Interfacial Microstructure and Growth Kinetics of Intermetallic Compound Layers in Sn-4 wt.%Ag/Cu-X (X = Zn,Ag, Sn) Couples

In the current study, the interfacial microstructures of Sn-Ag/Cu-X alloy (X = Ag, Sn or Zn) couples were investigated. The experimental results confirm that addition of Ag or Zn can effectively suppress the growth of the Cu₃Sn layer, while addition of Sn accelerates the growth of the Cu₃Sn layer. Meanwhile, the formation of voids is effectively suppressed by alloying the Cu substrate. The disappearance of voids and the absence of the Cu₃Sn layer were well explained in terms of the phase diagram and the diffusion flux: the Cu₃Sn phase is a nonequilibrium phase based on the Sn-Cu-Zn ternary phase diagram, since a high-Zn region is formed at the Cu₆Sn₅/Cu-Zn alloy interface; in addition, the high Sn diffusion flux in the Cu₆Sn₅ can suppress the growth of Cu₃Sn and the formation of voids.