Red copper connector and diffusion welding method thereof

Abstract

The invention provides a red copper connector and a diffusion welding method thereof, and relates to the technical field of metal welding, the diffusion welding method of the red copper connector comprises the following steps: taking a red copper base material, and performing nanocrystallization treatment on one side surface of the red copper base material through an ion impact method to form a welding surface; the annealed copper middle layer is placed between the two pieces of red copper base metal, the annealed copper middle layer makes contact with the welding face, and a connector to be welded is formed; and the connector to be welded is welded through a pulse current auxiliary diffusion welding method, the red copper connector is obtained, the welding temperature of the pulse current auxiliary diffusion welding method is 300 + / -5 DEG C, the pressure is 18-22 MPa, and the heat preservation time is 25-35 min. And low-temperature, rapid and small-deformation reliable connection of the red copper base metal is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal welding, in particular to a copper joint and a diffusion welding method thereof. Background Art

[0002] Copper boasts excellent workability, ductility, electrical and thermal conductivity, as well as excellent weldability, weather resistance, corrosion resistance, and mechanical properties. It is a key material for liquid cooling systems in the information and communications technology (ICT) sector. Researching advanced copper welding techniques to achieve reliable connections with minimal deformation at low temperatures is of great significance to the production and manufacture of liquid cooling systems in the ICT sector, as well as promoting the development of my country's electronics industry.

[0003] Currently, copper welding methods include fusion welding, brazing, and traditional hot-press diffusion welding. Fusion welding methods for copper connection primarily include Tungsten Inert Gas Welding (TIG), Metal Inert Gas Welding (MIG), and laser welding. In fusion welding, the base metal and filler material melt together to form the weld. During fusion welding, excessively high welding temperatures can cause significant copper grain growth, the incorporation of impurities and alloying elements, and the joint is prone to cracking. Brazing copper connections do not melt the base metal; instead, the brazing filler metal melts to fill gaps in the base metal. The composition of the brazed joint differs significantly from that of the base metal, and low-melting-point compounds are easily formed in the joint, weakening its performance. When traditional hot-pressing diffusion welding is used to connect copper, the base material does not melt and relies on interatomic diffusion to form a metallurgical connection. Hot-pressing diffusion welding needs to be carried out under high temperature, high pressure and long holding time conditions. The large heat input will cause the base material grains to grow, performance to degrade, and severe deformation to occur. Summary of the Invention

[0004] The problem solved by the invention is how to solve the problem that traditional hot pressing diffusion welding has high welding temperature, long holding time and high applied pressure, which causes the growth of grains inside the copper base material and the degradation of joint performance.

[0005] In order to solve the above problems, the present invention provides a copper joint and a diffusion welding method thereof.

[0006] In a first aspect, the present invention provides a diffusion welding method for a copper joint, comprising the following steps: S1: Take a copper base material and perform nano-processing on one surface of the copper base material by ion bombardment to form a welding surface; S2: Place an annealed copper interlayer between two copper base materials, with the annealed copper interlayer in contact with the welding surface to form a joint to be welded; S3: Welding the connecting body to be welded by a pulse current assisted diffusion welding method to obtain a copper joint, wherein the pulse current assisted diffusion welding method has a welding temperature of 300±5°C, a pressure of 18 to 22 MPa, and a holding time of 25 to 35 minutes.

[0007] Optionally, in step S1 , high-purity argon or high-purity nitrogen with a purity of ≥99.999% is selected as the ion beam working gas for ion impact.

[0008] Optionally, in step S1 , the ion impact method includes: fixing the angle between the surface normal of the copper base material and the ion beam direction to 50° to 55°, and maintaining the distance between the surface of the copper base material and the ion source to 30 to 50 cm.

[0009] Optionally, in step S1, in the ion impact method, the ion beam current is 3 to 8 mA, the ion beam impact time is 150 to 200 min, and the vacuum degree is maintained at 1.5×10 -2 to 1.7×10 -2 Pa.

[0010] Optionally, step S2 further includes: polishing the annealed copper intermediate layer with sandpaper, performing alkali washing, and then performing acid washing, washing in anhydrous ethanol after acid washing, and placing it between two copper base materials after drying.

