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Question about heat sinking?

AJ Pierson

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Hey guys (and gals), I did search first, but I didn't find anything that actually addressed my question.

I'm wondering about how to best remove heat from a diode, while using the minimum of material.

To be more specific, I know that both aluminium and copper are good conductors of heat, but which one is better for conducting from physical contact, and which one is better for shedding heat via the air (like as in a finned heatsink with a fan)?

I'm asking because I was thinking about building a high-current 445 (of course) labby with the best heat sinking I can come up with. I don't know if I should make the diode a press-fit into a copper slug, and then have an aluminium heat sink with fan, or put the diode in aluminium with a copper finned heat sink with fan, or maybe all I need is just one metal and not a combination?

See what I mean? I dunno, maybe I'm just over-thinking it. I just want the smallest way to remove as much heat as possible. The issue is that I don't know if I need to do all this multi-material acrobatics to achieve it.

I'm also thinking about TEC, but I don't want to complicate the issue with that right now.

Any input is greatly appreciated. Thanks all.:)
 

Misanthrop

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For this you will want the highest surface area possible within your heatsink...
and the best conductivity immediately from the diode (This would be copper)

Obviously copper would be your best medium for heat dissipation, but it comes at a higher cost than aluminium.
Aluminium is not as good at dissipating heat as an aluminium alloy if you can find a big chunk to work with.
Also be aware heat dissipation is not uniform and considering your going to be making a labby a "heat pipe" maybe possible to put in.. not sure how, but it could be.
Also if possible paint or powdercoat your heatsink black as black absorbs and radiates a lot more heat.

Edit: If possible definately use a fan. Even a tiny one can help a great deal.

I would put it into a slug, but with the slug being connected to the fins, so basically it's all one bit.

There is a good example on here of someone who did this, but not with copper.

Can't remember who though.
 
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sopark4000

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There's really no reason to use two different metals. For the best heat sink copper is the material to use although it is more expensive than aluminum obviously. There are a lot of unspecified variables in your question such as what kind of power you want, size etc.
 

Blord

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Read this, Merghart.com - Heatsinking laser reference
A little technical but all you need is reading the last part.

A good heatsink is made of one solid material ( aluminium, copper, silver, etc ) with alot of surface area to dissipate the heat.
Like this CPU cooler which is made for 100+watt CPU. Sure enough for 1W 445nm laser.



 
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Things

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^ Now THAT is what I call overkill! :D

You could put a 100W bar on that thing! :)
 

AJ Pierson

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Thanks to everyone for all that info. I'll definitely check out all those links.

My goal is to build the labby in two parts, with the driver connected to the head by approximately 1 meter of wire. I just want to keep the diode head as small as possible, while not killing it too soon with high current.

I have some reading to do.....thanks again.

Misanthrop: I think I know which other member's labby you mentioned. Whilst I was searching, I ran across a thread about Gksudo's 445 lab unit that he built using a solid brass block, with fan-cooled aluminium heatsink on top.
 

Benm

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The choice between copper and aluminium probably isn't that hard if you want to build a labstyle laser that is suitable for continous operation: take aluminium.

As long as the heatsink (including fins and such) is no bigger than a few inches on each side, the benefit of coppers greater thermal conductivity will be negible.

Aluminium is obviously cheaper and lighter, but has some other advantages too. For example, copper tarnishes in air, giving a layer of oxide and suphites and has a poor thermal conductivity. Aluminium oxidizes in air to, but this process stops when a very thin oxide layer is formed, and aluminium oxide is also a fairly good heat conductor.

You will find that virtually all heatsinks used in commercial electronic equipment are made from aluminium. There may be a few exceptions in ultra-high performace cpu coolers and such, but those use heatpipes and forced air too.
 




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