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Time to move to 4 layer board

Up to now I have stuck to 2 layer boards.

I've been working on a sepic converter, 10-32V in 4-18V, 0-1A out for a while. I have had problems resolving the conflict of needing a large open design so that I have enough copper for heatsinking fets and diodes and a compact design so as to keep high frequency loops small for good EMC.

On the latest prototype I've got enough vias and bottom side copper connected to the drain of the switching fet to keep it cool but this has taken a chunk out of the ground plane.

So I plan to go to 4 layer on the next version. Top for components, top and bottom for signal tracks and copper areas for heatsinking, a middle layer for ground plane and the other middle layer for power,

24V and 5V supplies.

My question is what is good practice for a grid of thermal vias to get maximum heat transfer from top to bottom layer without compromising the internal ground plane?

Reply to
Raveninghorde
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Going multilayer will change your life. Signal integrity is radically improved.

You can sneak a few traces onto that third layer, the nominal power pour plane. That can help a lot on 4-layer boards.

We flood over all plane connections, namely don't use thermals. That's best electrically and thermally. Thermals don't make sense these days, if they ever did. Reflow ovens and Metcal irons solder non-thermal boards just fine.

Vias won't compromise the ground plane, as long as they don't slice it apart. We do critical-signal, picosecond-speed boards that have thousands of vias.

John

Reply to
John Larkin

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