Hi Guenter, This large anisotropy for PCBs with Kevlar woven fiber reinforcement is very interesting. What were the CTEs in the x- and y-directions? Even with standard FR--4 there frequently is some x,y-anisotropy of about 1 to 2 ppm/C. The non-woven Kevlar matte you refer to will eliminate the anisotropy, but the CTE-constraint will be significantly less than you would get with uniform woven Kevlar. To you have a paper on this study-please send it to me. Werner Engelmaier Engelmaier Associates, Inc. Electronic Packaging, Interconnection and Reliability Consulting 23 Gunther Street Mendham, NJ 07945 USA Phone & Fax: 201-543-2747 E-mail: [log in to unmask] *************************************************************************** * 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] * ***************************************************************************