Dependence of grounded metal-plate´s approach speed on spark length for air discharges of electrostatic discharge generator

Electrostatic discharges (ESDs) due to the collision of charged metals cause serious malfunctions in electronic information devices. In particular, the faster collision provides the electronic devices with severer ESD events, while the underlying mechanism has not fully been elucidated, though it has been widely accepted that the approach speed affects a spark length. In this study, to investigate the dependence of the approach speed on sparks, we developed a novel setup for electronically measuring a spark length for air discharges of ESD generators (ESD guns) with a velocimeter based on laser Doppler effects, which was validated from two different types of empirical formulae derived from the Paschen´s law. Measurements of spark lengths were conducted by moving a grounded metal-plate to an ESD gun at three different approach speeds of 20 mm/s, 100 mm/s and 200 mm/s. The results showed that spark lengths exponentially decrease with the increase in the approach speed of the grounded plate.