Electrical Insulation of Conformally Coated Printed Circuit Boards: An Overview and a Study of the Influence of Pollution

Abstract

For application in harsh environmental conditions, printed circuit boards (PCB) are usually coated with a protective polymer typically of a 50-μm thickness that provides electrical insulation.

Optical Detection Method for Partial Discharge of Printed Circuit Boards in Electrified Aircraft Under Various Pressures and Voltages

“…Silicone is widely used as a conformal coating in the aerospace industry due to its good performance at extreme temperatures (−50 • C to +125 • C), excellent resistance to moisture, and stable chemical properties. According to the IPC-CC-830 standard, the typical thickness of the coating is 12.5-200 μm [17]. The silicone (type: FSC 400) is used for the conformal coating material for spraying on the PCB, and the thickness is controlled to about 40 μm.…”

“…Regarding PDs on PCBs, there are several studies about the breakdown characteristics and PD testing of PCBs under ac 50-Hz voltage, but there are few investigations of the PD characteristics on PCBs under ac voltage for other frequencies and square voltages, which are prevalent in real MEA/AEA power system [13]- [15]. Some work about the effect of conformal coating and the influence of external environmental changes on PCB PDs is done [16], [17]. However, these studies mainly focus on the electrical and physicochemical properties of the PCB itself, which cannot be applied to detect and forewarn about the PDs in MEA/AEA.…”