Thermal Adhesive vs Thermal Compound

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Yourrid
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Thermal Adhesive vs Thermal Compound

I’m rebuilding my Convoy L2 with a XHP50.2 and a RMM FET, and have a question which I couldn’t find an answer to on BLF.

Which dissipates heat from the MCPCB better; thermal adhesive, or thermal compound?

I understand there are a dozen of different types. But in general, which do you think does the job better?

TexasLumens
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I like the adhesive. Be aware though that if you want to swap out an LED later….. WHEW! You’re most likely going to nOT have fun. As well, I find that the compound is messy and remains that way forever. Good Luck with whatever you choose.
TL

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Enderman
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If you’re holding down the MCPCB with screws or something, use thermal compound.
Only use thermal adhesive if you also need to glue the thing down so it never moves again.

Lightbringer
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Enderman wrote:
Only use thermal adhesive if you also need to glue the thing down so it never moves again.

Emphasis on “never”.

Oh, and only if you’re positively absolutely 100%ly sure the LED is perfectly centered. Any bit of “slop” off-center, and if the reflector is a little too snug, it’ll at the very least try to push the LED laterally, possibly hard enough to try to break it free of its solder-pads.

At least with regular thermal ook, the whole star can slide around to some degree, provided it’s not also bolted down unbelievably tightly.

Then again, adhesive can keep the whole star from rotating around and yanking on the wires if something’s really grabbing at the LED while the bezel/cap/whatever is being torqued down.

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Enderman
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Lightbringer wrote:

Emphasis on “never”.

Well technically I once removed an MCPCB that was stuck on with arctic silver thermal adhesive, but it took some hammering of a flat head screw driver underneath and prying it apart Silly

Honestly I just recommend MX-4 to people, it’s great thermal paste.

lumenzilla
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I prefer compound over adhesive, at least I’ll still have a chance to nudge the LED a bit to make it perfectly centered.

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Enderman
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BTW I guess I never directly answered the question, but thermal conductivity goes like this:
liquid metal thermal compound > thermal compound > thermal adhesive > thermal pads

Obviously depending on the brand or quality you can have X that performs better than Y or the other way around, but in general this is the case.

Lightbringer
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Enderman wrote:

And if I had the time and patience, I’d just solder the (Cu) PCB right to the (brass) pill itself.

But similarly, everything needs to be perfectly centered while the solder is still liquid. So it’s a double-decker reflow job, LED and PCB.

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Enderman
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Lightbringer wrote:

And if I had the time and patience, I’d just solder the (Cu) PCB right to the (brass) pill itself.

But similarly, everything needs to be perfectly centered while the solder is still liquid. So it’s a double-decker reflow job, LED and PCB.


Use liquid metal.
Not only is it more thermally conductive than solder, but it is easier to create a good consistent bond between the pieces since it’s fluid, without heating up your components at all.
And it’s removable Smile

There are 3 main liquid metals:
Coollaboratory Liquid Pro
Coollaboratory Liquid Ultra
Thermal Grizzly Conductonaut

Both the Conductonaut and Liquid Pro have nearly identical conductivity, which is like 76W/mK or something like that, higher than solder.
However, the reason Liquid Ultra was made is because Liquid Pro had some issues with being very difficult to apply or something like that, so I would recommend staying away from the Pro.
The Conductonaut is as good as the pro, but is very easy to apply and works well, while having over 2x the conductivity of the Ultra (which translates to one or two degrees of temp difference IRL)

This is what I’ve found from my research, and I’ve recently bought some tubes of Conductonaut to put in my OptoFire thrower, maybe I can get some more lux out of it, will need to test Smile

Lightbringer
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Enderman wrote:
Use liquid metal.

Was tempted to at least try it, but I generally don’t push my critters all that hard. It’s nice to keep them as cool as possible anyway, but for now I’m pretty happy with AS5.

I might try pushing a 219B a bit past its comfort zone, and then something like LM might be worth it.

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Enderman wrote:
Lightbringer wrote:

And if I had the time and patience, I’d just solder the (Cu) PCB right to the (brass) pill itself.

But similarly, everything needs to be perfectly centered while the solder is still liquid. So it’s a double-decker reflow job, LED and PCB.


