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November 2010

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Subject:
From:
Bob Landman <[log in to unmask]>
Reply To:
Bob Landman <[log in to unmask]>
Date:
Thu, 18 Nov 2010 12:14:47 -0500
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text/plain (105 lines)
Michelle,

Its a thick layer of lead oxide that's the problem assuming the parts are tin-lead plated. Its a very tenacious film that fluxes will not remove.

Re-plating won't work unless you get rid of the oxide film first.  Before you try to re-plate (you'd use an elecroless nickel process), try a dip in 10% sulfuric or nitric acid to dissolve the oxide then wash in H20 then dry.

Then you'll have a clean base metal so that a good flux will permit soldering the parts.

We might be able to process the parts for you. Let me know if we can help.

Bob Landman
LDF Coatings, LLC
www.ldfcoatings.com

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, November 18, 2010 11:16 AM
To: [log in to unmask]
Subject: Re: [TN] Old obsolete parts failing test

Michelle,
there are ways, some of which have to be performed when all have gone home.
All depends on what components you point at.

If  it is a bad nickel you can test ultrasonic solder dip, use to fix most problems without causing damage to the parts.
If it is a bad nickel/exposed copper I recommend use of RA soldering.
If it is a bad nickel/exposed Kovar you can normally get a acceptable soldering by dipping the leads in Zinc Chloride one minute or two.

The last one deseves a warning, because you need a real good cleaning afterwards. Furthermore, the component can be damaged. And your QA will kill you.

Finally, you can strip the leads and dip the leads in chemical nickel/chemical gold baths. Expensive and time consuming,but if you have to do with extremly expensive components or obsolete parts, it can be a way to solve the problem.

You need a old chemo dog with stick and thick glasses to do the last one.

Inge


----- Original Message -----
From: "Michelle Masaitis" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, November 18, 2010 4:41 PM
Subject: [TN] Old obsolete parts failing test


Does anyone have any recommendations on parts that are more than 5 years
old for getting them to solder.  You can see that parts reflow around the 
lead,
but when you take the part off of the pads there is no solder on the bottom
of the lead.  These parts fail test, but then we add stronger flux and use 
hot
air to re reflow and the part passes.  The leads are not bent, they are 
flush to
the board.  We changed solder paste, which did help some, but not
completely.  I would like to use the parts without having to send them out 
to
get the leads tinned before placement.  These parts are obsolete so they are
hard to find parts.  Any recommendations?  Thanks for your input.

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