When referring to an “ESD Protected Area” or “EPA”, a lot of people imagine rooms or even whole factory floors with numerous workstations. This very common misconception leads to nervousness and even fear when it comes to implementing an ESD Control Programme. There is a concern regarding the cost and time implications to establish an EPA. However, most often, a simple ESD workstation or ESD Workbench is completely sufficient to fulfil a company’s needs to protect their ESD sensitive products. Today’s post will provide a step-by-step guide on:
An EPA is an area that has been established to control Electrostatic Discharge (ESD) effectively and its purpose is therefore to avoid all problems resulting from ESD damage, e.g. catastrophic failures or latent defects. It is a defined space within which all surfaces, objects, people and ESD Sensitive Devices (ESDS) are kept at the same electrical potential. This is achieved by simply using only ‘groundable’ materials for covering of surfaces and for the manufacture of containers and tools. All surfaces, products and people are bonded to Ground. Bonding simply means electrically connecting together. Movable items (such as containers and tools) are bonded by virtue of standing on a bonded surface or being held by a bonded person. Everything that does not readily dissipate charge must be excluded from the EPA.
An EPA can be just one workstation, or it could be a room containing several different workstations.
“The size of an EPA can vary greatly. An EPA may be a permanent workstation within a room or an entire factory floor encompassing thousands of workstations. An EPA may also be a portable worksurface or mat as used in a field service situation.”IEC TR 61340-5-2 User guide clause 22.214.171.124 General considerations for EPA
Creating an EPA at your existing workstation does not need to be complicated or expensive. There are just a few things you will need:
ESD protective working surfaces aid in the prevention of damage to ESD sensitive items (ESDS) and assemblies from electrostatic discharge.
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:
Your ESD working surface needs to be grounded using a ground cord. A ground wire from the surface should connect to the common point ground (in our example an Earth Bonding Point Plug) which is connected to ground, preferably equipment ground. Best practice is that ground connections use firm fitting connecting devices such as snaps or banana plugs to connect to designated ground points. For even more security, a binding post to ring terminal and permanent bolt connection to the mat is recommend; an example of this would be the 60474 Conical Cord. The use of alligator clips is not recommended.
Earth Bonding Point (EBP) plugs are designed to provide a common ground point for grounding using protective earth in an EPA. The plugs fit into the mains supply socket, making a connection with the earth conductor only. In place of the live and neutral pins are moulded insulating plastic pins to allow positive location in the socket.
Connectors on the front of the plug are available for connection via ground cords to the various elements of the EPA. Thus each element is held at a common potential.
Wrist straps are the most common personnel grounding device and are used to link people to ground. They are required if the operator is sitting. A wrist strap is made up of two components:
Note: instead of connecting your wrist strap to an Earth Bonding Point (EBP) bar described in #3, you can also connect it to the EBP plug. EBP bars fulfil the same function as EBP plug. However, they have been designed to be installed underneath bench tops where they are easily accessible to operators and where they are unlikely to be knocked and damaged or hinder the operator. The earthing cord of the bar needs to be connected to a suitable earth.
If operators are stood or if they are required to be mobile whilst handling unprotected ESD Sensitive Devices (ESDS), a footwear/flooring system can be used. In which case number 6 to 8 would be required.
Foot grounders are designed to reliably contact a grounded ESD floor and provide a continuous path-to-ground by removing electrostatic charges from personnel. They are easy to install and can be used on standard shoes by placing the grounding tab in the shoe under the foot.
Foot grounders must be worn on both feet to maintain the integrity of the body-to-ground connection Wearing a foot grounder on each foot ensures contact with ground via the ESD floor even when one foot is lifted off the floor.
ESD Flooring is an essential component in the flooring / footwear system when grounding moving or standing personnel. The path to ground from operators via heel grounders to ground is maintained by using dissipative or conductive flooring such as ESD Floor Matting, Titles, Epoxy or floor finish. In this example, we use a floor mat at the work bench.
ESD Flooring doesn’t just ground personnel; it also grounds ESD control items such as mobile carts or workstations.
Just like work surface matting, floor matting needs to be connected to ground. This ensures that any charges on the operator are dissipated through their heel grounders and the floor matting to ground. A floor mat grounding cord is used to link the floor mat to ground (in our example an EBP bar).
Alternatively, matting can be earthed via a strip of copper foil.
Below is a step-by-step guide on how you can create an ESD workstation at your existing workbench. If operators are not stood or mobile and you don’t need to ground them via a footwear/flooring system, then skip steps 9 to 13:13 Steps to Installing an ESD Workstation at your Existing Work Bench
To sum-up, in an EPA you:
With a few simple steps, you can convert your existing workstation into an ESD workstation. You will need: