Abstract: Sn35Bi0.3Ag/Cu welded joints were prepared at different welding time and temperature. The effects of welding time (1 ~ 9 min) and welding temperature (210 ~ 290 ℃) on the microstructure and mechanical properties of Sn35Bi0.3Ag/Cu welded joints were studyed by means of scanning electron microscope (SEM), universal tensile testing machine and ultrasonic scan machine. The results show that the Cu element diffuses into the welding interface and forms the (Cu₅Sn₆, Cu₃Sn) interface layer. The Ag₃Sn phase can inhibit the growth of interfacial layer. With the increase of welding time or welding temperature, the reaction layer thickens and the shear strength increases first and then decreases. The analysis of the fracture morphology of the welded joint shows that the fracture of the welded joint is jointly affected by Bi phase particles and Cu₆Sn₅ particles.The fracture of the welded joint occurs on the IMC / solder side. Bi phase particles and Cu₆Sn₅ particles affect the shear strength of the joint.In addition, when the welding time is 3 min and the welding temperature is 230 ℃, the brazing rate is the highest (99.14%) and the shear strength reaches the maximum value (51.8 MPa).