What is the best aluminum for heat sink?

John Larkin wrote:


Good idea--optics people know all sorts of magic tricks like that.
Thanks.
James Arthur
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John Larkin wrote:

I wonder if my uncle (recently retired old-school watchmaker) remembers. They had to produce two identical cubes such that any two surfaces would match in size/shape with detectable (by hand) stiction... using files and scrapers.
Clifford Heath.
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In the machinery lab, first semester, we had to make two pieces out of a steel rectangle, that would fit each other, like a male and female, like that: _________ | | | | \ / \ / \_____/ Then we had to make a nut and a screw that would screw into each other, from a cube of steel (nut) and a bar (screw). You were free to use any tool you liked, and the professor and his assistant would show you how to hold them, use them right, etc. You'd have to ask special permission to use the electric reciprocating saw, because freshmen had regularly broken the blade
--
Tzortzakakis Dimitrios
major in electrical engineering
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wrote:

I made a power supply (amplifier actually) for a Piezo stack that drove a tool head on a lathe at 20 - 20,000 Hz.
It could take a mounted round pin on the lathe, and cut it into a square pin with a pyramidal nose while the lathe spun at several hundred rpm.
It was used to cut contact lenses for thoroughbred horses. They were about one inch in diameter without the need for further optical polishing.
http://www.precitech.com /
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SuspendedInGaffa wrote:

Very cool stuff.
Cheers, James Arthur
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Eeyore wrote:

<http://www.onsemi.com/pub/Collateral/AN1040-D.PDF
--
W
. | ,. w , "Some people are alive only because
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Yes, that's the right AN. Great reading. Thanks.
--
John English


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All aluminum alloys have approximately the same conductivity (thermal and electrical). Pure aluminum (1199 is the purest) is maybe 20% higher conductivity than 356, 6061, 7075, etc.
Tim
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Addendum: all metallic alloys have higher resistivity (thermal and electrical) than either pure metal. For instance, sterling silver is more resistive than either silver or copper. I suppose aluminum alloys are fairly surprising in that regard, as they are still fairly conductive.
Tim
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On Mon, 4 May 2009 22:30:06 -0700 (PDT), Tim Williams

Better look again. Even Al suffers a hit, once the lattice, she is split.
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Well except for super conductors where some alloys are better.
George H.
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On Mon, 4 May 2009 22:25:07 -0700 (PDT), Tim Williams

Actually, I found it to vary quite a bit. Pure being best.
Copper is the one that I found remains the same, regardless of how wrought, and well into some alloys.
Regular 6061 T6 is 21% lower than pure Al in thermal speak.
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Usual Suspect wrote:

Do you have a choice ? If so, the alloy with the best thermal conductivity.
Graham
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On Tue, 05 May 2009 10:51:57 +0100, Eeyore wrote:

Isn't that exactly what he's asking?
Thanks, Rich
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copper is better. aluminium is cheaper. pure is better than alloy.
the less gap you get at each join the better, so a flat mirror finish on all surfaces is is ideal.
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copper is better. aluminium is cheaper. pure is better than alloy.
the less gap you get at each join the better, so a flat mirror finish on all surfaces is good.
Metal is much much better than heatsink paste so if you can solder or weld the spacer to the heatsink (with the apropriate solder and tools) so much the better.
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'Ya know, if you can clamp the assembly quite tightly (or even apply some persuation as a part of assembly), you could use pure aluminum to fill the space, no grease. It's soft stuff, about like lead. Oh, and use springy washers too, I suppose...
Tim
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wrote:

The best aluminum is copper!
After that, check the thermal conductivity of various alloys. They can vary a lot.
And make the spacer big to spread the heat laterally.
John
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wrote:

Yup, like this:
ftp://jjlarkin.lmi.net/Amp.jpg
The shiny things are copper heat spreaders, nickel plated. I did one DSRD-based [1] HV pulser that was built on a gold-plated copper block, water cooled; it looked great. You can get a peek of it here:
http://www.highlandtechnology.com/DSS/T220DS.html
John
[1] drift step-recovery diode
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