05 Octobre – Thesis defense - Georges Khoury
14 h Amphi J.P. Dom - laboratory IMS (building A31) / Talence campus
Investigation into the effects of thermomechanical fatigue on the evolution of the microstructure and the plasticity of SAC solder joints.
Nowadays, SAC alloys are widely used as soldering materials. The SAC solder joints have a dynamic microstructure which evolve excessively under different aging conditions. The characteristic of visco-plasticity of the SAC being extremely sensitive to its microstructure complicates the evaluation and the estimation of the life expectancy of the joints.
This work is aimed at improving the predictions of SAC solder joints reliability by contributing to expand knowledge on the evolution of the microstructure and the mechanical characteristic of visco-plasticity of SAC. This work consists in studying separately the evolution of microstructure and plasticity under the effect of aging.
The study of the microstructure allowed the gain of new knowledge on the coarsening under different aging conditions. This study also allowed the evaluation of the hypothesis of linear damage accumulation on the microstructural analysis basis and on the basis of a thermal cycle with all the different conditions that it presents.
The study of plasticity allowed the assessment of the effect of aging by thermal cycling on the mechanical strength of the SAC. This study also allowed the evaluation of the effect of not taking into account the evolution of the mechanical characteristic of plasticity on the estimation of the life expectancy of the solder joints using finite element simulations.