Fellow Technetters:

I had been measuring solder thickness on QFPs and found out that the
thickness on horizontal pads is slightly thicker than the vertical pads. I
know this is normal specially for a Vertical Hot Air solder leveler. But
what should be the limit? Also along with test, using an x-ray coating
thickness measuring machine, is it normal that the tin % composition on the
vertical pads lower than horizontal pads? I tried lowering the air knife
pressure thinking that high temperature depletes Sn, but I got similar data
on 200, 210, 220, 230 and 240 C air knife spray pressure.


Garret Dimaculangan

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