Dear Gita

-Due to the high coplanarity of the solderballs of BGAs and the variing
thickness of HAL surfaces theoretically OSP should be better. However, I
made several tests with BGAs on HAL pads and didn't face any problems so
far in this respect.

- I recomment NoClean flux. Tests, where we measured the surface resistance
underneath  QFP packages, suggest that flux residues are washed underneath
the component and trapped there. I belive that this effect is even worse
with QFPs. This trapping is disastreous with water soluble fluxes since
their residues are highly corrosive.

Best regards

Guenter Grossmann
Federal Institute of Technology
Reliability Lab.
Zuerich, Switzerland