Degradation Diagnosis During Active Power Cycling via Frequency-Domain Thermal Impedance Spectroscopy

The increasing reliability requirements of power electronic components demands for a better understanding of their application-dependent aging progression. Active power cycling is a commonly used accelerated-aging method for invoking degradation effects in the thermal path of power devices. For aging diagnosis during power cycling, usually step-response thermal impedance spectroscopy is applied utilizing a temperature-sensitive parameter for thermal sensing. This approach has multiple limitations: Degradation detection close to the power semiconductor is limited since the load step over-proportionally excites low-frequency components. The temperature-sensitive parameter is by itself prone to aging, leading to reduced accuracy or necessitates repeated calibration. To overcome these limitations, this paper proposes online thermal impedance spectroscopy in frequency domain for aging diagnosis during active power cycling. By doing so, aging effects in the thermal path can be detected and localized more robustly and with higher accuracy without testing interruption. Furthermore, by using a near-chip NTC sensor for thermal sensing, calibration effort can be reduced significantly. This paper evaluates the online thermal impedance spectroscopy using data from the active power cycling of an IGBT lead-frame power module with a near-chip NTC.