High-density diamond-copper composite heat dissipation material and vacuum infiltration preparation method thereof

Abstract

The application discloses a high-density diamond-copper composite heat dissipation material and a vacuum infiltration preparation method thereof, and relates to the technical field of metal-based composite heat dissipation materials. The material comprises a diamond reinforcing phase and a copper matrix. Diamond particles are classified according to particle size, and a Ti-Cu alloy coating is coated on the surface of the diamond particles. During preparation, the high-density composite heat dissipation material is obtained through cleaning and drying, coating deposition, cold isostatic pressing, vacuum infiltration, gradient cooling and grinding and polishing. The application can improve the interface bonding strength and the material density, reduce the interface thermal resistance, and improve the heat conduction performance and the thermal cycle stability.

Description

Technical Field

[0001] This invention relates to the field of metal-based composite heat dissipation materials, specifically to high-density diamond-copper composite heat dissipation materials and their vacuum melting infiltration preparation method. Background Technology

[0002] As electronic devices evolve towards higher power, miniaturization, and greater integration, the heat generated per unit area by chips and power modules continues to increase. The thermal conductivity, thermal expansion matching performance, and long-term service stability of heat dissipation materials have become crucial factors affecting the reliability and lifespan of electronic devices. While traditional metals such as copper and aluminum possess some thermal conductivity, their high coefficients of thermal expansion make it difficult to achieve a good match with materials like semiconductor chips and ceramic substrates. This can easily lead to thermal stress concentration during thermal cycling, resulting in interface cracking, solder fatigue, or device failure.

[0003] Diamond possesses extremely high thermal conductivity, a low coefficient of thermal expansion, and good chemical stability. Copper exhibits good thermal conductivity, electrical conductivity, and processing properties. Therefore, using diamond as a reinforcing phase and copper as a matrix to prepare diamond-copper composites is an important approach to obtaining high-performance thermal management materials. These composites combine the high thermal conductivity of diamond with the processing and bonding advantages of copper, showing promising application prospects in high-end heat dissipation fields.

[0004] However, existing diamond-copper composites still have significant shortcomings. First, the natural wettability between diamond and copper is poor, making it difficult for molten copper to fully penetrate the micropores between diamond particles during melting or sintering, easily leading to the formation of voids, cracks, and unbonded areas. Second, the interfacial bonding strength between diamond and copper is insufficient, resulting in high interfacial thermal resistance and preventing the full utilization of diamond's high thermal conductivity. Third, the packing density of single-size diamond particles is limited, easily forming large pores between particles, leading to insufficient filling of the copper matrix and affecting the material's density and mechanical properties. Finally, traditional powder metallurgy processes have long preparation cycles, and the material density often fails to reach the levels required for high-power devices, and delamination and cracking are prone to occur under thermal cycling conditions.

[0005] Therefore, it is necessary to provide new diamond-copper composite heat dissipation materials and their preparation methods. By improving the interfacial bonding between diamond and copper, increasing the packing density of diamond particles, and optimizing the melting and cooling processes, composite heat dissipation materials with high density, low interfacial thermal resistance, high thermal conductivity, and high stability can be obtained. Summary of the Invention

[0006] The purpose of this invention is to provide a high-density diamond-copper composite heat dissipation material and its vacuum melting and infiltration preparation method, in order to solve the problems of poor wettability between diamond and copper, weak interfacial bonding, high porosity, insufficient thermal conductivity and poor thermal cycling stability in existing diamond-copper composite materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution.

[0008] A high-density diamond-copper composite heat dissipation material comprises a diamond reinforcing phase and a copper matrix. The diamond reinforcing phase consists of graded diamond particles, including coarse diamond particles with a diameter of 20-40 μm and fine diamond particles with a diameter of 5-10 μm. The fine diamond particles fill the gaps between the coarse diamond particles, resulting in a denser packing structure, thereby increasing the preform density and reducing residual porosity during subsequent melting and infiltration.

[0009] The diamond particles are coated with a Ti-Cu alloy coating. The Ti-Cu alloy coating can form a TiC chemical bonding layer with the carbon elements on the diamond surface, which can improve the bonding strength between the diamond and the coating. On the other hand, the Cu elements in the coating can form a good metallurgical bond with the copper matrix, which can improve the wetting ability of the copper liquid on the diamond particle surface, thereby reducing the interfacial thermal resistance and improving the overall thermal conductivity of the composite material.

[0010] Preferably, the volume fraction of the diamond reinforcing phase is 55%-65%, and the volume fraction of the copper matrix is ​​35%-45%. Within this range, the material can maintain a high diamond content to improve thermal conductivity, while retaining sufficient copper matrix to ensure melt infiltration, overall density, and processability.

