The comments by Alan Cochrane need amplification: Temperature measurements during profiling on PWBs at and in PTHs show that the temperatures in and near the PTH copper barrel are as hot as anywhere on the assembly (the PWB and the PTH lands are hotter than most solder joints reflowed). The resin distant from the PTH barrel of course heats slower due to its lower conductivity. Tensile tests are not very good in determining ductility of foils, because of the large aspect ratios of thickness:width and thickness:gage length. That is why separate ductility tests (ASTM E-796, Standard Test Method for Ductility Testing of Metallic Foil, and IPC-TM-650, Test Method 2.4.2.1, Flexural Fatigue and Ductility, Foil) exist. One of the artifacts of the inadequate elongation measure is the misleading result that elongation goes up with foil thickness when in fact ductility does not. Even in full built electroless PWBs, that have uniform plating thicknesses and properties throughout the PTH barrel, do PTH barrel cracks occur near the center of the PWB (see IPC-TR-579, Round Robin Reliability Evaluation of Small Diameter Plated Through Holes in Printed Wiring Boards). For electrolytically plated PWBs the copper deposit near the center of the PWB can indeed be thinner and of lower quality (strength, ductility) because of the plating characteristics. 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 unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************