Trevor,

Check out the URL below.  The problem in this case study is too rapid a
cure, or a partial cure of the SMA.

http://www.residues.com/pdf/Cases30.PDF

Steve Mikell
Solectron Charlotte

-----Original Message-----
From: Trevor Goddard [mailto:[log in to unmask]]
Sent: Wednesday, November 01, 2000 12:08 PM
To: [log in to unmask]
Subject: [TN] solder under chip components


 Has anyone ever seen solder shorts under an smt resistor that has been
glued on a board and then wave soldered?
 The boards go through the standard surface mount process of screen printing
the glue, placement of components and curing the glue. Then the boards
receive solder reflow for the top side of the board, on to hand assembly and
then wave solder. During all in process inspection even after wave solder,
the boards look good. When the boards get to test it is a different story.
Randomly across the bottom side of the board, the side that was wave
soldered, we will get short conditions on various caps and resistors. If you
look at the component nothing appears to be wrong, but when the component is
removed you can see solder on the under side of the component and on the
pcb.
 This problem has just cropped up, so I find it a complete mystery.

Thanks in advance.


Trevor Goddard,
SMT Supervisor
XLTEK
(905) 829-5300 x 348
[log in to unmask] <mailto:[log in to unmask]>

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