Investigation of Partial Discharge in Aircraft Conformally-Coated Printed Circuit Boards

Printed circuit boards (PCB) are key components of any electronic system. The reliability of PCBs under operating conditions is an important factor to ensure the performance of the system. In recent years, the electrical power demand in more-electric aircraft has significantly increased. To provide more power, the operating voltage is increased which imposes a higher level of electrical stress on the insulation system of PCBs and, therefore, a higher risk of failure. Partial discharges in PCBs are more likely to happen within the air gap. To improve the insulation of PCBs, they are coated with an insulation material. In this study, test boards with two parallel traces were fabricated and coated based on aerospace industry approved standards. The boards were energized using a 60-Hz adjustable high voltage source. Partial discharges were measured for silicone-coated test boards under pollution and conductive particles conditions. The impact of pollution location on partial discharge was investigated. Besides, the breakdown voltage of test boards was measured under different coating conditions and low air pressure. An increased withstand voltage for coated boards was confirmed.