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.
The authors would like to acknowledge the financial support provided by the Harbin Youth Reserve Talents Project [Grant Number RC2014QN017012]. The authors would like to thank Professor Chen and Professor Ma at the center for material analysis and testing, who provided experimental help.