If the process in the EPA area requires the use of chairs, do they necessarily have to be ESD?
To the best of my knowledge,
- An EPA could be a big hanger with entire floor ESD safe and grounded and with multiple ESD safe work stations and operators with wrist straps all connected to same ground.
- An EPA could be even with just a single ESD safe work station and an operator with a wrist strap connected to ground without ESD safe floor base.
If your EPA falls under category 1 above, necessarily the chairs used Shall have to be ESD safe only and shall comply with ANSI-ESD STM12.1 / IEC 61340-2-3: Seating- Resistance Characteristics Measurements
If your EPA falls under category 2 above, using an ESD safe chair makes no sense as the usage of an ESD safe chair on a normal floor will not serve for ESD safety.
1 Like
Hi Hector,
For any ESD control item listed in table 3 of ANSI/ESD S20.20, each control item is optional. The user needs to determine if it is needed or not. Once a user determines if it is needed, then the qualification and compliance verification limits and testing are required.
Let’s take chairs for example. Remember, the chair itself needs to be examined on how it will be used and the risk or role it will play. The requirement for sitting operations is that an operator shall be grounded via a wrist strap system while seated. So unless there is a tailoring statement with data the chair is not the primary grounding system for personnel. It may be considered a backup way to ground people which is a reason for chairs. As esdtekniks pointed out, unless you have a ESD control floor, then even the backup would not work.
But what if there is a floor and it is decided that non ESD controlled chairs are used. Then they must be evaluated to see if they are a threat. How to do that? Treat it as a process essential insulator and use the limits in ANSI/ESD S20.20. If the chair is more than 30 cm away from the product, there is no threat. Typically that is the case as a person sitting in the chair will keep the chair more than 30 cm from the ESD sensitive item. But do your own evaluation to see if ESD control chairs are necessary or any other ESD control item.
3 Likes
Hector,
I will just add on to excellent advice on this thread thus far. Although ESD chairs are quite common, they are not a requirement. An ESD chair is only that if it is maintained to keep proper contact with an ESD safe floor. Chairs that are not ESD safe would be treated like any other required insulator at the station and tested as John mentioned. Either are acceptable practices, however you just need to insure your control plan identifies your seating type and method of verification to insure compliance. Hope all this helps.
Regards
Chris
1 Like
Dear experts,
a follow up question on this, what if the organization decide not to control the chair or include on the compliance verification, would that be acceptable if they only tested it under insulator requirement? No tailoring is required right since this is considered as optional?
thanks in advance.
1 Like
That is correct. If the chair is not part of the ESD control items, then they should be treated as process required insulators.
2 Likes
hi John,
thank you very much!