Characteristics of eutectic and near-eutectic Zn–Al alloys as high-temperature lead-free solders

Abstract

Lead-based alloys are conventionally used for soldering interconnections that are expected to perform at high temperatures. Because of the concerns of lead toxicity, the development of lead-free solders became important. Till now, none of the proposed alloys have the characteristics that can completely substitute the Pb-bearing solders for high-temperature soldering application. Recently, researchers studied many ternary and quaternary systems near Zn–Al binary eutectic composition and reported prospects in soldering applications. However, the bulk solder properties of the Zn–Al binary system near the eutectic composition is rare in the literature. In the present study, the microstructure and thermal, mechanical and electrical characteristics of eutectic and near-eutectic Zn–Al alloys are investigated as replacement of traditional lead-bearing high-temperature solders. Mechanical and electrical properties of Zn was enhanced by alloying with Al, without altering much of the thermal expansion co-efficient. Finally, the material properties of the prepared Zn–Al alloys and other Zn-based alloys are compared with the conventional Pb–Sn solders. Research shows, 7 wt% Al–Zn alloy has multiple times higher magnitude of ultimate tensile strength, Vicker’s microhardness and electrical conductivity than the traditional Pb–Sn high-temperature solders. The melting temperature of the alloys was a bit higher than the Pb–Sn solders. A suitable ternary element addition to the system can potentially replace the conventional Pb-based high-temperature solders.