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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