In-situ observation of electrode melting in multilayer-ceramic capacitors

Observations on sectioned and polished multilayer ceramic capacitors, which were subjected to controlled current-surge test conditions, are presented. Capacitors from several vendors were examined in situ under an optical microscope while current pulses of varying magnitude were applied at a constant voltage. Subsequently, some samples were further examined by scanning electron microscopy (SEM). The failure mechanism appeared to be the heat-induced local melting of internal electrodes, leading to blow-out or charring of the capacitor. In less severe cases, local melting and crack formation in the surrounding ceramic was observed. The primary change in capacitor properties was in the degradation of the insulation resistance (IR). In severe cases, this also led to an increase in the dissipation factor (DF).<>