The Challenge of Accurately Analyzing Thermal Resistances

Abstract:
In power electronic devices, estimation of chip temperatures is a mandatory step during the design phase. Developers have to rely on datasheet values regarding thermal resistances for this estimation. These values are well defined for solid materials; however the interface from power semiconductor to the heat sink depends on thermal grease and the mounting process. Measuring this part of the thermal path cannot be done directly. Several values need to be determined to calculate this value. Minor discrepancies during the measurements lead to massive deviations. This paper discusses the measurements to be done and the influence of inaccuracies.