Hi Everyone
We received some PCBs where the finish surface was good, but after we ran reflow about ten days, the ground plane with immersion silver coating that were not covered by solder paste look to be stained on surface. 
We known the chemical silver [Immersion Silver finish] surface is very sensitive to surrounding condition, it is easy to stain from oxygen/water vapour or production time exposure in the air.
We are looking for document on staining metal of the finished board. Has anyone else experienced something similar phenomenon or anyone have an idea to solve this?
Thanks
Tuyen Tran.

______________________________________________________________________
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] 
______________________________________________________________________