Leakage currents in degraded multi-layer ceramic capacitors

Leakage currents in new and degraded X7R type multi-layer ceramic capacitors show both ohmic and space charge limited behavior. The near-3/2 power voltage characteristic (I proportional to V to the 3/2 power) of new devices can be attributed to electron emission from electrode points. The quadratic behavior (I proportional to V squared) for moderately degraded devices represents space charge limited emission from planar electrodes. This emission may evolve from the point emission due to resistivity decreases that occur in the emission region as a result of ion movement. For these currents, electrons are believed to be the dominant charge carriers. Neither Schottky nor Poole-Frenkel currents were identified.