Copper-aluminum polymer diffusion hybrid welding method

Abstract

The invention relates to the technical field of copper-aluminum bars, in particular to a copper-aluminum polymer diffusion hybrid welding method which is characterized by comprising the following steps: S1, welding nickel sheets with bare copper: compounding the nickel sheets with the thickness of 0.1-0.3 mm on the welding surfaces of the copper bars; s2, nickel sheet polishing: mechanically polishing the nickel sheet until the surface roughness Ra is less than or equal to 0.8 mu m; s3, the aluminum row is polished, specifically, the welding face of the aluminum row is polished in a one-way mode through abrasive paper of 800-2000 meshes till the roughness Ra is smaller than or equal to 1.0 micron; s4, copper and aluminum composite welding is conducted, specifically, the copper bar with the polished nickel piece and the polished aluminum bar are composited through polymer diffusion welding, the welding temperature is 400-500 DEG C, the pressure is 10-20 MPa, and heat preservation is conducted for 30-60 minutes; the nickel sheet with the proper thickness is compounded on the welding surface of the copper bar, the binding force of a welding interface is enhanced, then the nickel sheet is subjected to precise mechanical polishing, it is ensured that the surface roughness of the nickel sheet reaches the extremely low level, the welding surface of the aluminum bar is subjected to fine grinding treatment, and the adaptability of the welding surface is improved; and tight combination of the copper bar and the aluminum bar is achieved at specific welding temperature, pressure and heat preservation time, and practicability is high.

Description

Technical Field

[0001] This invention relates to the field of copper-aluminum busbar technology, specifically a copper-aluminum polymer diffusion composite welding method. Background Technology

[0002] Copper is a metal with excellent electrical and thermal conductivity, widely used in various industries. However, due to its high density, products made of copper are heavy, causing significant inconvenience in transportation and use. Especially with the severe shortage of copper resources, the procurement cost of copper raw materials remains high. Aluminum is the second most conductive and thermally conductive metal after copper. Although its conductivity is only two-thirds that of copper, its density is only one-third that of copper. Because of its lighter weight, it is often chosen by the power and electronics industries.

[0003] Existing copper-aluminum composite bars are welded using copper-aluminum composite polymers. However, due to the different properties of the two materials, there is molecular repulsion during the bonding process, which creates gaps and increases the risk of cracking in the copper-aluminum bond, hindering its development. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a copper-aluminum polymer diffusion composite welding method. This method solves the problem that existing copper-aluminum composite bars, when welded with copper-aluminum composite polymers, suffer from the risk of cracking due to the different properties of the two materials causing molecular repulsion during bonding, which hinders their development. The technical solution adopted in this invention includes the following steps: S1. Bare copper welding nickel sheet: A nickel sheet with a thickness of 0.1-0.3mm is laminated onto the welding surface of the copper busbar; S2. Polishing nickel sheet: The nickel sheet is mechanically polished until the surface roughness Ra≤0.8μm; S3. Grinding aluminum busbar: The welding surface of the aluminum busbar is unidirectionally ground with 800-2000 grit sandpaper until the roughness Ra≤1.0μm; S4. Copper-aluminum composite welding: The copper busbar with polished nickel sheet is laminated with the ground aluminum busbar through polymer diffusion welding, with a welding temperature of 400-500℃, a pressure of 10-20MPa, and a holding time of 30-60 minutes.

[0005] A further improvement to the above scheme is that the nickel sheet is pure nickel or a nickel-based alloy with a nickel content ≥99.5wt% and is plated with a 0.5-2μm thick silver layer.

[0006] A further improvement to the above scheme is that step S1 uses resistance welding with a welding current of 5-8kA and an electrode pressure of 0.4-0.6MPa.

[0007] A further improvement to the above scheme is that in step S2, nano-diamond polishing fluid is used, and the polishing speed is 200-300 rpm. After polishing, the microhardness of the nickel sheet surface is increased by 10-15%.

