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The combination of electromigration effect and stress effect was investigated in lead free solder joints with a diameter of 300μm. One dimensional structures, metal (wire)-solder (ball)-metal (wire) was developed. Mechanical force and current could be applied serially or simultaneously. The current density of electromigration was 1∼5×103 A/cm2. The working temperature was 100-150°C. Tensile test and shear test were taken before and after electromigration to make the comparison. The tensile strain rate was 3μm/min. The experiment results show that, the samples broke at the middle of solder without applying current. However, after applying current of electromigration for 1 day, 2 days or longer, the failure always occurred at cathode interface. And the tensile strength was lower with longer electromigration time or higher current density. Shear test also illustrates the electromigration effect on mechanical property in composite solder joints.