At first glance it appears that pores in the gold are exposing the underling 
nickel/copper to a constituent of the tape (or contaminant) released at 
temperature.


On 7/29/2014 12:12 PM, John Foster wrote:
> We have been seeing a problem recently on several different CCA'S that we are having assembled.
> The boards are ENIG with plug and plate.  The assembly shop is assuring us that these gold areas are being
> Protected during the entire assembly process with kapton tape.
> I was thinking it was flux splatter since the areas are always almost perfectly circular.
> The locations are very random and range from nothing to what is in the picture.
> Is there any other mechanism that might be causing this? On our next run I am going to go to the shop
> To witness the taping. But I was curious if maybe it's some other cause.
> Mr. Gregory was kind enough to post a picture.
> http://stevezeva.homestead.com/spots.jpg
>
> Any thoughts would be appreciated
> Thank You
> John Foster
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