then use laser remelting process to treat the coating, perform surface morphology optimization, grain refinement and phase change, etc., and form a good metallurgical bonding interface with the substrate, improve the mechanical properties and thermal properties of the heat spreader, and finally perform annealing treatment to eliminate residual stress in the coating and further improve the mechanical properties of the coating. The preparation method is simple, the process is stable and reliable, the preparation speed is fast, the material size is not limited by the cavity size of the high temperature and high pressure synthesis press, and the prepared heat spreader has the performance advantages of high thermal conductivity, low thermal expansion coefficient, excellent thermal cycle performance and high bending strength, and has broad market application prospects.

[0010] In the present invention, cold air power spraying is used to spray the mixed powder onto the heat spreader substrate, which can ensure that the coating has excellent thermal conductivity, because cold spraying accelerates the powder particles to impact the substrate through high-pressure gas to cause plastic deformation, realizes coating deposition at low temperature, eliminates the poor coating performance caused by changes in powder composition and the adverse effects of high temperature on the substrate and coating, while if thermal spraying technology is used, the metal powder will react with the coating elements or the metal powder will directly react with the diamond through the coating, thereby reducing the thermal conductivity of the coating. In addition, if the surface of the diamond powder is not plated with metal first, it will also lead to poor interface bonding ability between the diamond and the metal powder, which will greatly reduce its thermal conductivity.

[0011] In a preferred solution, the particle size of the diamond powder is 5 to 100 μm. The inventors have found that the particle size of the diamond powder has a great influence on the thermal conductivity of the heat spreader substrate with a diamond coating on the surface. If the particles are too small, the thermal conductivity of the diamond is low. If the particles are too large, the thermal conductivity of the metal base cannot be further improved, which leads to an increase in production costs.

[0012] In a preferred embodiment, the thermal conductivity of the diamond powder is between 1000 and 2000 W / mK.

[0013] In a preferred embodiment, the metal in the metal coating is selected from at least one of Ti, Si, W and Cr.

[0014] In a preferred solution, the thickness of the metal coating is 10 to 500 nm. In the present invention, a metal coating is provided on the surface of diamond to improve the interfacial bonding ability and acoustic impedance of diamond and metal powder; this is because the wettability of diamond and metal is too poor, and there is a phenomenon of selective bonding, and Al4C3 is easily generated between diamond and aluminum matrix, which is easy to hydrolyze, thereby affecting the interfacial bonding effect, and the heat conduction between diamond and metal is carried out through phonon and electron coupling under the premise of good interfacial bonding, and the phonon and electron coupling ability of diamond directly with metal powder is relatively poor, and the coating can play a transitional role therein, thereby improving thermal conductivity, and the coating is too thin to achieve the transition effect, and of course, if it is too thin, it cannot be completely wrapped, resulting in a decrease in the bonding force between diamond powder and metal powder, and also reducing thermal conductivity.

[0015] In the present invention, the manner of setting the metal coating is not limited. In the present invention, as long as the thickness of the transition layer and the requirements of good bonding are met, the preparation method of the transition layer is not limited. For example, one of the electroplating, chemical plating, evaporation, magnetron sputtering, chemical vapor deposition, and physical vapor deposition in the prior art can be used. It is only necessary to ensure that the coating thickness is uniform, the surface is flat, and the adhesion with diamond is good.

[0016] In a preferred embodiment, the particle size of the metal powder is 10 to 100 μm. When the particle size of the metal powder is controlled within the above range, the thermal conductivity of the heat spreader substrate with a diamond coating on the surface is optimal. If the particles are large, the interface bonding strength between the diamond powder and the metal powder will decrease, and debonding or gaps may occur, which seriously affects its thermal conductivity.

[0017] In a preferred embodiment, the volume fraction of diamond powder in the mixed powder is 30% to 65%. The inventors have found that when the volume fraction of diamond powder is controlled within the above range, the thermal conductivity of the heat spreader substrate with diamond coating on the surface is optimal. If the volume fraction of diamond is too low, its thermal conductivity is even lower than that of pure metal. If it is too high, not only the thermal conductivity will be reduced, but also the cost will be increased.

