One big problem we have is that the parts are not hermetic. In fact we are
looking at a alternate part because of this. I am going to look into the
mechanism of oxidation.

Thanks for all of the ideas so far.

John


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bev Christian
Sent: Friday, October 17, 2003 11:42 AM
To: [log in to unmask]
Subject: Re: [TN] Question about wetting


John,
Are they non-solderable because the tin has oxidized, the tin has been
consumed as tin/nickel intermetallic that has then oxidized or the tin was
so porous the nickel has oxidized?  Also are the parts hermetic?  If they
are hermetic and you are sure they are just surface tin oxidized, throw them
in some dilute EDTA, wash with DI water, IPA and then retape.  If it
anything else you would have to use acid to dissolve off whatever layers are
there and then immediately re-tin.

Then there is an electrochemical way to strip off the bad layers called
ROSA.  But this assumes they are either hermetic or can be fixtured to just
immerse the leads.   I wouldn't want that job!   And Dave Hillman's ROSA
unit is not up and running at this time.  EMPF's??

regards,
Bev Christian
Research in Motion

-----Original Message-----
From: John Foster [mailto:[log in to unmask]]
Sent: October 17, 2003 2:14 PM
To: [log in to unmask]
Subject: [TN] Question about wetting


I have a  large inventory of trim capacitors that have exceeded the
manufacturers shelf
life by 2 years. Solderability testing has revealed inadequate wetting. The
parts are on
tape and reel. The plating is a thin layer of tin over nickel. We believe we
have a oxidation problem. Does anyone have any ideas AT ALL on how we can
recover these
parts. The part has gone obsolete I have 86,000 of these things that I
really really need to use.

Any help would be appreciated

Thanks
John Foster

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