A diamond / copper composite material and a preparation method and application thereof

Abstract

The application discloses a diamond / copper-based composite material and a preparation method and application thereof, and the composite material is prepared by constructing a "foam W" foam interface structure on the surface of diamond particles and combining gas pressure infiltration. The method solves the problems of weak traditional interface combination and low density, the obtained material has a thermal conductivity of 700-900 W / mK, a density of greater than or equal to 99.5%, can be directly electric spark wire cut, and is suitable for the field of high-power semiconductor heat dissipation.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite technology, specifically relating to a diamond / copper matrix composite material, its preparation method, and its application. Background Technology

[0002] Diamond / copper composites have significant application prospects in semiconductor heat dissipation and electronic packaging due to the high thermal conductivity of diamond (1100-2300 W / mK) and the good electrical and thermal conductivity of copper. However, current technologies suffer from low interfacial bonding strength and high thermal resistance between diamond and the copper matrix, and the difficulty in balancing the density and processing performance of the composite material limits its large-scale application.

[0003] Traditional methods improve wettability through a single interfacial layer (such as Ti, Cr, or their carbides), but suffer from problems such as high interfacial brittleness or incomplete reaction. Furthermore, solid-state sintering or melt infiltration methods easily lead to uneven diamond distribution and insufficient density, and cutting requires laser or waterjet cutting, resulting in high costs. Therefore, developing a method for preparing diamond / copper composite materials that combines high interfacial bonding strength, high density, and excellent processing performance is of great significance. Summary of the Invention

[0004] To address the problems of weak interfacial bonding, low density, and high processing difficulty in existing diamond / copper composite materials, the first objective of this invention is to provide a method for preparing diamond / copper composite materials. By constructing a gradient interfacial layer and optimizing the sintering process, the composite material achieves high thermal conductivity, high density, and electrical discharge machining (EDM) performance.

[0005] A second objective of this invention is to provide a diamond / copper composite material prepared by the above-described preparation method.

[0006] A third objective of this invention is to provide applications of the diamond / copper composite material prepared by the above-described preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention discloses a method for preparing a diamond / copper composite material. A W-Cu layer is deposited on the surface of diamond particles. The diamond particles containing the W-Cu layer are then heat-treated at a temperature ≥650℃ to obtain diamond particles containing a foamed W layer. These foamed W-Cu-layered diamond particles are placed in a mold, first heated to 800-900℃ and held at that temperature, then heated to 1150-1200℃. The foamed W-Cu-layered diamond particles are then immersed in molten copper, pressurized by introducing a protective gas, and held at both temperature and pressure to obtain the diamond / copper composite material.

[0009] The preparation method provided by this invention first involves heat-treating diamond particles containing a W-Cu layer. During the heat treatment process, since the W-Cu alloy film is a pseudo-alloy, Cu will precipitate from the alloy film when the temperature exceeds 650℃. During the precipitation process, the film will change from a dense and smooth appearance to a porous network structure, forming a foam W layer. This structure not only reduces the interfacial thermal resistance at the interface but also enhances the interfacial bonding force. Subsequently, the diamond particles containing the foam W layer are placed in a mold and first held at 800-900℃ to allow Cu to precipitate more fully, forming a more complete porous network W structure. At the same time, W reacts fully with diamond, forming a WC dotted structure at the interface, which can further promote interfacial bonding and improve strength. Then, the temperature is raised to 1150-1200℃ for gas pressure impregnation with copper liquid to obtain a diamond / copper composite material with high interfacial bonding strength.

[0010] In a preferred embodiment, the diamond in the diamond particles is selected from pure diamond or boron-doped diamond, preferably boron-doped diamond.

[0011] Experiments have shown that when boron-doped diamond is used as the matrix, the composite material obtained by combining it with W-Cu alloy-modified diamond particles using a matrix alloying and surface metallization coupling reinforcement method can further improve the thermal conductivity and thermal shock resistance of the composite material.

[0012] In a preferred embodiment, the diamond particles have a particle size of 100-700 μm, more preferably 500-700 μm. Experiments have shown that controlling the diamond particle size within this range results in the best performance of the final composite material. Within this range, a continuous porous network structure can be formed on the diamond surface, which is beneficial for the uniformity of interface modification. If the particle size is too small, the specific surface area will be too large, causing the porous network structure on the diamond surface to be too small and discontinuous, which is detrimental to interface uniformity. A relatively larger particle size, on the other hand, can achieve a more uniform interface, resulting in superior final performance.

[0013] The preferred method is to deposit a W-Cu layer on the surface of diamond particles using magnetron sputtering.

