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Liquid Heatsink Material

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Yeah Silicone doesn't transfer heat but rather shields from it. USAbro you obviously don't have experience with it otherwise you would've known that. You really need to stop trying to give advice because it is always wrong. Not being mean but you seriously need to stop. If he took your advice he would have destroyed his laser.

With that said, It looks like there's no cheap way of doing what you want scifiguy. Indium foil would be too pricy though wouldn't it? Arctic silver would be too for the amount you would need. Arctic alumina is cheaper but it's exactly that, cheaper.

I asked around about this a few years ago myself and didn't find an alternative that was both cost effective and a great solution. Would be better to just machine the part.
Hope that helps put things into perspective.
I've used it to dissipate heat before but it is an silicone based aluminum caulk I used for dissipating heat in servos for a water rocket launching mechanism.

Yeah, I did change my post but I fixed it again so people would know what I said. I can't remember exactly what I said but I think I got it right.
 

Encap

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Check this stuff out.

https://tds.us.henkel.com/NA/UT/HNA...2579CF0062C670/$File/STYCAST 5952-1 AB-EN.pdf

There are other good, thermally conductive, silicone encapsulants available, but not regular "high-temp" silicone like from the auto parts store. "High-temp gasket sealer" silicone, as our resident expert USABro suggested, is more of a thermal insulator than a thermal conductor. Sure, it'll pass some heat, but it'll hold in a lot more than it will conduct.
FWiW,
G
scifiguy ---- "good" is relative -----to give you an idea of how bad this stuff is as a themal conductor--- copper conducts 400 W/mk , Aluminum conducts 215 W/mk. This goop from henkel conducts 0.8 W/mk which is about the same as glass or concrete---gravel is 0.7 W/mk!

To answer your original question is: No there is not a decent thermal epoxy or similar material that can be used to fill out space in a host between an off the shelf heatsink and the head cavity of the host. ( yes there are many materials that could be used to fill the gap---none of them thermally conductive enough to be a decent heatsink extension thermally)

Best solution is to machine a metal part for the purpose as VisibleGreen mentioned already.
 
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scifiguy

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I appreciate all the discussion and suggestions. I plan to ask some of the thermal engineers at work, and see what they say. I'll report back what I learn. No doubt a machined chunk of copper or aluminum is by far the best.
 

Gadget

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Wow...I stand corrected. I didn't realize it was so low.
After looking at this table, it looks like you're right. Of course, there's nothing that's going to beat copper or aluminum, or any of the metals for that matter, but the op was asking for a formable solution, and that was the best I found. Still, it's several times better than "high-temp silicone".

(EDIT)
Thanks for setting me off on the path of really exploring material conductivity, Encap!
And, sorry scifiguy, you're not going to find any formable solution that will even APPROACH solid metal (of course).
(/EDIT)

-G
 
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Alaskan

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But, how thick can you apply it and how does that change the thermal transfer properties?
 

Sigurthr

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Not sure if it was missed when I said it before, but I'll repeat it since I see the conversation continuing....

INDIUM FOIL.

There's a right way to do things, and it isn't always easy, cheap, or available out of a squeeze tube.
 

Gadget

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On that note, Sig....I just looked up the thermal conductivity of indium, it's only 86 W/(m - K).

If a foil is going to be used, why not aluminum foil at 240 W/(m - K).

Scifiguy...foil might not be a bad idea. Light duty aluminum foil could be compressed (a little at a time in the gap) into a relatively solid mass. Of course there would still be small air gaps, but if you pack it in well, I think it would be a much better solution than any encapsulant. Plus this option would still leave you with a removable heat-sink.

FWiW,
G
 

ARG

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Not sure if it was missed when I said it before, but I'll repeat it since I see the conversation continuing....

INDIUM FOIL.

There's a right way to do things, and it isn't always easy, cheap, or available out of a squeeze tube.
It's not exactly a liquid though :p
 

Encap

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On that note, Sig....I just looked up the thermal conductivity of indium, it's only 86 W/(m - K).

If a foil is going to be used, why not aluminum foil at 240 W/(m - K).

Scifiguy...foil might not be a bad idea. Light duty aluminum foil could be compressed (a little at a time in the gap) into a relatively solid mass. Of course there would still be small air gaps, but if you pack it in well, I think it would be a much better solution than any encapsulant. Plus this option would still leave you with a removable heat-sink.

FWiW,
G
Are you sure you would not just be creating a a compressed aluminmum foil insulator becuase it is impossible to eliminate air bubbles in between the layers of foil and air bubbles keep IN heat rather than getting rid of it?
 
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Hemlock_Mike

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At one time there was a product called Arctic Silver epoxy.
I used it long ago but for small gaps where I also needed the glue.
There isn't much which will fill gaps thermally. Indium foil works
but also for small gaps.
HMike
 

CDBEAM777

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Well....Hmmmm.... ?? I have used Artic Silver Epoxy. It is a typical two (2) part epoxy.
Gets a good set in about 10 min. The thermal conductivity is about Than 7.5 W/mK .....so....the I-Foil is far superior....and is what I have seen used.

Optimal solution...IMNSHO...Copper press fit next to the diode, then Ally to dump the heat to atmosphere. But, this is not the most easy combination to achieve, especially the press/friction fit !!! Machining +/- .....1/1000 of an inch is not a piece of cake !!.....Well...at least for me.....but....then....I am a "Hack " machinist !!! Anyway...my 2cents !! Good luck...
 

Encap

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Sigurthr

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Indium is so soft it will fill voids like a liquid when compressed. It will actually ooze out of cracks.
 
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Grix

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I for one would like to see a laser head filled to the brim with mercury :)
 
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So, not to derail the thread a bit, but what would be good to use if you want to electrically isolate the laser module from the host? Cheapy hosts use plastic parts...
 

LaserCo

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So, not to derail the thread a bit, but what would be good to use if you want to electrically isolate the laser module from the host? Cheapy hosts use plastic parts...
Stuff like this? (1.5W/mk)
(Link)--> 200x200x0 5mm Heatsink Silicon Compound Thermal Conductive Pad 1 5W MK | eBay

I bought some small heatsinks and on their bottom sides they came with double-sided stickers with one top layer of easily peeled off - like wax paper, expose the "stickum"..

What I am guessing is this stuff, (it is like neoprene foam! yet real thin) may even be real being that I got it on ebay..

I can see how someone could mistake silicon caulk as being similar in conductivity as this stuff is... maybe
(Though NOT! if your intention is blab-blab in reply to every post possible - for some reason...)

I have a 1.5meter-ish? long roll of this stuff I orderd on ebay a while ago, it is 1" wide, I have not tested this stuff out yet.
 




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