Hi John, Phil Hinton is quite right about the solderability protection afforded by a palladium/gold finish. But please do NOT think of the thin Pd/Au finish as a 'solderable surface', it is not. The Pd/Au finish will protect the solderability of the surface beneath it, provided it was solderable prior the application of the Pd/Au layers; it promotes 'wetting' (in the sense of spreading, not the formation of a metallurgical bond) of the underlying surface by the liquid solder, because both Pd and Au are dissolve into tin at much higher rates than do Ni; the wetting (in the more commonly used meaning of spreading plus the formation of intermetallic compounds to form a metallurgical bond) to the underlying surface (copper or nickel) is certainly enhanced by the faster 'spreading of the liquid solder; the Pd and Au layers will totally disappear by dissolving into the tin to from PdSn and AuSn IMCs, which will disperse more or less throughout the solder joint depending on peak reflow temperature and the time above Liquidus temperature. 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] * ***************************************************************************