Correlation of silver migration with temperature-humidity-bias (THB) failures in multilayer ceramic capacitors

The normal voltage failures in multilayer ceramic capacitors (MLC) using the temperature-humidity-bias test (THB) are described. The cumulative failure data showed that the MLC failures occurred in several stages during the THB test, with the extent of failures depending on the quality of the capacitor lot and the bias voltage. THB failures increased after some of the MLC lots had undergone a barrel-plating operation, indicating moisture penetration and ionic contaminants as the likely cause of accelerating the failure rate. In the cross section of failed MLC, the authors observed large holes caused by high-temperature explosive events occurring inside the MLC. There were also internal cracks connecting electrodes of opposite polarity, with silver inclusions along the length of the cracks. These observations strongly suggested that silver migration was the cause of short-circuit paths, leading to subsequent failure of the MLC.<
>