Title of dissertation : MOISTURE IN MULTILAYER CERAMIC CAPACITORS

Title of dissertation: MOISTURE IN MULTILAYER CERAMIC CAPACITORS Daniel Noel Donahoe, Doctor of Philosophy, 2005 Dissertation directed by: Professor Michael G. Pecht Department of Mechanical Engineering When both precious metal electrode and base metal electrode (BME) capacitors were subjected to autoclave (120 oC/100 % RH) testing, it was found that the precious metal capacitors aged according to a well known aging mechanism (less than 3 % from their starting values), but the BME capacitors degraded to below the -30% criterion at 500 hours of exposure. The reasons for this new failure mechanism are complex, and there were two theories that were hypothesized. The first was that there could be oxidation or corrosion of the nickel plates. The other hypothesis was that the loss of capacitance was due to molecular changes in the barium titanate. This thesis presents the evaluation of these hypotheses and the physics of the degradation mechanism. It is concluded by proof by elimination that there are molecular changes in the barium titanate. Furthermore, the continuous reduction in capacitor size makes the newer base metal electrode capacitors more vulnerable to moisture degradation than the older generation precious metal capacitors. In addition, standard humidity life testing, such as JESD-22 THB and HAST, will likely not uncover this problem. Therefore, poor reliability due to degradation of base metal electrode multilayer ceramic capacitors may catch manufacturers and consumers by surprise. MOISTURE IN MULTILAYER CERAMIC CAPACITORS by Daniel Noel Donahoe Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2005 Advisory Committee: Professor Michael G. Pecht, Chair Professor Donald B. Barker Associate Research Scientist Sanka Ganesan Associate Professor Isabel K. Lloyd Associate Professor Patrick McCluskey ©Copyright by Daniel Noel Donahoe 2005