Dependence of breakdown fields on charge voltages for human ESD

Electrostatic discharge (ESD) events due to charged movement objects with low voltages give a fatal electromagnetic interference in high-tech information equipment. In order to clarify the mechanism, with a 6-GHz digital oscilloscope, we previously measured through a 50-Omega SMA connector the discharge currents due to collision of a hand-held metal piece from a charged human body from 200 V to 2000 V, and thereby estimated a gap breakdown field. As a result, we found that at charge voltages lower than 600 V breakdown fields are almost kept constant, while at charge voltages over 600 V the breakdown fields decrease with charge voltages, which could be explained from an empirical formula based on the Paschenpsilas law. In this study, with a 12-GHz digital oscilloscope, wideband measurements of the discharge currents were made through an IEC calibration target at a wide range of charge voltages from 200 V to 8000 V covering the ESD test voltages specified in the IEC standard. The corresponding breakdown fields were estimated, whose dependence on charge voltages was found to be roughly the same as that previously obtained.