[0008] A further improvement to the above scheme is that the grinding direction in step S3 forms an angle of 45-90° with the extension direction of the aluminum bar grains.

[0009] A further improvement to the above scheme is that the polymer diffusion welding layer in step S4 is a polyimide-silane composite with a thickness of 50-100 μm and a silane content of 3-8 wt%.

[0010] A further improvement to the above scheme is that the polyimide-silane composite comprises the following components: 85-92wt% polyimide resin γ-aminopropyltriethoxysilane 5-10 wt% 3-5 wt% nano-alumina particles.

[0011] A further improvement to the above scheme is that step S4 is carried out in a vacuum environment with a vacuum degree ≤5×10⁻³Pa, and argon protective gas is introduced during the welding process at a flow rate of 5-10L / min.

[0012] A further improvement to the above scheme is to cool the welded material at a gradient of 5-10℃ / min to below 150℃.

[0013] A further improvement to the above scheme is that it also includes step S5: performing ultrasonic testing on the weld interface, requiring the defect area to be ≤0.5mm².

[0014] The beneficial effects of this invention are: Compared to existing copper-aluminum busbars, this invention enhances the bonding strength of the welding interface by incorporating a nickel sheet of appropriate thickness onto the copper busbar welding surface. The nickel sheet is then precisely mechanically polished to ensure extremely low surface roughness, laying the foundation for high-quality welding. Simultaneously, the aluminum busbar welding surface undergoes meticulous grinding, further improving the compatibility of the welding surface. Under specific welding temperature, pressure, and holding time, polymer diffusion welding technology achieves a tight composite of the copper and aluminum busbars, improving welding strength and providing strong support for the composite application of copper and aluminum materials, demonstrating high practicality. Firstly, by using a nickel sheet as a transition layer on the surface of the copper busbar, the interfacial stress problem caused by the difference in thermal expansion coefficients during direct copper-aluminum welding is effectively solved. After mechanical polishing, the surface roughness of the nickel sheet is controlled at Ra≤0.8μm, which, combined with the fine grinding of the aluminum busbar (Ra≤1.0μm), provides an ideal contact interface for diffusion welding. Secondly, the copper-aluminum composite welding uses a medium-temperature welding range of 400-500℃, which ensures the full diffusion of polymer materials while avoiding damage to the base material from high temperatures. Furthermore, the pressure of 10-20MPa promotes atomic-level tight bonding at the copper-aluminum interface, and the heat preservation time of 30-60 minutes ensures the full progress of the diffusion reaction, thereby improving the mechanical strength and electrical conductivity of the copper-aluminum dissimilar metal welded joint. The bonding strength of the welded joint can reach more than 90% of that of the base material, and the process has good stability. Attached Figure Description

[0015] Figure 1 This is a perspective view of the copper-aluminum polymer diffusion composite welding method of the present invention; Figure 2 This is an exploded view of the copper-aluminum polymer diffusion composite welding method of the present invention; Figure 3 This is a schematic diagram illustrating the steps of the copper-aluminum polymer diffusion composite welding method of the present invention.

[0016] Explanation of reference numerals in the attached diagram: Nickel sheet 10; 20 copper bars; Aluminum busbar 30. Detailed Implementation

