Aluminum bar and conductive copper ring ultrasonic welding method and welding tool

Abstract

The aluminum bar and conductive copper ring ultrasonic welding method comprises the following steps that S1, the to-be-welded surface of an aluminum bar is treated through a plasma etching process, so that the welded surface of the aluminum bar is of a micro-convex structure, and the conductive copper ring is subjected to electrolytic polishing; s2, the conductive copper ring and the aluminum bar are pre-positioned, and then the aluminum bar is pressed through a pressing piece; s3, the conductive copper ring and the aluminum bar are welded to form a welding part in an ultrasonic torque welding mode; and S4, low-temperature aging treatment is conducted on the welding part. According to the ultrasonic welding method and the ultrasonic welding tool for the aluminum bar and the conductive copper ring, direct welding of the aluminum bar and the conductive copper ring can be achieved without an additional transition piece, the process is simplified, the material cost is reduced, and compared with a welding method depending on the transition piece, the conductivity is also remarkably improved; after the aluminum bar and the conductive copper ring are cleaned, a micro-convex structure is formed on the surface of the aluminum bar and then welding is performed, so that the welding stability is ensured.

Description

Technical Field

[0001] This invention relates to the field of aluminum busbar welding technology, and in particular to an ultrasonic welding method and welding fixture for aluminum busbars and conductive copper rings. Background Technology

[0002] In fields such as new energy vehicles and energy storage, aluminum busbars are widely used as conductive components due to their advantages such as low density and low cost, while conductive copper rings have become key conductive elements due to their excellent conductivity. The reliable connection between the two is crucial.

[0003] Currently, there are many shortcomings in the connection methods between aluminum busbars and conductive copper rings. Traditional fusion welding methods, such as arc welding, are prone to producing brittle intermetallic compounds between aluminum and copper due to the extremely high temperatures (5000℃-6000℃) during the welding process, leading to increased joint resistance and decreased mechanical properties. Brazing requires the use of filler metal, which not only increases costs but may also introduce impurities that affect conductivity. Furthermore, the wetting and spreading of the filler metal during brazing is difficult to control. Some existing ultrasonic welding methods rely on transition pieces to achieve aluminum-copper connections (using zinc foil as a transition layer or opening through holes between the copper and aluminum busbars and installing another transition piece of the same material in the through holes), which increases material costs and assembly steps. Moreover, the welding parameters are mostly statically set and do not consider the welding stress caused by the difference in thermal expansion coefficients between aluminum and copper (23.1×10-6℃ for aluminum and 17×10-6℃ for copper), affecting the long-term reliability of the joint.

[0004] A search revealed that Chinese patent application number "CN201910231780.3" discloses a method of ultrasonically welding an aluminum plate and a conductive copper ring after the aluminum plate has been treated by grinding, acid washing, and alkaline washing. The shortcoming of this patent is that impurities on the surface of the conductive copper ring can also affect the welding effect. Summary of the Invention

[0005] To address the technical problems existing in the background art, this invention proposes an ultrasonic welding method and welding fixture for aluminum busbars and conductive copper rings.

[0006] The present invention proposes an ultrasonic welding method for aluminum busbars and conductive copper rings, comprising the following steps:

[0007] S1. The surface of the aluminum busbar to be welded is treated with plasma etching to create a micro-protrusion structure. The conductive copper ring is then electrolytically polished. The diameter of the micro-protrusions on the aluminum busbar is 5-20 μm, and the spacing between the micro-protrusions is 10-30 μm. The surface roughness Ra of the aluminum busbar welding surface is controlled within 0.8-2.5 μm. This parameter range ensures that the micro-protrusions have sufficient ability to break the oxide film while guaranteeing the effective contact area with the copper ring.

[0008] S2. Position the conductive copper ring and the aluminum busbar in place, and then press the aluminum busbar with a clamping device;

[0009] S3. The conductive copper ring and aluminum busbar are welded together to form a welded part by ultrasonic torque welding.

