Good day,
Having recieved new batch of PCBs with OSP surface finish, I have noticed that some polygons not covered by solder mask and solder paste become darker after second reflow cycle compared to PCBs not being sent to reflow.
I wonder whether it is acceptable by IPC? What could be the reason of such color change?
Any input is appreciated. Thank you in advance.
Best Regards, Pavel Murtishev
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