); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] From: "Didier Juges" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] HP 5370B low frequency modulation Date: Mon, 23 Jul 2007 21:12:39 -0500 Message-ID: <[EMAIL PROTECTED]>
> Brooke, > > Thanks Bruce for the quick response, as always. > > In my business, we typically dissolve the gold by dipping the solder cup in > a hot tin pot, which is replaced regularly, before soldering the wires. This > has been blessed by the major defense contractors for military applications. > > Failure to do this typically results in weakening solder joints over time, > and delayed failures, particularly when there is mechanical and/or thermal > stress applied to the joint. Gold will dissolve very quickly into the Sn/Pb solder. If you have a too high gold content in the joint, it can form one of several Au/Sn mixtures which is brittle and will crack easilly. We had trouble with that under our BGAs so when the gold layer was too thick, the whole 400-500 ball BGA could crack loose of the board if you accidentilly hit the rather flimsy cooling flange. On another board we glued a nut to the top of the BGA and hanged 50-70 kg of it and while the board was clearly bent the BGA was still firmly hooked to it. Now that's the difference between a few um of gold too much or not. There are other cases where the gold-plating is not an issue. This has been covered in public sources, so a dig around would give some indication. Cheers, Magnus _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
