Those were golden words, Mike. We've found that the empirical 4% rule is of little use in practice, because you can get LOCAL concentrations even with a thin gold finish, all depends on the soldering process, as you mentioned. A good thing is that electrical failures due to gold embrittlement seem to be rather rare. We have soldered millions and millions of goldplated leads the last 30 years, and we have had just a few incidents. (I have seen some really scary cases, but still, very few on the long time scale)We have few components today with goldplated leads, and the few that remain will be goldfree too, if there are no special circumstances. (Historically, the 4% ghoast was first created by a Dr Becker at Ericsson, about 40 years ago. The 4% ghoast moved with the speed of light and the rule was adopted everywhere, as it seems. The same man presented a paper that warned about the dangerous silicon oil, that could spread as an invisible film and cause electrical disaster. With some common sense, you can handle both quite easily.) Inge -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner Sent: den 1 februari 2007 11:03 To: [log in to unmask] Subject: Re: [TN] Maximum Au lead plating thickness Just for late completeness: it will also depend on whether you are hand soldering, reflowing paste or wave soldering. Wave will wash a lot of the gold away [and dilute it into the solder pot before redepositing it], whereas hand or paste will just ad a finite amount of Sn to mix with the gold. Regards Mike -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian Sent: Wednesday, January 31, 2007 7:32 PM To: [log in to unmask] Subject: Re: [TN] Maximum Au lead plating thickness Karen, You won't find it because it does not exist. You want less than 4% by weight in the final joint for sure. Dr. Cotts of SUNY Binghampton would argue for much less. The reason you won't find a lead plating limit is that the results will depend on: 1) lead size 2) pad size 3) stencil thickness These will all affect the final joint concentration. Bev RIM -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Karen Walters Ebner Sent: Wednesday, January 31, 2007 2:01 PM To: [log in to unmask] Subject: [TN] Maximum Au lead plating thickness Hi We are looking for the IPC spec that calls out the maximum Au plating thickness on leads in order to prevent Au embrittlement. 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