Ceramic parts which are intended for soldering as opposed to gluing have a
Ni barrier for this very reason, but are otherwise the same, but when I read
this I did not see this as that sort of problem as if it were, pretinning
would make the problem worse not better. It could be you have some old and
therefore tarnished parts. You can verify this by giving them some abrasion
first, rub a few pieces on an alumina tile before soldering. Alternatively
if you don't mind writing off some devices shake up together in a bag and
they'll clean themselves. [This may give some chipped corners etc which is
why you have to write them off after doing your diagnostics]


Mike Fenner
Indium Corporation of Europe
T: + 44 1908 580 400
F: + 44 1908 580 411
M: + 44 7810 526 317
W: www.indium.com


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jean-Luc Lehmann
Sent: Wednesday, August 15, 2001 10:29 AM
To: [log in to unmask]
Subject: Re: [TN] Soldering to palladium silver


I have seen such problem on SMD component with silver-palladium terminal.
These were first intended to be used in hybrid  and assembled by conductive
glue, however we ended up using with reflow soldering and we had occurences
of "broken" terminal connection (the contact was not there anymore and the
part would eventually come loose (without its terminals).  The cause is
that the silver-palladium leach into the solder paste during the reflow
process at high temperature. The cure was to switch to tinned terminals.
If you really need to use these parts them you should try to use solder
with a small amount of silver wich will somewhat prevent leaching.

Jean-Luc Lehmann




                    "Marsico, James"
                    <James.Marsico@D        To:     [log in to unmask]
                    P.AIL.COM>              cc:
                    Sent by: TechNet        Subject:     [TN] Soldering to
palladium silver
                    <[log in to unmask]
                    >


                    13.08.01 12:56
                    Please respond
                    to "TechNet
                    E-Mail Forum.";
                    Please respond
                    to "Marsico,
                    James"





Has anyone come across any process or reliability issues when soldering
chip
capacitors with a palladium silver finish without pretinning first?  We
have
a customer who put us on stop work because they have an issue with this.
Any info will be appreciated.

Thanks in advance,

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879

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