ESD Systems - Questions And Answers

Hi,
We have several multi-drawer cabinets in which we store sensitive components in their ESD bags. The cabinets are ungrounded and on a non-conductive floor. We also have some metal free standing shelving with particle board surfaces which are also not grounded. I feel that these storage systems must be grounded in order for the ESD and antistatic packaging to function properly. Am I correct?

Yes, but you have two alternatives:

1) Store ESD sensitive items on grounded ESD surfaces

2) Store ESD sensitive items in enclosed ESD packaging that has ESD shielding property.

Per ESD-ADV53.1 ESD Protective Workstations Electrical Requirements “Workstation elements shall be connected to, and maintain electrical continuity to, the common point ground as follows:

Worksurfaces - Resistance: Between 1 x 10^6 ohms and 1 x 10^9 ohms

Surfaces of shelves and drawers intended to be used for unprotected ESD sensitive devices - Resistance: Between 1 x 10^6 ohms and 1 x 10^9 ohms”.

So if the ESD sensitive items are not in closed shielding bags, etc., the drawer or particle board surfaces should have 10^6 - 10^8 ohm grounded matting.

If surfaces are not conductive/dissipative and grounded, it would be considered outside the ESD protected area. And per ANSI/ESD S541 section 6.2 Outside an EPA “Transportation of sensitive products outside of an EPA shall require packaging that provides:

1. Low charge generation.

2. Dissipative or conductive materials for intimate contact.

3. A structure that provides electrostatic discharge shielding."

See Statshield ESD Shielding Bags and In Plan Handlers.

Per ANSI/ESD S541 section 7.2.2 Resistance of Dissipative Materials “A static dissipative material shall have a surface resistance of greater than or equal to 1.0 x 10^4 Ohms but less than 1.0 x 10^11 Ohms. Packaging materials that are in intimate contact with devices should be dissipative.”

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