In message <[email protected]>, dated Thu, 14 Dec 2006, Fred Townsend <[email protected]> writes
>I don't know what 'hard electroplated gold' is. Some sort of alloy I >guess. Without compsition the term means nothing to me. > It's pure gold, plated by a process that produces a hard, high-density deposit. >I'm sure you know why gold is used for a contact material, no oxides, >low resistance, etc. Our studies showed that failing boards had 50 to >70 um of gold over the base copper. The solution was to electroplate a >minimum of 250 um of nickel between the copper and gold. I believe this >is now a standard IPC specification. > >I suspect rhodium could be used in place of the nickel but the gold >would still be needed as nickel and rhodium both oxidize. Rhodium does not oxidize in air at normal temperatures; that occurs only around 600 C. It has been extensively used instead of gold as a contact material, being much harder. However, my Marconi Instruments bridge that has rhodium contacts on its main variable control has in fact suffered a disastrous amount of wear. This may be because the contact pressures were not optimized. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Politically unexceptionable seasonal greetings to all. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
