ESD Protected Area

11 Steps to an ESD Control Program

If you followed our tips to fight ESD, you will have already identified all ESD sensitive items in your factory. You’re now at a point where you realize that you need to implement ESD Control measures. But where do you start? There is so much information out there and it can be completely overwhelming. But don’t panic – today’s blog post will provide you with a step-by-step guide on how to set-up a suitable ESD Control Plan.

The Organization shall prepare an ESD Control Program Plan that addresses each of the requirements of the Program. Those requirements include:

  • Training
  • Product Qualification
  • Compliance Verification
  • Grounding / Equipotential Bonding Systems
  • Personnel Grounding
  • ESD Protected Area (EPA) Requirements
  • Packaging Systems
  • Marking

 The ESD Control Program Plan is the principal document for implementing and verifying the Program. The goal is a fully implemented and integrated Program that conforms to internal quality system requirements. The ESD Control Program Plan shall apply to all applicable facets of the Organization’s work.” [ANSI/ESD S20.20-2014 clause 7.1 ESD Control Program Plan]

The selection of specific ESD control procedures or materials is at the discretion of the ESD Control Program Plan preparer and should be based on risk assessment and the established ESD sensitivities of parts, assemblies, and equipment.” [ANSI/ESD S20.20-2014 Annex B]

  1. Define what you are trying to protect
    A prerequisite of ESD control is the accurate and consistent identification of ESD susceptible items. Some companies assume that all electronic components are ESD susceptible. However, others write their ESD Control Plan based on the device and item susceptibility or withstand voltage of the most sensitive components used in the facility. Per ANSI/ESD S20.20-2014 section 6.1 “The Program shall document the lowest level(s) of device ESD sensitivity that can be handled.” A general rule is to treat any device or component that is received in ESD protective packaging as an ESD susceptible item.

    An operator handling an ESD susceptible item
  2. Become familiar with the industry standards for ESD control
    A copy of ANSI/ESD S20.20-2014 can be obtained from the ESD Association. It covers the “Development of an Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices)” and “provides administrative and technical requirements for establishing, implementing and maintaining an ESD Control Program.”Also, consider purchasing the ESDA’s ESD Handbook ESD TR20.20-2016 for guidance on the implementation of the standard.
  3. Select a grounding or equipotential bonding system
    Grounding / Equipotential Bonding Systems shall be used to ensure that ESDS items, personnel and any other conductors that come into contact with ESDS items are at the same electrical potential.” [ANSI/ESD S20.20-2014 section 8.1 Grounding / Equipotential Bonding Systems]
    The elimination of differences in electrostatic charge or potential can be achieved in three different ways:
    – Equipment Grounding Conductor
    – Auxiliary Ground
    – Equipotential Bonding

    • Equipment grounding conductor:
      the first and preferred ESD ground is the electrical system’s ground or equipment ground. In this case, the ESD control elements and grounded personnel are connected to the three-wire electrical system equipment ground;
    • Grounding using auxiliary ground:
      the second acceptable ESD ground is achieved through the use of an auxiliary ground. This conductor can be a ground rod or stake that is used for grounding the ESD control elements in use at a facility. In order to eliminate differences in potential between protective earth and the auxiliary ground system it is required that the two systems be electrically bonded together with a resistance less than 25 ohms;
    • Equipotential bonding:
      in the event that a ground facility is not available, ESD protection can be achieved by connecting all of the ESD control elements together at a common connection point.
  4. Determine the grounding method for operators (Personnel Grounding)
    The two options for grounding an operator are:

    • a wrist strap or
    • footwear / flooring system

    Wrist straps must be worn if the operator is seated. We will talk about wrist straps in more detail at a later point. For now, remember to connect the coil cord part of the wrist strap to a Common Point Ground so that any charges the operator may generate can be removed to Ground.

    An operator using a wrist strap as a grounding method
    An operator using a wrist strap as a grounding method

    A footwear / flooring system is an alternative for standing or mobile workers. ESD footwear needs to be worn on both feet and only works as a grounding device if it is used in conjunction with an ESD floor. Just like with wrist straps, a future blog post will clarify the ins and outs of ESD footwear.

    An operator using a foot grounders on an ESD floor as a personnel grounding method
    An operator using foot grounders on an ESD floor as a personnel grounding method

    In some cases, both (wrist strap and foot grounders) will be used.

