Phase diagrams of Pb-free solders and their related materials systems

Replacing Pb-Sn with Pb-free solders is one of the most important issues in the electronic industry. Melting, dissolution, solidification and interfacial reactions are encountered in the soldering processes. Phase diagrams contain equilibrium phase information and are important for the understanding and prediction of phase transformation and reactive phase formation at the solder joints. This study reviews the available phase diagrams of the promising Pb-free solders, and their related materials systems. The solders are Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Zn, Sn-Bi, Sn-In and Sn-Sb. The materials systems are the solders with the Ag, Au, Cu, Ni substrates, such as Sn-Ag-Au, Sn-Ag-Ni, Sn-Cu-Au, and Sn-Cu-Ni ternary systems. For the Pb-free solders and their related ternary and quaternary systems, preliminary phase equilibria information is available; however, complete and reliable phase diagrams over the entire compositional and temperature ranges of soldering interests are lacking.