Thermodynamics and phase diagrams of lead-free solder materials

Many of the existing and most promising lead-free solders for electronics contain tin or tin and indium as a low melting base alloy with small additions of silver and/or copper. Layers of nickel or palladium are frequently used contact materials. This makes the two quaternary systems Ag-Cu-Ni-Sn and Ag-In-Pd-Sn of considerable importance for the understanding of the processes that occur during soldering and during operation of the soldered devices. The present review gives a brief survey on experimental thermodynamic and phase diagram research in our laboratory. Thermodynamic data were obtained by calorimetric measurements, whereas phase equilibria were determined by X-ray diffraction, thermal analyses and metallographic methods (optical and electron microscopy). Enthalpies of mixing for liquid alloys are reported for the binary systems Ag-Sn, Cu-Sn, Ni-Sn, In-Sn, Pd-Sn, and Ag-Ni, the ternary systems Ag-Cu-Sn, Cu-Ni-Sn, Ag-Ni-Sn, Ag-Pd-Sn, In-Pd-Sn, and Ag-In-Sn, and the two quaternary systems themselves, i.e. Ag-Cu-Ni-Sn, and Ag-In-Pd-Sn. Enthalpies of formation are given for solid intermetallic compounds in the three systems Ag-Sn, Cu-Sn, and Ni-Sn. Phase equilibria are presented for binary Ni-Sn and ternary Ag-Ni-Sn, Ag-In-Pd and In-Pd-Sn. In addition, enthalpies of mixing of liquid alloys are also reported for the two ternary systems Bi-Cu-Sn and Bi-Sn-Zn which are of interest for Bi-Sn and Sn-Zn solders. ΠSpringer Science+Business Media, LLC 2006.