The Should’s and SHALL’ s of ESD Control

0

When it comes to documenting and implementing an ESD Control Plan, determining what  “SHALL” or “Should” be implemented is important to consider. Whether a facility already has a formal ESD control Plan, is ESD Certified, or in the process of establishing an ESD Control Plan, these two little words are critical to the performance and compliance of the plan. This is doubly important for ESD Control Plans that are subject to audits or reviewed by customers or other third parties.

The ESD Association’s ANSI/ESD S20.20-2014 is the preeminent standard for the implementation of ESD control in an electronics assembly environment. The standard consists of eleven mandatory (SHALL) administrative and technical requirements. These requirements establish procedures and products as the basis for establishing an ESD Control Plan and for controlling static electricity generated by the human body to less than 100 volts. There may be situations where exceptions are made to the ESD Control Plan. For example, the human body must be grounded in an ESD Protected Area, but some operators will be exposed to high voltage, such as operators in a HIPOT test or energized product area. In this case, the requirement (grounding operators) would still be implemented for the other operators but a “tailoring statement” exempting anyone working around high voltage for personal safety would be added to the ESD Control Plan.

Let’s review the “SHALLs”. These are the mandatory elements outlined by ANSI/ESD S20.20-2014 for all ESD Control Plans:

  1. Both Administrative and Technical Requirements SHALL be included in the ESD Control Plan.
  2. The written plan SHALL document the lowest level(s) of ESD device sensitivity. The is very important in determining the class of the device and how devices will be handled in the EPA.
  3. An ESD Program Manager or Coordinator SHALL be assigned.
  4. Tailoring statements and rationale for the statements SHALL be documented as part of the written ESD plan. If for instance, continuous wrist strap monitors are implemented instead of periodic “touch” testing, it would be acceptable to eliminate maintaining written test logs.
  5. An initial and recurrent Training Plan SHALL be established for anyone handling ESD sensitive devices or entering the EPA. Employee training records SHALL be maintained.
  6. A Product Qualification Plan for the EPA Control items SHALL be established. Note that product qualification may be performed by you or a third party. The product manufacturer’s qualification data sheets and/or reports may also be used to qualify products for use in the ESD Protected Area.
  7. A Compliance Verification Plan SHALL be established for each technical requirement. The ESD/TR-53 is the reference for compliance verification of your ESD protective equipment and materials.
  8. A Grounding System for personnel and EPA (Electrostatic Protected Area) control items SHALL be established.
  9. The human body (personnel) SHALL be bonded or electrically grounded to the established grounding system. This is unless of course doing so would present a safety hazard. In this case, a tailoring statement would be included to justify not grounding the operators in these areas of the ESD Protected Area.
  10. An EPA where ESD sensitive devices are to be handled SHALL be established. This includes defining the boundaries in  writing and using signage. Keep in mind that this could be one workstation or an entire room.
  11. All Non-Essential Insulators SHALL be removed from the EPA. These include items such as plastic drinking cups, personal items, etc. If the insulator is Process Required implement ionization to neutralize static charges.
  12. If conductors are not grounded or “isolated”, the voltage potential of +/- 35 volts must be achieved. This requirement may be satisfied using ionization or grounding. Although this requirement is noted as a “must”, it can be considered a SHALL.

Now that we know what we have to do, or SHALL do, we must determine which EPA Control items we should implement. Factors such as the class of the devices, types and quantities of handling steps, and customer/supplier requirements should be considered. The EPA control items referred to in ANSI/ESD S20.20-2014 include:

  • Worksurfaces
  • Wrist Strap/Wristbands
  • Personnel Ground Connection
  • Footwear/ Foot Grounders
  • Flooring
  • Seating
  • Ionization
  • Shelving
  • Mobile Equipment/Worksurfaces (mobile carts)
  • Soldering and Desoldering Equipment and Hand Tools
  • Continuous Monitors
  • ESD Garments
  • Packaging Materials (note packaging materials are covered under a dedicated standard: ANSI/ESD S541).

Each of the above may be a “Should” but will become a SHALL when implemented into the ESD Control Plan. For example, if an ESD susceptible device is exposed (not in a shielding bag or in a finished good item), it SHALL be grounded. Grounding an ESD susceptible device is usually accomplished with a grounded ESD Worksurface and becomes a SHALL element of the ESD Control Plan. If the ESD susceptible device is only stored in a static shielding bag, then an ESD Worksurface might optional and remain a  “Should”. Another example would be for grounding the human body. You SHALL ground the body according to ANSI/ESD 20.20, but you “Should” do it via a wrist strap or Footwear/Flooring System. Except if the operator is seated, then a wrist strap (or Groundable Static Control Garment System) is required SHALL to ground a human body.

Leave a Reply