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Dear all ESD experts, I have some interesting questions about ESD gun discharge testing as follows: 1. Many books state that sometimes happening in ESD tests is that it failed at lower level i.e. 4kV but passed at higher level , i.e.6k. Why does it occur? Does it relate to the rise time of ESD waveform spec.(1 ns) for different max. current level when different discharge voltage is applying? 2. When perform an ESD testing on a portable equipment, i.e. a mobile phone of plastic housing with LCD displays, the internal wall of the housing is without conductive coating. For some particular test point of contact discharge, if it passes at +6kV but fails at -6kV. What does it indicate? Or pass at negative voltage and pass at positive voltage. Does it relate to when we apply a positive voltage, the current is injecting into the phone, and the electron (negative charge) is drawn from the phone, only positive charge is left on the phone, and vice versa. Is there any difference when apply the air discharge (pass in one polarity but fail in the other polarity test)? 3. During the direct contact discharge test, do I need to use a grounded probe to contact the EUT after the 10 discharge on each test point, or contact it between each discharge? I discovered that sometimes the EUT locked-up when I connect the grounded probe (but not the instant of discharge by the ESD gun) between each discharge, Why does it cause? Is there any difference “ the grounded probe contact made system lock-up” when the discharge voltage is positive or negative for a portable equipment. Is there difference for this kind of “lock-up” happen on air-charge test? 4. The phone is enclosed in a 100% plastic housing, of course it has some seams between the front and back housings, and there is a metallic part ( i.e. LCD frame, the shape is like a ring of diameter 50mm) which is mount on the “surface” of the housing, and the LCD frame does not touch any PCB inside the housing, when I perform the direct contact discharge on the LCD frame, the phone has some problems i.e. auto power reset, lock-up, etc. But when I perform the air-charge discharge test ( even for higher voltage level) at the location just next ( few mm distance away from the frame) on the housing, no such problem occurs, what is the reason? 5. The ESD test result becomes worse when I connect the charger cable to the phone, of course there is a bigger voltage difference inside the circuit when charging, any solution or suggestion for this problem? Thanks advance to any ESD experts can give me some advice, comment or share your experience. Best Regards, Johnny Leung. _________________________________________________________________________ Get Your Private, Free E-mail from Fouster System at http://www.idvweb.com This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. IEEE PSES Main Website: http://www.ieee-pses.org/ To post a message send your e-mail to [email protected] Instructions for use of the list server: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html 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://www.ieeecommunities.org/emc-pstc
