Hello all,
A customer has 1.0mm BGA SMD lands with gummy mask and ~0.4% solderability skips when edge dip tested.
By skip, I mean all surrounding lands solder beautifully, while the subject land takes no solder at all.
By gummy, I mean that pushing with hypodermic needle yields piled-up mask, not chipping mask.  Away from the SMD area, we get chipping mask.

Finish is ENIG, mask is BLUE.

I'm looking for comments on root cause, and maybe how to cost effectively collect more evidence.

We've got bitten by the uncertainty of FTIR testing before.  Differential solubility in mask stripper?

Thanks a million,
Chris

Chris Mahanna
Robisan Laboratory Inc.
317-353-6249


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