FROM: James D. Herard
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Subject: FAB: Electroless Tin



What does this customer want IN the vias (are there any?)

you'd need to tent the vias with a resist during
both E-less Sn (or SnPb) and during Ni/Au.

is SnPb ok instead of Sn?

How thick Au?

Is Immersion SnPb OK?
What is the substrate material (fr4, ptfe, polyimid?)
can the vias later be coated with soldermask or the like?

Have you thought about wave solder on the one side with a
hot air level or won't that be planar enough? (you'd need
to plug your vias then from the Au side after Au but before
Sn)

I'll review with our mfg eng's on this one.
we're doing an Immersion SnPb process today on a product,
and we have the NiAu ability, but I'm not sure of the
compatability of the resist systems needed for each of the
processes. (ie can you cover one while you do the other?
You can reach me at [log in to unmask]

Jim Herard
IBM Microelectronics
Endicott Pnl Mfg
Quality Engineering

James Herard  x77026  KBLE/014-3         Quality Engineer
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