Au-sn - X (x = Co, La, Er) System, Thermodynamic Optimization And Calculated

Due to the wonderful ductibility, excellent corrosion resistance, high electrical and heat conductivity, Au-20Sn eutectic sloder has been widely used in packaging of optoelectronic, aviation and spaceflight and so on. However, with the high price, the developing orientation of Au-Sn solder requires that the substitute be found to reduce the consumption of Au element.Recently, the reseach about substitute materials for noble elements in solder indicated that the rare earth metals can refine the mechanical performance, improve wettability, reduce the oxidization of solder, clean the grain boundary, and improve the fatigue intensity. Development of the relative phase relationship of solder is of much importance because of the abundant RE resources and its large markets.Combining the formation enthalpy of intermetallic compounds (IMCs) calculated by first principle approach with CALPHAD technique, Au-Co, Au-La and Au-Er binary systems are optimized, Au-Sn and Co-Sn binary system are modified, and Au-Sn-Co, Au-Sn-La ternary systems are calculated,1. Au-Co, Au-La and Au-Er binary systems are optimized by Thermo-Calc software using CALPHAD technique. Liquid and all the terminal solutions (Fcc, Bcc and Hcp) are modeled as substitutional solution. All the intermetallic compounds are treated as stoichemistric phases. Calculated thermodynamic data and equilibria data agree with the experiments.2. Based on the formation enthalpy of IMCs calculated by first-principle approach, the Au-Sn binary system are modified, and in order to fit well of the ternary system, the Sn-Co binary system are improved.3. Au-Sn-Co and Au-Sn-La ternary systems are calculated by Pandat software using CALPHAD technique. The solubility of ternary elements is added for some binary compounds, besides a stoichemistric ternary compound are added in Au-Sn-Co system. Calculated phase diagrams are identical with the experimental data.