Understanding ANSI/ESD S20.20 Requirements

Introduction

Electrostatic discharge (ESD) is a significant concern in environments where sensitive electronic components or energetic materials are handled. Effective ESD control programs are essential for protecting products, equipment, and personnel from the harmful effects of static electricity. ANSI/ESD S20.20 (S20.20) is the American National Standard that outlines requirements for establishing, implementing, and maintaining an ESD control program. One of the core requirements in this standard is “ground” and “grounding.”

Definition of Ground and Grounding

In the context of S20.20, ground refers to a conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth. Grounding is the act of creating this connection, typically to control or dissipate unwanted electrical charges. The term “bonding” is also used to describe this activity where one conducting body is purposely attached to ground.

Purpose of Grounding in ESD Control

The primary purpose of grounding within an electrostatic control program is to provide a safe and effective pathway for static charges to dissipate harmlessly to earth. By preventing static electricity from building up, the risk of discharges that might damage, disrupt, or cause system failures is reduced. It is important to understand that grounding only works with the conductive and dissipative items and materials in the workplace, including personnel. At the same time, it is important to understand that a charged and isolated conductor in the workplace or process forms a significant discharge risk if allowed to obtain an electrostatic charge. Frequently, an isolated conductor will obtain a charge by momentarily contacting ground while in the presence of an electrical field. Contacting ground in the presence of an electrical field charges an isolated conductor. A discharge occurs during the charging process, and then a second discharge may occur with the next contact to something in the process. A meticulous evaluation of every process where sensitive items are involved is necessary to identify isolated conductors and determine a mitigation strategy, if it is determined that a risk exists.

Key Grounding Requirements in ANSI/ESD S20.20

Fundamentally, grounding of personnel and equipment is the primary first step in developing an ESD control program plan that meets the S20.20 requirements. The simplest ESD control program protected area consists of a grounded person and a grounded place to work, such as a grounded table or tabletop. Grounding of a person is accomplished by a device that fits around the wrist and is bonded by wire to ground, generically called a wrist strap, or through conductive footwear worn by the person while standing on a conductive or dissipative floor that is grounded. A wrist strap grounding system is required for seated operations since people often do not have their feet on the floor when sitting on a chair. This is a hard or fixed requirement that is difficult to tailor around.

1. Common Ground Point: The standard requires the establishment of a common ground point in ESD‑protected areas. All ESD control elements—such as wrist straps, mats, and equipment—must be electrically connected to this point to ensure uniform potential.
2. Grounding Conductors: Conductive paths, such as wires or conductive flooring, are used to connect personnel and equipment to the common ground point.
3. Verification and Monitoring: Regular testing and monitoring of grounding connections are required to ensure continuity and effectiveness. This includes checking wrist straps, mats, and other ESD control devices for proper grounding.
4. Documentation: The ESD control program must include documented procedures for grounding and verification, as well as records of compliance and maintenance.

Types of Grounding in ESD Control

Every facility or operation has different needs and requirements when it comes to establishing a grounding reference. For most fixed sites, it’s best to use the main electrical or AC equipment ground when available. Most fixed locations will use various electrical machines, tools, technical equipment, and lighting equipment, so bonding to that ground makes the most sense to ensure that there is no difference in potential between the equipment and the ESD grounding system. However, not every operation can use the AC Equipment Ground. Therefore, ANSI/ESD S20.20 describes several types of grounding techniques, including:

• AC Equipment Ground: Components and personnel are connected directly to the ground point via conductors.
• Auxiliary Ground: A separate grounding system may be required in certain situations. When possible, the auxiliary ground and the facility ground should be bonded together to equalize electrical potential. A resistance of <25 ohms is suggested between the facility and auxiliary ground.
• Level 2 technical elements: Any ESD technical element that is connected in series to a common point ground or to a common connection point (equipotential bonding) through another technical element.
• Equipotential Bonding: Creating electrical connections between different elements in the ESD control program to ensure they all maintain the same electrical potential, reducing the risk of charge transfer.

Best Practices for Grounding

• Use only approved grounding devices and materials as specified by ANSI/ESD S20.20 and shown to comply with the requirements of ANSI/ESD S6.1‑Grounding.
• Ensure all personnel handling sensitive components wear properly grounded wrist straps, heel straps or footwear.
• Install and maintain conductive or static dissipative flooring and work surfaces.
• Regularly inspect and test grounding systems for continuity and effectiveness.
• Train staff on proper grounding procedures and the importance of ESD control.

Updates to the Standards

American National Standards Institute (ANSI) requires review of any standards or procedures that carry the ANSI designation. The ESD Association is an authorized standards developer and has responsibility for standards and procedures related to Static Electricity in the United States and represents the USA to the IEC through the US National Committee. The ESD Association Standards Committee is responsible for ensuring that the documents produced by the association are reviewed every 5 years. If the Standards Committee does not have any changes to a document, it will be reaffirmed and released for another 5 years. The ESD Association Standard for grounding, ANSI/ESD S6.1, has not had a significant revision in many review cycles. But the standard is under review as of this writing, and some significant changes will be forthcoming. It is recognized that the existing standard is intended for North American audiences as it follows the United States National Electrical Code, NFPA 70. Every country has its own Electrical Code, so there are differences in the way electrical service is designed and delivered. The revision of ANSI/ESD S6.1 will consider international electrical codes and terminology, and is anticipated to provide guidance on establishing ESD control grounds in countries beyond North America.

Conclusion

Ground and grounding are foundational elements of any electrostatic control program in accordance with ANSI/ESD S20.20. By establishing effective grounding practices, organizations can significantly reduce the risk of electrostatic discharge and protect valuable electronic components and systems.