Abstract
To investigate the effects of built-in inductors on current rising waveform for contact discharges of electrostatic discharge generators (ESD guns), we simultaneously measured discharge currents and the resultant magnetic near-fields, and compared their results with those for an ESD gun with a metal cylinder in lieu of the inductor. As a result, we found that the magnetic near-field waveform is deformed by the distortion of the current rising waveform for an ESD gun with an inductor, while the ESD gun with a metal cylinder produces no distortion for the current rising waveform despite its rise time (400 ps) shorter than the International Electrotechnical Commission (IEC) specification so that there is no distortion for the corresponding magnetic near-field waveform. Using the Heidler's formula for typical discharge current waveform specified in the IEC, we calculated current rising waveform and the resultant induced output voltage of a magnetic probe, which shows that these results do not agree with those for the built-in inductor, while there is good agreement for the metal cylinder. This finding implies that immunity test results can be affected by the frequency characteristics of a built-in inductor inside an ESD gun, and thus that not only rise time but also current rising waveform of discharge currents should be specified for ESD immunity testing.
