Effect of Co particles combined with rotating magnetic field on microstructure and properties of Sn35Bi/Cu joint

By means of scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray diffraction (XRD) analysis, universal testing machine and wetting furnace, the effects of Co particles and rotating magnetic field on the microstructure and properties of Sn35Bi/Cu joint are investigated. The results show that after combined treatment, the formation of fine CoSn₂ particles in the weld can effectively refine the weld microstructure of Sn35Bi/Cu, reduce the thickness of intermetallic compounds (IMCs) layer, improve the wettability of the filler metal and increase the shear strength of the joint. After combined treatment, the shear strength of Sn35Bi-Co/Cu joint is up to 56 MPa when Co content is 0.9 wt.%, which is 76% higher than that of Sn35Bi/Cu joint under conventional conditions, and the wetting angle of the composite filler metal is 19.1° when Co content is 0.6 wt.%, which is 40% lower than that of the conventional Sn35Bi filler metal.