Development of Method for Thermal Diffusivity Measurement of Thin and High Conductive Ceramics

Reliable operation of power modules under all conditions that may occur during their lifetime must be achieved by design. Thermal simulation is an important tool to optimize the thermal design with respect to chip temperature. This requires reliable data for thermal properties of ceramic substrates. The laser flash method is a widely used technique, however measuring thin and highly conductive ceramics such as silicon nitride (Si3N4) can be challenging. In this work, we identify a reliable method for determining thermal diffusivity by comparing different coating methods for sample preparation and investigating the influence of the measurement device on the results. We find that an automated graphite dip coating for sample preparation yields the best reproducibility and demonstrate that an offset in thermal diffusivity due to different sample preparation methods can lead to differences in simulated Rth of up to 3,5 %.