The microstructure and electromigration of Bi and Sn in Cu/Sn58Bi/Cu and Cu/Sn58Bi /Sn3.0Ag0.5Cu/ Sn58Bi/Cu structural composite solder joint, were researched under the current density of 1.0×104 A/cm2 at room temperature. Two kinds of solder joints changed their morphology at both anode sides and cathode sides after current stressing. Bi layer was formed in the anode side while Sn layer was formed in the cathode side. The microanalysis indicated that Bi was the major diffusion element from cathode to anode and the migration of atomic Bi was faster than atomic Sn. Furthermore, through the comparison of two kinds of solder joints, it was easy to find that Sn3.0Ag0.5Cu suppressed the migration of atomic Bi and atomic Sn during electromigration.
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