Hi Richard, You are talking about a problem previously termed 'post separation' and now 'innerlayer separation. It occurs mostly at layers 2 and N-1, sometimes also at 3 and N-2, and has to do with large thermal excursions during soldering processes which cause large thermal expansions in the epoxy of the FR-4 boards. The epoxy expands, causing large z-axis movement causing upwards rotation of the innerlayer attachments to the PTH/PTV barrels as well large radial compressive forces on the PTH/PTV barrels. This can cause separation either at the plating interfaces or in the copper foil of the innerlayers. Solution options are: reduction in the maximum temperature of the soldering process, using high Tg epoxy, using grade of copper foil with higher ductility. Werner Engelmaier Engelmaier Associates, Inc. Electronic Packaging, Interconnection and Reliability Consulting 23 Gunther Street Mendham, NJ 07945 USA Phone & Fax: 973-543-2747 E-mail: [log in to unmask] ############################################################## 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 ##############################################################