Hi Doug, The IEC 61000-4-2 standard is a loosely defined spec. It only specifies a few parameters for the discharge current and with pretty big tolerances (peak current has +/-10% tolerance, rise time has a range from 0.7 ns - 1 ns and current at 30 ns and 60 ns have +/-30% tolerance). Consequently it is possible for all the commercially available ESD generators to meet the specifications but still produce vastly different discharge current pulses. For example, one generator might produce a slowly falling first hump and another generator might produce a rapidly falling first hump as the fall time is not specified in the standard. This results in big differences in current derivatives (didt) which in turn results in big differences in the fields coupled by the two ESD generators to the EUT.
The standard does not specify the transient fields generated by the ESD generators which are a combination of fields caused by the discharge current at the tip of the generators and the fields caused by the faster currents inside the ESD gun bodies. This variation in fields among ESD generators is a bigger contributor to the un-reproducibility of test results (soft failures) than the variations in the discharge currents (hard failures) since the current is somewhat regulated by the spec but not the fields. Thanks, Ram EMC Engineer Apple Inc. ________________________________ From: Douglas Smith <[email protected]> To: emc-pstc <[email protected]>; Si-List <[email protected]> Sent: Wed, December 8, 2010 9:45:25 PM Subject: [SI-LIST] variations in ESD simulators Hi All, My latest monthly article is out! Technical Tidbit - December 2010 Comparing "IEC 61000-4-2 Compliant" ESD Simulators Abstract: IEC 61000-4-2 compliant ESD Simulators (150 pF/330 Ohm network) arerequired to meet a specified waveform. Results are presented here comparing the current waveforms delivered into a metal tabletop (Horizontal Coupling Plane of IEC 61000-4-2) by three different simulators. The results were not as uniform as expected. The data presented has implications for the reproducibility of ESD testing. The link to the article is: http://emcesd.com/tt2010/tt120210.htm[1] Doug -- -------------------------------------------------------------- ___ _ 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: [email protected][2] \ _ / ] \ _ / Web: http://www.dsmith.org[3] -------------------------------------------------------------- --- Links --- 1 http://emcesd.com/tt2010/tt120210.htm 2 mailto:[email protected] 3 http://www.dsmith.org ------------------------------------------------------------------ To unsubscribe from si-list: [email protected] with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: [email protected] with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: http://www.freelists.org/archives/si-list Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://product-compliance.oc.ieee.org/ Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
