Devices based on wide-band gap semiconductors such as SiC, GaN allow high power densities, size reduction, high integration and elevated operating temperatures. In this study, we present solutions for high temperature power packages based on finite element simulations and experimental approach. Analytical methods are used to investigate the best choice among the different selected materials for the substrates, the solder joints and the baseplate. Various power assemblies using SiC diodes have been fabricated. Their thermal performances are evaluated through the measurements of the thermal impedance and the thermal resistance and also finite elements simulations. The correlation between the simulation results and the experimental ones are discussed.