[0011] Optionally, step S2 further includes: polishing the annealed copper intermediate layer with 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper in sequence, placing it in a 10% NaOH solution for alkali washing for 10 to 15 minutes, and then placing it in anhydrous ethanol for ultrasonic cleaning for 10 to 15 minutes; then placing it in a 7% HCl solution for acid washing for 10 to 15 minutes, and then placing it in anhydrous ethanol for ultrasonic cleaning for 10 to 15 minutes after acid washing, and then placing it between two copper base materials after drying.

[0012] Optionally, the annealed copper intermediate layer has a thickness of 5 to 15 μm.

[0013] Optionally, in step S3, during the step of welding by pulse current assisted diffusion welding, the vacuum degree is 10 -1 to 10 -2 Pa, heating rate is 80 to 120 ℃ / min, welding temperature is 300±5 ℃, pressure is 18 to 22MPa, and holding time is 25 to 35 min.

[0014] Optionally, the preparation of the annealed copper intermediate layer comprises the steps of: taking high-purity copper with a purity of ≥99.99% and annealing it at 500 to 700° C. for 10 to 60 minutes in a vacuum or inert gas environment.

[0015] In a second aspect, the present invention provides a copper joint, which is manufactured by the diffusion welding method for a copper joint as described in any one of the above items.

[0016] The beneficial effects of the present invention's copper joint and diffusion welding method are as follows: the ion bombardment method utilizes the ionization of a working gas in a vacuum environment to form a plasma, thereby forming a high-energy ion beam to bombard the surface of the copper base material. The high-energy ion beam impact achieves grain refinement on the surface of the copper base material, thereby achieving nano-scaling of the copper base material surface and introducing a nanocrystalline structure on the copper surface; the nanocrystalline structure has a higher Gibbs free energy and grain boundary volume fraction, and thus has a higher diffusion rate and a strong tendency for thermally driven grain growth. Since the specific surface area and surface energy of nanomaterials are much greater than those of bulk materials, they have a strong tendency for thermally driven grain growth at lower temperatures, and thus can achieve mutual fusion at low temperatures. The annealed copper intermediate layer has low hardness and good plasticity, can fill interface pores during the diffusion welding process, effectively promoting the bridging of the connection interface pores. Therefore, the use of the annealed copper intermediate layer can improve the strength of the diffusion welded joint. The pulse current assisted diffusion welding method applies pressure and pulse current to the joint to be welded, generating Joule heat on the contact surface and the area near the contact surface, and forming a connection joint under the coupling effect of pulse current, Joule heat and pressure. The main heat source of pulse current assisted diffusion welding is Joule heat concentrated in the weld and its vicinity, with a fast heating rate. At the same time, electroplasticity, electrodiffusion and discharge plasma effects work together to activate the interface to be welded, and can promote the closure of interface pores to achieve metallurgical bonding of the joint. The connection temperature is low, the connection time is short and the connection pressure is small. The organic coupling of annealed copper intermediate layer, ion impact nano-crystallization and pulse current, the fast pulse current heating rate, the presence of electroplasticity, electrodiffusion and discharge plasma effects can effectively avoid the problem of nanocrystal growth of copper base material during heating. Combined with the characteristics of low hardness and good plasticity of annealed copper, it promotes the bridging of weld pores while reducing welding temperature, shortening welding time and reducing welding deformation, and realizes a reliable connection of copper base material at low temperature, fast speed and small deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of a diffusion welding method for a copper joint according to an embodiment of the present invention; Figure 2 This is the dynamic stress-strain curve of the T2 copper joint in Example 1. DETAILED DESCRIPTION

[0018] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the present invention description are only for the purpose of describing specific embodiments and are not intended to limit the present invention; As used herein, the term "including" and its variations are open-ended, i.e., "including but not limited to"; the term "based on" means "based at least in part on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; and the term "optionally" means "optional embodiments." Definitions of other terms are provided in the following description.

[0020] This embodiment provides a copper joint and a diffusion welding method thereof.

[0021] like Figure 1 As shown, a diffusion welding method for a copper joint provided by an embodiment of the present invention includes the following steps: S1: Take a copper base material and perform nano-processing on one surface of the copper base material by ion bombardment to form a welding surface; S2: Place an annealed copper interlayer between two copper base materials, with the annealed copper interlayer in contact with the welding surface to form a joint to be welded; S3: Welding the connecting body to be welded by a pulse current assisted diffusion welding method to obtain a copper joint, wherein the pulse current assisted diffusion welding method has a welding temperature of 300±5°C, a pressure of 18 to 22 MPa, and a holding time of 25 to 35 minutes.

