One of my client posted an response here on the use of the ESD garments- he was told that Garments are optional item as long as the person is adequately grounded (Via wrsit strap or Shoe flooring system) and he person body remains more than 12 inches away from the ESDS.
My experience sort of imply that the garments are needed. What do the rest of you think.
The company is planning to do away with all garments and ESD chairs in the manufacturing.
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When you use proper garment, I mean qualified first, you are sure that employees use them. Even it is little damaged, the garment is near the limit 10^11 ohms, you are still sure that there is no charging and no electrostatic field. Generally.
But what is in the case when each one employee uses different private garment. You know nothing. Nothing about the static fields inside your EPA. Twelve inches sometimes can be OK distance, but in one circumstance absolutely it could be too close for supression of voltage. And be realist, please. There does nobody touch PCBA to body? To garment? I do not believe in it.
I had a problem with too short apron due to one of Inventory Control operator kept the PCBA on his thigh dressed in jeans. That was major incompliance finding by one of auditor.
All of the ESD control items in table 3 of ANSI/ESD S20.20 or IEC 61340-5-1 are optional. The reason to use or not to use any of the ESD control items, such as chairs or garments, is really dependent on the ESD control system and sensitivies of the devices. The real question that needs to be answered is, “What does the ESD control item is required in my process.”
For example, ESD control chairs. A person setting in a chair is required to wear a wrist strap to ground them. So do I need an ESD control chair? Is my device really sensitive or expensive, maybe a chair would be a backup system if someone forgets to put a wrist strap on? Maybe the chair generates a high voltage that creates a field that is unacceptable. Maybe my process equipement is very sensitive and I don’t want the chair to generate any EMI noise that could result in internal discharges that a non-controlled chair may cause. There are many reasons to have a chair but if the person wears a wrist strap and the chair itself is no concern, then do you need and ESD control chair.
Same though process for garments. What does a garment do for your in your process. How well is a person grounded. That will suppress a field. Can a grounded person generate a field that would be a threat to the ESD sensitive devices. I can’t answer that but I could make measurements to figure that out.
Never add or delete and ESD control item without any data. Don’t rely on what someone said but investigate the reason behind the decision.