Hi Steve, as I understand it there are two basic finishes on passives:
1) Normal thickfilm type metallisation
2 Normal thickfilm type metallisation with nickel overcoat.
Normal thickfilm (Pd/Ag Pt/Ag) tends to dissolve in Sn60 Sn63 type solders.
These are for use in hybrid thick film apps with Ag epoxy, or they can be
soldered with Sn62.
For use with non silver loaded solders - the majority of SMT paste and wave
solder users - a nickel barrier is applied. This protects the underlying
metallisation.
The assertion that if the devices have wetted they will be OK, would seem to
be valid therefore if you have Sn62. Anything else needs to be verified.
If it is not possible to remove and replace the components with known good
devices, I think I would at least be doing torque or shear testing to try
and quantify what I got and then make a more informed decision. As you know
you can set up these testers to either test to destruction or to minimum
value.
Regards
Mike Fenner
Applications Engineer, European Operations
Indium Corporation
T: + 44 1908 580 400
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Steve Gregory
Sent: Tuesday, August 05, 2003 2:43 AM
To: [log in to unmask]
Subject: Re: [TN] commercial resistors and capacitors in high-rel mil appl
ications
Hi All,
Mike Weekes thread kinda' ties into my thread last week about dewetting
capacitors...
I got my corrective action report from the manufacturer, and they
acknowleged that there was insufficient nickel barrier plating. Their
minimum nickel thickness is called out to be a minimum of 50-micro-inches,
some of the caps that I sent them from the reel, measured down around
6-micro-inches. They have an explanation of how this could have happened,
and what they have done to prevent this from occuring in the future, but I'm
still wondering about reliabilty...
I was told over the phone that if they wet with solder, they would be
fine...but I don't have anything documented from them that states that...
How important is the barrier plating on capacitor terminations to
reliabilty? Should I ask them to document that there will be no reliabilty
concerns with the capacitors that came from this lot that have shown
visually good solder wetting?
Still don't have a "warm and fuzzy" about all this...
-Steve Gregory-
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