Evaluation of in-plane effective thermal conductivity for metalized ceramic substrates using a micro heater chip

Abstract

Metalized ceramic substrates are widely used as circuit boards for heat dissipation and electrical insulation in high output power modules and are becoming more important since the output power of the power devices has been increasing year by year. Designing a proper module structure requires not only measurements of constituting materials’ properties but also understanding of the heat transfer characteristic in a module structure. An accurate assessment method of thermal conduction properties for such metalized ceramic substrates is currently still missing. Under the circumstances we have developed a method for evaluating in-plane effective thermal conductivities of metalized substrates in a mounted state. The key point of this method is that a cavity is made between a metalized ceramic substrate and a cooling plate by interposing a ring-shaped structure to control a heat flow from the center to the periphery. The in-plane effective thermal conductivities of various kinds of metalized substrates could be evaluated by means of surface temperature measurements at two points on the substrate during power supply. The evaluated values were consistent with those of estimated ones calculated by the rule of mixtures.