[0018] The preferred solution is that the process parameters of cold air power spraying are: using He gas or N2 gas as the working gas, the gas temperature is 200-400°C, the gas pressure is 3.0-8.0MPa, and the spraying distance is 20-40mm.

[0019] In the present invention, the process parameters of cold air power spraying are controlled within the above range, and the thermal conductivity of the heat spreader substrate with diamond coating on the surface is finally obtained. Because during the spraying process, after the supersonic two-phase flow formed in the spray gun leaves the nozzle, the temperature, velocity and direction of the powder particles themselves change. When the particles pass through the throat of the spray gun, since the gas phase flow rate is higher than the particle velocity, the airflow will drag the particles at this time, so choosing a suitable spraying distance is the key to whether the particles can obtain the highest speed. In the cold spraying process, the greater the pressure of the carrier gas, the greater the kinetic energy obtained by the particles. When the particles hit the substrate, the greater the degree of plastic deformation of the particles, the lower the porosity of the prepared coating, the denser the coating, and the higher the bonding strength between the coating and the substrate interface; when the gas pressure is low, the coating prepared by cold spraying is loose, has more internal pores, and the bonding strength between the coating and the substrate is poor. The bonding ability of the coating and the heat spreader has an extremely important influence on its thermal conductivity. The better the bonding ability, the higher the thermal conductivity. The carrier gas temperature has a great influence on the quality of cold spray coatings. When the carrier gas temperature is low, defects such as voids and inclusions will occur during the cold spray process. As the carrier gas temperature increases, the particles are more fully plastically deformed to form a denser coating. However, too high a temperature may cause oxidation of diamonds, coatings and metal powders, resulting in a decrease in the thermal conductivity and mechanical properties of the coating.

[0020] Preferably, the process parameters of the laser remelting are: using He gas or N2 gas as the working gas, the gas flow adjustment range is 5-50L / min, the power is 1000-10000W, the scanning speed is 3-30mm / s, and the spot diameter is 1.2-5mm.

[0021] In the present invention, the process parameters of laser remelting are controlled within the above range, and the thermal conductivity of the heat spreader substrate with diamond coating on the surface is finally obtained. If the laser specific energy is smaller, the coating is not melted enough or only the surface is melted, the remelting path formed is narrow, the melting depth is shallow and there is almost no heat affected area. As the specific energy increases, the remelting path gradually widens, the melting depth increases, and the heat affected area gradually increases; if the laser specific energy is too large, the coating temperature is too high and it is easy to vaporize, and even more holes are generated. (Laser specific energy , P is laser power (W); v is laser scanning speed (mm / min); D is laser spot diameter (mm)

[0022] In a preferred embodiment, the annealing temperature is 200-300°C and the holding time is 4-10 hours. In the present invention, the annealing temperature is controlled within the above range, and the comprehensive performance of the final heat spreader is optimal. If the temperature is too low and the time is too short, the purpose of eliminating residual stress and bubbles in the coating cannot be achieved. If the temperature is too high, inevitable phase changes and reactions will occur in the coating, which will reduce the thermal conductivity of the coating. If the time is too long, the production efficiency is low and the production cost is high.

[0023] In a preferred embodiment, the heat spreader substrate is selected from a heat spreader upper substrate and a heat spreader lower substrate, and the heat spreader upper substrate with a diamond coating on its surface is assembled with the diamond coating on its surface to obtain a heat spreader with a diamond coating on its surface.

[0024] The lower substrate of the vapor chamber has a liquid wick structure. In actual operation, the upper substrate of the vapor chamber and the lower substrate of the vapor chamber with the liquid wick structure are connected, and then vacuumed, injected with liquid working medium, and sealed to obtain the vapor chamber.

[0025] In a preferred embodiment, the thermal conductivity of the heat spreader substrate is 400 to 800 W / mK, and the thermal expansion coefficient is 3.1 to 6.5×10 -6 K -1 The bending strength is 50-400MPa. The method of the present invention greatly improves the thermal conductivity of the heat spreader.