[0010] S4. Perform low-temperature aging treatment on the welded parts.

[0011] Preferably, in step S1, during the plasma etching process of the aluminum busbar: the plasma etching power is set to 500-800W, argon gas is introduced as the working gas, the argon gas flow rate is controlled at 15-25L / min, and the etching time is 30-60s.

[0012] Preferably, in step S1, during the electrolytic polishing of the conductive copper ring, the current density is controlled to be 15-35 A / dm³ using a phosphoric acid-sulfuric acid mixed electrolyte. 2 The electropolishing time is 15-50 s.

[0013] Preferably, the welding of the aluminum busbar and the conductive copper ring in step S3 includes an initial stage, a welding stage, and a pressure holding stage:

[0014] Initial stage: The oxide layer on the inner surface of the conductive copper ring is removed by using the micro-protrusion structure formed by plasma etching on the surface of the aluminum busbar.

[0015] Welding stage: When the temperature of the welding zone rises to 400℃-500℃, the clamping pressure is increased to 950−1250N, the torque vibration frequency is adjusted to 18-20kHz, and the amplitude is increased to 38-46μm to promote the rapid diffusion of aluminum atoms and copper atoms and form a metallurgical bond.

[0016] Pressure holding stage: Maintain clamping pressure at 1100-1250N, reduce torque vibration frequency to 15-17kHz, and reduce amplitude to 18-26μm to suppress microcracks that may be generated during welding.

[0017] Preferably, in the initial stage: the clamping pressure is 750-1050N, the torque vibration frequency is set to 15-17kHz, and the amplitude is 28-36μm.

[0018] Preferably, the torque vibration frequencies are equal during the initial stage and the pressure holding stage.

[0019] Preferably, in step S2, the aluminum busbar has a positioning protrusion, which is fitted inside the conductive copper ring, and the thickness of the conductive copper ring is greater than the thickness of the positioning protrusion.

[0020] An ultrasonic welding fixture for aluminum busbars and conductive copper rings includes a support block with a support portion for placing the aluminum busbar. The support block is provided with a clamping member, which fixes the aluminum busbar to the support portion. The clamping force of the clamping member on the aluminum busbar is equal to the clamping pressure of the ultrasonic welding.

[0021] Preferably, the support portion has multiple support protrusions, with any two adjacent support protrusions forming a gap, and any two adjacent sets of gaps being connected.

[0022] Preferably, the clamping component includes an L-shaped clamping block, which has a clamping part and a connecting part. The clamping part is used to clamp the aluminum busbar, and the bottom of the connecting part is placed on the support part, forming a cooling space between the connecting part and the support part.

[0023] The ultrasonic welding method and welding fixture for aluminum busbars and conductive copper rings proposed in this invention can directly weld the aluminum busbars and conductive copper rings without the need for additional transition parts, simplifying the process and reducing material costs. Compared with welding methods that rely on transition parts, the conductivity is also significantly improved. By cleaning the aluminum busbars and conductive copper rings to form a micro-protrusion structure on the surface of the aluminum busbars (so as to reduce the surface roughness of the aluminum busbars), and then performing ultrasonic torque welding, the method is simple and can achieve the initial positioning and fixation of the aluminum busbars and conductive copper rings, ensuring welding stability. Moreover, for aluminum busbars of different thicknesses and different conductive copper rings, only the clamping parts need to be adjusted, without the need to design special transition parts or customize chemical fixtures for different specifications of parts, which greatly reduces the process changeover costs and cycles in multi-variety, small-batch production scenarios.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the welding fixture of the present invention when clamping the aluminum busbar;

[0026] Figure 2 For the present invention Figure 1 Top view;

[0027] In the diagram: 1. Support block; 10. Support part; 2. Clamping part; 20. Clamping part; 21. Connecting part; 200. Groove; 3. Aluminum busbar; 4. Conductive copper ring; 5. Ultrasonic welding head; 6. Support protrusion; Detailed Implementation

[0028] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0029] like Figure 1 - Figure 2 The ultrasonic welding method for aluminum busbars and conductive copper rings shown includes the following steps:

[0030] S1. The surface of the aluminum busbar 3 to be welded is treated by plasma etching to give the welding surface of the aluminum busbar 3 a micro-protrusion structure. The diameter of the micro-protrusion structure on the aluminum busbar 3 is 5-20μm and the spacing between the micro-protrusion structures is 10-30μm. The surface roughness Ra of the aluminum busbar welding surface is controlled at 0.8-2.5μm. The conductive copper ring 4 is electrolytically polished.

