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electrostatic discharge (ESD)

Electrostatic discharges (ESD) are transient discharges of short duration. Such discharges can occur between solid, liquid and gaseous substances if they have different charges. They are usually accompanied by sparks or light effects.

Typical manifestations are the discharge of lightning, switching operations of powerful generators or motors, and the discharge of charged motor vehicles or human bodies. The discharges occur in extremely short time ranges from milliseconds down to nanoseconds. The discharge potentials can reach several kilovolts (kV) up to megavolts (MV) and damage components such as MOSFETs, Schottky diodes, light-emitting d iodes and also memory devices. The sensitivity of electronic components is divided into several classes.

ESD Classes with Voltage Values

ESD Classes with Voltage Values

In electronics, electrostatic charging of human bodies plays a significant role as the discharge could damage and destroy sensitive electronic parts, components and devices. The electrical energy that can build up in a human body is in the order of 10 milli-Joule (mJ) to 30 mJ, the electrostatic field can reach values between 100 V and 20 kV and depends very much on the floor covering and the air humidity. The high static charges cause short-term discharge currents of up to 30 A, with a current discharge of up to 100 A/ns. The electric field strength can reach values between 1 kV/m and 5 kV/m.

Protection against electrostatic discharges

Electrostatic discharges occur at workplaces, in cabling, automotive technology, device and circuit board technology, as well as in peripheral devices and monitors.

To protect ESD-prone components, Electrostatic Protected Areas (EPA) can be set up in the workplace area, equipped with conductive and grounded table coverings, conductive floors with ground potential reference surfaces (ERP) and grounded tools. To prevent electrostatic body discharges, the clothing and footwear of working personnel are made of antistatic material and the personnel themselves may be connected to ground potential via antistatic wrist straps or via a grounding strap.

ESD wrist strap, Photo: asmetec-shop.de

ESD wrist strap, Photo: asmetec-shop.de

In order to protect the user, measures for reducing electrostatic discharges and for health protection are described in the Display Screen Equipment Ordinance. In addition to static-induced discharge, there is also inductive-induced interference, electromagnetic interference (EMI).

Warning signs for Electrostatic Sensitive Devices (ESD)

Warning signs for Electrostatic Sensitive Devices (ESD)

The simulation and ESD testing of sensitive electronic components is carried out with standardized ESD models: the Human Body Model (HBM), the Charged Device Model (CDM) and the Machine Model (MM).

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Englisch: electrostatic discharge - ESD
Updated at: 13.08.2015
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