Aluminum heatsinks are better than copper heatsinks, when cheaper

I think that the standard aluminum heatsink (link) is a better value than the extended copper heatsink (link). I'll argue that cooler temps can be achieved with the aluminum heatsink by improving the thermal interfaces between the diode/heatsink and the heatsink/host than with the copper heatsink alone.

Sure, the copper heatsink has a little better thermal conductivity than aluminum, but not by much. The extended length of the copper heatsink contains a little more mass, but his extra amount will quickly fill with heat and not add much benefit.

The best gains will be had by removing the most heat from the diode. This means moving the most heat from the diode to the heatsink and then to the host. The copper simply doesn't compare a whole lot better than aluminum here. The copper does a little bit better, but most folks can benefit substantially just by adding some thermal interface material like thermal paste.

In other words, if you have a copper heatsink instead of an aluminum one, it will get hotter, faster, but it won't move heat out of the host faster.

Keep in mind, I've never possessed a high powered laser. My background is electrical and software engineering. Of course, theory doesn't always translate to reality.

(And please forgive my sensationalist title)

I really don't feel like getting deep into this, so, here is some evidence that suggests otherwise:

TheDukeAnumber1 said:

Simply put, copper outperforms aluminum in every way for the purpose of removing heat. Aluminum in many cases is used instead of copper because it costs less, is lighter, can be anodized to any color, and it can be extruded where copper cannot. Comparing the volumetric heat capacities of Al and Cu shows that when energy is applied to similar sized heat sinks, for every 1°C copper rises aluminum will rise 1.4°C, and similarly for every 1°F copper rises aluminum will rise 1.4°F. Ignoring thermal conductivity and comparing duty cycles, copper will run 40% cooler than aluminum and give an overall +40% to runtime. When you consider copper's thermal conductivity that's about twice that of aluminum, copper is much better suited to protect laser diodes from heat than aluminum.

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But if it is $15.50 cheaper, and you don't really need that %40 extra run time, then I would go for the aluminum.

And if your purpose for the laser needs a long duty cycle, then just go with a huge computer heatsink and make it a labby:thinking:

Philipd7 said:

I really don't feel like getting deep into this, so, here is some evidence that suggests otherwise:


But if it is $15.50 cheaper, and you don't really need that %40 extra run time, then I would go for the aluminum.

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Damn, I was going to post pretty much that exact explanation but I wasn't entirely sure I was correct so I never bothered. That one is worded way more elegantly anyway...

Thanks for digging that up.

diachi said:

Damn, I was going to post pretty much that exact explanation but I wasn't entirely sure I was correct so I never bothered. That one is worded way more elegantly anyway...

Thanks for digging that up.

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Thanks and you're welcome. I guess roaming around the forums for a while helps

I acknowledge that copper is a better material. In the case I'm talking about, the savings over copper is only $14, but I stick by the opinion that the copper's performance does not provide better value than the aluminum. If we were talking copper fins vs aluminum fins, maybe. However, in our case, the huge bottleneck is moving heat from the heatsink to the host. This part matters more than anything, whether your heatsink is aluminum or copper. I say get the aluminum heatsink and come up with some method of moving heat to the host.

This the the biggest issue I see so far though. Do people use thermal tape? Thermal paste? I will do some more experimenting and report back.

q3434 said:

I acknowledge that copper is a better material. In the case I'm talking about, the savings over copper is only $14, but I stick by the opinion that the copper's performance does not provide better value than the aluminum. If we were talking copper fins vs aluminum fins, maybe. However, in our case, the huge bottleneck is moving heat from the heatsink to the host. This part matters more than anything, whether your heatsink is aluminum or copper. I say get the aluminum heatsink and come up with some method of moving heat to the host.

This the the biggest issue I see so far though. Do people use thermal tape? Thermal paste? I will do some more experimenting and report back.

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It probably pays off when you're running a NUBM44 at ~7W - the extra cost is a small drop in the bucket compared to the other components.

I have a S4 build with the extended tapered copper sink running a M140 at about 1.7A.
I can feel the warmth on this host that I don't feel on and equally powered aluminum sinked 501b host. Both hosts having thermal paste. Yes there is a size difference between the two.
Wondering if this warmth is the copper sink doing a better job of drawing the heat away from the module.
Also curious why they make the cheaper modules out of plated brass when a aluminum module should make the diode run cooler and cheaper?

