Dynamic Conductivity Processes in Glass-Filled Polyimide Circuit Boards

Assessments of the risk of electrostatic discharge (ESD) due to spacecraft charging require knowledge of materials' conductivity in flight-like conditions. Due to the difficulty in measuring and modeling conductivity in space conditions, it is common to conservatively assume the minimum steady-state dark conductivity. This study investigates impacts of charging rate, temperature, electric field, and time on the dynamic conductivity of glass-filled polyimide circuit board materials. The chargestorage method of measuring conductivity was used on samples mounted on a cold plate in vacuum. Charging was performed incrementally with conductivity measured between electron exposures. Beam ramp down conditions were varied to investigate the impact of charging rate on the observed charge decay. Observed conductivity does not appear to depend on the rate of beam shut off. Conductivity does depend strongly on electric field, time, and temperature. These effects typically are studied separately.