Microstructures and mechanical properties of micro-resistance spot welded joint of silver-plated braided copper wire and copper

The microstructure and mechanical properties of 0. 1 mm silver-plated braided copper wire and 0. 07 mm copper micro-resistance spot welded joint were studied. The influences of different parameters on the mechanical properties of the joint were analyzed. The microscopic analysis of the typical joint was performed by scanning electron microscopy. The microstructure characteristics were analyzed. The results show that the joint is mainly formed by brazing-welding and fusion welding,and the four processes of silver element wetting and spreading,silver element diffusion,copper element melting and metal solidification are experienced in the formation process. There is a copper-silver two-phase and a single-rich copper phase formed in joint interface morphology,and the latter soldered joint microstructures have the characteristics of fusion welding. Within the parameters used in the tests,the maximum shear force of the soldered joint can reach 45 N. The welding time and the welding current have a great influence on the soldered joint performance within a certain range. When the resistance heat reaches the saturation interval,the shear resistance of the joint change little.