Gold thick film dissolves readily in [high] tin solder. This would not be a
high reliability process. 
I suppose a no or low tin lead-free solder is not under consideration for
low MP.

The rest of your question is really one for plating/component guy.
My 1/2 cent:
Plated copper to 400µ"  [10 µm] thick probably OK, possibly not - depends a
little on the quality/type of the plating, in any case not sure if/how this
could be done.
My mantra when presented with difficult, wood, unknown or otherwise
impossible surfaces to solder is always: when in doubt apply electroless
nickel. This makes it into an industry standard finish and as such one for
which standard fluxes and solders are available, have known behaviours and
process parameters are understood. Nickel is a standard finish for most
component manufacturers, or is at least easily accessible as eletroless.
Here this would be 4-6µm, then protect with immersion gold [silver if you
prefer]. 


Regards 
 
Mike Fenner 
Bonding Services & Products
M: +44 [0] 7810 526 317 
T: +44 [0] 1865 522 663
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Julie Silk
Sent: Tuesday, November 27, 2012 5:54 PM
To: [log in to unmask]
Subject: [TN] Termination finishes, Cu thickness under Ag, Au-Pt-Pd

I have 2 questions about termination finishes on an SMT ceramic component
with castellated joints.  
One is regarding a Au-Pt-Pd fired thickfilm which was claimed to be suitable
for soldering.  Does anyone have experience with this finish?  It seems like
a epoxy-bonding sort of finish, and we think we're getting leaching of the
metals into the solder joint -- with no remaining connection to the
component. 
Two is regarding an alternative that plates copper over the Au-Pt that is on
the ceramic, then Ag over the copper.  Is 200-400 microinches of copper
sufficient in this application?  With SAC solder, there is concern with
copper dissolution, but with an SMT process, that should be minimal.  This
thickness is below the minimum spec for copper thickness on a PCB after
soldering.  But this is a component.  Any input/thoughts on this?


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