Determining the Junction-to-Case Thermal Resistance of a Semiconductor Device from Its Cooling Curve

Abstract

The thermal resistance of a semiconductor device determines the limiting thermal regime that guarantees its operability: the higher the thermal resistance of a semiconductor device the larger its overheating can be. Therefore, the thermal resistances of commercial devices must be controlled. At present, the method for determining the junction-to-case thermal resistance using the structure functions of the differential and integral (cumulative) thermal capacitance is widely used. The heat flow function, a new thermal characteristic proposed in this work, allows us to determine the instant of time at which the heat front reaches the heat sink. In this case, the inflection point of the heat flow function corresponds to the junction-to-case thermal resistance found using a similar method. The cumulative thermal capacitance is determined from the heat balance equation. The structure functions are determined analytically without the numerical deconvolution procedure. Comparison of the proposed method with the well-known methods that use the structure functions show that, at the same values of parameters, the processing of the results is easier, the measurement time is shorter, and strict requirements for heat removal are not imposed. The proposed method can be used to compare the designs of devices and analyze defects in the thermal resistance of finished devices.