I believe you would not be far off to take the IEC waveform as the worst case.
The amount of charge is pretty well approximated by the IEC ESD simulator. The discharge waveform shape depends on the impedance of the source - the person holding it, and the ESD trace on the circuit pack (and its parasitics) -- and the target, which in the case of a backplane is essentially zero, with some inductive effects due to the connector termination on the backplane. There is sufficient capacitance to other traces and planes AFTER the backplane connector to make the discharge otherwise quite rapid. I would expect some effects due to trace and plane resonances; testing I did on one former employer's backplane showed pronounced resonances on power distribution, for example. However this will vary among cards in different slots. Personally, I do not like circuit card ESD traces -- why let ESD onto the backplane to begin with, when you have a nice, large metal object to dump it into in the chassis and card cage? There's good coupling from the trace to each side, and I've documented ESD effects on nearby cards. Cortland ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
