Contact angle and reactive wetting in the SnPb/Cu system

Wedi A, Baither D, Schmitz G

Abstract

Wetting with a low contact angle is a prerequisite for reliable solder connections. However, the contact angle is only an indirectmeasure of adhesion energy. To quantify this energy, we measured wetting angles of solder droplets as well as surface tension ofSnPb solders under systematic variation of composition. From the data, the effective interface energy is evaluated. Although surfacetension and wetting angle depend continuously on solder composition, the adhesion tension reveals distinguished plateaus which arerelated to different reaction products.