Effective use of power integrated circuit packages in automotive systems requires thermal models. This paper provides detailed information on the transient and steady state characterization and modeling of power SOIC packages. Sixteen and twenty four pin wide body SOICs are analyzed in FR4 and polyimide systems. Model extraction, generation, and validation are presented. To validate the model, data taken in an electronic fuel injection system is analyzed and then compared to the simulation results. The model results show 3 % correlation to the actual data.