Measurements of Thermal Resistance by Plateau Voltage Sampling

A new method for quantitatively measuring the increase in thermal resistance caused by power cycle degradation of power modules is presented. By utilizing the dependence of the plateau voltage on the junction temperature, the change in plateau voltage caused by self-heating was measured, and this was used to convert into the change in junction temperature and the increase in thermal resistance. In this paper, the proposed method demonstrates the capability to measure thermal resistance increases of 5–50%, and it is also shown that degradation of chips other than the device under test does not affect the thermal resistance measurement.