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Date: | Wed, 26 Jul 95 09:21:52 EDT |
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Eric,
Several things effect solder bridging for SOIC's mounted on the wave solder
side. Unfortunately, most are design related and if you can't change the
design, then you are restricted as to what you can do.
1. Orientation
Orient the parts (board) so the wave crest is perpendicular to the
to the long axis of the SOIC body.
2 Land Pattern
Add two dummy lands (pads) to trailing edge of the part; essentially use
a 16 pin pattern for a 14 lead part
Use soldermask between leads with no clearance; the soldermask pad is the
same size as the copper pad
Make the land as small as possible, 0.010-0.015" at each end of the
lead and 0.002" on each side of the pad; if you can't do an artwork spin,
change the soldermask to make the exposed solder surface of the land smaller
3. Shadowing
Make sure that the wave isn't shadowed by adjacent parts; keep parts at
least 0.100" from the SOIC body
Provide a clearance of at least 0.050" to adjacent pads of other components
4. Process
Use a dual wave or hot air leveling wave process; if you can't do this,
perhaps you could try a double pass, but I not sure that this will help
unless you readjust the wave between passes, the first pass being a "rough"
wave running deep and the second pass a "smooth" wave very shallow; this
approximates a dual wave machine.
Harry Parkinson
603-884-6760
From: US2RMC::"[log in to unmask]" "MAIL-11 Daemon" 25-JUL-1995 17:25:33.31
To: [log in to unmask]
CC:
Subj: Solder Bridges on SMT SOIC's
We have a big problem with Solder Bridging on our Bottom Side SMT
components in Wave Solder. These are Glued on at SMT then Waved in
Wave Solder. We have tried everything under the Sun and have
eliminated most of the Bridges but not all. Any suggestions.
ERic Bernal at Pragmatech, Sunnyvale, Ca
(408)734-0595
[log in to unmask]
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