[0022] In this embodiment, the ion bombardment method uses the ionization of a working gas in a vacuum environment to form a plasma, thereby forming a high-energy ion beam to bombard the surface of the copper base material. The high-energy ion beam impact achieves the refinement of the copper base material surface grains, thereby achieving nano-scaling of the copper base material surface and introducing a nanocrystalline structure on the copper surface. The nanocrystalline structure has a higher Gibbs free energy and grain boundary volume fraction, and therefore has a higher diffusion rate and a strong tendency for thermally driven grain growth. Since the specific surface area and surface energy of nanomaterials are much greater than those of bulk materials, they have a strong tendency for thermally driven grain growth at lower temperatures, and thus can achieve mutual fusion at low temperatures. The annealed copper intermediate layer has low hardness and good plasticity, which can fill the interface pores during the diffusion welding process, effectively promoting the bridging of the connection interface pores. Therefore, the use of the annealed copper intermediate layer can improve the strength of the diffusion welded joint. The pulse current assisted diffusion welding method applies pressure and pulse current to the joint to be welded, generating Joule heat on the contact surface and the area near the contact surface, and forming a connection joint under the coupling effect of pulse current, Joule heat and pressure. The main heat source of pulse current assisted diffusion welding is Joule heat concentrated in the weld and its vicinity, with a fast heating rate. At the same time, electroplasticity, electrodiffusion and discharge plasma effects work together to activate the interface to be welded, and can promote the closure of interface pores to achieve metallurgical bonding of the joint. The connection temperature is low, the connection time is short and the connection pressure is small. The organic coupling of annealed copper intermediate layer, ion impact nano-crystallization and pulse current, the fast pulse current heating rate, the presence of electroplasticity, electrodiffusion and discharge plasma effects can effectively avoid the problem of nanocrystal growth of copper base material during heating. Combined with the characteristics of low hardness and good plasticity of annealed copper, it promotes the bridging of weld pores while reducing welding temperature, shortening welding time and reducing welding deformation, and realizes a reliable connection of copper base material at low temperature, fast speed and small deformation.

[0023] Specifically, the copper base material can be T2 copper. T2 copper refers to a copper-silver alloy with a copper and silver content exceeding 99.9% (referenced in GB / 5231-2012). There are no specific requirements for phosphorus. According to GB / 5231-2012, the chemical composition of T2 copper is: Cu+Ag≥99.9%, Sb: 0.002%, As: 0.002%, Fe: 0.005%, Pb: 0.005%, and S: 0.005%.

[0024] Optionally, in step S1 , high-purity argon or high-purity nitrogen with a purity of ≥99.999% is selected as the ion beam working gas for ion impact.

[0025] In this optional embodiment, the copper base material is easily contaminated by oxidation. Impure oxygen reacts with copper to form CuO / CuO, reducing thermal conductivity to below 30 W / (m·K). When nitrogen or argon purity reaches 99.999%, the oxygen content on the copper surface drops to 50 ppm. High-purity gases keep plasma density fluctuations below 1%, ensuring a stable sputtering rate.

[0026] Optionally, in step S1 , the ion impact method includes: fixing the angle between the surface normal of the copper base material and the ion beam direction to 50° to 55°, and maintaining the distance between the surface of the copper base material and the ion source to 30 to 50 cm.

[0027] In this optional embodiment, an angle range of 50° to 55° balances sputtering yield and surface defect density, avoiding excessively deep grooves caused by vertical incidence. Angles greater than 55° are prone to shadowing. The distance from the ion source to the copper base metal surface is controlled between 30 and 50 cm, maintaining the ion energy density within the range of 0.5 to 2 keV / atom to ensure surface nanocrystallization without inducing deep lattice distortion. A distance greater than 50 cm from the ion source to the copper base metal surface results in decreased beam uniformity and a loss of more than 15% in edge efficiency.

[0028] Optionally, in step S1, in the ion impact method, the ion beam current is 3 to 8 mA, the ion beam impact time is 150 to 200 min, and the vacuum degree is maintained at 1.5×10 -2 to 1.7×10 -2 Pa.

