Wetting behavior of Sn–Ag–Cu and Sn–Bi–X alloys: insights into factors affecting cooling rate

Based on two experimental approaches: transient directional solidification and drop shape analyses, the measurements of cooling rates and contact angles (θ) of several solders of interest became practical. Three Sn–0.7Cu–(1; 2 and 3Ag) and four Sn–34Bi–(0Cu; 0.1Cu; 0.7Cu; 2Ag) alloys are investigated to determine their wetting behavior, compare to each other and bring to light their ability (or not) to control the initial cooling rate. In the case of SAC alloys, increase in Ag means decrease in both θ and cooling rate. An opposite correlation between cooling rate and θ is observed when Sn–34Bi and the Sn–34Bi–0.1Cu alloys are compared.