Guenter, I have not seen the specifics of your accelerated test and your test vehicle. However, your findings seem to agree with familiar trends on the effects of PWB properties on SMT assembly reliability. Can you provide the reference to the paper where you published the solder joint failure data? I am interested in bouncing your test data against predictive solder joint reliability models. Thank you very much. Jean-Paul Clech EPSI Inc., P. O. Box 1522, Montclair, NJ 07042 - USA tel: +1(201)746-3796 fax: +1 (201)655-0815 Home page: http://members.aol.com/Epsiinc1/index.html ****************************************************************************** * In a message dated 96-12-31 06:41:15 EST, you write: << Subj: Woven Kevlar Date: 96-12-31 06:41:15 EST From: [log in to unmask] (Guenter Grossmann) Resent-from: [log in to unmask] To: [log in to unmask] Hi Bob I can't give you any advice concerning the scale factors for PCB's with woven Kevlar. But we made a lot of investigation about the reliability of SMT solder joints on this type of material. Be careful !! A PCB with Kevlar can have an anisotropic CTE. The Kevlar is not always symmetrically woven ( depends on the distributor ). This means there are not the same amount of Kevlar strings in both weaving directions. As a result, we observed a stunning crack growth rate in the solder joints of ceramic components that are in the direction with just a few strings. on the other hand, components with plastic packages show fast growing cracks in the solder joints if set in the direction with many strings. I got really angry reactions from DuPond when I published this results. The folks these explained me that no woven Kevlar is used anymore in PCB's ( due to the problems explained in my report ) but a fleece with an irregular distribution of the Keflar strings leading to a less pronounced anisotropy in the CTE ( hopefully ). However, DuPond never gave us examples of this material for testing when I offered them the possibility of performing a series of reliability tests. So I can't tell you anything about this material. Anyway, it seems as if woven material is still used. Guenter Federal Institute of Technology Reliability Laboratory Zurich Switzerland >> *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************