[0014] In a further preferred embodiment, the magnetron sputtering process involves co-sputtering with a W target and a Cu target, controlling the power of the W target to be 90-120W, the power of the Cu target to be 30-70W, and the vacuum degree to be 0.1-2Pa.

[0015] In a preferred embodiment, the mass fraction of Cu in the W-Cu layer is 10%-60%. The W-Cu layer serves as the initial layer, preparing for the subsequent preparation of foam W. The mass fraction of Cu needs to be controlled within the above range. If it is too high, it will lead to a lack of W elements at the interface, making it impossible to form a porous network structure. If it is too low, it will be difficult for Cu elements to precipitate, also making it impossible to form a porous network structure.

[0016] In actual operation, the sputtering efficiency of W can be changed by varying the power of the Cu target and the W target, thereby altering the composition of the W-Cu alloy.

[0017] In a preferred embodiment, the thickness of the W-Cu layer is 300-600 nm. Controlling the thickness of the W-Cu layer within this range yields the best material performance. If the coating is too thick, W elements will accumulate at the interface, resulting in an indistinct porous network structure. Furthermore, an excessively thick interface will cause a sharp increase in interfacial thermal resistance, and the improvement in the thermal conductivity of the composite material will not be significant. Conversely, if the coating is too thin, the W elements will be dispersed at the interface, failing to form a porous network structure, resulting in weak interfacial adhesion and easy failure under thermal shock.

[0018] In a preferred embodiment, the heat treatment temperature is 900-1200℃, and the heat treatment time is 0.5-3 hours. During heat treatment, Cu will precipitate first, forming a foam-like W layer on the surface of the diamond particles. The W layer forms WC at the contact surface with the diamond, making the foam W layer more tightly bonded to the diamond.

[0019] In the actual process, after the heat treatment is completed, the diamond particles containing the foam W layer are placed in a graphite mold, vibrated and then placed in an impregnation furnace.

[0020] In a preferred embodiment, diamond particles containing a foam W layer are placed in a mold, heated to 800-900°C at a heating rate of 5-10°C / min, held at that temperature for 0.5-1.5 hours, and then heated to 1150-1200°C at a heating rate of 2-5°C / min, immersing the diamond particles containing the foam W layer into molten copper.

[0021] The preferred method involves pressurizing with protective gas as follows: first, control the pressure to 0.5-1 MPa and hold for 1-2 minutes; then increase the pressure to 4-5 MPa and hold for 5-10 minutes; finally, increase the pressure to 8-10 MPa and maintain the temperature and pressure for 0.5-1.5 hours. This staged temperature and pressure control avoids damage to the diamond particles and ensures material uniformity.

[0022] In the preferred embodiment, after heat preservation and pressure holding, the pressure is kept constant, and the temperature is first lowered to 850-900℃ and held for 1-1.5 hours, then lowered to 600-650℃ and held for 1-1.5 hours, followed by furnace cooling. Because the thermal expansion coefficients of diamond and copper differ significantly, rapid cooling can cause tensile and shear stresses at the interface, leading to interface cracking and hindering product molding. This invention employs the aforementioned gradient cooling method, which buffers the tensile and shear stresses at the interface due to the recrystallization of the copper matrix at high temperatures, thereby significantly improving the residual stress at the interface.

[0023] The present invention also provides a diamond / copper composite material prepared by the above preparation method.

[0024] The present invention also provides an application of a diamond / copper composite material prepared by the above preparation method, wherein the diamond / copper composite material is used in one of the following: a thermal conductive substrate for semiconductor devices, a heat sink for 5G base stations, or a heat sink for power modules of new energy vehicles.

[0025] Beneficial effects

[0026] Synergistic reinforcement of foam interface: The high strength of the foam structure provides strong buffering effect against interfacial thermal stress. Introducing a foam W-structure layer at the interface can improve the interfacial bonding strength and the wettability of the diamond surface, while reducing the interfacial thermal resistance by 50%.

[0027] High density and uniformity: The combination of foam W modification and air pressure infiltration results in a density of over 99.5%, and the diamond particles are evenly dispersed.

[0028] Processing performance optimization: Laser cutting is achieved by reducing hardness difference through interface control.

[0029] Excellent thermal conductivity: thermal conductivity can reach 700-900 W / (m·K), and the coefficient of thermal expansion can be adjusted to 4-7×10⁻⁶. -6 / K, matching the needs of semiconductor chips. Detailed Implementation

[0030] Example 1

[0031] On the surface of diamond particles with a particle size of 260 μm, a W-Cu alloy coating with a thickness of 600 nm (where the Cu content is 10 wt.%) was deposited by magnetron sputtering (dual target co-sputtering parameters: W target sputtering power of 100 W, Cu target sputtering power of 60 W, vacuum degree of 0.5 Pa, gas used is Ar, co-sputtering time of 20 min) to form an initial layer, which prepares for the subsequent formation of a porous network foam W structure on the diamond surface.

