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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 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:
- how to create an EPA at your workstation,
- what ESD control products are required, and
- how to correctly set them up.
An EPA is an area that has been established to effectively control Electrostatic Discharge (ESD) 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 the covering of surfaces and for the manufacture of containers and tools. All surfaces, products and people are bonded to Ground. Bonding means linking, usually through a resistance of between 1 and 10 megohms. 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 a number of different workstations. “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)].
Converting your Workstation into an 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:
1. Working Surface Mat
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:
- To provide a surface with little to no charge on it.
- To provide a surface that will remove ElectroStatic charges from conductors (including ESDS devices and assemblies) that are placed on the surface.
2. Working Surface Mat Grounding Cord
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 metallic crimps, snaps and banana plugs to connect to designated ground points. The use of alligator clips is not recommended.
3. Earth Bonding Point Plug
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.
4. Wrist Strap
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:
- a wristband that is worn comfortably around your wrist and
- a coiled cord that connects the band to Ground (in our example an Earth Bonding Point (EBP) Bar).
5. Earth Bonding Point Bar
Note: instead of connecting your wrist strap to an Earth Bonding Point (EBP) bar, you can also connect it to the EBP plug described in #3. EBP bars fulfil the same function as EBP. 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.
Where sitting personnel will be grounded via a wrist strap, this method is not feasible for operators moving around in an ESD Protected Area. In those situations, a flooring/footwear system is required.
6. Foot Grounders
Foot grounders are designed to reliably contact grounded ESD flooring 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.
7. Floor Matting
Floor matting is an essential component of 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.
Floor mats don’t just ground personnel; they are also used to ground ESD control items (e.g. mobile carts or workstations).
8. Floor Mat Grounding Cord
Just like working 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.
Installing an ESD Workstation
Below is a step-by-step guide as to who you can create an ESD workstation at your existing workbench:
|1.||Lay the working surface mat flat on the workbench with the stud(s) facing upwards.|
|2.||Connect the working surface mat grounding cord to the working surface mat.|
|3.||Plug the earth bonding point plug into the appropriate socket at the wall. Note: if you are located outside the UK, there are country-specific bonding points available.|
|4.||Connect the other end of the working surface mat grounding cord to the earth bonding point plug.|
|5.||Place the wristband on the wrist.|
|6.||Connect the coiled cord to the wristband.|
|7.||Attach the earth bonding point bar to the bench. Remember that it needs to be connected to a suitable earth.|
|8.||Connect the other end of the coiled cord to the earth bonding point bar.|
If your operators are standing or mobile and grounding via a wrist strap is not feasible, follow these steps:
|1.||Follow steps #1 to #4 above.|
|2.||Lay the floor mat flat on the floor with the stud(s) facing upwards.|
|3.||Connect the floor mat grounding cord to the floor mat.|
|4.||Attach the earth bonding point bar to the bench. Remember that it needs to be connected to a suitable earth.|
|5.||Connect the other end of the floor mat grounding cord to the earth bonding point bar.|
|6.||Place the foot grounders on the feet.|
To sum up, in an EPA you:
- ground all conductors (including people),
- remove all insulators (or substituting with ESD protective versions) or
- neutralise process essential insulators with an ioniser.
With a few simple steps, you can convert your existing workstation into an ESD workstation. You will need:
- Working Surface Mat
- Working Surface Mat Grounding Cord
- Earth Bonding Point Plug
- Wrist Strap
- Earth Bonding Point Bar
- Foot Grounders
- Floor Mat
- Floor Mat Grounding Cord