Hi John, The use of non-functional lands has a mixed impact on reliability. For FR-4 MLBs, non-functional lands have shown a slight reliability advantage (see IPC-TR-579, 'Round Robin Reliability Evaluation of Small Diameter Plated Through Holes in Printed Wiring Boards'), PROVIDED that the presence of the non-functional lands does not reduce the quality of the drilled holes and with it the resulting quality of the plated copper barrels (see Engelmaier, W., "Manufacturing and Reliability Issues of Small-Diameter/High -Aspect-Ratio Plated-Through-Holes and Vias", IPC Workshop Handout, March 1997). Also, for MLBs with highly CTE-constraining reinforcements (e.g., Kevlar fibers), the PTH/PTV copper barrels actually see larger stresses with non-functional lands (see Bhandarkar, S. M., A. Dasgupta, D. Barker, M. Pecht, and W. Engelmaier, "Influence of Selected Design Variables on Thermo-Mechanical Stress Distributions in Plated-Through-Hole Structures," ASME J. Electronic Packaging, Vol. 114, No. 1, March 1992, pp. 8-13). To give you a straight answer, the possible small reliability gain is not worth the possible manufacturing difficulties. 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] * ***************************************************************************