Category Archives: Question & Answers
As electronic technology advances, electronic circuitry gets progressively smaller. As the size of components is reduced, so is the microscopic spacing of insulators and circuits within them, increasing their sensitivity to ESD. Industry experts estimate that average electronics product losses due to static discharge range from 8 to 33%. Others estimate the actual cost of ESD damage to the electronics industry as running into the billions of dollars annually. It is therefore critical to be aware of the most sensitive items being handled in your factory as the need for proper ESD protection increases every day.
Here are some tips on how to get ahead of the game:
1. Establish and identify an ESD Protected Area (EPA)
An ESD Protected Area (EPA) is a defined space within which all surfaces, objects, people and ESD Sensitive Devices (ESDs) are kept at the same potential:
- All surfaces, products and people are linked to ground.
- Movable items, such as containers and tools, are bonded by virtue of standing on a grounded surface or being held by a grounded operator.
- Everything that does not readily dissipate a charge must be excluded from the EPA.
A good to place to start your fight against ESD is our example of an EPA as it lists all products required in a proper EPA.
Example of an EPA
A few things to remember:
- The ESD protected area should have signage to clearly identify where it is.
- Only trained or escorted people are to be allowed in the EPA.
- All conductors including Personnel must be grounded. Operators must either wear wrist straps or footwear in combination with an ESD floor. ESD worksurfaces (e.g. mats) are to be grounded.
- Wrist straps and footwear are to be tested daily. For wrist straps a conintuous monitor can be used instead.
- Periodic checks of installed products (e.g. ESD worksurfaces, ESD flooring etc.) are required.
- Remove all non-essential insulators or neutralise essential insulators with ionisers.
- Only handle unpackaged ESDs in an EPA when grounded.
- Wristbands are to be worn snug; the grounding tab of foot grounders must be placed under the foot in the shoe; ESD smocks need to cover all clothing on the torso.
- Use packaging with shielding properties to store or transport ESDS outside the EPA.
2. Identify ESD sensitive items (ESDs)
It is critical to be aware of the most sensitive item being handled in your factory. From goods-in through to dispatch packaging shielding properties should be used to protect ESDs during transport and storage. Any ESD sensitive item should be identified with the ESD sensitivity symbol, either on itself or its container. The ESD Sensitivity Symbol (also called Susceptibility or Warning Symbol) identifies items that can be damaged by ESD and should ONLY be unpackaged and handled while grounded at an ESD protected workstation.
3. Provide ESD control training
This is probably the most important point of all. You can have the best EPA in the world but if your staff don’t know about ESD and the problems it creates, it will be money wasted. People handling ESDs are still a major source of ElectroStatic charges and discharges. Operators need training and need to be vigilant that ESD control procedures are followed. In order for an ESD control programme to be effective, operators must be aware of:
- the threat of ESD,
- understand & adhere to the rules of controlling static electricity
- and know how to properly use ESD control items.
Antistatic is an ESD control property properly referred to as “low charging”. This is an important property for all bags used inside or outside of an ESD protected area (EPA). Specifically, it is important that the inside of the bag is low charging. This ensures that when the ESD Sensitive Device is inserted into the bag or otherwise moves, there is minimum electrostatic charge generation.
Dissipative is the electrical property of resistance so when grounded electrostatic charges will be removed to ground. This is an important ESD control property as the bag can be grounded; being dissipative provides an electrical path for an electrostatic charge to dissipate from the bag.
Shielding Bag used in an ESD Protected Area (EPA)
All bags inside the ESD Protected Area [EPA] should be both low charging and dissipative whether packaging ESD sensitive item or non-ESD sensitive items.
Packaging Standard EN 61340-5-3 clause 5.3 Outside an EPA:
“Transportation of sensitive products outside of an EPA shall require packaging that provides both:
a) dissipative or conductive materials for intimate contact;
b) a structure that provides electrostatic discharge shielding.
NOTE 1: If electrostatic field shielding materials are used to provide discharge shielding, a material that provides a barrier to current flow should be used in combination with the electrostatic field shielding material.
NOTE 2 Dissipative materials are preferred for intimate packaging in situations where charged device model (CDM) damage is a concern.”
View our offering of ESD Bags HERE.
Seeing ElectroStatic Discharge (ESD) damage is basically impossible. Damage to semiconductor device structure is NOT visible at ordinary magnifications of an optical microscope. If the microscope is capable of 1000X-1500X magnifications, you just might be able to “see” something. The method used, only occasionally as there is considerable expense, is by delayering and etch enhancement producing high magnification photographs using a scanning electron micrograph (SEM). See Images of ESD Damage, photos of Human Body Model (HBM) ESD damage provided by Hi-Rel Laboratories, Inc. at 6116 N Freya, Spokane, Washington 99217 (509-325-5800 or www.hrlabs.com). Used with their permission.
To have an ESD control programme conform to EN 61340-5-1 does the programme have to use all the ESD protected area ESD control items listed in Table 3? These are: working surfaces, storage racks, trolleys, flooring, ionization, seating, and garments.
No, you can decide which ESD control items to use.
Per EN 61340-5-1 clause 5.2.1 “ESD control program plan, The organization shall prepare an ESD control program plan that addresses each of the requirements of the program. Those requirements concern:
- compliance verification,
- grounding/bonding systems,
- personnel grounding,
- EPA requirements,
- packaging systems,
Each company has flexibility designing its programme as EN 61340-5-1 Introduction states: “Each company has different processes, and so will require a different blend of ESD prevention measures for an optimum ESD control program. It is vital that these measures are selected, based on technical necessity and carefully documented in an ESD control program plan, so that all concerned can be sure of the program requirements.”
The ESD control programme plan is to be written. We recommend starting by reviewing Annex A of User guide CLC/TR 61340-5-2:2008 “Example ESD Control Document based on IEC 61340-5-1”. It notes “The following document demonstrates the flow and required sections for an ESD control program as defined by IEC 61340-5-1. This program is based on one of the most basic ESD programs that can be implemented. In most cases, an actual ESD program will utilize more ESD control elements. Personnel are grounded by a wrist strap. Handling operations are performed at a grounded worksurface and ESD sensitive devices are moved from operation to operation inside a metallized shielding bag.”
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What happens if you staple ESD Bags shut? Does that damage the ESD Bag’s effectiveness? What if the ESD Bag is heat sealed shut & a staple on the seam is used to attach paperwork?
Vermason ESD Shielding Bags have a layer of metalized film which creates continuous conductive enclosure or Faraday Cage to provide electrostatic shielding protecting the ESD sensitive devices placed inside the Bag. The use of stapling to close ESD Bags is counter productive and not recommended. The metal staple provides a conductive path from the outside of the ESD Bag to the inside. The use of a metal staple would undermine the effectiveness of the ESD Bag making a conductive path for charges outside the Bag to charge outside the Bag to charge or discharge to ESD sensitive components inside the Bag.
To close the ESD Bag, it is recommended to heat seal, or use Vermason ESD Labels after the opening of the bag has been folded over.
To view Vermason ESD Labels Click Here
Or to view Vermason Antistatic Tape Click Here
Carefully locating the staple to only the seam of the Vermason Statshield® Bag would theoretically make it part of the “continuous conductive enclosure” and be acceptable. However, we are not aware of any end user using this method and cannot recommend it. The staple would be an exposed conductor that could charge or discharge to ESD sensitive devices.
To ask an ESD Question Click Here.