Uncertainty and its Reduction of Voltage Waveform Induced on Trace on Printed Circuit Board for Indirect Discharges from ESD-Gun onto Vertical Coupling Plane

Abstract

International Electrotechnical Commission (IEC) prescribes immunity tests (IEC610000-4-2) of electronic equipment against electrostatic discharges (ESDs), and specifies indirect discharges from an ESD-gun onto a vertical coupling plane (VCP) in the vicinity of equipment under test (EUT) for simulating personnel discharges to conductive materials being adjacent to the EUT. According to IEC 61000-4-2 2001-04, the VCP shall be placed at a distance of 0.1m from the EUT, and the indirect discharge of an ESD-gun should be conducted to the centre of a vertical edge of the VCP, while the reference arrangement of EUT and the angles of inclination and rotation of the ESD-gun are not specifically determined. In order to clarify to what extent EUT arrangements affect test results, using a simple printed circuit board (PCB) with a trace in lieu of EUT, we measured the voltages induced on the trace for indirect discharges from an ESD gun with different angles of inclination and rotation. As a result, we found that the peaks of induced voltages vary by a factor of 1.7 for indirect discharges onto the centre of a vertical edge of a VCP, while the indirect discharges onto the vertical edge from the back side of a VCP reduce the uncertainty of peak voltages by ±5%. The latter finding provides a new method for indirect discharges onto a VCP, whose test results are unlikely to be affected by EUT arrangements.