What is ESD

Electrostatic discharge is the discharge of a large amount of
charge into a chip. This charge can be fatal to a chip because it may physically
damage transistors that are hit with the charge, much like a structure that is hit
by lightning.
The magnitude of ESD can vary widely, but the duration of a pulse is usually
very short. An ESD event can result in junction failure, oxide breakdown,
unwanted charge injection, and fusing or opening of internal wiring.
The most common source of ESD is from the human body, when a person
incorrectly handles an IC. The resulting voltage can be in excess of 20,000V. Electrostatic
damage to electronic devices can occur at any point from manufacture to
field service. Damage results from handling devices in uncontrolled, lowhumidity,
or poorly grounded surroundings.
ESD protection structures are always built into the conduction paths from a
bonding pad to internal circuitry and are part of the pad cells. These structures
act as lightning rods and are intended to redirect unwanted charge away from
sensitive internal circuitry.