The fact that you can feel the warmth with the copper is a sign that it is drawing heat away from the source. This is good.

Also curious why they make the cheaper modules out of plated brass when a aluminum module should make the diode run cooler and cheaper?

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They probably make them about of thin brass as it is a copper alloy but it contains zinc to reduce the copper content.
As for cost if I assume that the brass has a content of 60% copper and 40% zinc then 1 tonne would cost $3826.10 based on the rates below. It still is a good conductor but is cheaper than pure copper. Depending on the ratio however, it could be possible that aluminium has a better thermal conductivity than brass if the copper content is low.

$2198.00 Zinc
$4911.50 Copper

The other reason I can think of comes down to material properties. Aluminium is lightweight and soft when in thin sheet form. If uses, it can make the product feel cheaper. By using brass it is stronger and slightly heavier making it feel more expensive with the golden copper look. But in truth, i don't really know why for definite. I can only postulate.

Quick quesion:
Is the point of the extended taper to not only give it more mass, but also to transfer heat to the air faster? (like the point of fins)

Copper wins, hands down. Aluminum is better for host's outer shell, imo.
Right after copper comes aluminum. Other materials are either not worth it, or have worse specs.
Also, I like heavy stuff. And copper is dense. It feels good to hold a heavy laser, light ones seem cheap to me. Keep in mind this are only personal preferences.

I vote for copper for heatsink and for aluminum or brass for the host.


But considering the prices too, and going for volume and surface area aluminum might win. However I think copper is a better option if space is an issue, i.e. the laser is portable.
If going for power, copper is worth it. I don't think it's smart to save a few buck if the build is using an expensive diode.

Do some tests, throw some numbers, otherwise this whole thread is pointless.

I think both metals have their up and down sides..

Wiki Quote:
"First and foremost, copper is an excellent conductor of heat. This means that copper's high thermal conductivity allows heat to pass through it quickly. Other desirable properties of copper in heat exchangers include its corrosion resistance, biofouling resistance, maximum allowable stress and internal pressure, creep rupture strength, fatigue strength, hardness, thermal expansion, specific heat, antimicrobial properties, tensile strength, yield strength, high melting point, alloyability, ease of fabrication, and ease of joining."

LINK: Materials for thermal conduction (2001), Chung, DDL, Applied Thermal Engineering

You should be aware that adding few percent alloy to copper or aluminum can cause Huge down shift to thermal conductivity.

Just few weeks ago I found a study of Heat Conduction and there was a Note for using more than one material in Heat sinks. It is not recommended to use high(er) Heat conductivity to transfer heat to low conductivity material. (Causing heat transfer bottleneck).
Heat source > copper > Aluminum

It's OK to use:
Heat source > Aluminum > copper

I will try to re-find link for that study..


Lately, I have been resourcing 99.9% pure copper chunks for future projects..
A bit larger chunk than beercan weight almost 5KG.



HI-RES IMG


Now it's beer time,
Alla salute! :beer:

I forgot to mention that Graphene would be most efficent material for heat transfer..


Physicists show unlimited heat conduction in graphene


So, does anybody know who could resource some Graphene heatsink's for us??!
:wave:

Considering graphene is a single sheet of carbon atoms, I'd say it is not really a feasible option.

The common surface treatments of aluminum (anodizing) are usually much more emissivity than copper, so aluminum can usually radiate heat faster.

The increased conductivity and specific heat capacity are totally worth it for sensitive semiconductor devices though. I wouldn't say aluminum is superior at all. You can even do a black oxide coating for copper, and that will give it a very good emissivity.

Cost might not be worth it for most handheld lasers, but copper's definitely got better specs on most counts.

ArcticDude said:

I forgot to mention that Graphene would be most efficent material for heat transfer..


Physicists show unlimited heat conduction in graphene


So, does anybody know who could resource some Graphene heatsink's for us??!
:wave:

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Graphite actually is quite good and easy to obtain. It's got little pieces of graphene in it.
Diamond is one of the best thermal conductors we've got.
Silver is another very good thermal and electrical conductor, so somebody could make a diamond and silver laser host.