Effect of Annealing Treatment on Electromigration Resistance of Low-Temperature Sn-57Bi-1Ag Solder Interconnect.

The effect of annealing treatment on the electromigration (EM) resistance of low-temperature Cu/Sn-57Bi-1Ag (600 μm)/Cu solder interconnects has been investigated. The annealing treatment of as-soldered Cu/Sn-57Bi-1Ag/Cu solder interconnects caused the obvious coarsening of Bi phases in the bulk solders and a slight reduction in the electric resistance of the solder interconnects. The coarsening of the Bi phases induced a decrease in the Bi/β-Sn phase boundaries and thus a decrease in the EM-induced atomic diffusion flux of Bi atoms during the subsequent current stressing, resulting in the segregation of a thinner Bi phase layer at the anode and a lower increase rate of electric resistance of the solder interconnects. The longer the annealing time, the higher the EM resistance of the solder interconnects. The reductions in both the effective diffusion coefficient of the Bi atoms and the electric resistivity of the bulk Sn-57Bi-1Ag solders induced by the annealing treatment were responsible for the higher EM resistance of low-temperature Sn-57Bi-1Ag solder interconnects. [ABSTRACT FROM AUTHOR]