ESD Systems - Questions And Answers

In direct answer to your question regarding: "is the any validity to a "wireless" ESD wrist Strap", my answer would be NO. No one that I know of has designed and produced one that actually works. The ones from the Far East do not perform (see answer #17 below). I know of only one design that will work, but no one has produced this as of yet. In answer to your second related question: "what is wireless ESD protection????" The only thing that may be applicable is forced air corona discharge ionization, which is widely available as "Air Ionizers". ESD Systems has several models to choose from. The only draw back is that the discharge times, depending on flux rates, air velocity and proximity may. What is the recommendation or guidelines in determining when Anti Static shielded bags are no longer any good, i.e. crinkled or have small puncture holes, and put out of service? - David, Richardson, TX

All your answers are in the MIL-B-81705C Standard document. Specifically, an anti-static shielding bag (type III) can be considered no good if it meets any of the following conditions: the bag delaminates as defined in section 4.8.4.1 in MIL-B-81705C, has a static decay rate exceeding 2.0 seconds, does not attenuate EMI at least 10 dB punctures over 6.0 lbs, doesn't shield an ESD event under 30 kV and has a surface resistivity greater than 1x10^12 Ohms/sq both inside and out and less than 1x10^5 Ohms/sq on the inside. In general, a shielding bag may still shield if it has crinkled or acquired small holes because of the Faraday affect, but it is safer to discard these bags and err on the conservative side. It would probably cost more to test and qualify the bag then to just replace it.

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