Tuesday, September 28, 2010

Why use an ESD seat?

I have read the IEC 61340-5-1/2 and we are building a new production area. If everyone who works with ESDS, uses wrist straps while seated, do they need to sit on an ESD chair? (The floor, the tables, the garments are ESD protected)
If they connected to ground via wrist strap, why should I connect them to ground via chair?

Firstly, the ESD chair is not for grounding personnel. The seat may have quite high resistance to ground, up to 10^10 ohms. For grounding personnel, we need a much lower resistance <35 Mohms and this cannot be achieved by contact with many seats. Contact between the seat and body is unreliable because there are layers of clothing in between!

The purpose of having an ESD seat is so that the material of the seat does not become charged and cause an electrostatic field and ESD risk.


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- Murk

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Anonymous said...

I think you are suporting those who make wrist straps. We have succesfully removed wrist straps and continous ground monitoring systems for seated personnel after grounding the person with ESD chair and achieving < 35Meg Ohms... but the evalaution was intensive due to the type of material to be used

Anonymous said...

I've been plagued by this concern for a while now and have been unable to find any concrete information on it.

We have ESD chairs, ESD work surfaces, and ESD flooring. Anyone entering the area must wear a jacket and straps. If someone were to sit on an ESD chair and their feet were to no longer have contact with the floor, would a wrist strap be necessary?

Static Doctor said...

In current standards, wrist straps are mandatory for seated personnel because they will take their feet off the floor and lose ground contact.