Part Of The Lead-free Solder System Phase Equilibrium And Interfacial Reaction Study

Lead-tin(Pb-Sn) solder alloys have been widely used in the morden electronics industry because their low melting points, good wettability, good corrosion resistance and reasonable electrical conductivity. However, due to increasing environmental and health concerns and legislation restriction over the use of lead, What's more, the development of packaging technology need developing solder alloys withstanding good mechanics properties as well as electrical properties. As far now, Designing new lead-free solder is leading to high-order system alloys. Phase equilibria information is needed for evaluation of candidate lead-free solder in terms of their melting behavior and of reliability. Due to lacking of the enough information about the phase diagrams especially ternary or higher-order systems, the CALPHAD(Calculation of PHAse Diagram) technique of phase equilibria calculation using thermodynamic descriptions from databases provides a powerful tool for obtaining such information. From the calculated phase diagrams the melting temperature range for solders, the solidification path, as well as the susceptibility to intermetallic formation with various substrates, can be predicted.According to the advantage of phase diagram calculation and phase transformation simulation in our group. The subject of this work is to study the phase equilibria information and microstructure evolution about lead-free solder.1. Using the CALPHAD technique, the experimental phase diagrams and thermodynamics data was collected, critically assessed and the uniform and newest lattice stability was adopted. The Au-Sb binary system was optimized, and the Au-In-Sb was extrapolated by integrating Au-In and In-Sb binary systems. A set of consistent parameters was obtained, on the base of which, a series of the Au-Sb and the Au-In-Sb representative diagrams were calculated and compared with the experimental results.2. Using the same method shown as above, the Au-Sn binary system was optimized, and the Au-Sb-Sn was extrapolated by integrating Au-Sb and Sb-Sn binary systems. A set of consistent parameters was obtained, on the base of which, a series of the Au-Sn and the Au-Sb-Sn representative diagrams were calculated and compared with the experimental results.3. On the base of thermodynamics database, the susceptibility to intermetallic formation and its sequence between the Sn-Ag alloys and Cu were predicted by using the CALPHAD technique. The non-equilibriurn solidification path was alsosimulated by using Scheil-Gulliver model.In summary, present work perfects the constructed solder alloys thermodynamics database of our group, and is the foundation of the work on extrapolating high-order systems, designing new solder alloy and simulation of interfacial reaction, as well as controlling the formation of the intermetallic and evaluation of the reliability, which will be very significant for the practically solder designing.