  5. Establish and identify your ESD Protected Area (EPA)
    ESD Control Plans must evolve to keep pace with costs, device sensitivities and the way devices are manufactured. Define the departments and areas to be considered part of the ESD Protected Area. Implement access control devices, signs and floor marking tape to identify and control access to the ESD Protected Area.
  6. Select ESD control items or elements to be used in the EPA based on your manufacturing process
    Elements that should be considered include: worksurfaces, flooring, seating, ionization, shelving, mobile equipment (carts) and garments.
  7. Develop a Packaging (Materials Handling & Storage) Plan
    When moving ESD susceptible devices outside an ESD protected area, it is necessary for the product to be packaged in an enclosed ESD Shielding Packaging. We will discuss ESD Packaging in more detail in a future blog post. All packaging, if used, should be defined for all steps of product manufacture whether inside or outside the EPA.

    An operator packing an ESD sensitive item into a Shielding Bag
    An operator packing an ESD sensitive item into a Shielding Bag
  8. Use proper markings for ESD susceptible items, system or packaging
    From ANSI/ESD S20.20-2014 section 8.5: “ESDS items, system or packaging marking shall be in accordance with customer contracts, purchase orders, drawing or other documentation. When the contract, purchase order, drawing or other documentation does not define ESDS items, system or packaging marking, the Organization, in developing the ESD Control Program Plan, shall consider the need for marking. If it is determined that marking is required, it shall be documented as part of the ESD Control Program Plan.
  9. Implement a Compliance Verification Plan
    From ANSI/ESD S20.20-2014 section 7.4: “A Compliance Verification Plan shall be established to ensure the Organization’s fulfillment of the technical requirements of the ESD Control Program Plan.”. Our next post will explain in detail how to create and implement a Compliance Verification Plan so stay tuned…
    However, developing and implementing an ESD Control Program is only the first step. The second step is to continually review, verify, analyse, evaluate and improve your ESD program:“Measurements shall be conducted in accordance with a Compliance Verification Plan that identifies the technical requirements to be verified, the measurement limits and the frequency at which those verifications occur. The Compliance Verification Plan shall document the test methods and equipment used for making the measurements. If the test methods used by the Organization differ from any of the standards referenced in this document, then there must be a tailoring statement that is documented as part of the ESD Control Program Plan. Compliance verification records shall be established and maintained to provide evidence of conformity to the technical requirements.The test equipment selected shall be capable of making the measurements defined in the Compliance Verification Plan.” [ANSI/ESD S20.20-2014 section 7.4 Compliance Verification Plan]
    Regular program compliance verification and auditing is a key part of a successful ESD Control Program.
  10. Develop a Training Plan
    From ANSI/ESD S20.20-2014 section 7.2: “Initial and recurrent ESD awareness and prevention training shall be provided to all personnel who handle or otherwise come into contact with any ESDS items.
  11. Make the ESD Control Plan part of your internal quality system requirements
    A written ESD Control Plan provides the “rules and regulations”, the technical requirements for your ESD Control Program. This should be a controlled document, approved by upper management initially and over time when revisions are made. The written plan should include following:

    • Qualified Products List (QPL): a list of ESD control items permitted to be used in the ESD Control Program.
    • Compliance Verification Plan: includes periodic checking of ESD control items and calibration of test equipment per manufacturer and industry recommendations.
    • Training Plan: an ESD Program is only as good as the use of the products by personnel. When personnel understand the concepts of ESD control, the importance to the company of the ESD Control Program, and the proper use of ESD products, they will implement a better ESD Control Program improving quality, productivity and reliability.

The importance of an ESD Protected Area (EPA)

In our last post, we talked about ESD: what it is, what types of ESD damage there are and what costly effects ESD can have. Missed our very first post? Catch-up here.
All caught up? Right, moving on. Today you will learn how to avoid ESD damage and protect your ESD sensitive items. So, let’s jump right in.

