Electrical failure of multilayer ceramic capacitors caused by high temperature and high humidity environment

In this paper, the electrical behavior of multilayer ceramic capacitors (MLCs) in strict dynamic high temperature-humidity-DC bias voltage (THB) conditions were studied and the failure model of MLCs under such conditions was proposed. It was found, if the environmental temperature and humidity rose too fast and the temperature of a MLC was lower than the dew point temperature of surrounding moist air, dewdrops would condense on the MLC surface. When DC voltage was applied, metallic ions from end terminations of the MLC would migrate along the condensed water film on the MLC surface and made a permanent short-circuiting path between two terminations. Silver and tin migrations were found by EDX detection in our experiment. It was also found that the applied DC electrical loading level had a strong influence on the fail rate of MLCs. The recovery rate of MLCs after the dynamic THB process decreased with applied DC voltage increasing. To reduce the effect of dewdrops of moist air on the reliability of MLCs, the method and speed of temperature and humidity rise are discussed.<
>