ESD Chairs: A Bridge Between Two Perfect Methods of Grounding

THE GIST:
ESD Chairs: A Bridge Between Two Perfect Methods of Grounding

The ESD floor prevents static only when shoes are in contact with the floor
When person is seated with his/her feet lifted, if they are not wearing a wrist strap, they are not grounded.
An ESD chair acts as a bridge between the ESD floor and conductive wrist strap.
- ESD chairs are electrically bonded to the ESD floor.
- ESD chairs also prevent charge generation on the person seated in the chair.
ESD chairs provide “belt and suspenders” protection against a random ESD event
ESD chairs eliminate the risk of compromised protection (from the time the person sits until he or she puts on a wrist strap).

In this episode, Dave and Rick explain how ESD chairs work and why they act as a bridge between two perfect methods of grounding (an ESD floor and wrist strap). The ESD floor grounds and prevents charge generation while people walk. Once the person sits and lifts his or her feet, they are no longer grounded. There may be a wrist strap at the work station, but until the person puts it on they’re a live wire. If they touch a component – or expensive prototype, for example – before putting on the wrist strap, any charge on their body will transfer to the component. ESD chairs ground the person in the chair, prevent charge generation and protecting against random ESD events.

“Any good process always takes into consideration the possibility of a compromise in the process. The ESD chair eliminates that possibility.”

THE GIST:
ESD Chairs: A Bridge Between Two Perfect Methods of Grounding

The ESD floor prevents static only when shoes are in contact with the floor
When person is seated with his/her feet lifted, if they are not wearing a wrist strap, they are not grounded.
An ESD chair acts as a bridge between the ESD floor and conductive wrist strap.
- ESD chairs are electrically bonded to the ESD floor.
- ESD chairs also prevent charge generation on the person seated in the chair.
ESD chairs provide “belt and suspenders” protection against a random ESD event
ESD chairs eliminate the risk of compromised protection (from the time the person sits until he or she puts on a wrist strap).

“Any good process always takes into consideration the possibility of a compromise in the process. The ESD chair eliminates that possibility.”

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Click to read EPISODE 6: Transcript

Static Bursts Episode 6: ESD Chairs: A Bridge Between Two Perfect Methods of Grounding

Rick: Welcome to Static Bursts – the info packed three-minute podcast from Staticworx designed for a quick listen.

Rick: Dave, could you explain to our listeners why ESD chairs play an important role in ESD-protected areas, even where a qualified ESD flooring system is already in place?

Dave: I walk into a lab, I have the right ESD footwear, I’ve qualified it, I know it works. Then I hop in a chair, which means my bench height might be almost like a bar height, which means my feet are going to come up off the floor. Now all of a sudden the ESD floor has nothing to do with me being grounded or not grounded. And maybe I have a wrist strap in front of me, but I haven’t put it on yet. And maybe in front of me on the lab bench is a circuit board. Maybe it’s a prototype. The minute I touch it, if I’m sitting in a regular chair, and my feet are no longer on the floor, I’m not grounded. That means that before I put that wrist strap on, I’m a live wire. I need the chair to make up for the fact that I’m no longer grounded on the floor and I have not put my wrist strap on yet.

That’s why people need ESD chairs. You have no charge while you’re walking on the floor with ESD footwear if you’ve qualified the floor properly. When you get in the chair, if the chair is electrically bonded to the floor, and it’s designed properly, and the chair we use will be designed to the ultimate standards that are required, you still won’t generate a charge. And even though you don’t have a wrist strap on if you make the mistake of reaching across onto the bench and touching a circuit board, or touching a prototype part that could be worth thousands of dollars, you in all likelihood will have very little charge on you. So the ESD chair, you could think of it as another form of being bonded to an electrically grounded floor.

Rick: ESD chairs are made of special materials that prevent charge generation and they are also electrically grounded through contact with the ESD floor so that any charge generation on a person’s body will be safely dissipated. Is it fair to say that ESD chairs provide redundant protection, somewhat akin to wearing a belt and suspenders?

Dave: They certainly are a belt and suspenders from the perspective that when I hop in the chair, I am sitting in an enclosure that is not going to charge up. And because that chair is grounded through the floor, the chances of me generating voltage is pretty close to zero.

Rick: And of course, it is always better to err on the side of caution when working with highly sensitive materials. Murphy’s Law is a good reminder that we can never be too safe.

Dave: Any good process always takes into consideration the possibility of a compromise in the process. And the ESD chair eliminates that possibility. Because you go from being totally grounded to being grounded through your clothing to the chair, to putting on the wrist strap. So the ESD chair is a bridge between two perfect methods of grounding.

We hope you learned something today. If you have questions about the podcast, give us a call at 617-923-2000 Thanks for listening.