抄録
Electrostatic discharge (ESD) is one of electromagnetic disturbance source. For an immunity test of ESD, IEC 61000-4-2 is standardized. In the standard, air discharge and contact discharge method is described to apply ESD to equipment under test. Air discharge, which is most commonly observed in field, is severer test than contact discharge. Air discharge is dependent on humidity, approaching speed to a grounded matter, structure of ESD generator, and so on. An ESD event during the time that a charged matter approaches a grounded matter has more significant effect on electronic equipment than an ESD event from a stationary charged matter with the same charging potential. This peculiar phenomenon is considered because rise time becomes faster and peak spark current becomes larger, but is not well understood due to the reasons such as difficulty of reproducibility. To promote the understanding of the spark discharge that occurs during the time that charged matter approaches grounded matter, the effect of changing the time of the charging voltage on the spark discharge from a stationary metal disk was measured. As a result of the experiment, the sparking voltage and peak spark current increased with a change in the time of the charging voltage, and the amplitude of the spark current spectra also increased with a change in the time of the charging voltage. The experimental results are considered from sparking resistance formula, and can be explained from the increase of sparking voltage qualitatively.
