Jack,
It's nice to have a report on the proceedings.
I posted the question on gold for BGA as presently I'm considering a trial
to deal with a specific situation. (If fellow technetters knew the details
they would all say "you can't do that"!)
Anyway, I live by HASL as a finish, all our boards are specified as this. I
have investigated and used alternative finishes but "NOTHING SOLDERS TO
SOLDER LIKE...........SOLDER." It's naturally the best solution. We build
the most complex assemblies including large QFPs and large SM connectors at
20 thou (mil) pitch. HASL is perfectly adequate for 20 thou (mil). The only
complaint that can be laid against HASL is the dome effect. I have spent
alot of time designing pad geometries, stencil apertures for them and then
monitoring the results.
We have NO PROBLEMS at 20 thou (mil) using HASL.
I would gladly argue with any one pushing alternative finishes. (I'm an
argumentative guy anyway!).
Electroless Ni and Immersion Gold have had a dodgy history right down the line.
Palladium is one of the most unsolderable metals around.
Organic Protectives leave alot to be desired in terms of handling and storage.
Alpha Level, or any of the Silver protective/finishes which preceeded it
have presented fabricators with processing nightmares. It was to be the
saviour of soldering, but never delivered.
In the past I have been impressed by a particular immersion tin process
though, but the fab house failed to deliver in many other areas.
I have never used 18 - 16 thou (mil) devices, if the situation arose, I
would still go with HASL. It's perfectly possible.
I'm dissapointed to hear that a HASL bashing session has taken place at this
conferrence. There's simply nothing better!
See ya!

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