[0011] Preferably, the mass percentage of coarse diamond particles in the diamond particles is 55%-65%, and the mass percentage of fine diamond particles in the diamond particles is 35%-45%. By combining coarse and fine particle sizes, the particle packing gaps can be reduced, resulting in a higher packing density for the preform.

[0012] Preferably, the Ti-Cu alloy coating thickness is 50-100 nm. If the coating is too thin, it is difficult to form a continuous and effective interface modification layer; if the coating is too thick, it may increase interfacial thermal resistance and affect the close packing of diamond particles. Therefore, controlling the coating thickness within the range of 50-100 nm can balance interfacial bonding strength and thermal conductivity.

[0013] The present invention also provides a vacuum melting and infiltration method for preparing a high-density diamond-copper composite heat dissipation material, comprising the following steps.

[0014] S1. The graded diamond particles are cleaned and dried to obtain clean diamond particles. Specifically, the graded diamond particles are ultrasonically cleaned in acetone and anhydrous ethanol in sequence to remove oil, impurities and adsorbates from the surface of the diamond particles. Then, they are vacuum dried to prevent moisture and contaminants from affecting the subsequent coating deposition.

[0015] S2. A Ti-Cu alloy coating is deposited on the surface of clean diamond particles using vapor deposition (CVD) to obtain surface-modified diamond particles. The preferred CVD method is magnetron sputtering. Magnetron sputtering uses a Ti-Cu alloy target with a Ti:Cu atomic ratio of 1:1, an argon atmosphere at a pressure of 0.3-0.5 Pa, a sputtering power of 200-250 W, and a sputtering time of 60-90 min. This step enables the formation of a continuous and uniform Ti-Cu alloy coating on the surface of the diamond particles.

[0016] S3. The surface-modified diamond particles are mixed with a binder and then loaded into a mold, followed by cold isostatic pressing to obtain a diamond preform. Polyvinyl alcohol is preferably used as the binder. The cold isostatic pressing pressure is 200-250 MPa, and the holding time is 5-10 min. Cold isostatic pressing ensures that the diamond particles are uniformly compressed in all directions, improving the strength and porosity of the preform. The porosity of the resulting diamond preform is no higher than 5%.

[0017] S4. Place the diamond preform and oxygen-free copper block in a vacuum infiltration furnace. Heating under vacuum conditions melts the oxygen-free copper and infiltrates it into the pores of the diamond preform, resulting in a composite infiltrated preform. The vacuum level in the vacuum infiltration furnace should not exceed 1×10⁻⁶. - 3 Pa, melting and infiltration temperature is 1100-1150℃, holding time is 60-90min. Under vacuum environment, oxide formation can be reduced, interface contamination can be avoided, and the copper liquid can promote full filling of the pores of the preform.

[0018] S5. Perform gradient cooling treatment on the fused infiltration composite preform. Gradient cooling includes first cooling to 800℃ at a cooling rate of 8-12℃ / min, and then cooling to room temperature at a cooling rate of 4-6℃ / min. Gradient cooling can reduce the residual stress caused by the difference in thermal expansion between diamond and copper matrix, and reduce microcracks and interface debonding during the cooling process.

[0019] S6. The cooled melt-infiltrated composite preform is then ground and polished to obtain a high-density diamond-copper composite heat dissipation material. The post-treatment preferably includes mechanical grinding and chemical mechanical polishing to remove the oxide layer, burrs, and surface defects from the material surface, ensuring that the surface roughness Ra is no higher than 0.5 nm.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses coarse and fine graded diamond particles as a reinforcing phase. The fine particles can fill the packing gaps between the coarse particles, increase the packing density of the diamond preform, and make it easier for the copper liquid to form a continuous and dense filled structure during the vacuum melting and infiltration process, thereby reducing the porosity of the material and increasing the density of the composite material.

[0021] 2. The present invention sets a Ti-Cu alloy coating on the surface of diamond particles. The Ti element forms a TiC chemical bond with the diamond, which improves the bonding stability between the diamond and the coating. At the same time, the Cu element forms a metallurgical bond with the copper substrate, which improves the wetting ability of the copper liquid on the diamond surface, thereby reducing interface porosity and interface cracks and reducing interface thermal resistance.

[0022] 3. The present invention uses a vacuum melting process to prepare diamond-copper composite material, which enables molten copper to fully penetrate into the pores of the diamond preform and reduces oxide inclusions and interface contamination, resulting in a composite material with high density and high thermal conductivity.

[0023] 4. The present invention uses a gradient cooling process to release the thermal stress during the cooling process, which can reduce microcracks, interface debonding and delamination in the material, and improve the structural stability and service reliability of the composite material under high and low temperature cycling environment.

