I would just like to thank everyone for so many thoughtful responses to what I originally considered a "boring question". I am quite surprised at the range of resin content in different materials (and how it affects the Dk). I guess nothing is ever easy anymore, eh? thanks again, Jack > -----Original Message----- > From: Olson, Jack C [SMTP:[log in to unmask]] > Subject: [DC] dielectric constant > > 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...) > > > ################################################################ DesignerCouncil 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 DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ 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 ################################################################