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From [log in to unmask] Thu Apr 10 18: |
22:14 1997 |
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Hi Jan-
I would suggest taking a look at how/where the shield plated thru
holes are connected to the internal board planes. If those plated thru
holes are connected to several of the internal planes then you have a
heat thieving condition impacting your ability to solder. Check with
your design folks and see if there is any possibility of getting some
relief or minimization the internal plane connections. You can also
look at adding a small amount of solder paste at the shield base to
help promote solder filleting - the solder paste will reflow during
wave soldering due to the temperatures involved. Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: SMD remelt
Author: [log in to unmask] at ccmgw1
Date: 4/9/97 3:15 AM
Hi all,
We have a minor problem at wave soldering shields on 8-layer FR-4.
The problem is that we need a very long dwell time (6-8secs) to get the
solder to wet all around the shield, it's very critical because it has
to be a tight joint. This leads to a high temperature at topside of the
board at soldering, and inside the shields we have SMD-ICs which joints
reach an temperature to about 209 degC.
But then if i raise the preheating temperature and lower the dwell time,
the shields won't get this tight joint and misses corners and some
long-sides, this cost some to rework.
Some additional info: Seho wave solderer, NO-CLEAN flux, We put some
extra flux around the shield, we use a chip-wave to get better wetting.
Anyone have more ideas?
/Jan Merstrand
Wave Soldering Technician
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