An optical method for evaluating the degradation mechanism of a developing RuO2 thick film resistor element for power modules

Abstract

We devised a simple and noninvasive method for evaluating the spacial distribution of local electron densities of a thick-film RuO2-based chip resistor using UVVIS- IR reflectance microscopy. After a long-term durability test for 874 h under an elevated temperature of 623 K, RuO2 resistors were thermally damaged, and their resistance became more than 10% higher. We identified the thermally damaged region by this new method and found that the thermal degradation is mainly due to an increase in the resistance between the Ag electrode and the RuO2 resistor film.