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December 1998

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Subject:
From:
David D Hillman <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 7 Dec 1998 17:56:44 -0600
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Hi Michael - I imagine that the TechNet community has had enough of this
HASL versus Fused solder debate (I think it has been lots of fun) but here
is one more item of interest that will clog up the wheels! The JSTD
solderability committees worked a DOE on the steam aging of several
different finishes including as plated but not fused solder. Many of the
committee members were highly skeptical that the finish would not be worth
a hoot after conditioning. Surprise - not only did the as plated finish
perform well but so did a gold finish that was under test! Get a copy of
the IPC-TR-465-3 "Evaluation of Steam Aging on Alternative Finishes Phase
IIA" either in CD or paper format if you want better details. The committee
findings and feelings could be summarized as:

a) Any finish, if done with good process control by a knowledgeable
fabricator, is solderable - HASL, as plated, fused, gold, etc.

b) HASL and Fused solder both have limitations, can be misapplied and can
be very unsolderable when mistreated or misfabricated

c) Your storage environment, your process and your use environment MUST be
understood from a board finish aspect. Ignore any of these three factors
and you'll have a debate on which is better in a flash.

Hope this helps.

Dave Hillman
Rockwell Collins
[log in to unmask]




"Hiteshew, Michael" <[log in to unmask]> on 12/01/98 10:19:09 AM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to "Hiteshew, Michael" <[log in to unmask]>

To:   [log in to unmask]
cc:
Subject:  [TN] HASL vs. Fused Solder For CCA Assembly




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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