[0017] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0018] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] like Figures 1-3 As shown in the embodiment of the present invention, a copper-aluminum polymer diffusion composite welding method is characterized by comprising the following steps: S1. Bare copper welded nickel sheet 10: A nickel sheet 10 with a thickness of 0.1-0.3mm is laminated on the welding surface of the copper busbar 20; S2. Polished nickel sheet 10: Mechanically polish the nickel sheet 10 until the surface roughness Ra ≤ 0.8 μm; S3. Grinding aluminum strip 30: Use 800-2000 grit sandpaper to grind the welding surface of aluminum strip 30 in one direction until the roughness Ra≤1.0μm; S4. Copper-Aluminum Composite Welding: The copper busbar 20 with polished nickel sheet 10 and the polished aluminum busbar 30 are composited by polymer diffusion welding at a welding temperature of 400-500℃, a pressure of 10-20MPa, and a holding time of 30-60 minutes. In this embodiment, by composited with a nickel sheet 10 of appropriate thickness on the welding surface of the copper busbar 20, the bonding force of the welding interface is enhanced. Subsequently, the nickel sheet 10 is precisely mechanically polished to ensure that its surface roughness reaches an extremely low level, laying the foundation for high-quality welding. At the same time, the welding surface of the aluminum busbar 30 is carefully polished to further improve the compatibility of the welding surface. Under specific welding temperature, pressure, and holding time, the polymer diffusion welding technology achieves a tight composite of the copper busbar 20 and the aluminum busbar 30, improves the welding strength, provides strong support for the composite application of copper and aluminum materials, and has strong practicality.

[0021] Firstly, by using a nickel sheet 10 as a transition layer on the surface of the copper busbar 20, the problem of interfacial stress caused by the difference in thermal expansion coefficients during direct copper-aluminum welding is effectively solved. After mechanical polishing, the surface roughness of the nickel sheet 10 is controlled at Ra≤0.8μm, which, combined with the fine grinding of the aluminum busbar 30 (Ra≤1.0μm), provides an ideal contact interface for diffusion welding.

[0022] Secondly, the copper-aluminum composite welding uses a medium-temperature welding range of 400-500℃, which ensures the full diffusion of polymer materials while avoiding damage to the base material from high temperatures. Furthermore, the pressure of 10-20MPa promotes atomic-level tight bonding at the copper-aluminum interface, and the heat preservation time of 30-60 minutes ensures the full progress of the diffusion reaction, thereby improving the mechanical strength and electrical conductivity of the copper-aluminum dissimilar metal welded joint. The bonding strength of the welded joint can reach more than 90% of that of the base material, and the process has good stability.

[0023] like Figures 1 to 2 As shown, the nickel sheet 10 is made of pure nickel or a nickel-based alloy with a nickel content ≥99.5 wt% and a 0.5-2 μm thick silver layer plated on its surface. In this embodiment, the nickel sheet 10 is made of pure nickel or a nickel-based alloy with a nickel content of over 99.5 wt%, ensuring high conductivity and corrosion resistance of the material. The 0.5-2 μm thick silver layer plated on the surface of the nickel sheet 10 improves the material's oxidation resistance and enhances the strength and reliability of the welded joint. The welded joint has high strength, good conductivity, and strong corrosion resistance, and the process is stable and controllable, greatly improving production efficiency and product quality.

[0024] like Figure 3As shown, step S1 employs resistance welding with a welding current of 5-8 kA and an electrode pressure of 0.4-0.6 MPa. In this embodiment, a 0.1-0.3 mm thick nickel sheet 10 is bonded to the welding surface of the copper busbar 20 by welding a nickel sheet 10 onto bare copper using resistance welding, achieving an efficient and stable connection. During the welding process, the 5-8 kA welding current ensures sufficient heat input, allowing the nickel sheet 10 and the copper busbar 20 to fully fuse. Simultaneously, the 0.4-0.6 MPa electrode pressure ensures close contact between the welding surfaces, contributing to improved welding quality. This enhances the strength and conductivity of the welded joint, and also improves welding efficiency and stability.

[0025] Step S2 uses nano-diamond polishing slurry at a polishing speed of 200-300 rpm, resulting in a 10-15% increase in the microhardness of the nickel sheet 10 surface after polishing. In this embodiment, mechanical polishing reduces the surface roughness of the nickel sheet 10 to Ra≤0.8μm, achieving a highly smooth surface. The use of nano-diamond polishing slurry at a polishing speed of 200-300 rpm not only maintains a good polishing effect but also increases the microhardness of the nickel sheet 10 surface by 10-15%, significantly enhancing its wear resistance and service life; and promoting the strength and reliability of the welded joint.

