Gidday Ingemar, (Gidday is likely a phonetic spelling of the Australian equivalent of Good Day). The geometry of a solder joint can be an indicator of improper wetting, which certainly can lead to solder joint failures, but in and of itself not very important for solder joint reliability with one exception--solder joint height. One also should avoid geometries causing stress concentrations, like solder-mask-defined soldering openings. The reason for all this is that solder joint failures (again with the possible exception of improperly wetted solder joints) are not stress-driven--they are strain-driven. Solder joints at typical operating temperatures (above -23oC) creep readily and therefore do not support stresses for long, they give. The most important design step for solder joint reliability is the reduction in the magnitude of the thermal expansion mismatch. I would recommend using the industry document IPC-D-279, 'Design Guidelines for Reliable Surface Mount Technology Printed Board Assemblies'. While the choice of the solder alloy can make some difference in the reliability of solder joints, this difference is small in comparison to other more significant factors, i.e. solder joint height, component size, delta-T, delta-CTE, lead compliance. You may be interested in a workshop on solder joint reliability I will be giving at ISHM-Nordic on September 21, 1997 near Oslo. You could get more information from Katarina Boustedt, Ericsson Microwave Systems, Core Unite Research Center Microwave and High Speed Electronics, SE-431 84 Molndal, Sweden, ph: +46 31 747 0219, fax: +46 31 747 0317, email: [log in to unmask] 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 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] * ***************************************************************************