Dear Liao, there are some PCB maker out there with the capability and willingness to test all, or selected traces of your board. Of coarse you have to pay for this service, as well as you have to pay for very tight impedance control. For mass production this is not the way to go. You have to make shure that the design works within all production variations. For special test cards, thats another story. We found a PCB maker in Germany for such test boards, and they guaratee a 6% tolerance for prototype volumes and test most of the traces. Unfortunately, they can only test single ended, thus you have to specify both impedances, and they will only guaratee the single ended to come out right. Let me know if you would like the contact data. BR Gert -------------------------------------------------------------------------- Absender ist HARTING Electronics GmbH & Co. KG; Sitz der Gesellschaft: Espelkamp; Registergericht: Bad Oeynhausen; Register-Nr.: HRA 5596; persönlich haftende Gesellschafterin: HARTING Electronics Management GmbH; Sitz der Komplementär-GmbH: Espelkamp; Registergericht der Komplementär-GmbH: Bad Oeynhausen; Register-Nr. der Komplementär-GmbH: HRB 8808; Geschäftsführer: Torsten Ratzmann -----Ursprüngliche Nachricht----- Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im Auftrag von BO-LIAO Gesendet: Sonntag, 30. August 2009 14:09 An: si-list@xxxxxxxxxxxxx Betreff: [SI-LIST] Control Impedance testing Dear Sir, My PCB supplier doesn't test control impedance on actual board. They said control impedance is measured on test coupon. Please advice if it is realistic and reliable to use the test coupon measured impedance? Is this an industry norm, or standard? Thank you. Best regards, Liao Bo ------------------------------------------------------------------ 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.net 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 ------------------------------------------------------------------ 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.net 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