An Electrostatic Discharge (ESD) is a sudden flow of electric current through a material that is normally an insulator. A lightning strike is an example of ESD where the insulator (air) breaks down resulting in a release of energy. ESD also occurs when built up static electricity is released. Static electricity is a build up of electrons from objects (e.g. nylon carpet) to another object, in this case a person. When that person goes near a metal object (usually earthed) then the electrons are transferred to it and the person receives a shock. If these electrons are passed through electronic equipment they can be damaged.
ESD is a serious issue in electronics, because the silicon-based integrated circuits can break down if exposed to high voltages. Preventative measures include:
- appropriate packing material
- conducting wrist straps and foot-straps
- anti-static mats
- humidity control
When a statically charged person or object touches an electrostatic discharge sensitive (ESDS) device, there is a possibility that the electrostatic charge could be drained through sensitive circuitry in the device. If the electrostatic discharge possesses sufficient energy, damage could occur in the device due to localised overheating. It is possible for electronic devices to be damaged by ESD that cannot be felt by the human body.
Damage from ESD falls into two categories:
- Catastrophic damage - the electronic device is rendered inoperable immediately.
- Latent damage - the electronic device appears to be working fine but could fail to operate properly at some time in the future.