Hi Dan, Air discharges are made anywhere on the product where an insulator covers possibly sensitive features.
Membrane keypads are a great example. The keypads contain traces and circuitry that may be sensitive to ESD. However, since the outermost layer is an insulator, making a contact discharge would not be a real world test. I believe that it may also damage the contact discharge relay in certain ESD generators. I can explain that in more detail if you would like. In my experience, membrane keypads are always tested with air discharge. There are other surfaces that offer more chance for interpretation and debate. The main sticking point here is the definition of insulation. Some people try to consider paint on a metal surface as insulation. In this case they will only make air discharges to painted metal surfaces. Others do not consider the paint as an insulator, they will poke the contact discharge tip down through the paint until it gets to bare metal and then make contact discharges. The same question arises with insulating passivation treatments such as black anodize treatment on Aluminum. Each product is different and each coating is different, this is where the compliance engineer has to use some honest judgement. My humble opinion is that I poke the tip through paints and passivation coatings of metals to perform contact discharges. If there is an actual piece of material such as a plastic overlay over the metal; then I use air discharge. I have a non-compliance collegue here that used to work on military projects. He has told me that there is a US military standard that actually classifies different metal treatments such as passivation coatings, paints and baked on enamels as "insulators" or not. However, I have never found this standard. In its absence, I have used the rule of thumb above. Chris Maxwell Design Engineer NetTest 6 Rhoads Drive, Building 4 Utica,NY 13502 email: chris.maxw...@gnnettest.com phone: 315-266-5128 fax: 315-797-8024 > -----Original Message----- > From: Dan Kinney (A) [SMTP:dan.kin...@heapg.com] > Sent: Friday, April 20, 2001 6:07 PM > To: Douglas C. Smith; Terry Meck > Cc: emc-p...@ieee.org > Subject: RE: ESD generators max Contact discharge level > > > While we're on the topic, I have a question (actually a couple) regarding > air discharge. Since contact discharge is the preferred method, as stated > in an earlier message and in EN61000-4-2, Paragraph 5, why would one > perform > the Air Discharge method? The same paragraph states "Air discharges shall > be used where contact discharge cannot be applied." What conditions would > make it such that contact discharge could not be applied? > > Thanks in advance. > Dan Kinney > Horner APG > > > -----Original Message----- > > From: Douglas C. Smith [SMTP:d...@emcesd.com] > > Sent: Friday, April 20, 2001 2:54 PM > > To: Terry Meck > > Cc: emc-p...@ieee.org > > Subject: Re: ESD generators max Contact discharge level > > > > > > Hi Terry and the group, > > > > Besides the question of finding a generator that can reach the level you > > mention, I am not aware of any natural ESD event that approaches the > > interference potential of even an 8 kV contact discharge. The problem > > comes in that high voltage air discharges have relatively slow > > risetimes, for 16 kV on the order of tens of ns, whereas contact > > discharges maintain a better than 1 ns risetime at all voltages. This > > makes for a much smaller dt to go along with the greater di to make a > > di/dt that is much higher, more than an order of magnitude, than you > > will see for these voltages in nature. > > > > Maybe if you were making atom bomb trigger mechanisms there would be a > > justification for this kind of testing, but not for real equipment. > > > > On the other hand very low voltage (and energy) events, such as jinjling > > change have very high di/dt because of the tens of ps risetimes that > > occur at low voltage. The combination of high voltage (and energy) with > > fast risetimes is too severe and meeting such a test is a waste of money > > for most equipment. > > > > Doug > > > > Terry Meck wrote: > > > > > > Hello again: > > > > > > Does anyone recall if there were any standard called for or ESD > > generator that simulated as the case may be => +-10 kV CONTACT > discharge. > > > > > > We have a customer that is specifying passing +-16 kV ESD without > > referring to AIR or Contact discharge. I am inclined to ask what they > > have in mind since I have not seen any generators that go that high in > the > > Contact mode. > > > I suspect the writer of the SOW knows nothing and the engineering > group > > only thinks Air Discharge. > > > > > > What do you all think? > > > > > > Terry J. Meck > > > Accu-Sort Systems Inc. > > > > > > ------------------------------------------- > > > 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: > > > majord...@ieee.org > > > with the single line: > > > unsubscribe emc-pstc > > > > > > For help, send mail to the list administrators: > > > Michael Garretson: pstc_ad...@garretson.org > > > Dave Heald davehe...@mediaone.net > > > > > > For policy questions, send mail to: > > > Richard Nute: ri...@ieee.org > > > Jim Bacher: j.bac...@ieee.org > > > > > > All emc-pstc postings are archived and searchable on the web at: > > > http://www.rcic.com/ click on "Virtual Conference Hall," > > > > -- > > ------------------------------------------------------- > > ___ _ Doug Smith > > \ / ) P.O. Box 1457 > > ========= Los Gatos, CA 95031-1457 > > _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799 > > / /\ \ ] / /\ \ Mobile: 408-858-4528 > > | q-----( ) | o | Email: d...@dsmith.org > > \ _ / ] \ _ / Website: http://www.dsmith.org > > ------------------------------------------------------- > > > > ------------------------------------------- > > 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: > > majord...@ieee.org > > with the single line: > > unsubscribe emc-pstc > > > > For help, send mail to the list administrators: > > Michael Garretson: pstc_ad...@garretson.org > > Dave Heald davehe...@mediaone.net > > > > For policy questions, send mail to: > > Richard Nute: ri...@ieee.org > > Jim Bacher: j.bac...@ieee.org > > > > All emc-pstc postings are archived and searchable on the web at: > > http://www.rcic.com/ click on "Virtual Conference Hall," > > ------------------------------------------- > 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: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: pstc_ad...@garretson.org > Dave Heald davehe...@mediaone.net > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > All emc-pstc postings are archived and searchable on the web at: > http://www.rcic.com/ click on "Virtual Conference Hall," ------------------------------------------- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
