Electronics > Projects, Designs, and Technical Stuff

DC load using a CPU cooler

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timb:


--- Quote from: SeanB on September 20, 2014, 09:53:32 am ---Upside down TO247 packages are better, lower thermal resistance. Plus you can fit a bigger die inside which has lower resistance to case as well. You probably will only get 9 under the thermal contact, you need a little room to bend the leads and board to attach them to. Use the thickest PCB you can get, otherwise you will need to machine a back brace to get even contact to all 9 dies, otherwise the warping of the board will cause the middle one and the ones not in the corners to not have good thermal contact. A back brace made from thick insulating material with cutouts for the lead stubs will probably be needed in any case, or a thinner one with an aluminum backing plate to give even pressure.

--- End quote ---

Wait, 9??? Look at the picture of the heatsink portion. (5th Picture)

That looks like *maybe* enough room for two TO-220 packages...

http://www.amazon.com/gp/aw/d/B006TCSH4Y/




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microbug:
Yes... I agree. I'll measure it up when I buy the heatsink.

EDIT: that link is correct, if anyone is wondering.

mrflibble:

--- Quote from: timb on September 20, 2014, 12:59:54 pm ---Wait, 9??? Look at the picture of the heatsink portion. (5th Picture)

That looks like *maybe* enough room for two TO-220 packages...

--- End quote ---

Heh, I was wondering the very same thing.

I don't know of any cheapo cpu coolers that would accomodate 9 TO-220 packages. You could do something custom, but that would automatically discard that "cheapo" word in there.

Image of the cooler being discussed. Inline because I am lazy today:

microbug:
Judging by the details on this page (4x8mm heat pipes), I'd say that the thermal pad is 32mm by 32mm or thereabouts. That's just enough for two TO-247 packages.

EDIT: I think it would just do 6 TO-220 packages, because in one dimension it is slightly more than 32mm. My current design (which needs some significant changes anyway) has an OPA4188 controlling 3 MOSFETs and acting as an amplifier for the DAC. I could stick in another OPA4188 and use 6 op-amps for 6 MOSFETs. I'm sure I can find a use for the two spare op-amps.

timb:
What you could do is get a 1cm+ thick square of copper and mount 4 to 6 FETs on it with the heatsink mounted in the center. (So basically you'd have 2 or 3 FETs mounted bent-legged-face-up on the copper just past where those heat pipes curve up.)

The copper pad could be thermal epoxied to the board.

This way you wouldn't require any reinforcements on the bottom either!


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