Effect of Trace Cu on Microstructure, Spreadability and Oxidation Resistance Property of Sn-xCu Solders

Abstract

Sn-xCu (x = 0.5, 0.7, 0.9, 1.1, 1.3) solders were prepared to investigate the influence of trace Cu on the microstructure, the spreadability and the oxidation resistance property of Sn-xCu lead-free solder. Researches have shown that the Cu content had a significant impact on the microstructure, the microstructure of Sn-0.7Cu solder was almost fine dendrites and others were composed of coarser dendrites. The liquidus temperatures of Sn-xCu were around 227℃, the peak of solidification temperature had vast difference and the biggest difference was 8.8℃. The peak of solidification temperature of Sn-0.7Cu was the smallest, with 192℃. The spreading rate of Sn-xCu solders greatly improved, in which Sn-0.5Cu improves by nearly 4 percents, Sn-0.7Cu improves by nearly 3 percents and the others improve by 2 percents around from 260℃ to 290℃. With the increase of Cu content, there were no obvious changes to solder with wetting power and wetting time, interfacial IMC thickness of Sn-xCu/Cu solders. The color of oxidation film deepened due to the serious oxidation with the increase of the temperature. The oxide slag of Sn-xCu solders decreased and then increased with the increase of Cu content, in which the oxide slag of Sn-0.7Cu solder was the lowest, about 18.5% of Sn-0.5Cu and 38% of Sn-1.3Cu.