Usefulness of Immunity Compliance Testing by ESD Generators for Contact Discharges compared to Air Discharges

抄録

Electrostatic discharge (ESD) immunity testing for consumer or industry electronic equipment is specified by the International Electrotechnical Committee (IEC) as IEC 61000-4-2, and has to be in compliance with both the tests of contact and air discharges. Contact discharge testing is most often used due to good repeatable testing results, despite the fact that air discharge testing can impose on equipment severe electromagnetic stresses of a few times larger discharge current peaks and faster rise-time in comparison with contact discharge testing. This is because air discharge testing results are significantly affected by many factors such as a test voltage, an approach speed, electrode surface conditions and climatic conditions. For this reason the IEC standard is unable to identify any specific current waveform for air discharges and thus provide its calibration procedure. Nevertheless, this standard is still mandatory testing for making a decision to pass or fail. In this study, as aiming to validate the usefulness of compliance test using ESD generators by contact discharges, current waveforms measured for air discharges to sphere and cone electrodes at an approach speed of 40 mm/s are shown at test voltages of 2 kV to 15 kV. The first peak current waveforms for air discharges to sphere electrodes at an approach speed of 80 mm/s are also exhibited under various different climatic conditions. Unstable air discharge phenomena and variations in the current waveforms are demonstrated in comparison with contact discharges. Results indicate that the first current peaks of contact discharges fall between the maximum and minimum of first current peaks caused by air discharges, and the rise times are between the fastest and the slowest rising slopes of air discharges. These findings show the usefulness of contact discharges as immunity compliance testing because they stably provide more moderate waveforms compared to those for air discharges.