One of the reliability concerns with multiple excursions of PWBs to soldering temperatures is the structural reliability of the PTH/vias both in terms of barrel cracking and innerlayer separation (post-hole separation). The more excursions and the higher the temperatures the higher the stresses. Smaller hole diameters, thinner plating, thicker PWBs are more susceptible. I teach a workshop "Design for Reliability and Quality Manufacturing of Plated-Through-Holes and Vias", to be given next at NEPCON West'97 and IPC Expo that deals with the subject you are asking about. Following is a short course description: For high-density electronic assemblies the diameters of plated-through-holes (PTH)/vias are becoming progressively smaller, while board thicknesses might increase. This has led to PTH/via failures after assembly or in the field, because the standard manufacturing processes can be inadequate to produce high quality and yields. High yields and long-term reliability can only be assured by a deliberate design effort that considers the specific damage mechanisms and stresses, resulting from further processing and operational use, threatening the integrity of the electronic assembly. Knowledge of the material properties and fatigue behavior of the PTH/via copper barrels, and assembly processes and use environments are necessary for the successful 'Design for Reliability' of high-performance, high-density electronic assemblies. The design information presented has been included in the industry document IPC-D-279, 'Design Guidelines for Reliable Surface Mount Technology Printed Board Assemblies'. 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. * *************************************************************************** * 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] * ***************************************************************************