[0026] In step S3, the grinding direction forms a 45-90° angle with the grain extension direction of the aluminum busbar 30. In this embodiment, by forming a 45-90° angle between the grinding direction and the grain extension direction of the aluminum busbar 30, the uniformity and bonding strength of the welded surface are improved. It can also optimize the heat conduction and distribution during the welding process to a certain extent, so that the welded surface of the aluminum busbar 30 can be unidirectionally ground with 800-2000 grit sandpaper, and its roughness can be effectively controlled to reach the fine standard of Ra≤1.0μm. The fine pretreatment process can significantly improve the strength and sealing of the welded joint, ensuring stable and reliable welding quality.

[0027] The polymer diffusion welding layer in step S4 is a polyimide-silane composite with a thickness of 50-100 μm and a silane content of 3-8 wt%. In this embodiment, by controlling the welding layer thickness between 50-100 μm and precisely adjusting the silane content to 3-8 wt%, the strength and stability of the weld joint are ensured. This allows the copper-aluminum composite welding technology to successfully combine the copper busbar 20 of the polished nickel sheet 10 with the polished aluminum busbar 30 using a polymer diffusion welding method. Under a welding temperature of 400-500℃ and a pressure of 10-20 MPa, after a heat treatment of 30-60 minutes, a polymer diffusion welding layer composed of a polyimide-silane composite is formed.

[0028] The polyimide-silane composite comprises the following components: 85-92 wt% polyimide resin, 5-10 wt% γ-aminopropyltriethoxysilane, and 3-5 wt% nano-alumina particles. In this embodiment, the polyimide resin, accounting for 85-92 wt%, provides excellent insulation performance and mechanical strength. The addition of γ-aminopropyltriethoxysilane (5-10 wt%) effectively enhances the adhesion and weather resistance of the material, enabling the composite to bond more firmly to various substrates. Furthermore, the 3-5 wt% nano-alumina particles not only improve the thermal conductivity of the composite but also further enhance its wear resistance and hardness, achieving efficient and reliable welding results.

[0029] Step S4 is performed in a vacuum environment with a vacuum degree ≤ 5 × 10⁻³ Pa. Argon protective gas is introduced during the welding process at a flow rate of 5-10 L / min. In this embodiment, by holding the weld at a temperature of 400-500℃ and a pressure of 10-20 MPa for 30-60 minutes in a vacuum environment with a vacuum degree ≤ 5 × 10⁻³ Pa, the high quality of the weld is ensured. The 5-10 L / min argon gas, as a protective gas, effectively prevents oxidation and contamination during the welding process, further improving the performance and reliability of the welded joint. The process is stable, and the welded joint has high strength and excellent electrical and thermal conductivity.

[0030] After welding, the temperature is gradually cooled to below 150°C at a rate of 5-10°C / min. In this embodiment, the copper busbar 20 of the polished nickel sheet 10 and the polished aluminum busbar 30 are successfully bonded together using a polymer diffusion welding method with copper-aluminum composite welding technology. This ensures the strength of the weld joint and greatly improves the bonding strength between the copper busbar 20 and the aluminum busbar 30. After welding, the temperature is gradually cooled to below 150°C at a rate of 5-10°C / min, effectively avoiding thermal stress and deformation of the weld joint and further improving the welding quality.

[0031] Step S5: Perform ultrasonic testing on the weld interface, requiring the defect area to be ≤0.5mm². In this embodiment, ultrasonic testing of the weld interface is an important means to ensure weld quality. This welding method promotes the interpenetration and bonding between copper and aluminum atoms through the diffusion effect of polymer materials, thereby forming a high-strength, high-density weld interface. It can accurately detect welding defects such as cracks and porosity, and requires that the area of ​​these defects be less than or equal to 0.5mm². This ensures the reliability and stability of the welded joint and improves the overall performance of the welded component.

