Hi Bev! You need to be careful with the Pd thickness. When soldering to
thick Pd plating layers you can potentially have problems with "Pd
embrittlement" of the solder joint. Pd and Sn for an intermetallic phase
(PdSn4) which behaves in the same fashion as the AuSn4 intermetallic phase
for gold embrittlement of solder joints. There are two industry reference I
know of off the top of my head - the NCMS Surface Finishes Study and a
Collins paper published at the 1996 SMI conference. If you keep the Pd
thickness between 9-15 microinches you should be able avoid the PdSn4 phase
with a controlled soldering processes. Also note that Pd has a very slow
diffusion rate so you may have to adjust your soldering process times. Good
Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]



                      Bev Christian
                      <[log in to unmask]        To:       [log in to unmask]
                      ET>                      cc:
                      Sent by: TechNet         Subject:  [TN] Thick Palladium on Leads
                      <TechNet@listserv
                      .ipc.org>


                      07/31/2003 12:28
                      PM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to Bev
                      Christian






Technetters,
I have searched the archives and all I have been able to find is one
informative e-mail from Phil Hinton from August 22, 1998.  Has anyone every
run across palladium as a thick undercoat?  if so, what, if any, grief did
it cost you?

regards,
Bev Christian
Research in Motion

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