Dwayne:
     Switching to gold will help with your fine pitch placement.  Vision is
     much better for pick & place.  Some things to consider if you have any
     mixed technology.  Retrain your operators to recognize what a good
     solder joint looks like with immersion gold.  This was probably one of
     our biggest issues.  Operators in our MIL environment were used to
     HASL and didn't understand what a good solder joint on gold was
     suppose to look like.  If the pad was not completely covered with
     solder it was rejected.  If the fillet is good, but does not cover the
     whole pad, is not grounds for rejection.  The other thing to consider
     is material handling.  Finger prints will not help (obvious).

     With solder paste the gold will desolve into the solder joint for each
     solder connection so it would be good to watch for gold embrittlement.
     You may need to specify your gold thickness.

     Hope this helps a little.

     Ron H.
     [log in to unmask]

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