I am recently bump into a problem where we found a certain percentage fallout of the open via. This is my very first time seeing this kind of problem and don't really have an idea why. It comes back from failure analysis with some images as posted. The first image looks like a corrosions on the copper plating while second image, the copper is totally open. I am checking the via plating thickness and it is within the spec. Some are saying it is caused by the copper plating during PCB fabrication but anyone please advice and explain what could be possibly causing all these issues? Supplier is blaming on the flux we are using.
Thanks in advance!