[0031] Specifically, during the pretreatment of aluminum busbar 3, the plasma etching power was set to 500-800W, argon gas was introduced as the working gas, the argon gas flow rate was controlled at 15-25L / min, and the etching time was 30-60s. The micro-protrusion structure formed on the surface of aluminum busbar 3 by plasma etching was used to remove the oxide layer on the inner surface of the conductive copper ring 4, creating conditions for subsequent atomic diffusion.

[0032] Specifically: During the pretreatment of aluminum busbars: Before etching, the surface of the aluminum busbar to be welded should be wiped with anhydrous ethanol to remove oil, dust and other impurities, and then dried before plasma etching (to avoid impurities affecting the etching effect).

[0033] Etching distance: The distance between the plasma spray gun and the aluminum busbar to be welded should be 8-15mm (too close and the substrate will be easily burned, too far and the etching will be insufficient).

[0034] Gas purity: Argon purity ≥ 99.99% (avoid introducing impurity gases for oxidation or contamination).

[0035] During the electrolytic polishing of the conductive copper ring 4, a phosphoric acid-sulfuric acid mixed electrolyte is used, with the current density controlled at 15-35 A / dm² and the electrolytic polishing time at 15-50 s. Specifically: the volume ratio of the phosphoric acid-sulfuric acid mixed electrolyte is 3:1; the electrolysis temperature is controlled at 40-60℃ (too low a temperature results in low polishing efficiency and poor surface finish, while too high a temperature can lead to over-corrosion of the copper substrate); the electrode connection is as follows: the copper ring is connected to the anode, and the stainless steel plate is connected to the cathode, with a distance of 50-80 mm between the two electrodes (incorrect electrode connection or improper spacing will affect the uniformity of polishing).

[0036] Post-processing: After electropolishing, immediately immerse the copper ring in deionized water for 3-5 minutes to remove residual electrolyte from the surface, then dehydrate with anhydrous ethanol and air dry at room temperature (to avoid residual electrolyte corroding the surface of the copper ring).

[0037] S2. Pre-position the conductive copper ring 4 and the aluminum busbar 3. The aluminum busbar 3 has a positioning protrusion, which is fitted inside the conductive copper ring 4. The thickness of the conductive copper ring 4 is slightly greater than the thickness of the positioning protrusion. After placing the conductive copper ring 4 on the positioning protrusion, the conductive copper ring 4 and the aluminum busbar 3 are pre-positioned. Then, the aluminum busbar 3 is pressed tightly by the clamping member 2.

[0038] Specifically, the welding fixture includes a support block 1, a support portion 10 for placing aluminum busbars 3, and a clamping member 2 on the support block 1. The clamping member 2 presses against the top of the aluminum busbars 3 and fixes the aluminum busbars 3 on the support portion 10. The clamping force of the clamping member 2 on the aluminum busbars 3 is equal to the clamping pressure of the ultrasonic welding. It should be noted that a high-temperature resistant pad can be provided above the clamping member 2, and a hydraulic cylinder or other components can be provided above the high-temperature resistant pad to apply different downward pressures to the pad, thereby adjusting the clamping force of the clamping member 2 on the aluminum busbars 3.

[0039] Preferably, the support portion 10 has a plurality of support protrusions 6, with any two adjacent support protrusions 6 forming a gap, and any two adjacent sets of gaps being connected, thereby facilitating the cooling of the aluminum busbar 3 while ensuring support for the aluminum busbar 3.

