Just to elaborate on this and other answers.
There are two types of ceramic component, nickel barrier and plain.
As Dave said the original components (plain) originated in the hybrid
thick film industry and were attached with Ag epoxy.
If these are soldered then the Pd/Ag will be leached off. This can be
slowed by the use of Sn62 instead of Sn63.
Solder processable, or SMT parts have a nickel barrier over the Pd/Ag
this prevents the leaching, the nickel itself is protected by Sn (/Pb)
coating. These can therefore be soldered with any alloy.
Solder joints made to Pd/Ag, also Sn62 joints under certain
circumstances, have a mat/frosted or even rough appearance. This
tendency can be reduced by (singly or in combination): reducing time
over liquidus, peak over liquidus, increasing ramp down rate after peak.
Regards
Mike Fenner
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
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Pb-free: www.Pb-Free.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Hillman
Sent: Wednesday, January 14, 2004 11:05 PM
To: [log in to unmask]
Subject: Re: [TN] Silver Palladium Termination
Hi Jim! I would be very suspect of any Ag/Pd terminations. The Ag/Pd
metallization does not "age" gracefully over time as both temperature
and humidity cause either sulfidation or oxidation issues. Additionally,
Ag/Pd terminations tend to diffuse very quickly into molten solder such
that depending on your solder process time/temperatures, you can be left
with a mechanical solder-to-component body joint which is not the
metallurgical joint you intended to create. Chapter 3.3.1 of the AWS
Soldering Handbook (ISBN 0-87171-618-6) has some good information. It is
my understanding that the Ag/Pd termination was originally developed for
use with conductive adhesives thus avoiding any diffusion/dissolution
issues. Apparently someone thought soldering to it was a good idea but
never checked with a materials engineer. Unfortunately the Ag/Pd
metallizations are making a "re-appearance" due to the Pbfree
activities. Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
"West, Jim"
<[log in to unmask] To: [log in to unmask]
M> cc:
Sent by: TechNet Subject: [TN] Silver
Palladium Termination
<[log in to unmask]>
01/14/2004 03:12
PM
Please respond to
"TechNet E-Mail
Forum."; Please
respond to "West,
Jim"
Hi,
Is there a different process required to solder to a silver palladium
termination? We have ran these through our normal process and noticed
that the parts with they type of termination do not look very good.
Within the same reel, we have noticed some of parts look like they have
some type of oxide build up because they have a dark gray appearance,
while the others have the silver appearance. Is this normal for this
type of termination? Should we treat these different within our process?
Thanks,
Jim
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