Effect of Zinc Addition on the Evolution of Interfacial Intermetallic Phases at Near-Eutectic 50In-50Sn/Cu Interfaces.

The effect of Zn addition on the evolution of IMC at near-eutectic 50In-50Sn/Cu interfaces was investigated at 210°C. In 50In-(50-x)Sn-xZn/Cu(x = 0, 6) diffusion couples, two types of intermetallic compound layers were observed: ε-Cu₃(In,Sn) adjacent to the Cu substrate and η-Cu₂(In,Sn) adjacent to the solder, which were formed though a solid–solid diffusion reaction and solid–liquid reaction, respectively. The growth of ε-Cu₃(In,Sn) was at the expense of η-Cu₂(In,Sn). In 50In-44Sn-6Zn/Cu diffusion couple, the growth of ε-Cu₃(In,Sn) was grain-boundary diffusion controlled and n (the time constant) was 0.31. But in the 50In-50Sn/Cu diffusion couple, due to the slow growth of η-Cu₂(In,Sn), the time constant of ε-Cu₃(In,Sn) was down to 0.19. With the addition of Zn in the 50In-50Sn/Cu couple, the diffusion of Cu was alleviated. Zn exhibited high activity and moderated the dissipation of the main atoms (In/Sn) in the solder. So the growth of Cu₃(In,Sn) was suppressed significantly. [ABSTRACT FROM AUTHOR]