[0026] The present invention also provides a heat spreader with a diamond coating on the surface prepared by the above preparation method.

[0027] Principles and advantages

[0028] The present invention provides a heat spreader with a diamond coating on the surface and a preparation method thereof. First, diamond with a certain thickness of 5 to 100 μm and metal powder are mixed, and then He gas or N2 gas is used as a gas source to embed it into the substrate material by cold spraying to improve its thermal conductivity. The coating is treated by laser remelting process to further improve its thermal conductivity, bonding strength and mechanical properties. A muffle furnace is used for heat treatment. Finally, the upper substrate on the heat spreader and the lower substrate with a liquid wick structure are connected, and then vacuumed, injected with liquid working fluid, and sealed to obtain a thermal conductivity of 400 to 800 W / mK and a thermal expansion coefficient of 3.1 to 6.5×10 -6 K -1 , a heat spreader with a bending strength of 50 to 400 MPa. The preparation method is simple in process and low in cost, and realizes the integrated design of heat sink and heat spreader, overcoming the defects of the existing technology for improving the performance of heat spreader, such as complicated process, long preparation time and high preparation cost. It is the first example of the simultaneous application of laser remelting deposition process and cold spraying technology to metal-based heat spreader, and this preparation technology has not been reported at home and abroad.

[0029] The advantages and beneficial effects of the present invention are:

[0030] 1. The present invention realizes the integrated design of heat sink and heat spreader. When preparing diamond metal matrix composite material, it is not necessary to use high temperature and high pressure synthesis press equipment to press diamond and metal powder. In actual use, it is not necessary to further undergo post-processing processes such as electroplating metal nickel and gold plating before it can be combined with the heat spreader. The preparation method is simple, the process is stable and reliable, the preparation speed is fast, and the material size is not limited by the size of the high temperature and high pressure synthesis press cavity.

[0031] 2. The metal vapor chamber prepared by the present invention directly sprays the surface-modified diamond and metal powder into the substrate of the metal vapor chamber by laser remelting assisted cold spraying, which improves the thermal conductivity and mechanical properties of the vapor chamber and reduces the thermal expansion coefficient of the vapor chamber, and can serve electronic devices with higher heat flux density. The thermal conductivity of the vapor chamber is 400-800 W / mK, and the thermal expansion coefficient is 3.1-6.5×10 -6 K -1 The flexural strength is between 50 and 400 MPa, which meets the market's higher performance requirements for heat spreaders and has broad market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic structural diagram of a heat spreader with a diamond coating on its surface and a preparation method thereof.

[0033] Figure 2 It is a schematic diagram of the structure of the heat spreader.

[0034] Figure 3 It is a schematic diagram of the structure of cold spraying.

[0035] Figure 4 It is a schematic diagram of the structure of the substrate coating.

[0036] In the figure: 10-heat plate system, 20-cold spray system, 11-liquid wick, 12-lower substrate, 13-support column 14-upper substrate, 15-cavity, 16-coating, 21-plating, 22-diamond, 23-metal powder, 24-gas heating device, 25-cold spray nozzle. DETAILED DESCRIPTION

[0037] In the specific implementation process, the present invention relates to a heat spreader with a diamond coating on the surface and a preparation method thereof. First, diamond powder with a particle size of 5 to 100 μm, metal powder with a purity of more than 99%, and a metal heat spreader commonly used in the market are prepared. A coating of 10 to 500 nm of elements such as Ti, Si, W, Cr, etc. is plated on the surface of 5 to 100 μm diamond by magnetron sputtering, molten salt method, or vacuum evaporation deposition method. The surface-treated diamond and metal powder are mixed by cold air spraying and then sprayed on the substrate of the heat spreader. The coating is then treated by laser remelting process, supplemented by a suitable annealing heat treatment process. Finally, the upper substrate of the heat spreader and the lower substrate with a liquid wick structure are connected, and then vacuuming, liquid working medium is injected, and sealing is performed to obtain a heat spreader with a thermal conductivity of 400 to 800 W / mK and a thermal expansion coefficient of 3.1 to 6.5×10 -6 K -1 The metal vapor chamber substrate with a bending strength of 50 to 400 MPa improves the performance of the vapor chamber and meets market demand. The specific steps of the method are as follows:

