Review of filament growths and corrosion effects caused by moisture films and dc bias between microcircuit conductors

Published information on dendritic or migratory filament growths and corrosion or other effects caused by electrolytic currents on hybrid microcircuits is reviewed. These effects have caused circuit malfunctions through high resistance shorts, leakage paths or circuit opens. Electrolytic currents are produced when there are condensed moisture films and dc bias between conductors. Residual salts such as chlorides are required for some but not all circuits for filament generation. Hermetic packaging, encapsulation, and coating are means used to restrict moisture from the circuitry and reduce or eliminate current formation. For these methods to be effective, proper precautions must be exercised in cleaning and processing operations prior to and during covering operations. Although the information was obtained mainly from microcircuit studies, there is much which is applicable to macrocircuits such as printed boards and connectors.