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Does PCB Mask colour affect thermal performance?

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Most plastics are relatively good absorbers in the thermal IR range. The main parts to avoid are clean metal surfaces, like copper, gold or aluminum. Here the solder mask gives quite some improvement, but likely little difference between the colors. 
Crude estimates for the emissivity are something like 90% for the solder mask and maybe 1% for a clean copper or aluminum and 0.1% for gold.

There is not much one can do to improve the radiative exchange other than getting reasonable good absorbers on both sides - especially avoid the good reflectors. The only way to get higher is getting the parts very close, to less than a some 2 ┬Ám. This can give added near field effects.

S. Petrukhin:
When I was in school, I was told that black bodies radiate better.  :)

But this color must be black for the range you want to emit. Black in the visible spectrum appears to a person, but it may not be black for thermal radiation.

The explanation for this phenomenon was given by Planck, who introduced quantum theory.

Hi there,

Actually that's almost completely wrong. Bare copper is THE WORST thing for _radiating_ away heat. The critical number is "emissivity" (which ranges from 0 to 1, or 0% to 100% if you like) and you want it as high as possible, ideally above 95%.

Yes, you want lots of copper to _conduct_ the heat way from your hot devices, but you want to cover as much as you can of that copper in soldermask to _radiate_ the heat off the board. And matte-black solder mask IS better than shiny green, although we're talking high 80%s to 95% so ...

That's also why the best heatsinks are black-anodized and matte finish, since this radiates as much heat away as possible. If shiny/bare metal was best at radiating heat, then heatsinks would be gold plated...

I am a circuit board engineer designing power-electronics and dealing with thermal dissipation in my day to day job. But in case you don't want to take my word for it  here is some reference material ...



Cheers, Dave E.


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