Development of high strength Sn-Mg solder alloys with reasonable ductility

Abstract

This study discussed the development of a series of new lead-free Sn-Mg solders by incorporating varying amounts of Mg (0.8, 1.5 and 2.5 wt. %) into pure Sn using disintegrated melt deposition technique followed by room temperature extrusion. All extruded Sn and Sn-Mg solder samples were characterized. Microstructural characterization studies revealed equiaxed grain morphology, minimal porosity and relatively uniform distribution of secondary phase. Better coefficient of thermal expansion was observed for Sn-2.5Mg sample when compared to conventional Sn-37Pb solder. Melting temperature of Sn-1.5Mg was found to be 212°C which is much lower than the conventional Sn-Ag-Cu or Sn-Cu (227°C) solders. Microhardness was increased with increasing amount of Mg in pure Sn. Room temperature tensile test results revealed that newly developed Sn-Mg solders exhibit enhanced strengths (0.2% yield strength and ultimate tensile strength) with comparable (if not better) ductility when compared to other commercially available and widely used Sn-based solder alloys.