SVEBA wrote:
> 
> Hi friends,
> In order to  make high produceability in the soldering process of boards,
> it is necessary to prepare the gold plated components before assembly. This is
> stated in ANSI/J-STD-001, which does not allow any gold at all on the component legs.
> 
> Is it, anyway, possible to specify a limit of gold thickness on the comp. connections, below which
> it is not necessary to extract the gold before soldering? Does anyone have a opinion
> about that?
> 
> Sven-Eric Backstrom
> Ericsson Saab Avionics
> Sweden
> 
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YES, this subject has come before. Gold in solder joint is a reliability
concern. It depends upon the amount of gold in the joint. Some say 2 %
by weight is ok while some say upto 3 % by weight is OK. 

Gold continues to react with solder (Sn) to form intermetallics even at
room temperature. So the trick is to see that all gold is uniformly
dissolved in the joint. My recommendation is to stay with 2% by weight
of gold in the joint. You can calculate what that will translate to in
terms of gold thickness. My experience is that up to 30 microinches of
gold thickness can be tolerated on leads of PIH components if you are
wave soldering on a dual wave machine. No data on SMT joints.

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