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August 2003

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Subject:
From:
"Morse, Carrie" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 21 Aug 2003 18:24:29 -0400
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text/plain (51 lines)
I have seen this, but, the root cause was not as you described.
Rather, the cause was excessive time during soak.
This excessive time in the soak zone cause the flux to burn off.
The flux burn-off then resulted in a condition which allowed the
spheres to oxidize.
This layer of oxidation then made it difficult to reach liquidus
for that new oxide, resulting in insufficiently flowed solder.

-Carrie

-----Original Message-----
From: Black, Paul [mailto:[log in to unmask]]
Sent: Thursday, August 21, 2003 3:20 PM
To: [log in to unmask]
Subject: [TN] Soft solder


Has anyone ever run into this issue with solder paste? A year ago, we had
some boards with paste that was soft after reflow, to the point that in some
cases you could move the leads that were supposedly soldered. The paste
manufacturer came in and made some changes to our oven profile, saying that
the recipe was not allowing the solder to remain in the liquidus state long
enough. We thought the problem was solved but recently had a couple of
failed boards returned by a customer and found the problem again. This is a
no-clean 63/37 paste.

Thank you,
Paul Black
Manufacturing Engineer
Kronos

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