[0029] In this optional embodiment, the ion beam impact time is 150 to 200 minutes, ensuring a nanocrystalline layer thickness of 300 to 500 nm. Maintaining a vacuum level suppresses gas molecule scattering and ensures an ion mean free path greater than 5 cm. This combination of ion beam current and impact time creates a gradient nanostructure on the copper surface, with a grain size of 12 ± 3 nm in the surface layer (0-100 nm) and 50 to 80 nm in the transition layer (100-400 nm). This gradient structure reduces phonon transmission anisotropy and increases thermal conductivity to 420 W / (m·K).

[0030] Optionally, step S2 further includes: polishing the annealed copper intermediate layer with sandpaper, performing alkali washing, and then performing acid washing, washing in anhydrous ethanol after acid washing, and placing it between two copper base materials after drying.

[0031] Optionally, step S2 further includes: polishing the annealed copper intermediate layer with 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper in sequence, placing it in a 10% NaOH solution for alkali washing for 10 to 15 minutes, and then placing it in anhydrous ethanol for ultrasonic cleaning for 10 to 15 minutes; then placing it in a 7% HCl solution for acid washing for 10 to 15 minutes, and then placing it in anhydrous ethanol for ultrasonic cleaning for 10 to 15 minutes after acid washing, and then placing it between two copper base materials after drying.

[0032] Optionally, the annealed copper intermediate layer has a thickness of 5 to 15 μm.

[0033] In this optional embodiment, the use of an ultra-thin annealed copper intermediate layer of 5 to 15 μm has significant metallurgical advantages and process adaptability, and can completely fill the interface pores during the diffusion welding process.

[0034] Optionally, in step S3, during the step of welding by pulse current assisted diffusion welding, the vacuum degree is 10 -1 to 10 -2 Pa, heating rate is 80 to 120 ℃ / min, welding temperature is 300±5 ℃, pressure is 18 to 22MPa, and holding time is 25 to 35 min.

[0035] Optionally, the preparation of the annealed copper intermediate layer comprises the steps of: taking high-purity copper with a purity of ≥99.99% and annealing it at 500 to 700° C. for 10 to 60 minutes in a vacuum or inert gas environment.

[0036] In this optional embodiment, the copper surface energy is increased from 1.72 to 1.25 J / m in a vacuum environment or an inert gas environment. 2 (reduced by 27%), significantly improving the subsequent diffusion soldering or plating bonding performance. For high-purity copper (Tm=1083℃), it takes 50 minutes to trigger recrystallization at 500℃, but only 8 minutes at 700℃.

[0037] Another embodiment of the present invention provides a copper joint, which is manufactured using the diffusion welding method for a copper joint as described in any one of the above items.

[0038] The present invention is further described below with reference to specific embodiments.

[0039] Example 1, diffusion welding of copper joints.

[0040] (1) Use 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper to polish the T2 copper base material, then ultrasonically clean it in anhydrous ethanol for 30 minutes, blow dry it and set aside; (2) Place T2 copper on the sample stage in a vacuum chamber, use high-purity argon (99.999%) as the ion beam working gas, fix the angle between the surface normal of T2 copper and the ion beam direction to 53°, keep the distance between T2 copper and the ion source at 40 cm, set the ion beam current to 5 mA, and shock for 180 min. During the shock process, the vacuum degree is maintained at 1.6×10 -2 Pa, after finishing, take out T2 copper for later use; (3) The 10 μm thick annealed copper intermediate layer was polished with 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper in sequence, and then placed in a 10% NaOH solution for alkaline washing for 12 minutes. After alkaline washing, it was placed in anhydrous ethanol for ultrasonic cleaning for 12 minutes; (4) Immerse the annealed copper intermediate layer after alkaline washing in 7% HCl solution and pickle for 12 minutes. After pickling, place it in anhydrous ethanol and ultrasonically clean it for 12 minutes. Blow dry and set aside. (5) The treated annealed copper intermediate layer was placed between two pieces of T2 copper nano-processed by ion impact, and then placed in a pulse current assisted diffusion welding device for welding. The vacuum degree was maintained at 5×10 -2 The welding process was carried out at a heating rate of 100°C / min, a welding temperature of 300°C, a pressure of 20 MPa, and a holding time of 30 min. The welded parts were then cooled in the furnace. After cooling, they were taken out to obtain a T2 copper joint.

[0041] The stress and strain rate of the T2 copper joint were tested and the dynamic stress-strain curve was prepared, such as Figure 2 As shown, the shear strength of the T2 copper joint is 98 MPa. In Example 1, a high-quality T2 copper joint can be obtained by low-temperature rapid connection under the parameters of 300°C-20 MPa-30 min.

