ESD Systems - Questions And Answers

1. In my shop floor, we have the dissipative floor (10⁷ Ohm). And we use the steel table, do we need to add a dissipative mat to avoid the CDM ESD hazard?

2. What is the difference between the conductive floor and dissipative floor? Are they the same thing?

3. Then how about the dissipative mat and conductive mat?

4. When my product needs to be packed, is it sufficient for anti-static reel. Then I don't need any more protection to put my product in reel into the carton?

5. Some supplier claim they have wireless wrist strap. Is it reliable? And how can I measure its function?

A: Yes. If you place ESD susceptible devices onto a plain steel table top you run the risk of damaging these devices because of the CDM. To eliminate this problem, you need to add surface resistance to work surface to control the discharge so as not to be an ESD event. This can be accomplished by using an ESD grounded soft mat. A conductive floor would imply it is not only conductive (able to conduct electricity) but also in the conductive range (< 1x10⁴ ohms). A dissipative floor still has the property to conduct current, but at a higher resistance (> 1x10⁴ ohms). Either should be fine for an ESD floor as long as it meets the ANSI/ESD-S7.1 standard or the ESD-STM97.1 or ESD-STM97.2 standards, all of which have their constraints listed in ANSI/ESD S20.20 which can be downloaded with out charge (no pun intended). Packaging should consider more than just being antistatic (low tribocharging). The ESD sensitive product needs to also be shielded, shunted and or grounded to minimize damage via ESD. Cordless wrist straps are still a joke. They don’t work and WILL most likely cause ESD damage via the HBM.

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