I want to thank those people who responded to my first email. All of their suggestions have merit, but are problematic one way or another at this stage. I should have added more detail in my previous email. My subcontractor has a (1) backplane that has two flex sections so it can be bent into a "U" shape for installation in a chassis. So along the length of the board, it starts rigid, goes through one flex section, a rigid center section, another flex section, and ends with a rigid section. There are ninety-six (96) traces total that pass across one or the other flex sections. The flex sections are 1 oz/ft^2 of copper, double-sided, on a 2-mil polyimide film, with a 1-mil polyimide film coverlay on each side of the exposed areas. This backplane has been assembled, i.e., it has active and passive components on it. One (1) trace has found to be broken and has high resistance (Ohms versus Milli-Ohms). That break was located by thermal imaging, since X-rays did not reveal the break. It was about 1/3 of the way into the center of the flex and not at the outside edge where it would be suspected. It was at the rigid-flex interface as was expected. Now, our customer is suspicious of all of the other 95 traces in the flex sections. I am trying to find ways to check the remaining traces before using this backplane in a Qualification unit. My subcontractor is presently making four-wire resistance measurements to check the remaining traces. Based on the X-rays we have seen, our subcontractor does not have the capability to produce X-ray images that will show a break. TDR might work. But since each trace is a different length, it will be difficult to determine whether a reflection is from a partial break or from a via near the edge of the rigid-flex interface. Thermal imaging might work, but we have to be careful to not damage any components. I was hoping that someone on SI-List would have another suggestion that would better than these. TJ Thomas L. Jackson, P.E. Senior Staff System Engineer Department L1-50, Remote Sensing System Engineering Lockheed Martin Space Systems Company Building 149 1111 Lockheed Martin Way Sunnyvale, CA 94089 Telephone: (408) 742-2013 Facsimile: (408) 742-7701 ------------------------------------------------------------------ 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