Hi Werner, I would like to clarify this point with you:- >I do not know where the notion >of "Cu diffuses into the Au" or that"Ni acts as a barrier layer to prevent the >formation of CuAu intermetallics" comes from, but that is not the case. If this is not true, then I too have been guilty of giving out misinformation. The solderability of a gold on copper surface deteriorates for some reason and I thought this was due to copper migrating into the gold to the surface. This also causes contact resistance to rise on edge connectors even with significantly thicker gold deposits on copper. The plating of Nickel on the copper reduces this and it would seem that the Nickel does act as a barrier. If this is not the reason then what is the mechanism, and why do we need to plate nickel on edge connectors? Best Regards Paul Gould [log in to unmask] Isle of Wight,UK ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################