[0024] 5. The high-density diamond-copper composite heat dissipation material obtained by this invention can achieve a density of not less than 99.5%, a thermal conductivity of not less than 600 W / (m·K), and an interfacial thermal resistance of not more than 8 × 10⁻⁶. -8 m 2 With a K / W ratio and a bending strength of not less than 280MPa, and a low and controllable coefficient of thermal expansion, it is suitable for high-power electronic devices and high heat flux density heat dissipation scenarios. Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to embodiments. It should be understood that these embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention. Conventional adjustments made by those skilled in the art to the raw material ratio, process parameters and processing methods without departing from the technical concept of the present invention should all fall within the scope of protection of the present invention.

[0027] Example This embodiment provides a high-density diamond-copper composite heat dissipation material. This composite heat dissipation material comprises a diamond reinforcing phase and a copper matrix. The volume fraction of the diamond reinforcing phase is 60%, and the volume fraction of the copper matrix is ​​40%. The diamond reinforcing phase uses graded diamond particles, wherein the coarse diamond particles have a particle size of 20-40 μm, and the fine diamond particles have a particle size of 5-10 μm. The proportion of coarse diamond particles in the total diamond particles is 60%, and the proportion of fine diamond particles is 40%.

[0028] In this structure, coarse diamond particles contact each other and form the main heat-conducting framework, while fine diamond particles fill the gaps between the coarse diamond particles, resulting in a relatively compact packing structure. This structure reduces large pores inside the preform, improves the uniformity of diamond particle distribution, and provides uniform and fine filling channels for subsequent copper melt infiltration.

[0029] In this embodiment, the diamond particles are coated with a Ti-Cu alloy coating with a thickness of 80 nm. The Ti-Cu alloy coating serves as an interfacial transition layer between the diamond particles and the copper substrate. Its inner side can form a TiC chemical bonding layer with the carbon elements on the diamond surface through Ti elements, while its outer side can form a metallurgical bonding layer with the copper substrate through Cu elements. Therefore, the bonding between the diamond particles and the copper substrate is no longer solely based on mechanical contact, but rather forms a stable interfacial bonding structure, thereby improving the problems of poor wettability, numerous interfacial pores, and high interfacial thermal resistance between diamond and copper.

[0030] The high-density diamond-copper composite heat dissipation material in this embodiment is prepared by the following method.

[0031] First, coarse diamond particles with a diameter of 20-40 μm and fine diamond particles with a diameter of 5-10 μm were mixed in a 60:40 ratio to obtain graded diamond particles. The graded diamond particles were then ultrasonically cleaned in acetone for 30 minutes to remove oil and organic impurities from their surface. Subsequently, the diamond particles were ultrasonically cleaned in anhydrous ethanol for another 30 minutes to further remove residual impurities. After cleaning, the diamond particles were dried in a vacuum drying oven to obtain clean diamond particles.

[0032] Then, a Ti-Cu alloy coating was deposited on the surface of clean diamond particles using magnetron sputtering. The magnetron sputtering used a Ti-Cu alloy target as the source electrode, with an atomic ratio of Ti to Cu of 1:1. Argon gas was introduced during sputtering, with the sputtering pressure controlled at 0.4 Pa, the sputtering power at 220 W, and the sputtering time at 75 min. Through magnetron sputtering, the Ti-Cu alloy coating was uniformly coated on the surface of the diamond particles, resulting in surface-modified diamond particles.

[0033] Subsequently, the surface-modified diamond particles were mixed evenly with a small amount of polyvinyl alcohol binder. After mixing, the mixture was placed into a graphite mold and formed using cold isostatic pressing. The cold isostatic pressing pressure was 220 MPa, and the holding time was 8 minutes. After forming, a diamond preform with a porosity of no more than 5% was obtained.

[0034] Next, the diamond preform and the oxygen-free copper block are placed together in a vacuum infiltration furnace. The vacuum infiltration furnace is then evacuated to a vacuum level of 1×10⁻⁶. -3 Below Pa. Then the temperature is raised to 1120℃ and held for 75 min. At this temperature, oxygen-free copper melts to form molten copper. Due to the Ti-Cu alloy coating on the surface of the diamond particles, the wettability of the molten copper on the surface of the diamond particles is improved. The molten copper can fully penetrate into the internal pores of the diamond preform and form a stable bonding interface with the Ti-Cu alloy coating to obtain a melt-infiltrated composite preform.

[0035] After the heat preservation process, the melt-infiltrated composite preform undergoes a gradient cooling treatment. Specifically, it is first cooled to 800℃ at a cooling rate of 10℃ / min, and then cooled to room temperature at a cooling rate of 5℃ / min. This gradient cooling process can alleviate the residual stress caused by the difference in thermal expansion coefficients between the diamond reinforcement phase and the copper matrix, and reduce microcracks, interface debonding, and delamination phenomena that occur during material cooling.

