Characterisation of electrostatic discharges from insulating surfaces

This paper investigates how the presence of a grounded backing plane influences the electrostatic discharge (ESD) characteristics from a charged polystyrene sheet. High-speed digital sampling techniques are used to capture discharge current waveforms via a specially designed current probe. Charge maps 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 resultant electrostatic discharge from the surface for a given initial surface charge density. The results suggest that the presence of an earthed metal backing plate can mean the difference between an incendiary and non-incendiary ESD. This has implications for the design of plastic components for use in sensitive flammable atmospheres.