Characterisation of electrostatic discharges from insulating surfaces

This paper investigates how the presence of a grounded backing plane influe nces the electrostatic discharge (ESD) characteristics from a charged polys tyrene sheet. High-speed digital sampling techniques are used to capture di scharge current waveforms via a specially designed current probe, Charge ma ps are obtained using a scanning electric field probe, the resultant scans giving clear indication of how the surface charge distribution contributes to the ESD. Data obtained indicate that the presence of a grounded backing plate close to a charged plastic surface has a significant effect on the re sultant electrostatic discharge from the surface for a given initial surfac e charge density. The results suggest that the presence of an earthed metal backing plate can mean the difference between an incendiary and non-incend iary ESD. This has implications for the design of plastic components for us e in sensitive flammable atmospheres. (C) 2001 Elsevier Science B.V. All ri ghts reserved.