What's the best for transfering heat?

What\'s the best for transfering heat?

I'm going to mod some lights and I wanted to know what transfered heat from the star to the heatsink best. Both my costco lights and my xm-3 had some white paste like stuff under them, what is it and is there anything better?

Re: What\'s the best for transfering heat?

The best (easily available) materials to transfer heat are: silver, copper, aluminium. In that order.

The white compound you found is probably "Arctic Silver" or some similar stuff used to fill the very small gaps between a CPU core and the cooler mounted on it (almost everything conducts heat better than air).

The best way to keep a Lux cool is probably to solder it directly on a massive silver disc of some sort.

-Connor

Re: What\'s the best for transfering heat?

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Connor said:
The best (easily available) materials to transfer heat are: silver, copper, aluminium. In that order.

-Connor

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As in "heat transfer" do you mean best conductor of electricity/etc.? Anyways, what he said is true... however, I do believe gold is the best conductor... although not too easily available/affordable... but usually it is gold plated over metal.

Re: What\'s the best for transfering heat?

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alexthehobbyist said:
[ QUOTE ]
Connor said:
The best (easily available) materials to transfer heat are: silver, copper, aluminium. In that order.

-Connor

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As in "heat transfer" do you mean best conductor of electricity/etc.? Anyways, what he said is true... however, I do believe gold is the best conductor... although not too easily available/affordable... but usually it is gold plated over metal.

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PLEASE look these numbers up before you post.

SILVER conducts HEAT and ELECTRICITY better that GOLD.

Period.

The "gold is better" is a common myth.

Re: What\'s the best for transfering heat?

And welcome to CPF.

/ubbthreads/images/graemlins/tongue.gif

Re: What\'s the best for transfering heat?

I want it to conduct heat not really electric. I have a heatsink, all I need is the stuff you put under the star/emitter to help transfer the heat better.

Re: What\'s the best for transfering heat?

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turbodog said:
And welcome to CPF.

/ubbthreads/images/graemlins/tongue.gif

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And hello to you to and all the Flashaholics at CPR. /ubbthreads/images/graemlins/grin.gif

Re: What\'s the best for transfering heat?

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Connor said:
The best way to keep a Lux cool is probably to solder it directly on a massive silver disc of some sort.



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I don't agree with this, while "a massive silver disc" will transfer heat, the end results depend on transfering it somewhere else. Like to a large surface area that can then give it to the air.

More importantly, even if you could get solder to stick to the LS (which you can't), heat would destroy the part long before solder would flow. I'd put it "The best way to kill a Lux is probably to solder it directly on a massive silver disc of some sort."

Doug Owen

Re: What\'s the best for transfering heat?

Some info on silver, copper, aluminium and gold:

47 - Ag - Silver
Electrical Conductivity: 62,9 10^6omg-¹cm-¹
Thermal Conductivity: 429 Wm-¹K-¹ (at 300 K)

29 - Cu - Copper
Electrical Conductivity: 60,7 10^6omg-¹cm-¹
Thermal Conductivity: 401 Wm-¹K-¹ (at 300 K)

13 - Al - Aluminum
Electrical Conductivity: 37,7 10^6omg-¹cm-¹
Thermal Conductivity: 237 Wm-¹K-¹ (at 300 K)

79 - Au - Gold
Electrical Conductivity: 48,8 10^6omg-¹cm-¹
Thermal Conductivity: 317 Wm-¹K-¹ (at 300 K)

As you can see, gold is neither a very good electrical nor thermal conductor. The reason why gold is used is because it will not oxidise easily or bind with other metals it comes in contact to (-> battery).

-Connor

Re: What\'s the best for transfering heat?

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Doug Owen said:
I don't agree with this, while "a massive silver disc" will transfer heat, the end results depend on transfering it somewhere else. Like to a large surface area that can then give it to the air.

More importantly, even if you could get solder to stick to the LS (which you can't), heat would destroy the part long before solder would flow. I'd put it "The best way to kill a Lux is probably to solder it directly on a massive silver disc of some sort."