The fundamental ESD Control Principles
We’ve established that ESD is the hidden enemy in the electronics industry. Therefore, the BIG question is: how exactly do you control ElectroStatic Discharge (ESD) in your workplace? Easy – just follow these ESD fundamentals:

  1. Ground all conductors including people
  2. Remove all unnecessary non-conductors (also known as insulators)
  3. Place ESD sensitive devices inside of shielding packaging when transported outside of an ESD Protected Area (EPA)

Per ESD Handbook ESD TR20.20-2008 section 2.4 “It should be understood that any object, item, material or person could be a source of static electricity in the work environment. Removal of unnecessary nonconductors, replacing nonconductive materials with dissipative or conductive materials and grounding all conductors are the principle methods of controlling static electricity in the workplace, regardless of the activity.

These are the essential principles of ESD Control. If you implement all three points above, you will be in control of ESD and your sensitive items will be protected. Well, that wasn’t hard, was it? Don’t be terrified – we’ll go through everything in detail. We’ll cover #2 and #3 in future points – today’s focus is #1.

Definition of an ESD Protected Area (EPA)
An ESD Protected Area (EPA) is a designated zone – all surfaces, objects, people and ESD Sensitive Devices (ESDs) within are kept at the same electrical potential. This is achieved by simply using ‘groundable’ materials for covering of surfaces and for the manufacture of containers and tools. This applies to all items with an electrical resistance of less than 109 ohms.

An EPA could be just one workstation or it could be a room containing several different workstations. It can be portable as used in a field service situation or permanent.

Example-EPA-Area
Example of an ESD Protected Area

The user guide CLC/TR 61340-5-2:2008 defines an EPA as follows:
An ESD protected area (EPA) is an area that is equipped with the ESD control items required to minimize the chance of damaging ESD sensitive devices. In the broad sense, a protected area is capable of controlling static electricity on all items that enter that work area. Personnel and other conductive or dissipative items shall be electrically bonded together and connected to ground (or a common connection point when a ground is not available) to equalize electrical potential among the items. The size of an EPA can vary greatly. A protected area may be a permanent workstation within a room or an entire factory floor encompassing thousands of workstations. A protected area may also be a portable worksurface or mat used in a field service situation.” [CLC/TR 61340-5-2:2008 Use guide clause 4.6 Protected areas (EPA)]

You’re probably wondering now, how exactly you can get all surfaces, objects and operators to the same electrical potential. Fear not – we’ve got you covered!

  1. Personnel Grounding
    As previously stated, a fundamental principle of ESD control is to ground conductors including people at ESD protected workstations.Wrist straps are the first line of defense against ESD, the most common personnel grounding device used, and are required to be used if the operator is sitting. The wristband should be worn snug to the skin with its coil cord connected to a common point ground which is connected to ground, preferably equipment ground.

    Wearing-Wrist-Strap
    Wearing a wrist strap and connecting it to a common point ground

    If you are not using a continuous or a constant monitor, a wrist strap should be tested while being worn at least daily. This quick check can determine that no break in the path-to-ground has occurred. Part of the path-to-ground is the perspiration layer on the person; an operator with dry skin may inhibit the removal of static charges and may cause a test failure.
    The wrist strap system should be tested daily to ensure proper electrical value. Nominally, the upper resistance reading should be ” [ANSI/ESD S1.1 Annex A, 3 Frequency of Functional Testing]

    A Flooring / Footwear system is an alternative for personnel grounding for standing or mobile workers. Foot grounders or other types of ESD footwear are worn while standing or walking on an ESD floor. ESD footwear is to be worn on both feet and should be tested independently at least daily while being worn. Unless the tester has a split footplate, each foot should be tested independently, typically with the other foot raised in the air.
    Compliance verification should be performed prior to each use (daily, shift change, etc.). The accumulation of insulative materials may increase the foot grounder system resistance. If foot grounders are worn outside the ESD protected area testing for functionality before reentry to the ESD protected area should be considered.” [ESD SP9.2 APPENDIX B – Foot Grounder Usage Guidance]

    Both ESD footwear and ESD floor are required. Wearing ESD footwear on a regular, insulative floor is a waste of time and money.

    Wearing-Foot-Grounders
    Wearing foot grounders on an ESD floor

    Part of the path-to-ground is the perspiration in the person’s shoes. The conductive tab or ribbon of foot grounders should be placed inside the shoe under the foot with the excess length tucked into the shoe. Thanks to the perspiration in the shoe, direct contact with the skin is normally not necessary.

    If an operator leaves the EPA and walks outside wearing ESD footwear, care should be taken not to get the ESD footwear soiled. Dirt is typically insulative, and the best practice is to re-test the ESD footwear while being worn each time when re-entering the EPA.

