Aluminum and silica contamination

Hi All,

I'm hoping there is a PCB expert or two hanging around. We're having some solderability issue on our boards. The finish is ENIG but it doesn't seem to be related to the finish process itself. We did SEM and EDX analysis and found aluminum and silica on the pads. Does anyone know where these contaminates could have come from in the PCB manufacturing process.

These contaminates are on bare boards direct from our supplier. The contaminates are not in high enough quantity to be visible under a 40x scope.

Thanks

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