[0032] A method for copper-aluminum polymer diffusion composite welding, characterized by comprising the following steps: S1. Bare copper welded nickel sheet 10: A nickel sheet 10 with a thickness of 0.1-0.3mm is laminated on the welding surface of the copper busbar 20; S2. Polished nickel sheet 10: Mechanically polish the nickel sheet 10 until the surface roughness Ra ≤ 0.8 μm; S3. Grinding aluminum strip 30: Use 800-2000 grit sandpaper to grind the welding surface of aluminum strip 30 in one direction until the roughness Ra≤1.0μm; S4. Copper-Aluminum Composite Welding: The copper busbar 20 with polished nickel sheet 10 and the polished aluminum busbar 30 are composited by polymer diffusion welding at a welding temperature of 400-500℃, a pressure of 10-20MPa, and a holding time of 30-60 minutes. In this embodiment, by composited with a nickel sheet 10 of appropriate thickness on the welding surface of the copper busbar 20, the bonding force of the welding interface is enhanced. Subsequently, the nickel sheet 10 is precisely mechanically polished to ensure that its surface roughness reaches an extremely low level, laying the foundation for high-quality welding. At the same time, the welding surface of the aluminum busbar 30 is carefully polished to further improve the compatibility of the welding surface. Under specific welding temperature, pressure, and holding time, the polymer diffusion welding technology achieves a tight composite of the copper busbar 20 and the aluminum busbar 30, improves the welding strength, provides strong support for the composite application of copper and aluminum materials, and has strong practicality.

[0033] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for copper-aluminum polymer diffusion composite welding, characterized in that, Includes the following steps: S1. Bare copper welded with nickel sheet: A nickel sheet with a thickness of 0.1-0.3mm is laminated onto the welding surface of the copper busbar; S2. Polished nickel sheet: Mechanically polish the nickel sheet until the surface roughness Ra ≤ 0.8 μm; S3. Grinding aluminum busbars: Use 800-2000 grit sandpaper to grind the welding surface of the aluminum busbars in one direction until the roughness Ra≤1.0μm; S4. Copper-aluminum composite welding: The copper busbar with polished nickel sheet is bonded to the polished aluminum busbar by polymer diffusion welding. The welding temperature is 400-500℃, the pressure is 10-20MPa, and the holding time is 30-60 minutes.

2. The method according to claim 1, characterized in that, The nickel sheet is pure nickel or a nickel-based alloy with a nickel content ≥99.5wt% and a silver layer of 0.5-2μm thickness plated on its surface.

3. The method according to claim 1, characterized in that, Step S1 uses resistance welding with a welding current of 5-8kA and an electrode pressure of 0.4-0.6MPa.

4. The method according to claim 1, characterized in that, Step S2 uses nano-diamond polishing slurry at a polishing speed of 200-300 rpm, which increases the microhardness of the nickel sheet surface by 10-15% after polishing.

5. The method according to claim 1, characterized in that, In step S3, the grinding direction forms an angle of 45-90° with the extension direction of the aluminum bar grains.

6. The method according to claim 1, characterized in that, The polymer diffusion welding layer in step S4 is a polyimide-silane composite with a thickness of 50-100 μm and a silane content of 3-8 wt%.

7. The method according to claim 6, characterized in that, The polyimide-silane complex comprises the following components: 85-92wt% polyimide resin γ-aminopropyltriethoxysilane 5-10 wt% 3-5 wt% nano-alumina particles.

8. The method according to claim 1, characterized in that, Step S4 is performed in a vacuum environment with a vacuum degree ≤5×10⁻³Pa. Argon protective gas is introduced during the welding process at a flow rate of 5-10L / min.

9. The method according to claim 1, characterized in that, After welding, cool the material at a gradient of 5-10℃ / min to below 150℃.

10. The method according to claim 1, characterized in that, It also includes step S5: performing ultrasonic testing on the weld interface, requiring the defect area to be ≤0.5mm².

Images