hi, one of my customers have built a 4 layers board as follows: ____________________________18 MIC COOPER (1/2 oz) ======================== ======================== 3 X 7628 ======================== ---------vcc-------35 mic cooper (1 oz) 0.711mm CORE ----------gnd-------35 mic cooper SAME AS ABOVE with multifunctional resin type materials, it's tg is 140 c. the end-user of this board have not specified any controlled impedance tracks , BUT some signals do carry 0.7 giga to up to 4 giga !!! could someone advise what is the dk of the epoxy at those rates, should other materials be used then std. epoxy resins (fr4 -gfn) any comment would be appreciated. Yisrael Leshman Octava Marketing zichron-yaakov ISRAEL [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] * ***************************************************************************