COST Action MP0602 - Handbook of High-Temperature Lead-Free Solders: Materials Properties, Vol.3, Chapter 5: Group Project Reports, GP5 - Modeling and experimental investigation of the microstructural changes in the interdiffusion zone of lead-free solder joints

The main purpose of this group project was the development of theoretical models and simulation techniques that predict the microstructural changes in the interdiffusion zone in lead-free solder joints. Different modelling techniques such as the phase field method, finite element elastic and viscoplastic modelling and the CALPHAD-method were combined to describe processes at different length scales. The modelling was highly supported by experimental studies, such as diffusion couple and annealing experiments, phase structure and composition characterization, 3D microstructure characterization techniques and mechanical testing to obtain the needed information for the simulations on the sequence of phase formation, diffusion and phase stability properties and the mechanical behaviour, and for validation of the modelling approaches. Different phenomena important in the life cycle of a solder joint have been considered, e.g. solidification of the solder, growth of the intermetallic layers and precipitates, Kirkendal voiding, and microstructural changes and viscoplastic deformation during loading.