TechNetters,
        I've been following the discussion of HASL vs. Fused Solder and the
problems regarding shelf life, wetting, etc. This makes me wonder what the
preferred finish is from the perspective of those who have to assemble the
CCAs to J-STD-001B, level II and level III.
        I'm almost left with the impression that Fused Solder provides a
more solderable finish, while I thought that HASL was the preferred finish
because of its high coplanarity, improving the ability to achieve high
quality solder joints on SMT or mixed through-hole/SMT assemblies.
        I realize that the quality of the bare PWB is most important as
first step. I'm sure anyone would prefer a high quality Fused Solder board
over a low quality HASL and vice-versa. But assuming that a PWB manufacturer
is capable of producing both types to a high level of quality, which finish
is preferred - in terms of shelf life and solderabilty?

 Michael Hiteshew
 Lockheed Martin Launching Systems
 [log in to unmask]
 (410) 682-1259

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