the use of high impedance circuitry and narrow conductor separations in current designs is generating increasing concern for the insulation resistance between conductive elements especially those used in high moisture environments. this concern is multiplied by the expanding use of electronic devices in a greater variety of environments and the desire for less heat generation within the device. the high insulation resistance of a dry printed circuit board can be degraded in high moisture environments by electrolytic conducting paths and/or electronic conducting filament growths between conductive elements. the essential ingredients for resistance degradation are bias and a moisture path linking the conductors. ions derived from the interaction of moisture with the material on or in the substrate enhance the electrolytic conduction. this material can be residue from processing and handling, air borne contaminate, or leachable constituents from the substrate. a moisture path can form from atmospheric condensate accompanying a temperature change, i.e., dew, or from water adsorption on hydrophillic sites or hydroscopic contaminants on the surface. methods for preventing the resistance degradation of printed circuit boards, e.g., cleaning, heating, using sealed enclosures, and board surface treatments with water repellants and coatings are discussed. (era citation 06:020728)