ESD Workplace Grounding

In the simplest of terms, static is created when two surfaces rub together or are pulled apart. As the two surfaces rub together or are pulled apart electrons are passed from one surface to the other, leaving one surface with too many electrons (negatively charged) and one surface with not enough electrons (positively charged). When a surface with more electrons meets a surface with fewer electrons, the electrons try to balance out by rapidly discharging to the surface with fewer electrons – creating a surge and a static spark. It is this rapid transfer of electrons that can overload the components.

In our page on ESD Personal Grounding, we cover how to effectively ground operators in an EPA (ESD Protected Area) but there are more layers to an ESD control system than just grounding operators. Full ESD protection needs ESD protect equipment such as furniture, flooring, packaging and storage and cleaning.

There is an international standard that is used to prove ESD controls are effective. This is called EN61340 and is covered more in our How can we protect against ESD FAQ. ESD equipment works on the same principle as personal grounding – to take any potentially harmful static charges away from ESDS devices and is widespread across an EPA. The below image is a typical multi-layered EPA using ESD personal grounding, ESD workplace products and ESD testing systems.

ESD Flooring

ESD flooring is an essential and often over looked component of an EPA. Conductive wheels on ESD trolleys and chairs and ESD shoes and ESD heel strips will all struggle to meet EPA requirements if not used on an ESD floor. In fact, many types of flooring will increase the ESD charges generated, increasing the risk. Standard vinyl and carpet floors are some of the most common and worst offenders. Walking across a carpet can create up to 30,000 volts – potentially 1,000 times more than some components can withstand.

ESD flooring that conforms to EN61340 requires specialist knowledge to be properly specified but is generally readily available and comes in several forms from tiles, to paint, to fully fitted ESD vinyl floors.

ESD Floor Tiles

ESD tiles are one of the most common types of ESD floors used, of these, interlocking ESD tiles are the most popular. These are made from hardwearing plastic that is impregnated with steel fibres. As they are full of conductive fibres and use an interlocking tooth system they can be easily laid without any special conductive adhesive or tackifiers. This allows individual tiles to be lifted or replaced if needed. Interlocking tiles can also be laid over damaged, dirty or damp floors, unlike tiles which require adhesive to hold them down. They often have long guarantees and can easily be moved or repaired, offering a great level of long-term investment.

ESD Floor Paint

ESD floor paint can be a more cost-effective option for ESD flooring. ESD paint is laced with special conductive materials and is made to specific requirements (paint is usually a great insulator). The big advantage of ESD paint is the relatively low cost and ease of laying.

ESD paint tends to come in two main grades; a heavy-duty polyurethane or a water-based acrylic paint.

In order to be fully effective ESD paint needs the substrate (the floor it is being painted onto) to be clean, dry and free of any grease, damp and damage. A proper undercoat is needed and two good, even coats of ESD paint are needed over the top of the primer.

ESD floor paint grounds to the building the same as ESD vinyl tiles and ESD carpet tiles. The main downside of ESD paint is (even the heavier wearing polyurethane paint) it’s prone to damage, wear and soiling. ESD painted floors need to be cleaned, checked for damage regularly and repaired probably more than any other ESD floor type.

Fitted ESD Floors

Some very specialist areas that include highly sensitive machinery or equipment may call for fully fitted ESD floors with special conductive vinyl and with welded joints. These are highly specialised, require expert fitting and are specified for very specific applications.

ESD Work Benches

ESD work benches are another vital component in an ESD-Protected Area (EPA). ESD benches use dissipative laminates on work surfaces and many use conductive paint as well on the frame. The dissipative laminate surfaces are bonded to the frame and the frame is connected to an Earth Bonding Point (EBP). This allows all working surfaces on the ESD work bench to have a path to ground. Using full ESD work benches as opposed to just ESD mats has a simple advantage. Using only ESD mats on non-ESD benches means that only the surface of the mat is ESD safe. Mats are also often made of a foam-like material (as opposed to the hard laminate of the ESD bench) and this material can become damaged and impregnated with dirt. Damage and dirt on ESD mats will reduce the effectiveness of its dissipative and conductive properties. To ensure ESD mats remain effective they have to be replaced on a semi-regular basis (depending on how heavy the usage is).

