WARNING: this is a very unexciting question... My software does some basic signal integrity analysis, and I just noticed it defaults the dielectric constant for regular FR4 to 4.7 I was under the impression that most FR4 is at 4.2-4.3 these days (more resin? thinner cores? can't remember...) Even a brief response will be appreciated! Jack ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################