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What Welding Defects Are Caused by an Uneven Lap Surface Between the Copper Flexible Connection and the Copper Busbar in Polymer Diffusion Welding?
Oct 26,2026
The polymer diffusion welder relies on high temperature and pressure to make atoms at the lap interface diffuse into each other to form a metallurgical bond. If the lap surface between the copper flexible connection and the copper busbar is uneven, the workpiece cannot fit completely, and multiple welding defects are produced.
I Local Cold Joints, Interrupted Interface Bonding
1.The lap surface is uneven; after pressing, only the raised positions contact each other, gaps exist in the sunken areas, forming local cold joints.
2.The sunken positions easily accumulate oil, oxide scale, and impurities; after welding pressure, impurities are sealed at the interface, forming an isolation interlayer.
3.The effective bonding area becomes smaller, and welding strength is unstable.
II Inclusions and Void Defects Appear
1.Dust, copper chips, and other debris remain in the sunken areas of the lap surface; after pressing and closing, they form inclusion defects.
2.The air inside the gaps is hard to fully discharge, forming internal voids under high-temperature conditions.
III Local Overpressure Damages the Workpiece, Poor Forming Appearance
1.Pressure concentrates at the raised positions of the lap surface, local pressure is overloaded, the copper flexible-connection wires are squeezed and broken, causing wire damage.
2.The same workpiece has two defects simultaneously, the raised position bears excessive pressure and suffers overpressure damage.
IV Deteriorated Conductivity, Local Overheating Burnout
1.The contact resistance in the cold-joint area increases, and local temperature rise is too high.
2.The same workpiece has both over-burned and non-welded areas, and product resistance fluctuates greatly.
3.Current distribution is uneven, and local heat is too high.
V Abnormal Graphite Tooling Wear
1.The graphite pad plate bears excessive local force, easily chipping and cracking at the edge.
2.The workpiece repeatedly rubs and squeezes the graphite working surface, accelerating mold wear and shortening mold service life.
3.Unbalanced force causes lateral shifting of the workpiece, the weld-spot position shifts, further amplifying the welding defects.
Wuxi Haifei Intelligent Equipment Co., Ltd. https://www.haifeiwelder.com/
Wuxi Haifei Intelligent Equipment Co., Ltd. has been focusing on the R&D and production of diffusion‑welding equipment for 17 years. The company has passed ISO9001 Quality Management System Certification, China Compulsory Certification (3C) and CE Certification. It is a National High‑tech Enterprise, a Specialized, Refined, Differential and Innovative Enterprise of Jiangsu Province, a Specialized, Refined, Differential and Innovative Enterprise of Wuxi, and a Gazelle Enterprise in the Southern Jiangsu National Self‑Dependent Innovation Demonstration Zone.
Should you be interested in our diffusion‑welding equipment, please contact us: 400‑0510‑750
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Wuxi HAIFEI Intelligent Equipment Co., Ltd.
Wuxi HAIFEI Welding Equipment Co., Ltd.
Add: 28 Shuiyun Road, Yuecheng, Jiangyin, Jiangsu Province, China. (Postal Code: 214404)
Mobile: +86 18915302352
Email: wushijie@jshaifei.com