John Woodgate wrote:
In message <mailto:[email protected]> <[email protected]>, dated Thu, 14 Dec 2006, Fred Townsend <mailto:[email protected]> <[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. OK I thought I understood electroplating and I thought I understood the gold molecule. If we are going to change it's density then don't we have to change it's molecular structure or are we just changing it's mechanical structure... squeezing out the 'air' so to speak. Assuming this to be true (I am skeptical) how do we do this in electroplating? Use more electrodes? Different platting solution? Higher plating current? Please elaborate. Fred Townsend 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. ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- 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
