You did not say where your 'post separations', now renamed 'inner layer separations (ILS)' occurred, nor what the design (MLB thickness, PTH/PTV diameter, plating thickness, foil type & thickness) and processing (HASL, wave, reflow, manual soldering) details of your MLB are. ILS can occur in one of three failure modes: (i) within the inner layer copper foil, (ii) at inner layer copper foil/electroless copper flash interface, (iii) at electroless copper flash/electrolytically plated copper interface. Depending on the failure mode, the solution is different, but etchback may not be adequate. You may have manual soldering operations (run too hot) that simply put too much loading on your PTH/PTV structures. For (i) change to HTE copper foil, for (ii) you may have inadequate smear removal or some problem in your processing, and for (iii) you have some processing problem. In any case, I would recommend using IST testing to monitor the effects of your changes on the reliability of your PTH/PTV interconnect structures. Werner Engelmaier Engelmaier Associates, Inc. Electronic Packaging, Interconnection and Reliability Consulting 23 Gunther Street Mendham, NJ 07945 USA Phone & Fax: 201-543-2747 E-mail: [log in to unmask] *************************************************************************** * 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] * ***************************************************************************