  2. Working Surfaces
    ESD working surfaces, such as mats, are typically an integral part of the ESD workstation, particularly in areas where hand assembly occurs. The purpose of the ESD working surface is two-fold:

    1. To provide a surface with little to no charge on it.
    2. To provide a surface that will remove ElectroStatic charges from conductors including ESDS devices and assemblies) that are placed on the surface.

    ESD mats need to be grounded. A ground wire from the mat should connect to the common point ground which is connected to ground, preferably equipment ground. For electronics manufacturing a working surface resistance to ground (RG) of 1 x 106 to less than 1 x 109 ohms is recommended.
    The single most important concept in the field of static control is grounding. Attaching all electrically conductive and dissipative items in the workplace to ground allows built-up electrostatic charges to equalize with ground potential. A grounded conductor cannot hold a static charge.” [Grounding ANSI/ESD S6.1 Foreword]
    Per ANSI/ESD S20.20 section 6.2.1.2 Grounding / Bonding Systems Guidance, “In most cases, the third wire (green) AC equipment ground is the preferred choice for ground.
    Best practice is that ground connections use firm fitting connecting devices such as metallic crimps, snaps and banana plugs to connect to designated ground points. The use of alligator clips is not recommended.

    The working surface must be maintained and should be cleaned with an ESD cleaner. Regular cleaners typically contain silicone, and should never be used on an ESD working surface. ESD Handbook ESD TR20.20-2008 section 5.3.1.14 Maintenance “Periodic cleaning, following the manufacturerís recommendations, is required to maintain proper electrical function of all worksurfaces. Ensure that cleaners that are used do not leave an electrically insulative residue common with some household cleaners that contain silicone.

  3. Other moveable objects
    Moveable items (such as containers and tools) are grounded when placed on a grounded surface or being held by a grounded operator. Everything that does not readily dissipate charge must be excluded from the EPA (refer to #2 of our ESD Control Principles above). Regular plastics, polystyrene foam drink cups and packaging materials, etc. are typically high charging and have no place at an ESD protective workstation.

    Intention of an ESD Protected Area (EPA)We’ve learnt in our previous blog post that ElectroStatic discharge (ESD) can damage components and products that contain electronics. A lot of the time, this damage is not detected during quality inspection and can cause significant problems further down the line.An ESD Protected Area (EPA) is an area that has specifically been created to control ESD; its purpose is therefore to avoid ALL problems resulting from ESD damage. Workers need to understand AND follow the basics of ESD control to limit the generation of electrostatic charges as well as limit and slow discharges in the EPA.Recognizing an ESD Protected Area (EPA)
    An ESD Protected Area must be clearly identified using signs and/or aisle tape. This ensures operators and visitors are alerted when entering (or leaving) an ESD Protected Area which require special precautions (grounding via wrist straps and/or foot grounders etc.). It also indicates that they are entering (or exiting) areas where exposed ESDS items can be handled safely.Remember to be consistent throughout your shop floor, i.e. use the same signs. This will avoid confusion for your operators.

    EPA-Caution-Sign
    Example of an EPA caution sign

    While signs are one way of indicating the boundaries of an EPA, it is not the only way. Any alternate method that alert the personnel that an EPA begins is acceptable to ANSI/ESD S20.20. Some of the alternate ways to mark the boundaries of an EPA are:

    • tape on the floor
    • different color floor tiles
    • different color carpet
    • any other way to establish boundary conditions

    Anyway to distinguish the boundaries of an EPA would be acceptable as long as the personnel are aware of the indications and take the proper precautions while inside the EPA.” [ESD TR20.20-2016 section 9.1.2 EPA Boundary Indicators]

    Building an ESD Protected Area (EPA)
    A basic form of an ESD Protected Area is a workstation consisting of the following components:

    • An ESD working surface mat
    • A grounding cord
    • A wristband
    • A coiled cord
    • A common point ground

    To set-up an EPA:

    1. Connect the ESD working surface mat to the common point ground using the grounding cord.
    2. Link the operator to the common point ground using the wristband and coiled cord.

    Congratulations – you’ve just created an ESD Protected Area!
    By following the above steps, each component (the ESD mat and the operator) is kept at the same electrical potential (ground). Any ElectroStatic charge (ESD) is removed to ground via the common point ground.