Cavity detection on organic coatings by electrostatic measurements: A detailed study using FR4 fiberglass epoxy laminates

Surface potential measurements after corona charging are reported on metal–insulator structures with artificial defects. On organic anticorrosion coatings, potential cartography shows clear evidence of bad adhesion areas. A detailed analysis has been carried out on printed circuit board composite epoxy fiberglass insulating plates with a calibrated cavity, on which potential decay and return data clearly exhibit a particular response compared with non-voided plates. This response is analyzed in terms of material polarization and charge injection from the interface. We conclude from this analysis that charge injection from the cavity is enhanced, whereas polarization is reduced in the cavity area.