Electrical failure of multilayer ceramic capacitors subjected to environmental screening testing

The electrical failure of multilayer ceramic capacitors (MLC´s) subjected to environmental screening testing (EST) environments is systematically studied in this work. Based on results obtained from comparative EST environments, it is shown that a thin water film can appear on the MLC surface as a result of water vapor condensation caused by extreme changes in environmental conditions. Further, the electromigration of end termination materials such as silver and tin on this moisturized surface under an electrical loading, as confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyzes, is uniquely found to be the major failure mechanism for the lowering of insulation resistance of the MLC. Hence, its eventual electrical failure can arise from the excessive leaking current causing charring or permanent damage. The formation and condensation of water vapor on the MLC surface is found to be caused solely by the rapid change of high temperature and high humidity in a custom designed EST environment. A major implication of this work is that the design of an optimal EST program for any electronic product must take full account of the possibility of water condensation on the device surface as this can be a potential root cause for electrical failures and reliability problems