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Mon, 4 Aug 2008 08:23:11 -0500 |
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Another problem with the QFN center pad is the thermal vias in the pad, and
their effect on solder distribution. We don't get a lot of feedback from
manufacturing, but we do know we were having soldering issues, even after
segmenting the stencil. They are using a 4 pad pattern, with a step down,
but were still complaining. I moved the thermal vias into the web of the
stencil (non-pasted areas), thinking maybe the vias were either drawing solder
away unevenly or outgassing and lifting the part. I don't know the effect it
had, but the complaints stopped.
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