Each of us has experienced electrostatic discharge at some point. When this happens, the body becomes charged with several kV and discharges in a few nanoseconds on a conductive surface.
The short discharge time ensures that the person does not suffer any injuries except for an unpleasant tingling in the finger. Modern semiconductor transistors, which operate at low voltages of around 5 V, can suffer serious damage from such discharges. This phenomenon is simulated by the ESD test.
The standards and procedures in this area include the following:
- IEC 61000-4-2 – ESD
This test refers to equipment that may be exposed to static electricity discharges due to environmental and installation conditions, such as low relative humidity, floor coverings with low conductivity (synthetic fibers), or clothing made of vinyl fibers. Discharge voltages in excess of ten thousand volts are achieved and discharge currents of over 30 A flow for a few nanoseconds. Due to the short duration of the discharge, a healthy person is not at risk, but the semiconductor on a circuit board can be destroyed very easily with these amounts of energy. Contact discharge is the preferred test method here, as it has a very high reproducibility.
Air discharges must be used where contact discharge is not possible, for example on non-conductive surfaces. Since the propagation path during air discharge is strongly dependent on the voltage, all intermediate levels up to the test level must also be tested in this discharge mode. During a discharge, an electromagnetic field is also always generated. In order to simulate a discharge on a device in the vicinity of the test object, the contact discharge on coupling plates at a defined distance from the test object is always tested as well.
Carsten Möller Carsten Möller
Head of EMC Laboratory
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