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From [log in to unmask] Wed Jan 15 15: |
03:25 1997 |
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Good Morning TechNet!
Isn't the trend of shrinking component pitch sizes wonderful!! I have
tinned .5mm pitch components successfully but the trend for bridging
definitely increases. One solution that helps is to either create a
nitrogen blanket around your solder pot or to just have a stream of
nitrogen running across your solder pot. The nitrogen helps change the
surface tension in your favor. You also will use quite a bit of
nitrogen! One other thing you could try is to deposit solder paste on
a non-reflowable surface (PTFE or ceramic) matching your component's
footprint and run that through a reflow oven. Good Luck.
Dave Hillman
Rockwell Collins
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: ASSY : pretinning of fine-pitch devices
Author: [log in to unmask] at ccmgw1
Date: 1/14/97 6:59 PM
In the near future I have to start with pretinning of molded ring
carriers with a 0.5 mm leadpitch (CQFP256 and a 64 pin Dual Flatpack) ?
For 0.65 mm pitch devices we do it without any solder bridging, but I'm
afraid that the 0.5 mm pitch makes it a bit more critical.
We use a simple tinpot with a component holder and a lever to enable
steady vertical speed and a controlled dipping depth. Dross is skimmed
off manually after each component. Flux is RMA.
Since production volumes are relatively small we cannot afford to lose
many of these (expensive) components for process development. There is
very limited time between receiving the components and starting with
board-assembly, and I don't think I have dummies available by the time
the production starts. All this means that the pretinning just has to
work, without much process adjustments or equipment changes.
Should I be worried about this ? Does anyone have experience with
pretinning of 0.5 mm pitch devices ?
All comments and technical advices are wellcome.
--- Daan Terstegge ---
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