Electrochemical Migration of Copper in Adsorbed Moisture Layers

Abstract

Electronic devices are subject to failure through various electrochemical processes including moisture adsorption, corrosion, electrodeposition, current leakage, etc. The object of the present investigation was to characterize the effects of a contaminant on the moisture-adsorption process on a model electronic device. In addition the growth of “dendrite-like” structures on deliberately contaminated devices under humid conditions has also been examined. The electronic devices consisted of two copper conducting lines deposited on α-alumina substrates, which were contaminated with controlled amounts of cupric chloride. In order to assess the effects of the contaminant, the water up-take characteristics of the unmetallized substrate were determined on both clean and contaminated α-alumina as a function of relative humidity. In addition, the effects of contamination on dendrite-like growth was investigated in experiments where a 30 V bias was applied across the conducting lines. The resulting growth patterns follow the irregularities of the substrate and are quite different from classical dendrites grown in bulk solutions.