Why is my ESD wriststrap failing with nitrile gloves on?

Question

I have recently ordered some nitrile gloves for the cleanroom of which I am lab manager. I noticed that when I wear the gloves and test the ESD wrist straps, they are all failing. Can someone please explain? I didn't think the gloves would interfere with the wrist straps.

Answer 1

Nitrile is not a particularly conductive substance. In fact it is probably a decent insulator for non-critical purposes. You shouldn't count on health care or maintenance type gloves being an insulator for purposes of electrical safety (especially as they are so easily pierced), but they are presumably insulating enough at low voltages to fail an ESD test.

You likely need to consider the entire design of your process and procedures, not just what some bench meter says (regardless if it appears to approve or disprove). Perhaps parts never leave protective packaging or fixtures. There are also purportedly ESD gloves sold which may be more suitable for your process (or required procedures) than those made for the health care market.

Answer 2

Nitrile gloves are a good ESD material and they work well to dissipate any static charge that a person gets on themselves. However, the ESD testers have a very tight test range. Unfortunately because Nitrile is static dissipative, they will not pass the ESD tester which is designed to test just the resistance of the wrist strap. So, the gloves increase the total resistance above the range of the tester. If the person tests their wrist strap without the gloves on and passes, then they are fine after putting the gloves on. Be sure that the wrist straps are in direct contact with skin and not worn over the gloves.