Interfacial reactions of tin-zinc-bismuth alloys

A variety of lead-free solders are now commercially available. Of those suitable for mass soldering perhaps the ones closest to a direct, drop-in, replacement for tin-lead are the tin-zinc-bismuth alloys. For mosi tin-based solders it is the tin which is the active element and dominates the all-important interfacial reactions. As a result they have many properties in common. The addition of zinc, however, radically alters this picture. Zinc oxidation products are formed at the surfaces. Zinc intermetallic compounds are also formed in preference to tin-compounds at the substrate interfaces. The nature and implications of these changes are outlined for the common basis materials.