[0038] Step 1 Material selection: The particle size of diamond is 5 to 100 μm, and the shape is a regular octahedral structure; the coating element is selected from commercial pure powder with a purity of more than 99%; the metal powder used for cold spraying is commercial pure powder with a purity of more than 99%; the substrate is a heat spreader substrate commonly used in the market.

[0039] Step 2: Coating: A single coating or a composite coating of 10 to 500 nm of Ti, Si, W, Cr and other elements is coated on the diamond surface in step 1 by magnetron sputtering, molten salt method or vacuum evaporation deposition method. The coating thickness is uniform, the surface is flat and the adhesion with diamond is good.

[0040] Step 3: Spraying: Use cold spraying equipment to mix the surface treated diamond and metal powder in step 2 and spray them directly onto the substrate of the heat spreader. The operating conditions of the cold spraying equipment are: He gas and N2 gas as working gas, gas temperature of 200-400°C, gas pressure of 3.0-8.0MPa, and spraying distance of 20-40mm.

[0041] Among them, the cold spraying equipment can refer to a cold air power spraying device or other commercial cold spraying, power spraying or low-pressure cold spraying equipment mentioned in the Chinese invention patent (patent number: 01128130.8, authorization announcement number: CN1161188C).

[0042] Step 4 Remelting: The coating in step 3 is treated by laser remelting process. The working conditions of the laser are: He gas N2 gas is used as the working gas, the gas flow adjustment range is 5-50L / min, the power is 1000~10000W, the scanning speed is 3~30mm / s, and the spot diameter is 1.2~5mm.

[0043] Step 5: Heat treatment: Use a muffle furnace to perform an annealing heat treatment process on the metal soaking plate in step 4. The heat treatment temperature range is 200 to 300° C. and the insulation time is 4 to 10 hours.

[0044] Preparation of step 6: Connect the upper substrate of the heat spreader and the lower substrate with a liquid wick structure, then evacuate, inject liquid working fluid, and seal to obtain the heat spreader.

[0045] The obtained metal heat spreader substrate has a thermal conductivity of 400-800 W / mK and a thermal expansion coefficient of 3.1-6.5×10 -6 K -1 The bending strength is 50-400MPa, which greatly improves the thermal and mechanical properties of the metal heat sink. Compared with the existing preparation technology, it has the advantages of high product performance, simple process, fast preparation speed, low cost, and convenient large-scale production, and has broad market prospects.

[0046] The embodiments of the present invention are described in detail below. They are implemented based on the technical solution of the invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0047] Example 1

[0048] A 50nm W coating is plated on the surface of diamond with an average particle size of 20μm by vacuum evaporation deposition. The diamond powder containing the W coating is mixed with pure aluminum particles with a particle size of 30μm to obtain a mixed powder, wherein the volume fraction of the diamond powder containing the W coating in the mixed powder is 50%, and it is sprayed onto the substrate of the metal heat spreader by cold spraying equipment, using He gas as the working gas, the gas temperature is 200℃, the gas pressure is 5.0MPa, and the spraying distance is 30mm. The coating is then treated by laser remelting process, using He gas as the working gas, the gas flow adjustment range is 15L / min, the power is 2000W, the scanning speed is 10mm / s, and the spot diameter is 3mm. The prepared heat spreader substrate is vacuum heat treated at 200℃ for 5h. Finally, the upper substrate of the heat spreader is connected to the lower substrate with a liquid wick structure, and then vacuumed, infused with liquid working fluid, and sealed to obtain the heat spreader. In this embodiment, the obtained metal heat spreader substrate was subjected to the measurement of thermal conductivity, thermal expansion coefficient, thermal cycle properties and mechanical properties, wherein the thermal conductivity was 587 W / mK, the thermal expansion coefficient was 4.1×10 -6 K -1 After 200 thermal cycles at -50℃~150℃, it still maintains a thermal conductivity of 530W / mK and a bending strength of 221MPa, meeting the market requirements for metal vapor chambers.

