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<p>This study investigates the ultrasonic welding of tinned copper (Cu) wires to T2-grade copper (Cu ≥ 99.9 wt.%) terminals under different welding energies. A thermal shock stability test consisting of 150 cycles was conducted to evaluate changes in the mechanical performance and corrosion resistance of the welded joints. The joint microstructure and elemental diffusion behavior were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results show that thermal shock cycling led to an approximately 20% increase in joint hardness, while simultaneously increasing electrical resistance and brittleness, particularly for joints welded at 11,000&#xa0;J which adversely affected their thermal shock stability. Thermal shock exposure significantly promoted the diffusion of the Sn coating, accelerating the formation of brittle Cu–Sn intermetallic compounds (IMCs) at the joint interface. Moderate IMC formation enhanced metallurgical bonding between the Cu wires, resulting in improved shear strength of the welded joints. However, excessive Sn diffusion reduced the protective effect of the Sn layer on the Cu wire, leading to a deterioration in the corrosion resistance of the joint. These results reveal a clear trade-off between mechanical strength and corrosion resistance, highlighting the importance of controlling welding energy and interfacial microstructural evolution to achieve balanced joint performance under thermal shock conditions.</p>

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Microstructure and corrosion resistance analysis of ultrasonically welded joints in tinned copper wires before and after thermal shock

  • 期刊论文

  • 发表日期：

    2026年3月27日

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  • Jinshan Chen,
  • Lun Zhao,
  • Zeshan Abbas,
  • Lan Zhang,
  • Fayu Wu,
  • Liya Li,
  • Jianxiong Su,
  • Zixin Guo

摘要

This study investigates the ultrasonic welding of tinned copper (Cu) wires to T2-grade copper (Cu ≥ 99.9 wt.%) terminals under different welding energies. A thermal shock stability test consisting of 150 cycles was conducted to evaluate changes in the mechanical performance and corrosion resistance of the welded joints. The joint microstructure and elemental diffusion behavior were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results show that thermal shock cycling led to an approximately 20% increase in joint hardness, while simultaneously increasing electrical resistance and brittleness, particularly for joints welded at 11,000 J which adversely affected their thermal shock stability. Thermal shock exposure significantly promoted the diffusion of the Sn coating, accelerating the formation of brittle Cu–Sn intermetallic compounds (IMCs) at the joint interface. Moderate IMC formation enhanced metallurgical bonding between the Cu wires, resulting in improved shear strength of the welded joints. However, excessive Sn diffusion reduced the protective effect of the Sn layer on the Cu wire, leading to a deterioration in the corrosion resistance of the joint. These results reveal a clear trade-off between mechanical strength and corrosion resistance, highlighting the importance of controlling welding energy and interfacial microstructural evolution to achieve balanced joint performance under thermal shock conditions.