Processing and characterization of zinc-silver based high temperature solder alloys

Abstract

Replacing the lead (Pb)-containing solders with the Pb-free solders in electronic products has been a global trend due to environmental and human health concerns for the toxicity of the element Pb. Many kinds of Pb free solder alloys have been proposed to date. Zinc (Zn) based Pb-free solder can be a promising alternative of Sn-Pb solder because of its competitive price and mechanical properties. In this research Zn based solder alloys were developed by addition of silver (Ag) and magnesium (Mg) through conventional casting method. The changes in tensile strength, melting behavior, microhardness and microstructure associated with the addition of relatively high melting point noble metal namely Ag were investigated in this work. A significant change in microstructure, microhardness and strength were found with the change of Ag content. Furthermore, the effects Mg addition on the mechanical and thermal properties along with microstructure of the promising candidate Zn-Ag based alloys were extensively reported. A great change in structure was found when Mg was added to Zn-Ag binary alloy including evolution of eutectic phases along with grain refinement. Chemical composition of the alloys was confirmed by XRF analysis. A more interesting point is that the addition of Mg with Zn-Ag alloy increases the microhardness and strength to a large extent. The melting behavior of the solder alloys were studied by DSC analysis. The chemical composition of a particular phase was confirmed by EDS analysis. Both the Zn-Ag alloys and Zn-Ag-Mg alloy show good conductivity in terms of IACS%. Also, the bonding nature of the developed alloys with copper substrate was studied where an intermetallic layer was found at the interface of Cu and solder alloys.