Effect of Change in the Time of Charging Voltage on Spark Discharge from a Metal Disk

Abstract

Electrostatic discharge (ESD) is a source of electromagnetic disturbance. For an ESD immunity test, IEC 61000-4-2 is standardized. In the standard, the air discharge and contact discharge method are described for the application of ESD to equipment under test. Air discharge, which is most common in the field, is a more severe test than contact discharge. Air discharge is dependent on the humidity, the speed of approach to grounded material, the structure of the ESD generator, and so on. An ESD event while charged material approaches grounded material has a more significant effect on electronic equipment than an ESD event from stationary charged material with the same charge potential. This peculiar phenomenon is considered because the rise time becomes faster and the peak spark current becomes larger, but is not well understood for reasons such as the difficulty of reproducibility. To promote an understanding of the spark discharge that occurs while a charged material is approaching a grounded material, the effect of change in the time of the charging voltage on the spark discharge from a stationary metal disk was measured. The experiment showed that the spark voltage and peak spark current increased with a change in the time of the charging voltage, and that the amplitude of the spark current spectra also increased with a change in the time of the charging voltage. The experimental results are considered in terms of the sparking resistance formula, and can be explained qualitatively in terms of the increase of spark voltage. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(3): 1–9, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20991