It may not be there on the incoming boards. Quite often plating issues are exacerbated by reflow temperatures.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Tuesday, July 29, 2014 6:14 PM
To: [log in to unmask]
Subject: Re: [TN] Trying to figure out possible mechanism for contamination

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



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