Mechanism of prebreakdown process in Ni-BaTiO3 multilayer ceramic capacitors

The local insulation resistance (IR) degradation in Ni-BaTiO3 multilayer ceramic capacitors (MLCCs) was studied, especially in the degradation stage immediately before the electrical breakdown. We named this stage the prebreakdown, which we induced by controlling electric load. We prepared four samples at different stages of prebreakdown. The conduction characteristics of these samples were studied by evaluating the temperature dependence of IR and I-V characteristics. The temperature dependence of IR was evaluated also by reversed voltage loading in highly accelerated life tests (HALTs). The results indicated that the conduction characteristics changed from electrode-limited conduction in fresh MLCCs to bulk-limited conduction in prebreakdown MLCCs. The growth and formation of conductive paths at a local degradation area were also suggested by the data of samples at different stages of prebreakdown. On the basis of these results, we discussed the mechanism that leads to the breakdown of Ni-BaTiO3 MLCCs.