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May 1998

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Subject:
From:
JON MOORE <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 18 May 1998 15:31:39 -0400
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Are these caps on the topside or bottom side going through the wave?

>>> "Kane, Joseph" <[log in to unmask]> 05/14/98 10:33am >>>
We are experiencing failures of .25% film capacitors, presumably from
heat
damage during wave solder.  Top side preheat temperatures measured
210F,
within the process range we like.  Tried cooling it down to 163F topside,
got more solder defects, and some caps still going out of tolerance.  We
suspect that parts can't take thermal transfer during transit through the
wave, where topside gets about 100F warmer (of course part bodies see
less).
Manufacturer says no, it's our preheat, still too high at 163F, even though
they claim that the film can withstand 284F in the preheat zone.  Boards
are
at least 10 layers with planes, and soldering cooler than 163 will mean lots
of defects, especially where the RMA doesn't dry out or activate properly.
Speeding up the conveyor results in lots of top side insufficients.  Hand
soldering works, but is expensive.  Can't live with these parts, can't flush
them.  Should we consider cooler preheat, or are there other wave solder
tricks we can try?

Joe Kane
Lockheed Martin Control Systems

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