The solder joint failures in printed circuit boards (PCB's) which control most of the functions in modem cars are mainly caused by the different thermal coefficients of expansion of all the components involved in the boards. During validation tests, PCB's are subjected to cycles of severe thermal shocks, which promote complex stress - strain distributions in the solder joint. The stresses and strains involved during the thermal cycling can be derived by numerical methods. For this purpose, before modeling the given electrical connecting configuration, a good description of the mechanical behavior of the considered materials is needed. In the present work, a comparative study is carried out of the flow behavior at relatively high homologous temperatures of eutectic Sn-Pb and Sn-Ag soldering alloys. For this purpose, uniaxial compression and tensile tests were performed at diverse strain rates and temperatures. Results showed that at relatively low temperatures the deformation response can be considered to be controlled by the same mechanism in both alloys. However, the Sn-Pb eutectic displayed superplastic behavior at high temperatures, depending on the initial eutectic micro structure.