Comparison of simulation and measurement of thermal resistance of surface mounted power packages for high power density ballasts

The power density of power systems is often dominated by the package of power electronic components. Using smaller packages results in lower cost but also in poorer thermal performance and higher heat sinking effort. However, if one considers general side conditions, it is possible to reach the same thermal performance even with a smaller package. This paper discusses two methods of defining the thermal junction-ambient resistance and the commonly used wave solder assembly technology. It also describes the test setup and the results of tests done with various packages and transistors.