Hi Dave, Yes, I do think that inner layer foil cracks are more probable with1/2 oz copper as compared to 1 oz, especially with Standard E1 foil which can be shipped down to 2% elongation under IPC-MF-150. While foil with such lousy ductility is not shipped very often, it does happen. And when it happens, that foil also will have lower strength, higher etch rates, and higher electrical resistivity. 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]