7.7. Electrostatic Discharge

Electrostatic Discharge (ESD) may damage electronic parts, assemblies, and equipment. ESD is a transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field. The human body is the most common cause of damage to electrostatic discharge (ESD) sensitive devices. Simply walking across a carpet in low humidity may generate up to 35,000 V of static electricity.

Modern electronics are increasingly sensitive to ESD. Even a few hundred volts can damage components during testing, handling, repair, or assembly. Discharges below 4,000 V are imperceptible but still hazardous.

Identification of Electrostatic Discharge Sensitive Components

The following are various industry symbols used to label components as ESD sensitive.

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Figure 7.11 Symbols indicating ESD sensitivity

Handling Electrostatic Discharge Sensitive Components

Observe all precautions necessary to prevent damage to ESDS components before attempting installation. Bring the device and everything that contacts it to ground potential by providing a conductive surface and discharge paths. As a minimum, observe these precautions:

  • De-energize or disconnect all power and signal sources and loads used with unit.

  • Place the unit on a grounded conductive work surface.

  • The technician should be grounded through a conductive wrist strap (or other device) using 1 M series resistor to protect operator.

  • Ground any tools, such as soldering equipment, that will contact the unit. Contact with the operator’s hands provides a sufficient ground for tools that are otherwise electrically isolated.

  • Place ESD sensitive devices and assemblies removed from a unit on a conductive work surface or in a conductive container. An operator inserting or removing a device or assembly from a container must maintain contact with a conductive portion of the container. Use only plastic bags approved for storage of ESD material.

  • Do not handle ESD sensitive devices unnecessarily or remove them from the packages until they are actually used or tested.