Desco - Questions And Answers

In a stockroom with stationery flat metal shelving to store to material to assemble PCBs are the shelves required to be grounded if the complete area utilizes ESD wax on the floor, or the floor is ESD epoxy, all employees in the area wear two heel straps, the majority of the material is in static shieling or sealed vapor barrier bags, the remainder of material may be unbaged reels or oringinal packaging, but placed in black conductive/disipative bin boxes?

All workstations are ESD safe and when seated wrist straps are used. –Anonymous, Hudson, MA

ANSI/ESD-S20.20-1999, ESD Association Standard for the Development of an Electrostatic Discharge Control Program for – Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices) recommends that shelving be less than 1x10⁹ ohms. This would imply that the shelves be grounded. This will ensure that the packaging won’t be charged at a potential other than ground, thereby minimizing the occurrence of an ESD event when handling stored items.

Your last paragraph, “All workstations are ESD safe and when seated wrist straps are used.“ kind of concerned me because just grounding the operator doesn’t ensure an ESD Safe Workstation, there are other concerns to be considered to, as you may already be well aware of.

I will list them here for completeness:- Charge Prevention (remove all generators, if needed then control them with ionizers or topical sprays.)- Grounding (ground all conductors – this of course includes the operator, but also the workstation, the worksurface and all hand tools, packaging, etc.)- Shielding (when items are not being handled, they should be stored in shielded packaging to minimize charge induction from static fields)- Neutralization (when a charge generator is necessary for use at an ESD Safe workstation, then it must be controlled, ionization is one of the best methods for this control)- Education (even with all the proper tools in place, if the bench operators or the line supervisors are not properly trained then infractions to the program may occur routinely without corrections)

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