[0032] Diamond particles coated with a W-Cu alloy with a Cu content of 10 wt.% were heat-treated at 950℃ for 0.5 h to obtain diamond particles with a porous, network-like W-shaped structure.

[0033] The diamond particles in the W layer of foam were loaded into a graphite mold, compacted, and then placed in an impregnation furnace. The temperature was first increased to 800℃ at 5℃ / min and held for 30 min. Then the temperature was increased to 1200℃ at 2℃ / min. The mold containing the diamond particles was then immersed in molten copper and pressurized with nitrogen gas. The initial pressure was 1 MPa. After holding the pressure for one minute, the pressure was increased to 5 MPa and held for 5 min. Then the pressure was increased to 10 MPa and held for 1 hour.

[0034] Pressure holding and cooling: During cooling, the furnace temperature is reduced to 900℃ and held for 1 hour, then reduced to 600℃ and held for 1 hour, and then cooled with the furnace.

[0035] Comparative Example 1

[0036] Other conditions were the same as in Example 1, except that only a W target was used for magnetron sputtering. The performance of Example 1 and the comparative example is shown in Table 1.

[0037]

[0038] As can be seen from Table 1, compared with a single W metal coating, the special structure formed by the W-Cu alloy film during the preparation of composite materials can not only improve the thermal conductivity of the composite materials, but also improve the interfacial bonding and thermal shock resistance of the composite materials.

[0039] Example 2

[0040] On the surface of diamond particles with a particle size of 550 μm, a W-Cu alloy coating with a thickness of 600 nm (where the Cu content is 20 wt.%) was deposited by magnetron sputtering (dual target co-sputtering parameters: W target sputtering power of 100 W, Cu target sputtering power of 60 W, vacuum degree of 0.5 Pa, gas used is Ar, co-sputtering time of 15 min) to form an initial layer, which prepares for the subsequent formation of a porous network foam W structure on the diamond surface.

[0041] Diamond particles coated with W-Cu alloy with a Cu content of 10 wt.% were heat-treated at a temperature of 900℃ for a duration of 0.5 h. After heat treatment, diamond particles with a porous mesh-like foam W structure layer were obtained.

[0042] The diamond particles in the W layer of foam were loaded into a graphite mold, compacted, and then placed in an impregnation furnace. The temperature was first increased to 800℃ at 5℃ / min and held for 30 min. Then the temperature was increased to 1200℃ at 2℃ / min. The mold containing the diamond particles was then immersed in molten copper and pressurized with nitrogen gas (initial pressure 1MPa, pressure increased to 5MPa after holding for one minute, pressure increased to 10MPa after holding for 5 min, pressure held for 5 min). After reaching 10MPa, the temperature and pressure were maintained for 1 hour.

[0043] Pressure holding and cooling: During cooling, the furnace temperature is lowered to 900℃ and held for 1 hour, then lowered to 600℃ and held for 1 hour, and then cooled with the furnace.

[0044] Comparative Example 2

[0045] Other conditions were the same as in Example 1, except that only a W target was used for magnetron sputtering. The performance of Example 2 and Comparative Example 2 is shown in Table 2.

[0046]

[0047] A comparison between Table 2 and Table 1 shows that increasing the diamond particle size significantly improves the thermal conductivity of the composite material and further enhances its resistance to thermal shock. This indicates that the diamond particle size has a significant impact on the thermal conductivity and resistance to thermal shock of the composite material.

[0048] Example 3

[0049] On the surface of diamond particles with a particle size of 550 μm (the diamond is boron-doped diamond with a boron doping amount of 0.5 wt%), a W-Cu alloy coating with a thickness of 600 nm (where the Cu content is 20 wt.%) was deposited by magnetron sputtering (dual target co-sputtering parameters: W target sputtering power of 110 W, Cu target sputtering power of 40 W, vacuum degree of 0.5 Pa, gas used is Ar, co-sputtering time of 20 min) to form an initial layer, which prepares for the subsequent formation of a porous network foam W structure on the diamond surface.

[0050] Diamond particles coated with W-Cu alloy with a Cu content of 10 wt.% were heat-treated at a temperature of 900℃ for a duration of 0.5 h. After heat treatment, diamond particles with a porous mesh-like foam W structure layer were obtained.

