Hi Mike:
        It seems that the copper is separating from the NiFe and
oxidizing or a lot of intermetalics are forming at the interface of the
different metals and the joint becomes brittle.  As far as alternatives,
I have seen, power resistors terminations made out of NiFe and coated
with Eutectic solder.  This product has had no returns.
        Regards,
        Ramon
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Michael McMonagle
Sent: Wednesday, March 08, 2006 10:32 AM
To: [log in to unmask]
Subject: [TN] Glass Seal Pin & Finish Materials - Suggestions?

We are looking for experiences on the best base materials and finishes
for feedthrough pins on glass hermetic seals. We use some small single
feedthroughs in an industrial sensor that sees a variety of shock,
vibration and abuse during its expected 3-5 year lifespan. The current
pin is Alloy 52
(NiFe) with a finish of 50uin of Cu topped off with 100-300uin of Sn/Pb.
The pins are staked into the metal case that houses the sensor, which is
then soldered into a small PCBA that is used for interconnecting the
sensor to input/output wires. We occasionally see field failures between
the PCBA soldered to the pin. Though the joint visually exhibits good
wetting and fillet, the joint loses physical adhesion at the solder/pin
interface and becomes open or intermittent. Are there better
alternatives for base pin materials and finishes that could provide a
more robust assembly? TIA for all inputs and insights..

Mike

 


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