[0049] Example 2

[0050] The magnetron sputtering technology is used to coat the diamond surface with an average particle size of 10 μm with an 80 nm W coating. The diamond powder containing the W coating is mixed with pure aluminum powder with a particle size of 40 μm to obtain a mixed powder, wherein the volume fraction of the diamond containing the W coating in the mixed powder is 45%. The mixed powder is sprayed onto the liquid wick of the metal heat spreader by cold spraying equipment, using N2 gas as the working gas, the gas temperature is 270 ° C, the gas pressure is 3.0 MPa, and the spraying distance is 20 mm. The coating is then treated by laser remelting process, using N2 gas as the working gas, the gas flow adjustment range is 15 L / min, the power is 5000 W, the scanning speed is 20 mm / s, and the spot diameter is 3 mm. The prepared metal heat spreader substrate is vacuum treated at 250 ° C for 8 hours. Finally, the upper substrate of the heat spreader and the lower substrate with the liquid wick structure are connected, and then vacuumed, filled with liquid working fluid, and sealed to obtain the heat spreader. In this embodiment, the obtained metal heat spreader substrate was subjected to the measurement of thermal conductivity, thermal expansion coefficient, thermal cycle properties and mechanical properties, wherein the thermal conductivity was 621 W / mK, the thermal expansion coefficient was 3.7×10 -6 K -1 After 200 thermal cycles at -50℃~150℃, it still maintains a thermal conductivity of 560W / mK and a bending strength of 243MPa, meeting the market requirements for metal vapor chambers.

[0051] Example 3

[0052] A molten salt method is used to coat a 200nm Ti coating on the surface of a diamond with an average particle size of 30μm. The diamond powder containing the Ti coating is mixed with a copper powder with a particle size of 50μm to obtain a mixed powder, wherein the volume fraction of the diamond containing the Ti coating in the mixed powder is 50%. The mixed powder is sprayed onto the substrate of a metal heat spreader using a cold spraying device, using He gas as the working gas, the gas temperature is 250℃, the gas pressure is 6.0MPa, and the spraying distance is 25mm. The coating is then treated with a laser remelting process, using He gas as the working gas, the gas flow adjustment range is 15L / min, the power is 6000W, the scanning speed is 25mm / s, and the spot diameter is 4mm. The prepared metal heat spreader substrate is vacuum treated at 250℃ for 4h. Finally, the upper substrate of the heat spreader is connected to the lower substrate with a liquid wick structure, and then vacuumed, infused with liquid working fluid, and sealed to obtain a heat spreader. In this embodiment, the obtained metal heat spreader substrate was subjected to the measurement of thermal conductivity, thermal expansion coefficient, thermal cycle properties and mechanical properties, wherein the thermal conductivity was 613 W / mK, the thermal expansion coefficient was 4.5×10 -6 K -1 , after 200 thermal cycles at -50℃~150℃, it still maintains a thermal conductivity of 580W / mK and a bending strength of 217MPa, meeting the market requirements of metal heat sinks.

[0053] Comparative Example 1

[0054] The other conditions are the same as those in Example 1, except that the thickness of the W coating is 1 μm. Finally, the thermal conductivity of the heat spreader substrate is measured to be 327 W / mK, and the thermal expansion coefficient is 6.7×10 -6 K -1 After 200 thermal cycles at -50℃~150℃, the thermal conductivity is 296W / mK and the bending strength is 233MPa, which is lower than the thermal conductivity of most vapor chambers on the market.

