Re: Using a PCB as a heatsink

MassiveProng a écrit :
On Fri, 16 Feb 2007 08:09:29 +1300, Terry Given <my_name@xxxxxxxx>
Gave us:

John Larkin wrote:
On Thu, 15 Feb 2007 04:33:03 -0800, MassiveProng
<MassiveProng@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:


On Thu, 15 Feb 2007 05:35:18 +0000, Eeyore
<rabbitsfriendsandrelations@xxxxxxxxxxx> Gave us:


And a solder mask adds a minute amount of thermal resistance, not
enough to worry about.
I'd have thought so myself.
A blanket is a blanket is a blanket. Period.

It's like resistors in series. A couple of mils of solder mask in
series with inches of air. And the mask material is a much better heat
conductor than air. So the mask adds a small fraction of a percent to
overall theta, not enough to matter. It probably improves radiation a
bit, more than it impedes conduction.

John
I've never looked at solder mask in this respect, but I did the calcs once on powder-coating. Its a surprisingly good blanket (after all, its plastic). The conclusion was: dont powder coat heatsinks. So we anodised it instead - "it" being a flat Al plate

disclaimer: I had no idea they were going to be powder coated until I saw one; some marketing guy decided he wanted everything black.....

Cheers
Terry


If you make sure to have it grit blasted before the anodize, you'll
maximize its thermal efficiency. Matte black IR paint (not just any
***) will make it radiate AND thereby convect to the surrounding air
even better still, further maximizing the capability of the sink.

The finish extrusion typically places on the Aluminum is usually too
smooth for my tastes, but I used to make fully traceable Black Body
calibration sources for NIST, so what do I know?


So you should have no pb giving us some emissivity figures and back of the envelop convection/radiation ratio at usual temperatures. Right?

I tend to prefer figures to "taste".


--
Thanks,
Fred.
.

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