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September 2004

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Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 10 Sep 2004 11:48:36 -0500
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Hi Gaby! Do you know what the component lead surface finish is (what
type/kind of plating)? Some plating types - like bright acid tin plating -
could be the source of the solderballs.  And yes, the 002B surface mount
simulation test would be helpful in determining root cause.

Dave Hillman
Rockwell Collins
[log in to unmask]



                      Gabriela Bogdan
                      <gabriela@NETVISI        To:       [log in to unmask]
                      ON.NET.IL>               cc:
                      Sent by: TechNet         Subject:  [TN] Tin plating on leads HELP!!!
                      <[log in to unmask]>


                      09/10/2004 11:24
                      AM
                      Please respond to
                      TechNet E-Mail
                      Forum; Please
                      respond to
                      Gabriela Bogdan






Dear friends,
After assembly, on all circuits there was one fine pitch PLCC from a
certain vendor which had lots of small solder balls between the leads, even
on the solder mask dam between them.
Other PLCC's with the same pitch were clean.
We tried to see the amount of solder balls by X-ray, and found many more
behind the leads.
At first we thought that our solder paste was the culprit, but seeing that
other components were "normal" , we looked closer to the leads by X-ray,
and saw a lot of small voids only along the leads of the bad component,
these voids reaching to the upper end of the leads, where the solder paste
did  not reach. Visually, the upper part of the leads was very rough.
I suppose that the tin plating of the leads contained additives which epand
during soldering, even burst out, and "spit" the molten solder all around.
If this is the case,how could I reject such components during incoming
inspection?
Should I do a solderability test for each batch on a printed ceramic plate?
Gaby

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