Fundamental study of surface roughness dependence of thermal and electrical contact resistance

For thermal management of electrical equipment, thermal contact resistance is one of the important parameters. However, thermal contact resistance is dependent on various factors, for example surface roughness, the contact pressure and the hardness of the material. Therefore, quantitative evaluation is difficult. Nowadays, CFD (Computational Fluid Dynamics) analysis is widely used in thermal design of electronics. However, unknown thermal contact resistance is always a problem for accurate temperature estimation. In this study, we examined surface roughness and material hardness dependence of thermal contact resistance and electrical contact resistance for simple estimation of thermal contact resistance. Measurement of thermal contact resistance takes a long time and electrical resistance measurement is much shorter. If thermal contact resistance can be estimated from electrical contact resistance, thermal contact resistance can be known in short time, and this method can support accurate CFD analysis. The materials to be measured are Al1070 and S45C, and three patterns (Ra = 0.2, 3.2, 12.5 μm) of surface roughness are examined. After the measurement of thermal and electrical contact resistance, we examined the ratio between electrical contact resistance and thermal contact resistance for the faster estimation of thermal contact resistance using the concept of Wiedemann-Franz law and Lorentz number like experimental constant.