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Better heat conduction with Ag

Zar

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Silver is a great heat conductor, that's why we use it as a thermal paste for computer processors, mixed with silicon

There are many designs that would improve heat conductivity, ribs etc.
What if on the inside I would use thermal paste for a processor, and for the outside I would use silver, to better release heat from the aluminum body?

Silver can be applied very easily by electrolysis
 



Benm

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The most obvious reason is that it's not used in the place where it matters much. You could silver-plate an aluminium heatsink i suppose (and certainly a copper one), but that will not improve overall performance much.

When designing portable lasers, it is important to get good heat exchange between the body and ambient air. This is helped best by using things like fins to increase the surface area.

Another big thermal resistance can be that between laser diode and heatsink, and there it could be very useful to use a superior thermally conductive compound, possible silver based.

As far as the actual heatsink goes: aluminium is an excellent choice when considering price, machineability and such. Copper can potentually perform better since it has about double the thermal conductivity of aluminium. Silver, however, is only about 5% more thermally conductive than copper, and given the difference in cost this would rarely be worthwhile. And that is considering making heatsinks out of solid silver metal, not juts coating them with a thin layer.

If you look at it per kilogram rather than per unit of volume aluminium actually outperforms copper: copper (and silver) may have double the thermal conductivity by volume, but copper is roughly 3 times as dense as aluminium. So if you want to design a heatsink with a limited weight, you'd probably be able to fashion a better performing one out of aluminium compared to copper or silver.
 

IsaacT

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There is a guy on the forum who makes Silver hosts with Fantasy-based designs and etchings.
 

Zar

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im gonna quickly join jewelry school hahah, no yeah I get it, I was just thinking that silver coating would be a good substitute for the surface area, there have to be enough space between the ribs to allow for easy air flow, if thats not there then it traps the hot air instead, tricky stuff, we have to take examples from big guys, high end cars etc, maybe think gun barrel

we can speculate, but every theory should be tested :friend:
 

paul1598419

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Yeah. The thermal conductivity of copper is 401 watts/ meters X degrees Kelvin, while the thermal conductivity of silver is 427 W/m K. For a heat sink, not worth the money. Diamonds, however, have a thermal conductivity of 3300 W/m K for synthetic diamond, because the more carbon 12, the better the thermal conductivity. That is why I make a heat sink compound that is 50% silver based silicone and 50% diamond crystals by weight. The Grit, or size of the crystals are between 25 microns and 100 microns.
 

IsaacT

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Someone needs to make a diamond host. Now that would be a bitchin laser.

I recommend 462.
 
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Zar

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all carbon is 12 unless its radioactive lol, why not use carbon fiber, hows the heat conductivity of that?
 

Bionic-Badger

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Unless your host has a lot of fins to dump that heat into the air, all that conductivity is really not really going to do you much good. The main use of copper for hosts is not for its superior conductivity, but because it has so much mass and heat capacity that it can store a lot of the heat the diode produces. Were the material really meant for moving that heat into the environment, we'd see a lot of fins to provide surface area for moving that heat into the air like in computer heat sinks.

Most people aren't bothering with that in hosts though. It's too bulky, fragile, and most people aren't running their lasers for long durations anyway.
 

paul1598419

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All natural diamond are not carbon 12. They contain impurities and some carbon 14 as well as other carbon isotopes. That is why the thermal conductivity of natural diamond is about 2200 W/m*K. It is the carbon crystal structure of diamond that makes it so extremely thermally conductive. Carbon in any other form is junk for a heat sink. The reason that cut diamonds have a slang name as "ice" is not because it looks like ice, but if you take a 3 to 5 carat diamond and put it in your mouth it will be and stay cold.
 

RayJay

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The reason that cut diamonds have a slang name as "ice" is not because it looks like ice, but if you take a 3 to 5 carat diamond and put it in your mouth it will be and stay cold.

You know i actually did that once. I was in possession of a rather large diamond(4.1 carat) and a whole bunch of smaller ones(around 1/2-1 carat each) and was told that they would stay cold.. So i put the smaller ones in my mouth and i could kind of tell that they weren't getting hot but then i put the larger one in at it was cold! Not like ice cube cold but it didn't get hot at all. Was a weird sensation.
 

paul1598419

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That's the diamond's crystal matrix structure that causes that. It truly is amazing if you ever get the opportunity to try it. And it is the reason that my heat sink compound is so efficient.
 

BShanahan14rulz

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Graphene does what diamond does, but only in two dimensions, not three, since it is a two-dimensional crystal structure, innit? Not sure what kind of use that would have, heat spreader maybe, for a non-radiative heatsink? All this thermal stuff can get confusing, sometimes it's best to just overkill with a big chunk of fairly cheap alu or copper and be done.
 

paul1598419

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Graphene is a single layer carbon crystal that does have good thermal conductivity at room temperature, but decreases as the layers are stacked and the more the layers the worse the thermal conductivity. It is usually produced as a tubular single layer structure that is still being investigated for uses for it. I remember when the first graphene structure was introduced several years ago, and it was thought that it would be used as a tether for orbiting satellites around the earth.
 

Zar

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okay silver has about the same, slightly better performance than copper, thing is, copper gets oxidized and looks like crap, if you do an electrolysis, it will look more pleasing, and will increase the heats ability to leave the host more efficiently, even without ribs, with ribs it would be even better, but that would be up to you
 

paul1598419

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Yeah. I've got a copper host and I'm thinking of polishing it and then spraying it with acrylic spray. Maybe two coats ought to do it. Also, the clear acrylic will look shiny on the polished copper.
 

Zar

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Yeah. I've got a copper host and I'm thinking of polishing it and then spraying it with acrylic spray. Maybe two coats ought to do it. Also, the clear acrylic will look shiny on the polished copper.

dont know about that, when I have more time i will take a silver spoon and perform an electrolysis with it and see how that works out, you could just give the host to pros to silver it, will definitely be better than acrylic, shouldnt be that expensive, though what do i know..
 




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