[0040] Preferably, the clamping member 2 includes an L-shaped clamping block, which has a clamping part 20 and a connecting part 21. The clamping part 20 is used to clamp the aluminum busbar 3, and the bottom of the connecting part 21 is placed on the support part 10. A cooling space is formed between the connecting part 21 and the support part 10 to facilitate cooling during the welding process. Preferably, the thickness of the clamping part 20 is less than the thickness of the connecting part 21, and when the ultrasonic welding head 5 is welding it, there is a certain distance between the ultrasonic welding head 5 and the clamping member 2. Preferably, the clamping part 20 has an arc-shaped groove 200, and the clamping member 2 is provided in two sets. The grooves 200 of the two sets of clamping members 2 form a receiving space, and the ultrasonic welding head 5 is located in the receiving space.

[0041] S3. The conductive copper ring 4 and the aluminum busbar 3 are welded together by ultrasonic torque welding to form a welded part. The ultrasonic welding head 5 is used to weld the conductive copper ring 4 and the aluminum busbar 3.

[0042] The welding of aluminum busbar 3 and conductive copper ring 4 includes an initial stage, a welding stage, and a pressure holding stage:

[0043] Initial stage (total duration of this stage is less than 70ms): Apply a clamping pressure of 750-1050N to the ultrasonic welding head 5, set the torque vibration frequency to 15-17kHz and the amplitude to 28-36μm, and use the micro-protrusion structure formed by plasma etching on the surface of the aluminum busbar 3 to break the oxide layer on the inner surface of the conductive copper ring 4.

[0044] Welding stage (total duration of this stage is 60-220ms): The temperature of the welding area is detected in real time by an infrared temperature sensor. It should be noted that the infrared temperature sensor is 5-10mm away from the welding interface and directly facing the center of the overlapping area to avoid monitoring deviation. When the temperature of the welding area rises to 450℃, the clamping pressure is increased to 950-1250N, the torque vibration frequency is adjusted to 18-20kHz, and the amplitude is increased to 38-46μm to promote the rapid diffusion of aluminum atoms and copper atoms and form a metallurgical bond.

[0045] Pressure holding stage (total duration of this stage is 220-320ms): Maintain clamping pressure of 1100-1250N, reduce torque vibration frequency to 15-17kHz, and reduce amplitude to 18-26μm to suppress microcracks that may be generated during welding.

[0046] After the pressure holding stage, the pressure of the clamping parts 2 on the aluminum bars needs to be kept constant. After naturally cooling to room temperature (25±5℃), the pressure is released to avoid joint cracking due to pressure release during the cooling process.

[0047] S4. Perform low-temperature aging treatment on the welded parts by placing the joint in an environment of 120℃ for 60 minutes to eliminate residual welding stress. Then, clean the surface of the welded joint with alcohol to remove residual welding slag and other impurities.

[0048] Preferably, the torque vibration frequencies are equal during the initial stage and the pressure holding stage.

[0049] This invention enables direct welding of the aluminum busbar 3 and the conductive copper ring 4 without the need for additional transition parts, simplifying the process and reducing material costs. Compared with welding methods that rely on transition parts, the conductivity is also significantly improved. By cleaning the aluminum busbar 3 and the conductive copper ring 4 to form a micro-protrusion structure on the surface of the aluminum busbar 3 (i.e., increasing the surface roughness of the aluminum busbar 3), and then performing ultrasonic torque welding, the simple method can achieve the initial positioning and fixation of the aluminum busbar 3 and the conductive copper ring 4, ensuring welding stability. Moreover, for aluminum busbar 3 of different thicknesses and different conductive copper rings 4, only the clamping part 2 needs to be adjusted, eliminating the need to design special transition parts or customize chemical fittings for different specifications of parts, greatly reducing the process changeover cost and cycle in multi-variety, small-batch production scenarios.

[0050] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0052] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature.

