The objective of this project is to develop lead free solder alloys with superior mechanical and physical properties. For various reasons (some mentioned above), Sn-based multicomponent alloys with alloying elements, Ag, Cu and/or Bi are likely to be the most promising [2] [8]. For further improvement of Sn-based solder joints, in this work the effects of alloying and/or micro-alloying elements (e.g., Bi, Ag, Cu, Zn, Al, Sb, Ge, Se…) on microstructure, mechanical properties, interfacial reactions, wettability, reliability and melting behavior of Sn-based solders are investigated.