Concerning Heatsink Materials

photongeek · Nov 6, 2007

Here's a nice chart indicating the thermal conductivity of various materials. I think our Axisz modules are just plated steel which is a relatively poor conductor but these units are the foudation of our projects so we're stuck with them. So, select the heatsink material wisely. Aluminum is best unless we can afford to use a large piece of silver.

http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

rog8811 · Nov 6, 2007

I think you will find that all of the Aixiz cases are made of brass, some chrome plated....you will also find that they are tapered, I turn them parrallel before inserting them in the heatsink to ensure good thermal contact.

Regards rog8811

photongeek · Nov 6, 2007

OK. Thanks Rog. I stand corrected on the Aixiz material.

Kenom · Nov 6, 2007

Excellent find Photon. I've always wondered if Brass was better thermal conductor than aluminum. Now I know.

pseudonomen137 · Nov 6, 2007

photongeek said:
Aluminum is best unless we can afford to use a large piece of silver.

Copper is actually a good choice too. Its machinable, nearly as good as silver (significantly better that aluminum), and you can still quote copper prices by the pound instead of the tr. ounce (downsides are its more reactive, heavier, and does cost a reasonable bit more than Al).

Tallaxo · Nov 6, 2007

Copper is indeed a much better thermal conductor than Aluminium, however be very wary in allowing the 2 metals to be in contact with each other for extended periods, especially where moisture in air is involved.

All metals have a property called Nobility and each metal is assigned a number. This number is known as the Galvanic number.

Aluminium has a galvanic number of 1
Copper has a galvanic number of 8

The big difference between the 2 is the potential of an unwanted electrolytic reaction of the 2 metals in the presence of an acidic atmosphere or simple moisture from the air, causing severe corrosion to the aluminium(as it has the lower number).

Another downside to using copper is the increased probability of unwanted currents induced by exposing the heatsinked laser to a strong magnetic field. A very brief exposure to a copper heatsink, can induce a current that will kill a laser diode in the blink of an eye. Aluminium is your safest and cheapest bet for a heatsink.

Jase

Benm · Nov 7, 2007

There is one important sidenote on aluminium: The quoted number is for the pure metal only. Aluminium parts sold for construction (I/U-beams, bars, rails, rods, etc) are usually aluminium alloys. This is good because it can improve strength and other desireable qualities for typical use, but does severly degrade thermal conductivity.

Btw, typical 'thermal grease' or glue has a value in the order of 1 W/mK, which explains why you should never use more than really required.

photongeek · Nov 8, 2007

Kenom said:
Excellent find Photon. I've always wondered if Brass was better thermal conductor than aluminum. Now I know.

Glad you found it useful Ken.
I have no idea why I assumed the shaft collar I'm using for a heatsink was aluminum. It appears to be nothing more than plated steel which isn't that good a conductor. Until I can make a good aluminum piece, I'm doubling the collar to increase heatsink mass on the entire length of the axisx module. The whole thing is mounted on the outside of the Dorcy thereby exposing it to ambient air. I hope this will wick off enough heat.

photongeek · Nov 8, 2007

Excellent research guys!!! This thread is becoming an education in metallurgy and thermodynamics (brings back good and bad memories

). Let's face it, this forum is an education!

JECS · Nov 9, 2007

might as well add a bit. copper may be a better conductor but aluminum (pure) will dissipate the heat faster than copper. i would pick aluminum for a few reasons. that^. its cheaper, especially if you make your own ingots and machine them down. havent worked much with copper but aluminum is very easy to work with. plus it doesnt pass electricity as well as copper. i think like 40% less or something (over a good distance anyways) so there is less of a chance a lethal spike could go through the heatsink

photongeek · Nov 9, 2007

Yesterday I ordered a one foot long piece of 2011 alloy aluminum round bar stock. It's one inch in diameter. Kind of a rip off @ $18.00/ft plus shipping but I wouldn't know as this is the first I've bought. This alloy is supposed to be the easiest to machine. I'll cut off a one inch piece and drill it to enable a snug (vise pressed) fit of the module. This should be a good heatsink for our application. I'll still mount it outside of the Dorcy head to allow maximum heat transfer to ambient air.

JECS · Nov 9, 2007

dont forget if you want a really snug fit you can always make it 1/32 smaller than the host stick it in the freezer for a while to shrink it then stick it in the host. dont expect to ever get it out though. id imagine the conductivity between the host and heatsink would be quite a bit better from this. not really much point to it but maybe a bit more wow factor?

photongeek · Nov 12, 2007

The only lathe I have is my Dremel Moto Lathe so this should be interesting

This is for aesthetics only as I just intend to polish the raw stock. The major deal will still be trying to drill the sucker for best module fit. We shall see!

photongeek · Nov 12, 2007

Here's what I've got so far. Not easy on the tiny Moto Lathe so it's not as finely accurate as of yet and, I still have to drill it. The closest bit is 29/64.
My cousin has volunteered to cut about a half a dozen of these on a full sized lathe so I'm hoping for a better finish and tighter tolerances.
The benefit of mounting this to the outside (with just a few tight wraps of PVC tape) of the Dorcy is that you can fit your circuit mods in the head. Cooling is also improved.
It's starting to look like a little LightSaber.

philguy · Nov 13, 2007

Aw crap! Now I payed a fortune for a custom-made perlite aixiz module to be driven in a vacuum chamber, and now that! Man, all for nothing.

j/k, but it's a good list! Also shows you why it's easier to burn wood that to heat a metal to the same temperature!

zerafiel · Nov 13, 2007

Actually I consult this list as it lists it in order and also shows the electrical conductivity and notes. Wikipedia is always good for something.

http://en.wikipedia.org/wiki/List_of_thermal_conductivities

Did you know one of the ways to test diamond is by their high thermal conductivity?

Concerning Heatsink Materials

photongeek

0

rog8811

0

photongeek

0

Kenom

0

pseudonomen137

0

Tallaxo

0

Benm

0

photongeek

0

photongeek

0

JECS

0

photongeek

0

JECS

0

photongeek

0

photongeek

0

Attachments

philguy

0

zerafiel

0

Online statistics

Forum statistics

Share this page