New lead-free, Sn-Zn-In solder alloys

In view of the need for a lead-free, drop-in replacement for the widely used 40Pb-60Sn near-eutectic solder (m.p. ~183°C), new Sn-Zn-ln based alloys with substantially the same melting point have been developed. It is shown that the alloying additions of In to the Sn-Zn binary system result in a suppression of the melting point to 175-188°C, and at the same time significantly improve the wetting characteristics. While a relatively active flux may be required for good solderability in air atmosphere, the recent manufacturing trend of using inert atmospheres is likely to allow acceptable manufacturability using less active fluxes in the future.