Robert, Surprising you have this problem in GI mat'l. Sure you do not have this in GF mat'l ?. That is to say your plating may be suspect. Also, see if your etchback attack is more severe on prereg, so that the plating looks like "ACCORDIAN". This, even if your plating quality is good (tensile elongation strengths), may cause barrel cracks. This is very common for plating cracks. The root cause of differential etch-back lies somewhere else. Are prepreg and core from same supplier ?. Is the prepreg completey cured ? Good luck Rush Accurate Engg Inc. ############################################################## TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################