Heat Extraction


Natro

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Jun 16, 2010
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Is there much room within the Pandora itself to allow for things like adding heat sinks or heat spreaders? In the cases of overclocking, it would be good to have ways to get the heat out!
 
Natro said:
Is there much room within the Pandora itself to allow for things like adding heat sinks or heat spreaders? In the cases of overclocking, it would be good to have ways to get the heat out!
It doesn't get that hot anyway. Owners of the Motorola Milestone have been overclocking as much as what the pandora will be able to (remember they have the same soc), and they say it doesn't get that much hotter (and doesn't drain much more battery). The only times where the pandora really heat up where when the charging procedure where acting up, and for some reason it got incredibly hot without charging, but other than that.

The battery blocks a direct way to the cpu, so if you wanted to put a heat sink, you would have to work with the battery out.
 
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MWeston once explained that the whole PCB acts as a heatspreader and the OMAP which is underneath the PCB dissipates the heat through the BGA.
One idea I was speculating about back then is to add a thin copper sheet on top of the RAM and solder it to the SD card slots. A bit thermal grease on top of the RAM and a piece of thin foam on the case would ensure a proper fit. It has to be determined by experimenting how much space there is between the OMAP's RAM and the case first.
 
mali said:
One idea I was speculating about back then is to add a thin copper sheet on top of the RAM and solder it to the SD card slots. A bit thermal grease on top of the RAM and a piece of thin foam on the case would ensure a proper fit. It has to be determined by experimenting how much space there is between the OMAP's RAM and the case first.

I was actually thinking of something very similar as I was staring at the hackers guide picture. I just cant tell from the picture how much room there really is between the chips on the board and the outer case.

Another idea I had would be to essentially cut out an area in the Pandora case between the battery and the board and fill the hole with a solid piece of aluminum or other metal. I was not sure, however, if that would do more harm than good if the case is insulating the board from the heat generated by the battery.
 
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It would certainly be better to not expose the battery to heat. I suppose the battery is much cooler than an overclocked OMAP and batteries don't like heat at all. A very small piece of foam on top of the copper shouldn't allow too much heat reaching the battery, I suppose.
 
I'm thinking of removing my right nub in order to increase heat dissipation. I don't use it, because it is dead.
 
I highly doubt attaching copper strips and thermal paste will do anything.
Squidge did some surface temp measurements on the omap chip itself at higher clocks and the result was no major change in the temperature.
Also most of the heat will come from the battery anyway.

Theres a couple issues i see with the copper strip idea. Would there be enough pressure on the strip and thermal paste, there might air gaps preventing heat flow. Assume heat transfers to the copper strip, where does it go, ok you attach it to the sd cards then where? There really isnt a good transfer to the air.
 
Pickle said:
Assume heat transfers to the copper strip, where does it go, ok you attach it to the sd cards then where? There really isnt a good transfer to the air.

The idea would not be to transfer the heat into the air since, as you pointed out, there is no air flow to speak of. The main principle here is a heat spreader which effectively cools the hot spots by transferring the heat evenly over a larger surface of heat conductive material. Its somewhat like the concept behind a bed of nails.
 
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A few years ago I did some overclocking experiments on my x50v and adding a small piece of copper to thermally connect it to its shielding cage made the difference and I got it stable above 700MHz. Ok, the PXA got very hot anyway. The OMAP is much cooler in general I have to admit.
 
Mali, In the overclocking thread with your Milestone you mention that it gets noticeably hotter in the 1GHz range. Is most of that heat from the battery? If so, I wonder if the Pandora would even have a similar issue. From what it sounds like, heat from the OMAP chipset is not really that much of a concern.
 
Nope, the battery doesn't get hot in the Milestone. The heat comes from below the camera which is where the OMAP is, I suppose. I expect the battery of Pandora to not heat up at all, as the discharge rate is much lower compared to its capacity. If the battery in Pandora gets hot it's because the OMAP sits directly above.

edit:
Yep, the heat comes from the OMAP.
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Natro said:
I was actually thinking of something very similar as I was staring at the hackers guide picture. I just cant tell from the picture how much room there really is between the chips on the board and the outer case.

Another idea I had would be to essentially cut out an area in the Pandora case between the battery and the board and fill the hole with a solid piece of aluminum or other metal. I was not sure, however, if that would do more harm than good if the case is insulating the board from the heat generated by the battery.
The spacing between the PCB and the battery compartment plastic is 3mm. If I remember correctly, I think the POP stack is 1.7mm tall.

The battery compartment plastic is 1mm thick but I don't think a direct thermal connection to the battery from the CPU is a good idea.
 
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MWeston said:
The spacing between the PCB and the battery compartment plastic is 3mm. If I remember correctly, I think the POP stack is 1.7mm tall.

The battery compartment plastic is 1mm thick but I don't think a direct thermal connection to the battery from the CPU is a good idea.

I agree. It seems then that the best idea is Mali's concept to transfer heat to one or both of the SD card casings via a copper/aluminum plate. The more metal the better!
 
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Polossatik said:
A cnc'd Alu (or copper?) case is the ultimate heatsink... :D

As long as you don't plan to use the wi-fi
 
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paulguy said:
A copper case would look so awesome for about 5 minutes until it starts to corrode.

plus you could market the Pandora as a fitness device too since it would weigh a ton!
 
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