Xiaofei He, Michael H. Azarian, and Michael G. Pecht
Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park, MD 20742, USA
Electrochemical migration can occur on printed circuit boards when exposed to moisture or condensed water drops, thus causing dendrite electro deposits, which can give rise to short circuits. This study used the Nernst Planck equation and impedance measurements to model the kinetics of electrochemical migration under condensed water drops between copper conductors on printed circuit boards. The time needed for an embryonic dendrite to appear at the cathode and for it to grow from cathode to anode was calculated by the model and confirmed experimentally. It was found that by determining the electro active ion surface concentration at the anode with the help of impedance measurement, and by considering migration and diffusion in the bulk ion transport, the model matched the experimental results quantitatively. The model was also extended to non-condensing conditions by comparing the conductances in bulk water and moisture films. Historical models were applied to the experimental results and compared with the model of this study.
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