Correction of Delay-Time-Induced Maximum Junction Temperature Offset During Electrothermal Characterization of IGBT Devices

摘要

The lifetime evaluation is strongly influenced by the measurement accuracy of the junction temperature with the V_ce(T) method during power cycling test (PCT). However, the measurement delay time t_md, the time between which the load current is switched off and the test pulse is applied, induces a maximum junction-temperature offset ΔT_jm. The JEDEC [1] suggested square root t method is found only to be suitable for devices with surface-close heat generation and will induce errors for other devices such as IGBTs. In this article, two novel methods, the simulated ΔZ_th and the Cauer thermal model, are proposed. The principle and accuracy of these two methods are discussed in detail. Furthermore, the measured Z_th curve, or the Foster thermal model method, is proven not suitable for the correction of the maximum junction-temperature offset, as it will induce the same error as the square root t method.