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Date:	Mon, 14 Sep 2015 13:04:10 -0700
From:	Larry Doolittle <ldoolitt AT recycle DOT lbl DOT gov>
To:	"Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject:	Re: [geda-user] 5630 LED footprint
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Nicklas -

On Mon, Sep 14, 2015 at 09:35:41PM +0200, Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> >   * From experience, I think polymer insulates much more than metal
> > So If the above is true I think the polymer would squash the dominant form
> > of dissipation and bare metal is better.
> Yes but layer is thin and emissivity is different.

Run the numbers and I think you'll find otherwise.

Cooling by radiation scales as the fourth power of
temperature, or really T_object^4 - T_environment^4.
It's hugely important above 1000 Kelvin, not so much
when you're talking about a 320 Kelvin object and a
290 Kelvin environment.

Heat carried away by moving air (convection) is all that matters
for electronics.  Unless you can get the cooling you need through
direct contact of aluminum, since the conductivity of aluminum
is 9000 x greater than that of still air.

  - Larry

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