[0051] The diamond particles in the W layer of foam were loaded into a graphite mold, compacted, and then placed in an impregnation furnace. The temperature was first increased to 800℃ at 5℃ / min and held for 30 min. Then the temperature was increased to 1200℃ at 2℃ / min. The mold containing the diamond particles was then immersed in molten copper and pressurized with nitrogen gas (initial pressure 1MPa, pressure increased to 5MPa after holding for one minute, pressure increased to 10MPa after holding for 5 min, pressure held for 5 min). After reaching 10MPa, the temperature and pressure were maintained for 1 hour.

[0052] Pressure holding and cooling: During cooling, the furnace temperature is lowered to 900℃ and held for 1 hour, then lowered to 600℃ and held for 1 hour, after which it is cooled with the furnace. The performance comparison between Example 3 and Example 2 is shown in Table 3.

[0053]

[0054] By employing a matrix alloying and surface metallization coupled reinforcement method, Cu-B alloy (B content of 0.5 wt.%) was used as the matrix and combined with W-Cu alloy modified diamond particles. The resulting composite material exhibited further improvements in thermal conductivity and resistance to thermal shock.

[0055] Comparative Example 3:

[0056] The other conditions are the same as in Example 1, except that the diamond particles containing the foam W layer are placed in a mold, vibrated and then placed in an impregnation furnace and heated directly to 1200°C.

[0057]

[0058] As can be seen from Table 4, the step heating mode of placing diamond particles containing foam W layer in the mold, first heating to 800-900℃, holding at that temperature, and then heating to 1150-1200℃ can not only improve the thermal conductivity of the composite material, but also improve the interfacial bonding and thermal shock resistance of the composite material.

Claims

1. A method for preparing a diamond / copper composite material, characterized in that: A W-Cu layer is deposited on the surface of diamond particles, and then the diamond particles containing the W-Cu layer are heat-treated at a temperature ≥650℃ to obtain diamond particles containing a foamed W layer. The diamond particles containing the foamed W layer are placed in a mold, first heated to 800-900℃ and held at that temperature, and then heated to 1150-1200℃. The diamond particles containing the foamed W layer are then immersed in molten copper, and a protective gas is introduced to pressurize them. After heat and pressure holding, a diamond / copper composite material is obtained.

2. The method for preparing a diamond / copper composite material according to claim 1, characterized in that: The diamond in the diamond particles is selected from pure diamond or boron-doped diamond. The diamond particles have a particle size of 100-700 μm.

3. The method for preparing a diamond / copper composite material according to claim 1, characterized in that: A W-Cu layer is deposited on the surface of diamond particles by magnetron sputtering. The magnetron sputtering process involves co-sputtering with a W target and a Cu target, controlling the power of the W target to be 90-120W, the power of the Cu target to be 30-70W, and the vacuum degree to be 0.1-2Pa.

4. The method for preparing a diamond / copper composite material according to claim 1, characterized in that: In the W-Cu layer, the mass fraction of Cu is 10%-60%; The thickness of the W-Cu layer is 300-600 nm.

5. The method for preparing a diamond / copper composite material according to claim 1, characterized in that: The heat treatment temperature is 900-1200℃, and the heat treatment time is 0.5-3h.

6. The method for preparing a diamond / copper composite material according to claim 1, characterized in that: Diamond particles containing a foam W layer are placed in a mold and heated to 800-900℃ at a heating rate of 5-10℃ / min, and held for 0.5-1.5h. Then, the temperature is increased to 1150-1200℃ at a heating rate of 2-5℃ / min, and the diamond particles containing the foam W layer are then immersed in molten copper.

7. The method for preparing a diamond / copper composite material according to claim 1, characterized in that: The process of introducing protective gas and pressurizing is as follows: first control the pressure to 0.5-1MPa, hold the pressure for 1-2 minutes, then increase the pressure to 4-5MPa, hold the pressure for 5-10 minutes, then increase the pressure to 8-10MPa, and maintain the temperature and pressure for 0.5-1.5 hours.

8. The method for preparing a diamond / copper composite material according to claim 1, characterized in that: After the heat preservation and pressure holding are completed, keep the pressure constant, first lower the temperature to 850-900℃ and hold for 1-1.5 hours, then lower the temperature to 600-650℃ and hold for 1-1.5 hours, and then cool with the furnace.

9. A diamond / copper composite material prepared by the preparation method according to any one of claims 1-8.

10. The application of a diamond / copper composite material prepared by the preparation method according to any one of claims 1-8, characterized in that: The diamond / copper composite material is used in one of the following applications: thermal conductive substrate for semiconductor devices, heat sink for 5G base stations, or heat sink for power modules in new energy vehicles.

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