Jeff - From experience we have found that un-balanced stack-ups can cause warpage to the extent that quad-flatpacks can not be attached, >0.010"/inch. I assume from your message that you are faced with a situation where you have 3 planes in a given board, 5v, 3.3v, and ground. The recommendation we have received in laying-up this type of stack in a 6 layer board is: Signal Voltage Signal - "filled with Ground" Ground Voltage Signal The "odd" plane lair should be balanced by filling the "odd"signal layer with poured copper to help reduce built in stress. Large copper areas additionally should be broken in to hatched patterns (positive-image mesh) to balance the copper area for platting. I hope this helps. Jeffrey McGlaughlin BFGoodrich Avionics Systems Inc. Columbus, Ohio *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * 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] * ***************************************************************************