Jim What software are you using to model your coupon? Polar has an online modeling service which uses a field solver and I have found it to be very accurate. Best regards Lee J. Lee Parker, Ph.D. JLP Consultants LLC 804 779 3389 ----- Original Message ----- From: Jim Henderson<mailto:[log in to unmask]> To: [log in to unmask]<mailto:[log in to unmask]> Sent: Tuesday, November 15, 2005 9:28 AM Subject: [TN] impedance testing Hello, If there are any impedance testing gurus out there I have a question for you. We are testing an edge coupled offset strip line coupon. We modeled the stack up to give us 100 ohms differential. When we test the coupon we get around 130 ohms. We have done a microsection of the coupon and modeled the coupon data and Polar says we should have 105 ohms, within tolerance. We had a 4 panel lot and it is consistent across the board. The coupon is constructed correctly. My question is, other than what I am seeing on the microsection should I look for to find the culprit of the high reading? Any help would be great. Jim Henderson Colonial Circuits --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask]<mailto:[log in to unmask]> with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]<mailto:[log in to unmask]>: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]<mailto:[log in to unmask]>: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives<http://listserv.ipc.org/archives> Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16<http://www.ipc.org/contentpage.asp?Pageid=4.3.16> for additional information, or contact Keach Sasamori at [log in to unmask]<mailto:[log in to unmask]> or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------