Its about 3ohms per mil. The upper limit is 7mils at this point the soldermask is essentially infinite. Quite significant I would think. Source : Verifying the accuracy of 2S solvers on Zo Calculation - Dr Eric Bogatin. Slides available from the GigaTest website : http://www.gigatest.com <http://www.gigatest.com/> Best Regards Charles Grasso Senior Compliance Engineer Echostar Communications Corp. Tel: 303-706-5467 Fax: 303-799-6222 Cell: 303-204-2974 Email: charles.grasso@xxxxxxxxxxxx; <mailto:charles.grasso@xxxxxxxxxxxx; %20> Email Alternate: chasgrasso@xxxxxxxx <mailto:chasgrasso@xxxxxxxx> ------------------------------------------------------------------ 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: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.org List archives are viewable at: //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