[0042] Example 2, diffusion welding of copper joints.

[0043] (1) Use 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper to polish the T2 copper base material, then ultrasonically clean it in anhydrous ethanol for 30 minutes, blow dry it and set aside; (2) Place T2 copper on the sample stage in a vacuum chamber, use high-purity argon (99.999%) as the ion beam working gas, fix the angle between the surface normal of T2 copper and the ion beam direction to 50°, keep the distance between T2 copper and the ion source at 30 cm, set the ion beam current to 3 mA, and shock for 200 min. During the shock process, the vacuum degree is maintained at 1.5×10 -2 Pa, after finishing, take out T2 copper for later use; (3) The 5 μm thick annealed copper intermediate layer was polished with 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper in sequence, and then placed in a 10% NaOH solution for alkaline washing for 10 min. After alkaline washing, it was placed in anhydrous ethanol for ultrasonic cleaning for 10 min. (4) Immerse the annealed copper intermediate layer after alkaline washing in 7% HCl solution and pickle for 10 minutes. After pickling, place it in anhydrous ethanol and ultrasonically clean it for 10 minutes, then blow dry and set aside; (5) Place the treated annealed copper intermediate layer between two pieces of T2 copper nano-processed by ion impact, and place them in a pulse current assisted diffusion welding device for welding. The vacuum degree is maintained at 10 -2 The welding process was carried out at a heating rate of 80°C / min, a welding temperature of 295°C, a pressure of 18 MPa, and a holding time of 35 minutes. The welded parts were then furnace cooled. After cooling, they were removed to obtain a high-quality T2 copper joint with a low-temperature quick connection.

[0044] Example 3, diffusion welding of copper joints.

[0045] (1) Use 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper to polish the T2 copper base material, then ultrasonically clean it in anhydrous ethanol for 30 minutes, blow dry it and set aside; (2) Place T2 copper on the sample stage in a vacuum chamber, use high-purity argon (99.999%) as the ion beam working gas, fix the angle between the surface normal of T2 copper and the ion beam direction to 55°, keep the distance between T2 copper and the ion source at 50 cm, set the ion beam current to 8 mA, and shock for 150 min. During the shock process, the vacuum degree is maintained at 1.7×10 -2 Pa, after finishing, take out T2 copper for later use; (3) The 15 μm thick annealed copper intermediate layer was polished with 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper in sequence, and then placed in a 10% NaOH solution for alkaline washing for 15 minutes. After alkaline washing, it was placed in anhydrous ethanol for ultrasonic cleaning for 15 minutes; (4) Immerse the annealed copper intermediate layer after alkaline washing in 7% HCl solution and pickle for 15 minutes. After pickling, place it in anhydrous ethanol and ultrasonically clean it for 15 minutes. Blow dry and set aside. (5) Place the treated annealed copper intermediate layer between two pieces of T2 copper nano-processed by ion impact, and place them in a pulse current assisted diffusion welding device for welding. The vacuum degree is maintained at 10 -1 The welding process was carried out at a heating rate of 120°C / min, a welding temperature of 305°C, a pressure of 22 MPa, and a holding time of 25 minutes. The welded parts were then cooled in the furnace. After cooling, they were removed and finally a high-quality T2 copper joint with a low-temperature quick connection was obtained.

[0046] Comparative Example 1: Diffusion welding of a copper joint without using an annealed copper intermediate layer.

[0047] (1) Use 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper to polish the T2 copper base material, then ultrasonically clean it in anhydrous ethanol for 30 minutes, blow dry it and set aside; (2) Place T2 copper on the sample stage in a vacuum chamber, use high-purity argon (99.999%) as the ion beam working gas, fix the angle between the surface normal of T2 copper and the ion beam direction to 53°, keep the distance between T2 copper and the ion source at 40 cm, set the ion beam current to 5 mA, and shock for 180 min. During the shock process, the vacuum degree is maintained at 1.6×10 -2 Pa, after finishing, take out T2 copper for later use; (3) Two pieces of T2 copper with nano-sized surfaces after ion impact are placed opposite each other in a pulse current assisted diffusion welding device for welding. The vacuum degree is maintained at 5×10 -2 The welding process was carried out at a heating rate of 100°C / min, a welding temperature of 350°C, a pressure of 20 MPa, and a holding time of 30 minutes. The welded parts were then furnace cooled. After cooling, they were removed and finally a T2 copper joint without an annealed copper interlayer was obtained.

