Cost-efficient in-situ end-of-life prognostics of power dies and LEDs by junction temperature measurement

Abstract

Lifetime (or health) monitoring in modern power electronics & luminaries continuously gains in importance, especially if safety-relevant applications are in the focus. Moreover, technology development of such devices requires fast and if possible continuous assessment of structural integrity. This work proposes a simplification of transient thermal testing (TTA) of LEDs by condensing measurement data analysis into one characteristic value to be stored and compared to successive or previous measurements for damage evaluation. Our custom-built in-situ monitoring system is based on microcontroller (uC) functionalities and can be used as stand-alone solution for reliability testing without any other electronic equipment. For quantitative assessment of measurement system performance we used Luxeon Z LEDs with different thermal interface materials. Pre-calibrated samples were inspected for structural integrity before and after cycling tests by X-Ray inspection. Measurement concept as detection for failure at thermal interface or die attach was qualitatively proven by correlation with structure function evaluation.