Doug Owen

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You need to get the heat away from the LED as quickly as possible. A flat and massive cooling element made from pure silver would be the best material posssible. "Transfering the heat somewhere else" is exactly what you want to do, and silver is the best material for it. Copper is almost as good and cheaper.

-Connor

Re: What\'s the best for transfering heat?

I repeat.
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lasercrazy said:
I have a heatsink, all I need is the stuff you put under the star/emitter to help transfer the heat better.

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Re: What\'s the best for transfering heat?

do you need GLUE too?
or do you want it to be removable?
ArcticSilver epoxy stuff works good.
arcticAlumina epoxy stuff is lesser
i have been using J&B weld, with good results, NOT the quick trash, its different.
but I ALWAYS make sure there is as much metal to metal contact first, then clamp it hard to achieve metal to metal as best as possible, then cure it for the FULL TIME, before heating.

if you want it removable arcticsilver5 is a thick paste, after you clamp and HEAT it, then keep it clamped lightly, like with a modamag sink and optics or reflectors crushing down on it, it would work good.

all the cruddy white stuff sucks, and gets worse over time, but EVEN arcticsilver5 gets cruddy overtime vrses arcticsilver epoxies. the oil in that non glue stuff always dissapates eventually in the heat, leaving a drier blob of metalized goop.

BTW you can solder an emitter to a copper sync without destroying it, and you can destroy it TOO /ubbthreads/images/graemlins/smile.gif done both them, and would never attempt it again, even if the finished one works great.

Re: What\'s the best for transfering heat?

get heat sink compound from an electronic store, dont know if radio shack carries it. it is white paste form and when you are done applying to surfaces... wash your hands(because you will get it on them). reason being, it burns (what little amount is on your fingers), when you rub your eyes.

Jim

Re: What\'s the best for transfering heat?

the stuff at radioshack is really bad, worse than what you can get at a hardware store.
i still use it, but its the lowest quality of any of the stuff i have found. it will certannly work, but that is all.

Re: What\'s the best for transfering heat?

In my experience, I no longer use any type of epoxy. I use Ceramique by Artic Silver. It is not an epoxy. Then use mechanical fasteners. The key to good heat transfer is not the holding strength, its the mechanical pressure between the two mating surfaces.

For example, take the CPU/Heatsink Fan. The pressure applied to the CPU by the heatsink clip is what transfer the heat.

Another example, electic stoves. Place a boiling pot of water, turn the stove on to the highest setting and push down on the pot. The time to get the water to boil will be shorter than if you didn't push down on it.

Just my 2 cents.

Re: What\'s the best for transfering heat?

carbon black is somewheres up there.good luck finding some.

Re: What\'s the best for transfering heat?

I just ordered some acticsilver5 and Ceramique.

Re: What\'s the best for transfering heat?

Lasercrazy,

You did good! If you are really "anal," lap the bottom of the aluminum star board flat and hope your sink is flat to match. The key to thermal transfer is maxamizing surface area and minimizing the thickness of the interface compound! Both of those compounds are up to the task.

Larry

Re: What\'s the best for transfering heat?

what larry said /ubbthreads/images/graemlins/grin.gif

been favoring AA grease on slug, getting just the right amount to fully cover metal slug without ozzing out to plastic base.

then a tiny drop of super glue to base of emitter. wicking action will pull superglue all the way around.

press down firmly for 2-3 minutes and you are done. you now have an emitter that is firmly glued down with proper thermal compound and retain option of removing emitter without damage.

Re: What\'s the best for transfering heat?

That's already been done. /ubbthreads/images/graemlins/grin.gif

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tvodrd said:
Lasercrazy,

You did good! If you are really "anal," lap the bottom of the aluminum star board flat and hope your sink is flat to match. The key to thermal transfer is maxamizing surface area and minimizing the thickness of the interface compound! Both of those compounds are up to the task.

Larry

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