ESD Systems - Questions And Answers

Recently our purchasing has given me some shielding bag for qualification as a alternate source. How can I qualify this shielding bag? What are the criteria to look for? I can measure the resistivity of the bags, but how can I measure the decay time. I have a charge plate analyzer and megohmeter. Please advise.

The ANSI/ESD-S20.20-1999 lists recommended resistance ranges for conductive (< 1x10^4 ohms) and dissipative (>= 1x10^4 to < 1x10^11 ohms) packaging as well as shielding packaging to have the energy from a 1,000 volt (100 pF) discharge shall be less than 50 micro joules +/- 6 micro joules. Refer to standard ESD S11.31 Shielding Materials – Bags for the energy constraints and EOS/ESD S11.11 and ESD DS11.12 for resistance constraints and ESD ADV 11.2 for the Low Charging [yet to be defined] constraints. Static Decay tests can be performed using MIL-PRF-81705D; FTMS 101C, M4046.1 standards.

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