custom heatpipes anyone?

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matt_garman

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robinlawrie said:
ok, apart from a few discontinued products, and an eye wateringly expensive demonstration kit, ive not found a reasonable source for some diy heatpipes (ideally with the blocks for each end)

i was thinking of something like this as an option for my amp (ti3255)

http://zelfbouwaudio.nl/forum/download/file.php?id=109472&mode=view

in the same case.


anyone got any suggestions?
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Have you looked at fanless computer cases? Often marketed as home theater cases (htpc), or sometimes for industrial applications? The Alaska Euler is an example, but there are many shapes and sizes.

So the tpa3255 can do around 500 Watts at 1% distortion (can go higher but you won't want to listen). It's 90% efficient there, so 50 watts of heat to cool. But realistic music signals (i.e. not sinewave), higher impedance speakers, and/or a general desire to preserve one's hearing, and I don't think you'll ever have anywhere near 50 watts to dissipate.

Most of those computer cases rate the highest TDP CPU they can support. That Euler case I mentioned above is rated for a 35 watt CPU (ought to be plenty for tpa3251). Mini ITX form factor is easily big enough to design a decent tpa32xx PCB.

Thoughts?
 
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robinlawrie

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heatpipes are not too expensive there, but blimey their mounting blocks are outrageous.

15 pounds for a 60mmx40mmx10mm aluminium chunk.. i need at least 4 ( i was hoping to use two on each side for the heatsink, so, 6 of them.. thats £90 just for those little pieces of aluminium. )

i could get some machined of course.. but i would have *thought* that buying ready made ones would be cheaper.
 
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OlegSh

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Such mounting blocks can easily be done at home using thick aluminum plates and drill press. Just use a drill bit which ensures tight fit of the heat pipe. You can also use two plates screwed tightly together and then drill along their joining surface. This would allow easy mounting and removal of the heat pipes when one part of the mounting block is permanently attached to the heatsink.
 
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robinlawrie

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Ok so i got some aluminium blocks machined. Unfortunately i left a heatpipe with the guy to make sure the hole was right. He tried a 6mm hole, and the 6mm heatpipe would not enter. So he used a 6.1mm bit. Now the pipes fit, but there is a tiny amount of wiggle. So not a tight fit. Doh.

I guess fill the gap with heatsink paste? Wrap heatpipe in a sheet of foil? (probably too thick) i read somewhwre about soldering heatpipes, but i also read they burst if they get too hot.

Suggestions most appreciated. Gotta be a way to fill tgat gap.
 
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robinlawrie

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ok so in the absence of opinions, ive decided to try low temperature solder paste. the heatpipes ive got have to be kept below 200 degrees.. so ive found some solder paste with a melting point of 137 degrees.

Solder Paste Sn42/Bi58 no clean Lead-Free Low Temperature Melts 138C 281F by ChipQuik - - Amazon.com

i plan to coat the inside of the hole, and the outside of the tube, then get everything fitted and lined up. then stick the whole assembly in the oven at 140 degrees.



it wont actually bond to the aluminium blocks, but it should fill the gaps at least partially ( ive no idea about the actual metal content.. ive read generically that the pastes contain around 90% metal)

opinions anyone? gotta be better than just filling with heatsink paste
 
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robinlawrie

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jcx said:
its not impossible to 'tin' Al - can be looked up, maybe not practical for inside of hole - then there are solderable elctroplating options...
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in my imagination the actual bond between the solder and the AL shouldnt be important. As long as it fills and small gaps and conducts heat better than thermal paste. Not sure if i am right about that. maybe wetting of the surface is the only way itll actually "fill" ths space properly...?

having said that its gonna be squeezed in there pretty well.

i did read that a) when soldering, the heatpipes can swell slightly, which would be good... i also read that this low temp solder can expand slightly when it cools.. which is, also, good!
 
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robinlawrie

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Joined 2008
johnnyx said:
You could cut a slot on one side of the hole, and then use a screw to squeeze the slot together and tighten the hole around the pipe.
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yeah i did consider that as an option.. however the geometry of my blocks and the space available makes that pretty impossible.. plus any squeezing would introduce a bend on the surface which has to contact with the chip/heatsink. could be polished out after i guess.
 
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