ESDガンのテーパー型垂直結合板への間接放電に対する発生磁界のばらつき低減と実験検証

Abstract

The International Electrotechnical Commission (IEC) prescribes in IEC 61000-4-2 immunity tests of electronic equipment against electrostatic discharge (ESDs), in which indirect discharges of an ESD gun onto a vertical coupling plane (VCP) in the vicinity of equipment under test (EUT) are specified for simulating human discharges to conductive materials being adjacent to the EUT. According to IEC 61000-4-2 2008-04, the VCP shall be placed at a distance of 0.1m from EUT to be tested, and the indirect discharges of an ESD gun should be conducted to the centre of a vertical edge of the VCP, though the reference arrangement of EUT is not specifically determined. In the previous study, we measured electromagnetic fields due to indirect discharges of an ESD gun onto a VCP to investigate their variations with respect to EUT positions, which showed that indirect discharges onto a vertical edge from the back side of a VCP are very likely to reduce the above-mentioned variations, while the induced voltage levels become low. In the present study, to cope with this problem, we proposed a tapered-type VCP in lieu of the IEC-specified VCP, and by using a magnetic field probe in place of EUT, we measured its induced voltages of a magnetic field probe for indirect discharges of an ESD gun onto the VCP, and examined the variations in peaks and waveform energy with respect to the probe positions. As a result, we found that the tapered-type VCP suppresses the variations in peaks by 71% and waveform energy by 40% compared to the IEC-specified VCP. To further validate the above findings, as an actual EUT, we used a commercially available ESD detector for an impulsive electric field to reveal that the tapered-type VCP provides 16%-reduced variations in its detection rates with respect to the detector positions in comparison with the present VCP.