John, I go with random gold flash plating defects and as Joyce indicated, a quick check under the SEM would tell you whether there was Sn or Ni visible in the center of the defect. That at least gives you a direction to travel towards. If plating defect, will be there on the incoming boards... Steve Creswick Sr Associate - Balanced Enterprise Solutions http://www.linkedin.com/in/stevencreswick 616 834 1883 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Foster Sent: Tuesday, July 29, 2014 6:59 PM To: [log in to unmask] Subject: Re: [TN] Trying to figure out possible mechanism for contamination Thanks for all of the responses. There are through hole plugged vias on a very Definite grid which are very visible. They are on a 2mm grid. But other than that There are no structures in this area. The spots are very random and very hit and miss some boards Clean as a whistle other boards like this. I certainly have a lot of ideas to check out now. I was also wondering about These black dots in the center of each of the spots. It just seems strange. I was thinking that was the nickel plating underneath the ENIG. This is really not my expertise so I really do appreciate all of the input John ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________