potting pill vs copper chunk or wire

SteveoMiami

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Which of the 3 is better for keeping a pill cool or at least slowing the heating process down.

1. 2 ton epoxy with 1500 grit silicon carbide

2. wound copper wire covered by the epoxy

3. chunk of copper soldered in(paste solder between pill and round chunk then heated with torch) and covered with the epoxy
 

jkpq45

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Arctic Silver makes a conductive "thermal epoxy." A bit more expensive, but conducts heat and keeps things where you put them.

For option 1, not sure what the silicon carbide is for. Smoothing the surface?

Option 3 sounds the best, but modify it to include the AS product I mentioned above.
 

Tana

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More solid metal, the better... always make both surfaces as smoother as possible (sand with 1500 grit sand paper, do not polish) then attach to each other... soldering is OK, but once you have flat metal to metal contact, THIN layer of AA thermal epoxy will do (that you then squeeze out as much as possible by forcing two metals together - in some kind of vise)...
 

SteveoMiami

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jkpq45 my number 1 option is a homemade thermal epoxy that would have better thermal properties than arctic alumina. That stuff is just epoxy with alumina in it and its a little too expensive to fill flashlight heads and whatnot with it. So mixing 2 ton epoxy with the silicon carbide and making a paste is a cheaper solution that should have better thermal properties than the artic alumina
 
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That stuff is just epoxy with alumina

It is not ! Aluminium or silver is in that stuff is milled down to nano size and encapsulated that mean it is not electrical conductive because of nano size is there much less epoxy and that means much faster thermal transport!
 

SteveoMiami

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Alumina is not electrical conductive because its an oxide, oxides are not conductive. Either way its really expensive to pot using arctic alumina or silver. From the research i have done on this forum what seems to be the best homemade thermal epoxy is mixing the 2 ton epoxy about 1 to 1 with silicon carbide. if there is something better please let me know. Right now I think i have a solid copper rod that I can cut pieces from and put in my pills but I need the thermal compound to fill the gaps around an on top of the chunk of copper.
 

SteveoMiami

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would it be better to have my amc7135 chips sitting on the copper that im putting inside with no compound inside? What about a steel epoxy? it would be conductive so what If I fill most of my voids with this and then seal the top off with thermal adhesive. Or fill with a bunch of old solder and cover with a thermal adhesive.
 
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Blazer296

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OK, keep in mind first post newb here, but I have a question as well.

What about a layered approach as follows?

This would be done inside a tube structure like copper pipe cap or whatever as an outer shell, followed by layers.........................
1) non-conductive powder of choice, just thick enough to cover the chips and make a "level" surface and provide good contact with all the components on the board(s)
2)thin layer of thermal adhesive like AA quickly followed by.........
3) a interference/press fitted cylindrical heat-sink pushing it all together tightly.

Of coarse all "holes" would have to be sealed to keep the powder in.

What I am thinking is the powder would readily fill all the spaces around the odd shaped components and allow for us to get back to a flat surface area to apply a heat-sink with minimal use of the more expensive epoxy.
Surely with the powder compressed, and "sealed" by the layer of AA it would still help with vibration damage.

Another good thing, assuming this would work, you could carefully cut it open and extract the board(s) at a later date and the powder would be easy to clean off of since it wont adhere to them.

Again, sorry if the idea is seriously flawwed, I am just getting into all this and have much to learn I'm sure.

Jim
 

DrafterDan

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I suppose it would work, but why go through the headache? There are some non-conductive, ready-made epoxies already out there. I use non-corrosive straight silicone when I'm potting the space between the driver and the underside of the pill. Anywhere else, I'm using arctic thermal epoxy.
Generally I don't worry too much about having to go back in and remove things. I'll just build another pill.
 

Blazer296

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My understanding is the straight silicon will not transfer heat well. I thought that was one of the primary reasons for potting?

Anywhere else, I'm using arctic thermal epoxy.

I would think potting a driver like that would get $$ fairly quick.

Thanks,
Jim
 
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