From Power SO to E-Pad packages: a thermal bargain?

Facing the demand of low cost solutions for medium power applications from various segments of the electronics market, a full thermal study comparing existing power SMD package families and new e-pad structures is performed. Different body sizes and pin counts are considered. The study consists of thermal modeling analysis carried on using FLOTHERMreg. Thermal simulation results with different PCB configurations are presented. The thermal dissipation mechanism for those packages through the metal bottom case to the PCB is described. The copper exposed area dimension soldered onto the PCB is identified as the dominating factor controlling the total package thermal resistance. Consequently the limits of applicability of new small body e-pad packages versus the old style power SMD's are finally defined