On 29 August 1995, Allen Ahlert wrote:
  
     >> We are studying use of Ni-Au plated circuit boards. One concern   
     >> which arose is that some of the gold will be dissolved as the board 
     >> crosses the solder wave and gradually contaminate the pot. Is this 
     >> a valid concern?
     >> We have never had a copper contamination problem even though we     
     >> solder many copper boards. We use a dual wave solder and RMA flux.
     >> Thanks,
     >> Allen Ahlert
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  Allen,
  
      First things first, can I have your dross?..(just joshin'*GRIN* B^D)
  
  At my last company we had a customer (MIPS Computers now owned by Silicon 
  Graphics) that we assembled boards for, that used some very fast custom 
  PTH static ram that had gold-plated leads and had Ni/Au plating on the 
  PCB...the SRAM was installed about 20+ times on a board...and we ran the 
  assemblies quite regularly.
  
      We sent solder samples out once a month to be analyzed and eventually 
  did get one sample back that stated our gold concentration was out of 
  spec...(BTW, we used Alpha Analytical Labs). 
  
      But before we were informed of that, a few times that we were running 
  mostly the MIPS boards and not much else, we would get grainy solder 
  joints. As long as we were waving a good mix of MIPS and other product, 
  we wouldn't experience the problem...I imagine it was because in the 
  daily replenishing of bar solder into the solder pot, we were keeping the 
  concentration low enough to not be a problem.
  
  But that's what you'll see if the gold content gets high...grainy solder! 
   
  
       
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                      |  @@ /      Steve Gregory                          
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  ....the views expressed above are my own, not my employers...