Investigation of cooling capability of ceramic substrates for power electronics applications

Abstract

This study investigates the cooling capability of ceramic substrates, which are commonly used in power electronics. Ceramic substrates are pivotal in thermal management because they address the challenges posed by the concurrent trends of miniaturisation and power enhancement in power electronics. Therefore, a detailed numerical study of the cooling capabilities of Al2O3 and AlN substrates with various thicknesses from 0.05 mm to 3 mm in a model configuration with defined liquid cooling is conducted. This model configuration represents a commonly used stack-up for real power electronic modules. The results of the numerical study are verified through experimental measurements. It was demonstrated that for low substrate thicknesses (0.3–0.6 mm), similar cooling capabilities can be achieved by a combination of more efficiently cooling, less thermally conductive, and less expensive substrate. However, AlN is highly efficient for cooling in applications requiring substrates with thicknesses greater than 1.0 mm. The present study proved that increasing the thickness of the AlN substrate has a negligible effect on cooling efficiency. Based on the results of the numerical study, which is verified by experimental measurements, it is possible to design the optimal thickness of the ceramic substrate, flow rate of the cooling medium, and material of the ceramic substrate to achieve the required power dissipation from the substrate without exceeding the maximum defined operating temperature.