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March 2002

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Subject:
From:
Michael Bell <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 18 Mar 2002 10:04:04 +1200
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Hi all,

I have stumbled across a problem with heat dissapation on an RF type PCA.
Our customer has designed the PCB with 0.3mm via's underneath various
components, (power transistors), and now this is causing a thermal
dissapation problem.  The part manufacturer had the following suggestions...


"Manufacturing suggestions,
To properly use the parts in a manufacturing environment, it is recommended
that an additional reflow process is used to ensure solder has filled the
thermal vias beneath the part.

The steps are as follows:
1. Apply solder paste to area containing thermal vias.
2. Reflow the board and the solder paste will wick through the via holes.
3. Cover the backside of the board beneath the power amplifier with Kapton
tape and reflow the part to the board. The solder will remain in the via
holes and the power amplifier will be properly connected to the
thermal/ground pad below it."

Is anyone performing such a process???  What implications and problems does
anyone have with trying to gasket the stencil over these filled via's???
What other issues are there?

Cheers

Mike

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