Use liquid metal.
Not only is it more thermally conductive than solder, but it is easier to create a good consistent bond between the pieces since it’s fluid, without heating up your components at all.
And it’s removable Smile

There are 3 main liquid metals:
Coollaboratory Liquid Pro
Coollaboratory Liquid Ultra
Thermal Grizzly Conductonaut

Both the Conductonaut and Liquid Pro have nearly identical conductivity, which is like 76W/mK or something like that, higher than solder.
However, the reason Liquid Ultra was made is because Liquid Pro had some issues with being very difficult to apply or something like that, so I would recommend staying away from the Pro.
The Conductonaut is as good as the pro, but is very easy to apply and works well, while having over 2x the conductivity of the Ultra (which translates to one or two degrees of temp difference IRL)

This is what I’ve found from my research, and I’ve recently bought some tubes of Conductonaut to put in my OptoFire thrower, maybe I can get some more lux out of it, will need to test Smile


There’s also galinstan. Which is way cheaper and some reports say that it is Coollaboratory Liquid Ultra.

Also with such advices it’s best to always remind to never use liquid metal in alu flashlights as it’s highly corrosive for them.

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Enderman wrote:
Lightbringer wrote:

Emphasis on “never”.

Well technically I once removed an MCPCB that was stuck on with arctic silver thermal adhesive, but it took some hammering of a flat head screw driver underneath and prying it apart Silly

Honestly I just recommend MX-4 to people, it’s great thermal paste.

I’ve had good results heating the pill/shelf with heat gun or soldering iron—- MCPCB pops off much easier—-The adhesive has a melting point

snakebite
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good compound has better heat transfer than any thermal epoxy.
i have never used any in a flashlight but i have used steel filled epoxy(jbweld) to mount luxeon altilon and star boards in lamps.
works surprisingly well and cheap.
i also put jbweld around the edge of the pcb in 9 led cheapies that i put the hi cri 5mm in to transfer more heat to the tube.
it makes a difference you can feel.

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Enderman wrote:
Lightbringer wrote:

And if I had the time and patience, I’d just solder the (Cu) PCB right to the (brass) pill itself.

But similarly, everything needs to be perfectly centered while the solder is still liquid. So it’s a double-decker reflow job, LED and PCB.


Use liquid metal.
Not only is it more thermally conductive than solder, but it is easier to create a good consistent bond between the pieces since it’s fluid, without heating up your components at all.
And it’s removable Smile

There are 3 main liquid metals:
Coollaboratory Liquid Pro
Coollaboratory Liquid Ultra
Thermal Grizzly Conductonaut

Both the Conductonaut and Liquid Pro have nearly identical conductivity, which is like 76W/mK or something like that, higher than solder.
However, the reason Liquid Ultra was made is because Liquid Pro had some issues with being very difficult to apply or something like that, so I would recommend staying away from the Pro.
The Conductonaut is as good as the pro, but is very easy to apply and works well, while having over 2x the conductivity of the Ultra (which translates to one or two degrees of temp difference IRL)

This is what I’ve found from my research, and I’ve recently bought some tubes of Conductonaut to put in my OptoFire thrower, maybe I can get some more lux out of it, will need to test Smile

This says none of those products are to be used with aluminum heatsinks, and that’s awfully restrictive since most of our flashlights have an aluminum pill.

http://www.tomshardware.com/reviews/thermal-paste-performance-benchmark,...
http://www.thermal-grizzly.com/produkte/25-conductonaut

It could be a good match for builds with a brass or copper pill or at least a copper spacer.

The low mode should be lower.

Reviews: Efan IMR18350 700mAh 10.5A, <a href="http://

kramer5150
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I’m sure the OP is well on his way by now. FWIW, I use AS5. Its messy as all hell though, so a little dab in the center of the MCPCB/star goes a LONG way. I put a couple small dabs of JB weld at the perimeter of the MCPCB, and while its still wet I assemble everything so the LED is centered and compressed flat and let the JB weld dry.

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I read that oslon black led doesn’t need a lot of thermal paste.. so thermal tape might be the best option.

The_Driver
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Newlumen wrote:
I read that oslon black led doesn’t need a lot of thermal paste.. so thermal tape might be the best option.

This statement doesn’t make much sense to me. The Osram Black Flat has a very high power density. It requires carefully designed heatsinking to get optimal performance. This is best done by not conducting current through the flashlight body (because of the not electrically neutral, central solder pad of this LED). This allows you to use a standard dtp pcb, polished and screwed down onto the body with a very thin layer of thermal paste or liquid metal etc.