Effect of welding parameters on resistance thermocompression microwelded joint of insulated copper wire

Insulated copper wire has been widely used in many industries, but the insulating coating must be removed before welding because it will hinder the formation of joints. Therefore, in this work, the resistance thermocompression microwelding process for insulated wire without removing the coating in advance was proposed. Through detailed mechanical testing and metallurgical examination, the effects of welding voltage on the joint appearance, joint macro-/microstructure, joint breaking force, and joint fracture mode were investigated. The results showed that joints were achieved by solid-state bonding. As the welding voltage was further increased, the joint breaking force increased first and then decreased. Corresponding to the change of the welding voltage, the fracture mode of the joints changed from interfacial fracture to partial pullout fracture. The fracture position also moved backwards gradually, which was caused by the expansion of the bonding area, the improvement of the interfacial strength, and the amount of heat input. Finally, an orthogonal experiment was conducted to investigate the significance level of three parameters. Under the optimal for joint breaking force parameters (2.1 V, 24 ms, and 12 N), the average achievable force was 1.1723 N, which was about 83.7% of the breaking force of the as-received wire.