Effects of Trace Chromium Addition and Rapid Solidification on Characteristicsof Sn-9Zn Alloy Solder and Solder/Copper Joint Interface

Sn-9Zn and Sn-9Zn-0.1Cr (mass fraction/%) alloy solders were prepared by vacuum melting, and then the rapidly solidified Sn-9Zn-0.1Cr alloy solder was obtained by a single roll method. The effects of the trace chromium addition and rapid solidification on the solder microstructure, wetting properties and corrosion resistance, as well as on the growth kinetics of intermetallic compound (IMC) layers at the solder/copper joint interface during aging at 85℃, were investigated. The results show that the addition of 0.1wt% chromium could inhibit the aggregation of zinc-rich phases and refine the eutectic structure in the Sn-9Zn alloy solder, increase the maximum wetting force and shorten the wetting time of the alloy solder, and inhibit the formation and the overgrowth during aging of the interfacial IMC layer of the solder/copper joint. The zinc-rich phase in the rapidly solidified Sn-9Zn-0.1Cr alloy solder was granular and dispersed in β-Sn dendrites, the structure was finer and more uniform, and the corrosion resistant was significantly improved; but the growth rate of the interfacial IMC layer during aging at 85℃ slightly increased compared with that of the as-smelted alloy solder.