ESD_01_Introduction

Static electricity is an electrical charge at rest. Electrostatic discharge is the transfer of charges between bodies at different potentials caused by direct contact or induced by a charged field.

This charge can transfer electrons within a body (polarization) or from one body to another (conductive charging). The magnitude of the charge is primarily dependent on the size, shape, composition and electrical properties that make up the bodies. Charges are a combination of voltage and current.

In a neutral atom, the number of electrons is equal to the number of protons.


3 Protons (+) = 3 Electrons (-)


Electric discharge occurs when there is an absence or excess of electrons.

The prime method of generating static is by rubbing or separating materials, commonly known as the Triboelectric Method. The term "triboelectric" comes from the ancient Greek word tribo, which means to rub. A triboelectric charge is defined as, "an electrical charge generated by frictional movement, or separation of two surfaces".

Triboelectrification of materials occurs anytime two dissimilar materials are in contact with each other; the outer atoms of one of the materials will strip some of the electrons from the other. The additional energy of rubbing will cause a larger exchange of electrons, creating a greater charge. Rapid movement will increase the effect.

Another method of ESD is the Inductive method or a redistribution of electrical charge in an object, caused by the influence of nearby charges. Triboelectric and Inductive methods are summarized below.

Triboelectric method:

  • Pertaining to electricity generated by friction.
  • Static charge generation by contact and separation of materials.
  • Prime method in the electronics industry.

Inductive method:

  • Electric fields surround electrostatically charged objects.
  • Electric fields influence the properties of materials placed in the field.
  • No physical contact between objects.

Thunderstorms create electrostatic charges whenever warm, moist air mass collides with a cold, dry air mass. The warm air rises above the cold air. The upward and downward movement of air causes a charge of electricity to build-up on clouds that are formed. When the charge on the clouds gets large enough, a discharge takes place, and we see that discharge as a bolt of lightning.

The same process is responsible for generating a static charge on our body anytime we move. If the conditions are right, the simple act of people moving about can generate static charges of up to 35,000 volts.

The higher the humidity the lower the static charge generated. The moisture in the air lowers the surface resistance of materials by letting wet particles create a conductive film over an insulating surface. This film allows the surface charge to be redistributed reducing the charge concentration.

Common electrostatic occurrence:

The electronics industry is concerned with static electricity's inconspicuous discharge currents and their damaging effects on electronic parts. Chemical and explosive industries are primarily concerned with the sparks that are associated with static electricity. These sparks can trigger a fire or explosion during certain stages of the processes