*From*: "Graham Davies" <GrahamDavies@xxxxxxxx>*To*: si-list@xxxxxxxxxxxxx*Date*: Fri, 29 Apr 2005 21:28:30 -0000

This is, of course, related to my search for a good 6-layer stackup. What is the impedance of a PCB trace (microstrip) with the following parameters: Width ......................... 6.00 mil Height above return plane ..... 3.20 mil Thickness ..................... 1.35 mil (1 ounce copper) Dielectric rel. permittivity .. 4.2 These are the answers I get from various tools: 41... ohms (http://www.icd.com.au/) 41.69 ohms (http://www.emclab.umr.edu/pcbtlc/microstrip.html) 41.69 ohms (TraceSim version 1.0.0) 41.69 ohms (http://www.technick.net/public/code/cp_dpage.php? aiocp_dp=util_pcb_imp_calculator) 41.7 .ohms (http://www.sunmantechnology.com/resources/cal_cat00.shtml) 46.14 ohms (ZTOOL Impedance Calculator V1.2) 47.31 ohms (http://www.rogers-corp.com/mwu/mwi_java/mwij_vp.html) 50.89 ohms (http://www.csgnetwork.com/boardrunimpcalc.html) 51.27 ohms (TxLine version 1.1) Does anyone have an idea as to why these calculators give results that vary by 20% and which are more reliable? Graham. ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx 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: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu

**Follow-Ups**:**[SI-LIST] Re: Finding the impedance of a PCB trace***From:*steve weir

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