Nickle is normally used between Gold and Copper to prevent the Gold from spontaneously alloying with the Copper, and disappearing after a time. You are apparently currently using ENIG...Electroless Nickle, with immersion Gold...typically the Gold is less than 0.25 micron thick. When the folks in the UK used to have a standard set by their telecom people which allowed, or even specified (!!!!) Gold over Copper, the Gold needed to be 1 micron + thick, to delay this alloying process. ENIG, properly done, has nearly an infinite shelf life before it must be soldered. Gold over Copper will have a finite shelf life, dependent on Gold thickness. Does this help? Rudy Sedlak RD Chemical Company --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------