Re: Utility of copper pours on four-layer boards

Jim Thompson wrote:
On Wed, 09 Apr 2008 12:33:46 +1200, Terry Given <my_name@xxxxxxxx>
wrote:


Joerg wrote:

[snip]

And something has to protect the copper or it'll look like the roof of a Gothic cathedral some day ;-)


i think it was HFPC '96 where there was a great paper on PCBs as heatsinks. ISTR there was almost no difference with or without solder mask.

by the time one tosses in a few gazillion thermal vias, I suspect the effect of solder mask drops into the noise floor.

and yeah, the dT cant be too high. This latest PCB I have I am pouring the heat into an enclosure via the PCB. Which is why the really hot part is astonishingly close to a corner.

and I'm swapping watts for dollars with nice FETs - DirectFETs are pretty darned good; stray L is so low on this design I dont need any of my snubbers, so next rev I'll toss 'em and replace with a pour :)

Cheers
Terry


About 30 years ago I did an off-line switcher (using MJE13000-series
bipolars) for GenRad's PSP portable tester. Because of some exquisite
snubbing (by yours truly :-) it ran so cool I didn't need any heat
sinks on the flags. So cool, in fact, that I _once_ grabbed a flag to
see how "cool" it was... unfortunately it was "hot" with 400V P-P...
producing great uproarious laughter amongst the technicians ;-)

...Jim Thompson

LOL! Would you believe I am designing a proportional base drive circuit for an MJE13003..... 70's here I come. Except I'll use Si not Fe (Mn, Zn etc)

Cheers
Terry
.

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