Present status of Sn–Zn lead-free solders bearing alloying elements

Recently, the Sn–Zn family of alloys, which possesses many attractive advantages such as relatively low melting point, cheap cost and the environmentally friendly component of Zn, has been widely used in electronic industry as one of the most potential replacements for the traditional Sn–Pb solders. However, there’re still some arguments on its shortcomings about the poor wettability and the weak oxidation resistance, which definitely limits its further application in lead-free electronic manufacturing. In order to overcome these disadvantages and further enhance the properties of Sn–Zn lead-free solders, alloying elements such as RE, Bi, Ag, Al, Ga, Cu, etc. were selected by lots of researchers as alloys addition into the solders. This paper summarizes the effects of alloying elements on the wettability, oxidation resistance, mechanical properties and microstructures of Sn–Zn lead-free solder alloys.