AN3960

What is ESD ?

Doc ID 022082 Rev 1

5/21

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What is ESD ?

ESD is the sudden and momentary electric current that flows between two objects at

different electrical potentials.

ESD immunity is a category of electromagnetic compatibility (EMC) - the branch of electrical

sciences which studies the unintentional generation, propagation and reception of

electromagnetic energy with reference to its unwanted effects.

EMC describes the ability of a piece of equipment or a system to function satisfactorily in its

electromagnetic environment without introducing intolerable electromagnetic disturbances

to anything in that environment.

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Causes of ESD

One of the causes of ESD events is static electricity. Static electricity is often generated

through the separation of electric charges when two materials are brought into contact and

then separated, for example, rubbing a plastic comb against dry hair, removing some types

of plastic packaging. In these cases, the friction between two materials creates a difference

of electrical potential that can lead to an ESD stress.

Another cause of ESD damage is through electrostatic induction. This occurs when an

electrically charged object is placed near a conductive object isolated from ground. The

presence of the charged object creates an electrostatic field that causes electrical charges

on the surface of the other object to redistribute. Even though the net electrostatic charge of

the object has not changed, it now has regions of excess positive and negative charges. An

ESD stress may occur when the object comes into contact with a conductive path. For

example, charged regions on the surfaces of styrofoam cups or plastic bags can induce

potential on nearby ESD sensitive components via electrostatic induction and an ESD

stress may occur if the component is touched with a metallic tool.

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Risks of ESD

ESD is a serious issue in solid state electronics, such as integrated circuits (ICs). ICs are

made from semiconductor materials such as silicon and insulating materials like silicon

dioxide. Either of these materials can suffer permanent damage when subjected to high

voltages.

The damaging effects of ESD poses unacceptable risks in many areas of technology and it

is necessary to control such interference and reduce the risks to acceptable levels through

the:

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Simulation and testing of electronic devices using models

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Definition of standards