The simulation support for design of power electronics is highly required due to safe time to market, to handle the materials and the architecture complexity and to reach the required reliability. Detailed material models of Ag-sintered joints for use in simulations (FEA), especially for thermo-mechanical stability studies, make a valuable contribution. The authors determined material models with the nonlinearities as time and temperature effects in Ag sintering joints for FEA analysis. Further, mechanical measurements of thermo-mechanical behavior due to influences of microstructure formation, such as porosity (and distribution) is shown. Process parameter variations lead to variability of porosity and has been investigated on chip bonding as well as on lap shear specimen for mechanical measurements.