Highly Accelerated Life Stress Testing (HALST) of Base-Metal Electrode Multilayer Ceramic Capacitors

摘要

An improved highly accelerated life stress testing (HALST) and modeling method was developed and applied to evaluate the reliability of BME capacitors. General reliabilities of multilayer ceramic capacitors (MLCCs) with precious-metal electrodes (PMEs) and base-metal electrodes (BMEs) are discussed. A combination of leakage current and mean-time-to-failure (MTTF) measurements under accelerated life stress conditions have been used to distinguish and separate the MTTF data into two failure groups: slow degradation and catastrophic. The slow degradation failures, characterized by a near-linear leakage increase against stress time, fit well to an exponential model over an applied field. A characteristic exponential growth time, τ_(SD), is defined to describe the reliability life of this failure mode. The two separated MTTF data groups have been fitted to the 2-parameter Weibull model. When data points in the catastrophic subset are used for reliability modeling, the data points of the slow degradation subset are treated as suspensions, and vice versa. MTTF of most BME capacitors reveals an exponential dependence on an applied electric field due to the mixed failure modes. The initial MTTF data for slow degradation failures appears to follow the exponential law, and that for catastrophic failures follows the conventional power law. The reliability model developed with respect to mixed failure modes and acceleration factors agrees well with the HALST results - not only with the MTTF data, but also with the failure modes (catastrophic or slow degradation). BX life has been used to replace MTTF for predicting the reliability life of BME capacitors at 125°C and 2x rated voltage (V_r), the condition that all MLCCs are subject to pass at at least 1,000 hours life test for consideration for high-reliability space applications. This B0.8 approach can be used to select BME capacitors that exhibit the potential for passing the regular life test when evaluated using the quick turnaround HALST method developed in this work.