[0048] Comparative Example 2: Hot-press diffusion welding of copper joints.

[0049] (1) Use 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper to polish the T2 copper base material, then ultrasonically clean it in anhydrous ethanol for 30 minutes, blow dry it and set aside; (2) Place two pieces of T2 copper opposite to each other and place them in a hot pressing diffusion welding device for welding. The vacuum degree is maintained at 5×10 -2 The welding process was carried out at a heating rate of 100°C / min, a welding temperature of 700°C, a pressure of 20 MPa, and a holding time of 60 min. The welded parts were then furnace cooled. After cooling, they were removed to obtain a T2 copper joint formed by hot-press diffusion welding.

[0050] Effect embodiment The shear strength and deformation rate of the T2 copper joints prepared in Example 1, Comparative Examples 1, and 2 were tested using standard methods. The test results are shown in Table 1.

[0051] Table 1 Shear strength and deformation rate data of T2 copper joints in Example 1, Comparative Example 1, and Comparative Example 2

[0052] It can be seen from Table 1 that the shear strength of the T2 copper joint prepared in Example 1 is as high as 98 MPa, and the deformation rate is as low as 0.03%. The T2 copper joint prepared in Example 1 has small deformation, high strength and good performance.

[0053] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A diffusion welding method for copper joints, characterized in that: The following steps are involved: S1: taking a copper base material, performing nano-processing on one surface of the copper base material by ion bombardment to form a welding surface; S2: placing an annealed copper intermediate layer between the two copper base materials, with the annealed copper intermediate layer in contact with the welding surface to form a connection body to be welded; S3: Welding the to-be-welded connection body by a pulse current assisted diffusion welding method to obtain a copper joint, wherein the pulse current assisted diffusion welding method has a welding temperature of 300±5°C, a pressure of 18 to 22 MPa, and a holding time of 25 to 35 minutes.

2. The diffusion welding method of a copper joint according to claim 1, characterized in that: In step S1 , high-purity argon or high-purity nitrogen with a purity of ≥99.999% is selected as the ion beam working gas for ion impact.

3. The diffusion welding method of a copper joint according to claim 1, characterized in that: In step S1 , the ion impact method comprises: fixing the angle between the surface normal of the copper base material and the ion beam direction to 50° to 55°, and maintaining the distance between the surface of the copper base material and the ion source to 30 to 50 cm.

4. The diffusion welding method of a copper joint according to claim 1, characterized in that: In step S1, in the ion impact method, the ion beam current is 3 to 8 mA, the ion beam impact time is 150 to 200 min, and the vacuum degree is maintained at 1.5×10 -2 to 1.7×10 -2 Pa.

5. The diffusion welding method of a copper joint according to claim 1, characterized in that: Step S2 further includes: polishing the annealed copper intermediate layer with sandpaper, performing alkali washing, and then performing acid washing. After acid washing, the intermediate layer is washed in anhydrous ethanol, dried, and placed between the two copper base materials.

6. The diffusion welding method for a copper joint according to claim 5, characterized in that: Step S2 also includes: the annealed copper intermediate layer is polished with 800 mesh, 1000 mesh, 1500 mesh, and 2000 mesh sandpaper in sequence, and then placed in a 10% NaOH solution for alkali washing for 10 to 15 minutes, and then placed in anhydrous ethanol for ultrasonic cleaning for 10 to 15 minutes; then placed in a 7% HCl solution for pickling for 10 to 15 minutes, and then placed in anhydrous ethanol for ultrasonic cleaning for 10 to 15 minutes after pickling, and then placed between the two copper base materials after drying.

7. The diffusion welding method for a copper joint according to claim 1 or 6, characterized in that: The thickness of the annealed copper intermediate layer is 5 to 15 μm.

8. The diffusion welding method for a copper joint according to claim 1, characterized in that: In step S3, the vacuum degree is 10 -1 to 10 -2 Pa, and the heating rate was 80 to 120 °C / min.

9. The diffusion welding method of a copper joint according to claim 1, characterized in that: The preparation of the annealed copper intermediate layer comprises the following steps: taking high-purity copper with a purity of ≥99.99% and performing annealing treatment at 500 to 700° C. for 10 to 60 minutes in a vacuum or inert gas environment.

10. A copper joint, characterized in that: The copper joint is made by the diffusion welding method according to any one of claims 1 to 9.

Images