yep, looks like ENIG is lifting over some of the filled vias.

At 09:23 AM 7/29/2014, Steve Herring wrote:
>It looks to me like their Screen Printer is doing a poor job of 
>under stencil wiping, leaving solder paste on the underside of the 
>stencil that gets transferred to the gold areas on the edge of the pcb.
>During reflow, the small balls of paste flow into nice circles.
>Not all stencil wiping paper is created equal.
>
>Steven E. Herring
>Engineering Manager
>Pennatronics
>75 Technology Drive
>California, Pa 15419-0638
>P 724-938-1800 x 214
>F 724-938-1809
>[log in to unmask]
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of John Foster
>Sent: Tuesday, July 29, 2014 12:13 PM
>To: [log in to unmask]
>Subject: [TN] Trying to figure out possible mechanism for contamination
>
>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
>L3 Communicatons
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