[0055] Comparative Example 2

[0056] The other conditions were the same as those in Example 1, except that the volume fraction of the diamond powder containing the W coating in the mixed powder was 70%. Finally, the thermal conductivity of the heat spreader substrate was measured to be 571 W / mK, and the thermal expansion coefficient was 4.7×10 -6 K -1 After 200 thermal cycles at -50℃~150℃, it still maintains a thermal conductivity of 550W / mK and a bending strength of 243MPa, which meets the performance requirements of metal heat sinks. However, the production cost is high and the performance is slightly reduced, which does not meet the market production requirements.

[0057] Comparative Example 3

[0058] The other conditions were the same as those in Example 1, except that the annealing temperature was 350°C. Finally, the thermal conductivity of the heat spreader substrate was measured to be 601 W / mK, and the thermal expansion coefficient was 5.5×10 -6 K -1 After 200 thermal cycles at -50℃~150℃, the thermal conductivity still maintains 370W / mK and the bending strength is 147MPa. After the hot and cold cycles, the thermal conductivity drops significantly and the mechanical properties are poor, which does not meet the application requirements of metal heat sinks.

[0059] Of course, the above are only preferred embodiments of the present invention. The present invention may also have many other implementation modes. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a heat spreader with a diamond coating on the surface, characterized in that: The surface of diamond powder is plated with metal to obtain diamond powder containing a metal coating, the diamond powder containing the coating is mixed with metal powder to obtain a mixed powder, and then the mixed powder is sprayed on the surface of a heat spreader substrate by cold air power to obtain a heat spreader substrate containing a composite coating, the composite coating on the surface of the heat spreader substrate is laser remelted to obtain a heat spreader substrate containing a laser remelted coating, and then the heat spreader substrate is annealed and heat treated to obtain a heat spreader substrate with a diamond coating on the surface.

2. The method for preparing a heat sink with a diamond coating on the surface according to claim 1, characterized in that: The particle size of the diamond powder is 5 to 100 μm; The thermal conductivity of the diamond powder is 1000-2000 W / mK.

3. The method for preparing a heat sink with a diamond coating on the surface according to claim 1, characterized in that: The metal in the metal coating is selected from at least one of Ti, Si, W and Cr; The thickness of the metal plating layer is 10-500nm.

4. The method for preparing a heat sink with a diamond coating on the surface according to claim 1, characterized in that: The particle size of the metal powder is 10 to 100 μm; In the mixed powder, the volume fraction of diamond powder is 30% to 65%.

5. The method for preparing a heat sink with a diamond coating on the surface according to any one of claims 1 to 4, characterized in that: The process parameters of cold air dynamic spraying are: using He gas or N2 gas as the working gas, the gas temperature is 200-400°C, the gas pressure is 3.0-8.0MPa, and the spraying distance is 20-40mm.

6. The method for preparing a heat sink with a diamond coating on the surface according to any one of claims 1 to 4, characterized in that: The process parameters of the laser remelting are: using He gas or N2 gas as the working gas, the gas flow adjustment range is 5-50L / min, the power is 1000-10000W, the scanning speed is 3-30mm / s, and the spot diameter is 1.2-5mm.

7. The method for preparing a heat sink with a diamond coating on the surface according to any one of claims 1 to 4, characterized in that: The annealing treatment is carried out at a temperature of 200 to 300° C. and a heat preservation time of 4 to 10 hours.

8. The method for preparing a heat sink with a diamond coating on the surface according to any one of claims 1 to 4, characterized in that: The vapor chamber substrate is selected from a vapor chamber upper substrate and a vapor chamber lower substrate. The vapor chamber upper substrate with a diamond coating on its surface is assembled with the lower substrate with a diamond coating on its surface to obtain a vapor chamber with a diamond coating on its surface.

9. The method for preparing a heat sink with a diamond coating on the surface according to any one of claims 1 to 4, characterized in that: The thermal conductivity of the heat spreader is 400-800 W / mK, and the thermal expansion coefficient is 3.1-6.5×10 -6 K -1 , the flexural strength is 50~400MPa.

10. A heat spreader with a diamond coating on its surface prepared by the preparation method according to any one of claims 1 to 9.

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