What Is Electrostatic discharge (ESD)

Electrostatic discharge (ESD) is the release of static electricity when two objects come into contact. Familiar examples of ESD include the shock we receive when we walk across a carpet and touch a metal doorknob and the static electricity we feel after drying clothes in a clothes dryer. A more extreme example of ESD is a lightening bolt. While most ESD events are harmless, it can be an expensive problem in many industrial environments.

ESD first requires a build-up of an electrostatic charge. This occurs when two different materials rub together. One of the materials becomes positively charged; the other becomes negatively charged. The positively-charged material now has an electrostatic charge. When that charge comes into contact with the right material, it is transferred and we have an ESD event.

Manufacturers of electronic devices incorporate measures to prevent ESD events throughout the manufacturing, testing, shipping, and handling processes. For example, an employee may wear a wrist strap when working with devices or may wear ESD control footwear and work on an ESD floor mat that causes the electrostatic charge to go into the ground instead of into the device. Sensitive devices can be packaged with materials that shield the product from a charge.

ANSI/ESD S20.20 is the multi-industry standard for the development of ESD control programs that protect today’s increasingly sensitive electronic components, assemblies, and equipment from costly ESD damage and reduce down-time. Using the standard’s control methods and guidance, an organization can develop an ESD control program that protects devices down to 100v (class 1a) or less.

ANSI/ESD S20.20 is based on these fundamental static control principles:

  • All conductors in a given facility must be bonded or electrically connected and attached to a known ground or contrived ground;
  • All necessary non-conductors in a facility cannot be allowed to lose their electrostatic charge by attachment to or connection with ground; and
  • Moving or transporting ESD-sensitive items outside of an electrostatic discharge protected area requires the use of static protective materials.

What is ANSI/ESD S20.20-2021?

An American National Standard, ANSI/ESD S20.20-2021 provides administrative and technical requirements for establishing, implementing, and maintaining an ESD control program.

ANSI/ESD S20.20-2021 applies to organizations that manufacture, process, assemble, install, package, label, service, test, inspect, transport, or otherwise handle electrical or electronic parts, assemblies, and equipment susceptible to damage by electrostatic discharges.

ANSI/ESD S20.20-2021 has been released in Dec 2021, to replace its former version of ANSI/ESD S20.20-2014.

Primary Changes to ANSI/ESD S20.20-2021 are:

  • Definitions were added for ESD control items, insulator, conductor, isolated conductor, and unprotected ESDS item.
  • Wording for tailoring was updated.
  • Update made to allow qualification for ESD control items that stay on-site to be done at the lowest relative humidity (RH) on the site.
  • Qualification records were updated to require including supporting technical reports.
  • Explanation was added that the flooring/footwear system cannot use compliance verification data for qualification.
  • Note was added to the compliance verification plan that calibration does not imply the equipment can make measurements.
  • A statement that compliance verification of the grounding system is not required was added.
  • The insulator section was updated with a field measurement of where the ESDS item is handled.
  • For isolated conductors, the inclusion of non-contact electrostatic voltmeters and electrostatic field meters were included with a note on measurement issues.
  • ANSI/ESD STM4.2 was deleted as a qualification for worksurfaces in Table 3, “EPA ESD Control Items.” This table also added point-to-point requirements to groundable static control garments and groundable static control garment systems.
  • Table 4, “Packaging Requirements,” was added. This table summarizes ANSI/ESD S541-2019: Packaging Materials For The Protection Of Electrostatic Discharge Susceptible Items requirements.
  • New Section 8.4.1, “United States Department of Defense (DoD) Packaging Requirements,” was added.
  • New Informative Annex C, “Tailoring,” was added. New Informative Annex E,” Statement of Direction,” was added.