Many ESD benches also have EBP’s built into them that the operator can be connected directly to, reducing the number of cords and link cables needed to link an operator to a mat and then to an EBP.

ESD Chairs

ESD Chairs are one of the must-have items of ESD furniture in an EPA as ESD chairs provide a vital path to ground. Getting in and out of a chair and moving around while sitting in it, can generate a lot of static.

ESD chairs use ESD fabric or ESD vinyl materials with metal frameworks, combined with conductive wheels, castors or glides to provide a route to earth for any static charges. ESD chairs work best when placed on an ESD floor.

ESD Shelving, Racking, Packaging and Trolleys

When not working on ESDS devices it is important to ensure they are stored properly and can be safely moved around an EPA and possibly to areas outside the EPA (such as dispatch). There may also be the need to ship ESDS devices to your customers and in order to ensure they arrive undamaged, proper ESD safe packaging is essential.

ESD shelves, racking and trolleys all work on the same principals as ESD matting and ESD benches; they provide a grounded surface to store ESDS devices on. As with all permanently fixed ESD furniture, ESD racking and shelving units need to have an EBP to provide a path to ground.

Some ESD racking and shelves are made from bare metals like steel with bonded points around its frame, others use painted metal frames with dissipative laminates. It is also possible to line non-ESD shelves with ESD matting, as long as a path to ground is provided.

ESD trolleys must always have conductive wheels and ESD safe shelves (usually ESD laminate, paint or steel). As with all ESD wheeled items, they are only fully effective when used on ESD floors.

ESDS devices should also be stored in proper ESD safe boxes, containers and bags to add further protection not only from ESD damage but also from physical damage. This allows them to be transported safely from point to point and even through non-EPAs.

ESD packaging in the form of metallised shielding bags, transit ESD boxes, ESD safe bubble wrap (normally pink) and rigid ESD boxes allow ESDS devices to be transported worldwide.

Cleaning ESD Safe Equipment

Cleaning ESD products needs some consideration as well. Dirt is a very good insulator and even a very thin layer of dirty can render ESD safe equipment completely useless. ESD floors are particularly prone to becoming over soiled and need regular cleaning to prevent an insulating layer building up across its surface.

Special ESD safe cleaners have to be used. This is for a very simple reason; normal cleaners run the risk of adding an insulating residue to the ESD equipment or they can degrade or adversely affect the ESD properties of the ESD safe equipment.

ESD safe cleaners are designed to remove dirt and grime without affecting the equipment’s ESD safe properties, in fact, most ESD safe cleaners will leave a very thin dissipative layer on the ESD equipment, boosting its effectiveness.

Other equipment includes ESD vacuums which are made of conductive materials so they don’t hold any static charge.

Ionisers

Ionizers are a blanket control device that covers an area with neutrally charged air. Ionizers comprise of a fan and special nozzles that produce positive and negative charges in equal measure. The fan then disperses the charged air over an area. The area covered can be very small; as produced by spot ionizers or a wide area, across entire rooms in fact.

The principal is to prevent the imbalance of electrons on surfaces that causes static discharge. By having an equal measure of protons (positive charge) and electrons (negative charge) the ionized air corrects any imbalance of electrons on a surface. If the surface has not enough then the electrons in the ionized air adhere to the surface, neutralizing the charge. If the surface has to many electrons then the protons adhere to the surface, neutralizing the charge.

This means that any surface in an ionized airflow should always have the correct balance of electrons and protons to maintain a neutral charge, and thus not be able to hold a static charge.

Ionizers are very good at this and in the right circumstances are very effective. But they do have some downsides. They can be costly to run for long periods and they are often rather delicate and prone to collecting dust. This can make keeping them clean difficult.

They should also not be used as a primary means of ESD control on conductors or people.

Summary

In order for an EPA to meet the international standards of EN61340, there are multiple layers of protection needed; from personal grounding products to furniture, flooring, storage and shipping equipment.

Understanding why these products are needed, how they protect your ESDS devices (thus saving you money) and how they are used and monitored is essential in ensuring your ESD controls are effective. If ESD damage has occurred you often won’t know it until it is too late and devices are failing in the field.