David,
Now that you have your connector handbook open could I ask if you would
check to see if there is any information about the use of silver and tin
as matting surfaces. I have a toggle switch that has a yellow brass
movable contact with a silver button that contacts a tin plated copper
button on the stationary side of the contact. Historically we avoid the
use of gold and tin as matting surface because of the galvanic potential
between the two materials and the possibility of fretting corrosion but
I don't remember seeing any information concerning silver and tin
Regards,
George
George M. Wenger, Andrew Corporation
Reliability / FMA Engineer
Base Station & Subsystems Group
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Wednesday, March 02, 2005 7:03 PM
To: [log in to unmask]
Subject: Re: [TN] Microcircuit Palladium Lead Finish (Good or Bad)?
Hi folks! Wow, what a way to named - "the guy who cuts up his water
pipes"! Well, its better than Doug's "It depends"! I do have some
information that might be helpful - the following info is taken from
Volume
4 Materials of the Connectors and Interconnections Handbook published by
the Electronic Connector Study Group Inc. (sorry, no ISBN available)
which
is a really good resource on connector materials.
- Pd wears better than Au for an equal plating thickness and can provide
an
adequate end of life contact
- Pd is somewhat less galvanically active toward copper and nickel than
corresponding deposits of either Au or rhodium
- 60Pd40Ag is recognized as a good contact material for industrial and
telecommunications applications
- Pd can tarnish due to sulfur contributing sources
- Pd can form frictional polymer in sliding contact applications that
are
exposed to organic vapors. The frictional polymer can increase contact
resistance.
I would recommend that you talk to the folks at Tyco or the J.M. Ney
Company - a Pd finish is being used widely in electronics applications
and
you just need to confirm that your application/use environment is
appropriate. Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
Charles Caswell
<CharlesC@FESCORP
.COM>
To
Sent by: TechNet [log in to unmask]
<[log in to unmask]>
cc
Subject
02/28/2005 06:33 Re: [TN] Microcircuit Palladium
AM Lead Finish (Good or Bad)?
Please respond to
TechNet E-Mail
Forum
<[log in to unmask]>
; Please respond
to
Charles Caswell
<CharlesC@FESCORP
.COM>
I don't have the spec available but I would think that Palladium finish
in
a
gold socket would be fine. I would not want to solder directly to
Palladium
however. Maybe Dave ( the guy who cuts up water pipes from his house! )
could
give us some insight.
-----Original Message-----
From: - Bogert [mailto:[log in to unmask]]
Sent: Friday, 25 February 2005 5:06 PM
To: [log in to unmask]
Subject: [TN] Microcircuit Palladium Lead Finish (Good or Bad)?
February 25, 2005
MIL-PRF-38535 microcircuit specification is confusing since in one
section
it
identifies that to select a lead finish, include a suffix letter as part
of
the part number. The available suffix letters are Finish "A", "B",
"C":,
"D"
and "X". "D" is for Palladium. "X" means either "A", "B", or "C"
Finish
However, Appendix A of the specification indicates that only lead
Finishes
"A" through "C" (or "X") are allowed.
It appears that Finish "D", Palladium finished microcircuit leads are
not
allowed. Is this true? If so, why the apparent prohibition on
Palladium
lead finish?
The question relates to selecting the lead finish for a microcircuit
that
is
mounted in a socket having Gold-plated socket contacts. Normally, one
should
specify a Gold-plated microcircuit lead (Finish "C") to mate with the
Gold-plated socket contact. However, from a galvanic corrosion
standpoint,
either Gold or Palladium should be ok.
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