I have seen cracked inner layers caused by drilling. When this is the case the cracks are apparent in as rec'd x-sections and usually do not get bigger after thermal stress. The grain structure of the copper at hole wall is also larger than the rest of the inner layer trace due to the heat generated by less than optimum drilling parameters Susan Mansilla Robisan Laboratory ############################################################## 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################