Bill, A couple things to keep in mind. Many tools model plating in such a way = as to make the trace thicker and wider than its original size = (electroless) when in fact your plating maybe done in such a way that it = is only on top of the trace (electro) making it thicker only. You may = have noticed making a trace thicker (1/2oz to 1oz) has only a small = effect on impedance. So, if you ignore your plating I bet you will = notice your numbers come in line with the fabrication house numbers. = Another factor that people need to keep in mind is that many of us have = always assumed that 1/2 oz copper is .0007" thick. Well it has come to = my attention that core manufactures have decided to save themselves a = buck of two and are depositing copper at the low end of the spec = thickness. I have had several samples measured and it is almost always = .00063" thick for half oz copper. Ken Robinson -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of bdempsey85 Sent: Wednesday, November 05, 2003 5:40 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Embedded uStrip - double check me I would like a double check on my coated uStrip impedance calculations. I am getting feedback from my PCB fabricator that my numbers are >10% off. Here are the parameters: 5 mil wide trace, 0.5 foil with add'l 1oz plating (approx 2.1 mils thickness) 4 mil trace to plane, Er ~ 4.3 LPI soldermask ~ 0.8 mils thick I compute 51 ohms...how about you? Thanks, Bill ------------------------------------------------------------------ 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 archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages=20 Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ 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 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