Effect of Defect Dynamics on Reliability of Base Metal Electrode Multilayer Ceramic Capacitor
YOUSEFIAN P. 1, RANDALL C. 1
1 Penn State University, University Park, United States
Base metal electrode (BME) multilayer ceramic capacitors (MLCCs) are widely used in aerospace, medical, military, and communication applications, requiring a high level of reliability. The continued development of BaTiO3-based MLCCs has contributed to further miniaturization by reducing the thickness of each dielectric layer. However, MLCCs may achieve higher volumetric capacitive efficiency while experiencing higher electric field conditions, raising concerns about their reliability. To improve the reliability of MLCCs, the transient mechanisms of insulation resistance degradation must be understood and develop metrologies that can better screen MLCCs in their production and quality control. One of the most important degradation processes in MLCCs is driven by the electromigration of oxygen vacancies within the microstructure under an applied electric field. The burn-in test is a screening procedure to eliminate components with a higher probability of infant mortality failures. During this process, components are exposed to high temperatures and voltages relative to their design. The effect of the burn-in test on the dynamics of oxygen vacancies was studied using thermally stimulated depolarization current (TSDC), impedance spectroscopy, and in-situ high-accelerated lifetime testing (HALT). The TSDC results unveiled that the burn-in test caused intragranular and transgranular migration of oxygen vacancies, which will not be relaxed afterward. These electromigrations can be dissociated from locally associated defect complexes, pile up of vacancies at a grain boundary, and transgranular migration. Mean time to failure (MTTF) data gathered from in-situ HALT demonstrated that burn-in tests were ineffective at detecting infant mortality failures and negatively impacted the overall reliability of BME MLCCs relative to manufactured components. Moreover, we demonstrated that the annealing process is insufficient for MLCCs recovery and cross-section of degraded and recovered MLCCs were investigated by kelvin probe force microscopy (KPFM) under a dc bias voltage. MTTF data were also fitted to empirical and physical-based lifetime prediction models. The limitations of existing lifetime prediction models and the shortcomings of using the MTTF in predicting the lifetime of MLCCs will be discussed, along with future perspectives on the reliability of MLCCs evaluation.