Design of lead-free solder alloy and alloy phase diagram calculation

The principles for lead-fsee solder alloy design and the importance of phase diagram study as well as the calculation of phase diagram(CALPHAD) approach in the lead-free solder alloy design are discussed. Based on CALPHAD approach two potential lead-free solder alloys, i.e., the Sn-Zn-In(x(Zn)0.11, x(In)=0.100.14)ternary alloy and the Sn-Zn-In-Ag(x(Sn)=0.800, x(In)=0.090, x(Zn)=0.075, x(Ag)0.035)quaternary alloy are recommended as lead-free solder alloy instead of the Pb-Sn eutectic solder alloy. The further work for decreasing the content of In and Ag in Sn based Pb-free multi-component alloy with excerlent properties is brief discussed.