Our HASL solder thickness spec. is 0.3 to 1.5 mils.  Is it unreasonable 
to expect using a horizontal HASL process that 1.5 mils will be the actual 
max. on 100% of the pads on both sides of the board, even with fine pitch (< 
= 20 mils)?
    My guess is that the surface tension of the molten solder on the fine 
pitch pads, its low mass and the surrounding geography, make it difficult 
for the air knives to do consistant leveling.
    Some of our product mix here is Mil Spec work.  Converting the boards 
with fine pitch on both sides to Au/Ni may be more pain than it is worth.
    Any inputs on this subject will be greatly appreciated.

Norm Dill
MQC Specialist
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(716) 242-4210