[0054] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for ultrasonic welding of an aluminum busbar to a conductive copper ring, characterized in that, Includes the following steps: S1. The surface of the aluminum busbar (3) to be welded is treated by plasma etching process so that the welding surface of the aluminum busbar (3) has a micro-convex structure, and the conductive copper ring (4) is electrolytically polished. S2. Position the conductive copper ring (4) and the aluminum busbar (3) in advance, and then press the aluminum busbar (3) with the clamping member (2). S3. The conductive copper ring (4) and the aluminum busbar (3) are welded together by ultrasonic torque welding to form a welded part; S4. Perform low-temperature aging treatment on the welded parts.

2. The ultrasonic welding method for aluminum busbars and conductive copper rings according to claim 1, characterized in that, In step S1, during the plasma etching process of the aluminum busbar (3): the plasma etching power is set to 500-800W, argon is introduced as the working gas, the argon flow rate is controlled at 15-25L / min, and the etching time is 30-60s.

3. The ultrasonic welding method for aluminum busbar and conductive copper ring according to claim 1, characterized in that, In step S1, during the electrolytic polishing of the conductive copper ring (4), the current density is controlled at 15-35 A / dm2 and the electrolytic polishing time is 15-50 s using a phosphoric acid-sulfuric acid mixed electrolyte.

4. The ultrasonic welding method for aluminum busbars and conductive copper rings according to claim 1, characterized in that, The welding of the aluminum busbar (3) and the conductive copper ring (4) in step S3 includes an initial stage, a welding stage, and a pressure holding stage: Initial stage: Using the micro-protrusion structure formed by plasma etching on the surface of the aluminum busbar (3), the oxide layer on the inner surface of the conductive copper ring (4) is broken; Welding stage: When the temperature of the welding zone rises to 400℃-500℃, the clamping pressure is increased to 950−1250N, the torque vibration frequency is adjusted to 18-20kHz, and the amplitude is increased to 38-46μm to promote the rapid diffusion of aluminum atoms and copper atoms and form a metallurgical bond. Pressure holding stage: Maintain clamping pressure at 1100-1250N, reduce torque vibration frequency to 15-17kHz, and reduce amplitude to 18-26μm to suppress microcracks that may be generated during welding.

5. The ultrasonic welding method for aluminum busbars and conductive copper rings according to claim 4, characterized in that, Initial stage: Apply clamping pressure of 750-1050N, set torque vibration frequency of 15-17kHz, and amplitude of 28-36μm.

6. The ultrasonic welding method for aluminum busbars and conductive copper rings according to claim 4, characterized in that, The torque vibration frequencies are the same during the initial stage and the pressure holding stage.

7. The ultrasonic welding method for aluminum busbar and conductive copper ring according to claim 1, characterized in that, In step S2, the aluminum busbar (3) has a positioning protrusion, which is fitted inside the conductive copper ring (4). The thickness of the conductive copper ring (4) is greater than the thickness of the positioning protrusion.

8. An ultrasonic welding fixture for aluminum busbars and conductive copper rings, characterized in that, Includes a support block (1), on which there is a support part (10) for placing aluminum strip (3), and a clamping member (2) is provided on the support block (1). The clamping member (2) fixes the aluminum strip (3) on the support part (10), and the clamping force of the clamping member (2) on the aluminum strip (3) is equal to the clamping pressure of the ultrasonic welding.

9. The ultrasonic welding fixture for aluminum busbar and conductive copper ring according to claim 8, characterized in that, The support portion (10) has a plurality of support protrusions (6), and any two adjacent support protrusions (6) form a gap, and any two adjacent sets of gaps are connected.

10. The ultrasonic welding fixture for aluminum busbar and conductive copper ring according to claim 8, characterized in that, The clamping component (2) includes an L-shaped clamping block, which has a clamping part (20) and a connecting part (21). The clamping part (20) is used to clamp the aluminum strip (3). The bottom of the connecting part (21) is placed on the support part (10). A cooling space is formed between the connecting part (21) and the support part (10).

Images