Surface tension and wetting behaviour of molten Cu–Sn alloys

The surface and interfacial properties of the Cu–Sn system as basic system of the multicomponent alloys proposed as lead-free soldering materials have been studied. The surface tension of the Cu–Sn system has been measured over the whole composition range by using the sessile drop method in the temperature range between 430 and 1300 K. The results obtained are compared with the available literature data and with theoretical values calculated by the compound formation model (CFM) and quasi-chemical approximation for regular solutions (QCA). The study of the wetting behaviour of Cu–Sn on a metal substrate has been performed by measuring the contact angles of four Sn-rich alloys on a pure Ni-substrate and by the metallographic characterization of the solder/Ni interfaces.