Variability is endemic to HASL systems. The process doesn't respond very
well to statistical controls, since blowing hot air across different
feature topologies is more akin to weather systems and need to be treated
with chaos theory rather than statistics. We are a board shop and produce
lots of boards by HASL. We are happy with specs like 750 +/- 700. Suggest
that if you want flat for assembly and no variability use either immersion
gold or Entek.

At 12:42 PM 9/23/02, you wrote:
>Hello all,
>
>Have been looking for some kind of spec for HASL thickness and
>uniformity. Having problems with small to fine pitch parts where HASL is
>causing problems.
>
>Only reference I can find so far is in 2221 where it says HASL is
>checked not by mechanical thickness, but by the ability to solder per
>JSTD003.
>003 only talks about being able to solder - not about variability of
>HASL causing problems.
>
>My SMT people are giving me a hassle about the HASL......
>
>Any suggestions??
>
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