Micro porous ceramic heatsinks. For Raspberry Pi et al

[wilfred]

I've only just found out about these ceramic heatsinks existence. Specifically with regard to the RPi this one was referenced on the Element-14 community site.
https://au.element14.com/amec-thermasol/mpc151525t/heat-sink-ceramic-15-15-2-5-std/dp/1892471?COM=embedded-link_May%20CMPNULL

It interests me because it is non conductive and therefore will not short electrically and nor will it interfere with the WiFi and Bluetooth.

Has anybody here got any user experiences with them on the RPi or just generally. One particular question I have is how do they benefit from a fan in comparison to the conventional finned aluminium heatsink? The micro pores don't intuitively seem to lend themselves to forced air movement. Perhaps that's just wrong thinking and I'm stuck in the conventional groove.

Would a 22 x 22mm heatsink perform better than a 15 x 15mm one? On the 14 x 14mm SoC in the Rpi that is. I'm thinking that if the ceramic heatsink retains less internal heat than say an aluminium one then any heatsink overhanging the CPU will be that much less effective and just create a longer internal path for whatever heat escapes through the edges. I think it probably would be better but not much.

Any thoughts appreciated.


This is the original post where I first saw these.
https://www.element14.com/community/community/raspberry-pi/raspberrypi_projects/blog/2016/03/03/raspberry-pi-3-cooling-heat-sink-ideas

[baltersice]

I have found one in a very flat TV, that I wanted to repair and was intrigued, too.
Their advantage is of course the huge surface area, that can radiate heat very well. But the thermal conductivity on the other hand is horrible.
So [speculation] they are probably good when they are about as large as the chip they are supposed to cool, but it makes little sense to make them larger. [/speculation]
I guess that that is reason why they used it in the flat TV, there was very little space and the ceramic heat sink gets a lot of surface area in there.

The interfacing surface was very rough, so a gap-filling thermal interface material has to be used.

[Kleinstein]

Large surface are sounds a little like marketing ...   . From the technical side the rather low thermal conductivity makes it more like an useful spacer, but not a good heat sink. It is not such a good thermal insulation either. The large surface is more for absorbing the smell of ...  .

So I would definitely prefer a real heat sink from a good heat conductor.

[mikerj]

If you are interested enough to read the results and find a flaw in the test procedure then I'd be interested in it. But it seems reasonable to me.

The primary flaw is they are comparing a 2mm ceramic heatsink with a 6mm thick aluminium one.  Comparing like for like (i.e. a 2mm thick aluminium or copper heatsink) would have been more useful.

[wraper]

If you are interested enough to read the results and find a flaw in the test procedure then I'd be interested in it. But it seems reasonable to me.

The primary flaw is they are comparing a 2mm ceramic heatsink with a 6mm thick aluminium one.  Comparing like for like (i.e. a 2mm thick aluminium or copper heatsink) would have been more useful.

What the pint in 2mm aluminium heatsink? It means a heatsink without any fins with surface area of the chip itself. No significant improvement guaranteed. And ceramic heatsink proves it, the same performance as without heatsink at all. Only change is that it slows down heating and cooling due to it's own thermal mass. But no improvement at giving the heat away to ambient.
EDIT: such heatsink would do any good if the chip itself was tiny, of if it had exposed metal surface in center.

[Ian.M]

These were discussed in some detail few weeks back: see https://www.eevblog.com/forum/projects/micro-porous-heatsinks/

From the link Wilfred posted in reply #3, it seems the ceramic heatsink does little except add thermal mass.  The Pi fitted with it reached a peak temperature 0.5 deg C higher than the control (unheatsinked) Pi.  That's insignificant in relation to the probable measurement error, but its fairly obvious that the product sucks even worse than we suspected.

[mikerj]

The primary flaw is they are comparing a 2mm ceramic heatsink with a 6mm thick aluminium one.  Comparing like for like (i.e. a 2mm thick aluminium or copper heatsink) would have been more useful.

What the pint in 2mm aluminium heatsink? It means a heatsink without any fins with surface area of the chip itself. No significant improvement guaranteed. And ceramic heatsink proves it, the same performance as without heatsink at all. Only change is that it slows down heating and cooling due to it's own thermal mass. But no improvement at giving the heat away to ambient.
EDIT: such heatsink would do any good if the chip itself was tiny, of if it had exposed metal surface in center.

The point is you'd only use a 2mm heatsink if you didn't have room for a larger one, so the choice between 2mm or 6mm is stupid if you have room for 6mm and need the performance it gives.

[wraper]

The primary flaw is they are comparing a 2mm ceramic heatsink with a 6mm thick aluminium one.  Comparing like for like (i.e. a 2mm thick aluminium or copper heatsink) would have been more useful.

What the pint in 2mm aluminium heatsink? It means a heatsink without any fins with surface area of the chip itself. No significant improvement guaranteed. And ceramic heatsink proves it, the same performance as without heatsink at all. Only change is that it slows down heating and cooling due to it's own thermal mass. But no improvement at giving the heat away to ambient.
EDIT: such heatsink would do any good if the chip itself was tiny, of if it had exposed metal surface in center.

The point is you'd only use a 2mm heatsink if you didn't have room for a larger one, so the choice between 2mm or 6mm is stupid if you have room for 6mm and need the performance it gives.

The "point" in ceramic heatsink is that it supposedly saves space. Then find 6mm ceramic heatsink of the same size (doubt there are such available) because testing useless vs useless don't produce any meaningful result.

[Ian.M]

... Then find 6mm ceramic heatsink of the same size (doubt there are such available) because testing useless vs useless don't produce any meaningful result.

So get a tile saw and make one.  Its fairly obvious that a slice of any random dark coloured unglazed ceramic tile wont be significantly worse than the Amec Thermasol one and might be significantly better! 

[redhotiron2004]

http://in.element14.com/amec-thermasol/fch25255t/heat-sink-25mmx25mmx5mm-ceramic/dp/2499019
I want to know whether this heatsink dimentions of 25mm×25mm×5mm would for the raspberry pi 3 without any problem or not?


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