I’ve made my own heatsink tonight using the “Gordon” method. I’ll post more details tomorrow, but FYI the finished heatsink is 14mm x 14mm and 12mm deep.
I have also made one. Before I describe it: I know it is overkill, but a good “furkle” means using what is available in the junk box.
I used a 25mm diameter 11mm high copper slug from the centre of an old PC CPU heatsink and a 2mm plate of aluminium.
The two parts were screwed together with heatsink compound between the parts, The aluminium plate is attached to the Slice case using thermal transfer tape and there is heatsink compound between the copper slug and the CM3 CPU.
It runs very cool in normal use. I have yet to test it with high CPU. I will report back here with the results when I have tested it further.
The heatsink compound shows good contact between the CPU and heatsink. The heatsink does not move the CM3 module much when assembled, I measured it with some Blu-Tack
My concern is that a heatsink used in any position other than with the Slice horizontal is that the heatsink could come loose and short out the circuitry and let the smoke out. As y’all know all electronic items are made of smoke: when the smoke comes out, they stop working!
My Slice is vertical resting on the left side.
I used high temperature kapton tape to secure the heatsink assembly to the Slice case, just in case the thermal transfer tape adhesive fails.
UPDATE 28 January: Without heatsink will throttle clock inside a minute. With the heatsink and closed case after 1hour of 4 CPUs at 100% the max temp is 50 Deg C. looks good so far
Raspberry Pi Compute Module 3 has been released
Here’s my step-by-step for the home made heatsink.
I worked out (by adding to a pile of pennies on the CM3 chip until the case top was just proud) that the heatsink needed to be 12mm deep, and the size of the chip is 14mm square.
I ordered three things from eBay, for a total cost of about £7.50: a small piece of 0.5mm thick copper sheet, some thermal grease, and a pack of epoxy resin.
I then marked out the copper sheet into 14mm squares, and cut it up with a pair of snips. Then degrease all the pieces of copper, the inside of the Slice case top, and the top of the CM3 chip with isopropyl alcohol.
Next make a stack of the copper pieces, sandwiched with thermal grease. I needed 17 pieces of copper to achieve the required 12mm height.
Next I worked out the position in the Slice case top, and stuck the heatsink into position with thermal grease. Then with the epoxy resin, I “drizzled” a little of the glue onto the sides of the heatsink to hold it all together, and finally used the epoxy to glue the heatsink to the inside of the case top. This is what the final result looked like:
The very last stage was to apply thermal grease to the bottom of the heatsink, and then assemble the case. When I put the case together by resting it in position, the case was split by about 0.5mm, and when bolted together this slack is easily taken up my the flexibility of the CM3 in its socket.
As for temperatures, before the heatsink (and without the case top) the CM3 idled at 54 degrees, and under heavy load was reaching 85 degrees, and throttling the CPU back to 600MHz. With the heatsink the idle temperature is about 42 degrees, and under load maxes out at 48-50 degrees, with no sign of the on-screen thermometer.
I’m not really sure what I was expecting temperature-wise, so it’ll be interesting to compare notes once you’ve done your tests, and see if your solid heatsink is any more efficient than my sandwich approach.
FYI the idle temp was after the Slice had just been sitting there overnight, and the load test was after writing a Kodi backup using the Backup app, which typically takes about 5 minutes on my setup.
Ideally, Pimoroni ought to be getting some 14x14x12mm copper blocks machined to sell as the Real Deal
In theory it will as the layer approach will not be as efficient. However the copper slug I am using is somewhat ‘overkill’ as you can see from the pictures (recent edit to post).
It seems like your solution is Good Enough so I don’t expect much cooler running than you get. Anyway cool enough is all that is needed.
I have dropped hints that the folks should make a suitable sink. My concern about running with no heatsink is heat inside the case: HDDs don’t like running hot. The sink will fix that!
…the copper slug I am using is somewhat ‘overkill’ as you can see from the pictures (recent edit to post).
It might be overkill, but yours looks much more workmanlike!
To safely locate your copper slug you could swap your 2mm aluminium “shim” at the bottom for a 2mm copper sheet at the top, cut to fit exactly inside the top of the Slice case.
Thank you both! Off to the workshop…
Good idea, and I would have prefered to use copper but the aluminium was all that was available at the time. My copper sheet is at another location about 65 miles away (long off topic story )
while straying off topic, ever so slightly, is your forum handle photography related?
Compute Module 3 ordered! Will need to make the heatsink next week in our workshop. I will report back.
A quick and easy CM3 heat-sink hack, with pretty amazing results. I call it "thinking inside the box"
Sorry for lack of lots of pictures, but you can get the idea I hope.
I took a piece of copper pipe, actually a sleeve joint for half inch pipe with no stops or solder, just a plain little copper cylinder really. Cost pennies at the hardware store.
Put it in between some pages of an old magazine that was handy, and squashed it slowly in the vice until it was 12mm deep. The top and bottom become flat (as flat as I thought I needed, anyway), like so:
I then positioned it on top of the chip with some double sided tape on top and put the top case on. Lifted off again and there it was, showing me where I needed to fix it.
I marked the position, scraped off the paint to bare metal and fixed it in. That’s when pictures stopped because it got messy…
I ran a line of mixed up quick setting epoxy along either side and some thermal paste between them (started worrying about chemical reactions, but no smoke so carried on).
It set pretty quick (it may not have been rock solid, but the next phase would help it set hopefully).
I spread some thermal paste on the chip, screwed it all together and powered on for testing.
When I first ran the CM3 (case closed, with no heat-sink) I indexed my NAS movie library.
The temp kept maxing out at 85 and throttling the chip to 600, (nasty little thermometer icon).
With the heat-sink installed the temp at idle after power on was 35. Left it for a while and it didn’t budge.
So I scrubbed the library and reindexed the same source,
The maximum temperature reached was 48 degrees.
Nice one, simple but effective
on my “overkill 'sink” on a second test I have had CPUs at 100% for several hours and the temp stays around 49-51 deg, room temp 21 deg.
That’s correct. My first career when leaving school was as a professional photographer, after a photographic apprenticeship at Rolls-Royce.
planed to mass produce it and go on kickstarter with it maybe? Sounds funny of course but as lot of us would just like to go with tested and out of the box ready to install solution
Love it! Very clever and simple.
I went for an easier and quicker solution. I had some ready to assemble copper-cooler laying around.
They have the perfect size, and come with stickytape. I attached one to the cm3 and another one to the case. They barely touch when the case is closed. I put some cooling paste between them. Working like a charm.
One can get them on ebay or amazon. Got mine here
I’ve got some of them here, too. They were my first thought, but since they are only 5mm high I didn’t expect them to work well in that case (and even 2 stacked wouldn’t help since the height doesn’t match).
What are your temperatures under load for some hours?
Edit: Since you seem to be from Germany, where did you order your CM3?
Ordered my cm3 in UK via Farnell.
Cant tell you the exact size of the coolers, as i’ve used them all now, but they were a perfect fit for me. Temperature stays fine, even under load .