In the framework of the COST 531 European Project, the investigation of ternary and multicomponent systems relevant to the lead-free soldering materials is in progress.
The results so far obtained in the experimental and computational investigation of the In-Au-Sn system are here reported.
A number of samples have been prepared on the basis of literature data and preliminary calculations made in order to check equilibria on selected compositions in the 130°C isothermal section.
Samples have been synthesized by induction melting of the pure elements: The samples were annealed at 130°C for 40 days and then quenched in cold water, and were investigated by optical and scanning electron microscopy (SEM) with an OXFORD INCA Energy 300 which allowed a chemical analysis by energy-dispersive-spectrometry (EDS). XRD examination was performed on powder samples using the Debye method. The values of the lattice parameters were refined using a least-squares routine.
Isothermal equilibria reported in the literature have been confirmed. However, DSC measurements carried out on samples having compositions close to the Au4In3Sn3 phase, suggest an incongruent decomposition of the ternary phase. Thermodynamic modelling has been improved according to these preliminary results. New experiments are in progress in order to confirm a few more still uncertain points.