[0036] Finally, the cooled fused composite preform was subjected to mechanical grinding and chemical mechanical polishing to remove the oxide layer, burrs, and processing defects from the material surface, yielding a high-density diamond-copper composite heat dissipation material. The resulting composite heat dissipation material has a density of not less than 99.5%, a thermal conductivity of not less than 600 W / (m·K), and an interfacial thermal resistance of not more than 8 × 10⁻⁶. -8 m 2 • K / W, flexural strength not less than 280MPa, coefficient of thermal expansion 4×10 -6 / ℃ to 6×10 -6 / ℃.

[0037] As can be seen from this embodiment, the present invention improves the packing density of the reinforcing phase by using graded diamond particles, enhances the interfacial bonding between diamond and the copper matrix through a Ti-Cu alloy coating, improves the filling density of the copper matrix through vacuum infiltration, and reduces residual thermal stress through gradient cooling. Therefore, the resulting composite heat dissipation material has the characteristics of high density, good thermal conductivity, stable interfacial bonding, and high thermal cycling reliability, and can be used in high heat flux density heat dissipation scenarios such as third-generation semiconductor power devices, aerospace electronic equipment, laser devices, microwave devices, and supercomputing chips.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A high-density diamond-copper composite heat dissipation material, characterized in that, The material comprises a diamond reinforcing phase and a copper matrix. The diamond reinforcing phase is composed of graded diamond particles, including coarse diamond particles with a diameter of 20-40 μm and fine diamond particles with a diameter of 5-10 μm. The surface of the diamond particles is coated with a Ti-Cu alloy coating. The copper matrix fills the pores between the diamond particles and forms a bonding interface with the Ti-Cu alloy coating.

2. The high-density diamond-copper composite heat dissipation material according to claim 1, characterized in that, The volume fraction of the diamond reinforcing phase is 55%-65%, and the volume fraction of the copper matrix is ​​35%-45%.

3. The high-density diamond-copper composite heat dissipation material according to claim 1, characterized in that, The coarse diamond particles account for 55%-65% of the total diamond particles, and the fine diamond particles account for 35%-45% of the total diamond particles.

4. The high-density diamond-copper composite heat dissipation material according to claim 1, characterized in that, The thickness of the Ti-Cu alloy coating is 50-100 nm.

5. The high-density diamond-copper composite heat dissipation material according to claim 1, characterized in that, In the Ti-Cu alloy coating, Ti forms a TiC chemical bonding layer with the carbon elements on the diamond surface, and Cu forms a metallurgical bonding layer with the copper substrate.

6. The high-density diamond-copper composite heat dissipation material according to claim 1, characterized in that, The high-density diamond-copper composite heat dissipation material has a density of not less than 99.5%, a thermal conductivity of not less than 600 W / (m·K), and an interfacial thermal resistance of not more than 8 × 10⁻⁶. -8 m 2 ·K / W.

7. The vacuum melting and infiltration method for preparing the high-density diamond-copper composite heat dissipation material according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Clean and dry the graded diamond particles to obtain clean diamond particles. S2. A Ti-Cu alloy coating is deposited on the surface of the clean diamond particles using a vapor deposition method to obtain surface-modified diamond particles. S3. The surface-modified diamond particles are mixed with a binder and then loaded into a mold and subjected to cold isostatic pressing to obtain a diamond preform. S4. Place the diamond preform and the oxygen-free copper block in a vacuum melting furnace, heat the furnace under vacuum conditions to melt the oxygen-free copper and penetrate into the pores of the diamond preform to obtain a melting-infiltrated composite preform. S5. Perform gradient cooling treatment on the melt-infiltrated composite preform; S6. After cooling, the melt-infiltrated composite blank is ground and polished to obtain a high-density diamond-copper composite heat dissipation material.

8. The vacuum melt infiltration preparation method according to claim 7, characterized in that, In step S1, the graded diamond particles are ultrasonically cleaned sequentially with acetone and anhydrous ethanol for 20-40 minutes, and then vacuum dried.

9. The vacuum melt infiltration preparation method according to claim 7, characterized in that, In step S2, the vapor deposition method is magnetron sputtering, the magnetron sputtering uses a Ti-Cu alloy target, the atomic ratio of Ti to Cu is 1:1, the sputtering atmosphere is argon, the gas pressure is 0.3-0.5 Pa, the sputtering power is 200-250 W, and the sputtering time is 60-90 min.

10. The vacuum melting infiltration preparation method according to claim 7, characterized in that, In steps S4 and S5, the vacuum degree inside the vacuum melting furnace is no higher than 1×10⁻⁶. -3 Pa, the melting and infiltration temperature is 1100-1150℃, and the holding time is 60-90min; the gradient cooling treatment includes first cooling to 800℃ at a cooling rate of 8-12℃ / min, and then cooling to room temperature at a cooling rate of 4-6℃ / min.

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