Potting Drivers - Budget reversable option?

Plasti-Dip and copper and JB Weld are all better than air. Is Plasti-Dip enough easier to work with that it makes the lower performance acceptable? I don't think so. 'Better than' doesn't mean it'll work well enough to make a real-world improvement.

Liquid sodium metal is sometimes used to cool automobile valves. I don’t know if a driver is hot enough to liquify it, anyway it reacts violently with water or air. Next best is water, but it tends to pick up ions and hydrolize. I tried alcohol, but it softened the epoxy. Oil has been used in consumer led products. Freon has been used in computers, including the CDC 7600 and the Cray II.

Bare ram vs heat spreaders is convection, for a driver its conduction.

With ram and heat spreaders you are running into where the bare surface of the ram chips provided better convection (transfer to air) then the spreaders. Spreaders are just flat colored metal thats trying to look cool. No fins to improve convection.
When you have a driver enclosed inside an airtight host you need to conduct heat to the host before it can be shed.

Yep, nearly anything is better then air for conducting heat away from your driver.
As long as you don’t use wool, cotton, sawdust, sprayfoam or anything else that comes with tiny pockets of air. :stuck_out_tongue: :beer:

No, you're missing the point here. It's the same amount of effort to use Plasti-Dip and JB Weld, yet they have vastly different heat transfer abilities. Does it make sense to use the material that doesn't work as well, simply because it's 'better than nothing'?

No, no-no, I think your missing the point. /joke :beer:

I was never arguing against JB weld.

Plastidip is better then air, JB weld is much better then Plastidip.

And where do the common products used for potting come into play? Like Fujik? What about Arctic Alumina Thermal Adhesive? Either of those could be prevented from sticking in a similar manner that stops the JB Weld, so why aren’t they considered?

Just got my first AA yesterday. Trying to figure out the best situation to use it.

I think JB Weld is, possibly, better thermally than Arctic _____ epoxy. I don't have a way to measure it though. I do know it's easier to get, and in much larger quantities, and at a far far lower price (JB 'Industro-Weld' is regular long-cure-time JB Weld, just in GIANT tubes that last several lifetimes). But some shy away from it because it has iron particles in it, and is magnetic, though I've never had it do anything strange to electronics (it's non-conductive when cured).

Fun tip: mix some isopropyl in (acts as a solvent) with the 'Steel' paste, and you have a pseudo-ferroflluid that goes psychedelic in the presence of a strong magnet.

edit: Fun tip #2: Mix a batch of 1/3 Steel, 1/3 Hardener, and 1/3 Permatex Ultra Grey RTV silicone... no spoilers, just try it. :bigsmile:

What about various doughs, like that doughy eraser material, or that stuff used to put up posters, or even play-do? There's this if you can find a vendor.

This might be an excuse for me to buy a thermometer w/thermocouples.

The three usual ways to transfer heat are conduction, convection and radiation.
Good heat conductive materials are mostly metals that might cause short circuits, but there are others commonly used to cool electronics.
Air transfers heat by convection in all but the smallest systems. But its density (and therefore heat capacity) and heat conductivity are low. Most other fluids transfer heat better, but they have other problems.
Hard anodized aluminum radiates infra-red radiation well, but that works best if the thing to be cooled is quite hot. (I am confident in this. My boss looked it up when I told him my intuition should not be trusted.)

AA is kinda expensive to be using as a potting compound, isn’t it? It’s like 8 bucks for 5 grams.

I dont think so. Arctic stuff is developed to stick "ok" and transfer heat well. JB weld is developed to stick like hell and the rest is just a side effect. Arctic Alumina might even be better, but Arctic Silver certainly is. Its just expensive as hell..

Also, I cant really follow your arguing about RAM. If heatspreaders made of aluminium increase the surface area by a factor of 3, the chips will run cooler.

What happens? :P

'Designed to' and 'does' are two different things. Primarily, it's designed to appeal to people with enough spare cash to spend $15 on a tiny little tube of fairy dust (er... fairy juice?). Anyway, the thermal compounds market is ripe for exploitation of magical thinking, much the same as the 'audiophile' community where people pay a thousand bucks for a generic power cord and swear it makes a dramatic improvement in the sound quality.

Now explain to me how a flat rectangle of aluminum has more surface area than a PCB with eight multi-legged chips and capacitors and resistors soldered to it.

Use a copper heatspreader linked to the pill with copper wire (s). Take advantage of that super high heat conductivity. That's my plan. Some potting will just be used to accommodate components of different height and to prevent shorts.

Well, Arctic Silver has about the same thermal conductivity as some silver based thermal greases and a lot of tests show it has a pretty good thermal conductivity.

JB weld is in the range of <1W/mK. Arctic Silver is about 8. I agree with your point about hifi voodoo, but unless someone measures the difference between JB weld and AS to be negligible, I still use AS to glue my stars down. Fujik is about 1W/mK too.

I'm not sure we are talking about the same with the RAM heatsinking. The chips are usually not glued to the board, the large aluminium bars are glued to the chips. I doubt that no heatsinking would be better than 2 aluminium bars.

What about some jbweld mixed with aluminium powder…?
What about these stuff for filling car dents?

The uhu 2k glue I always use for repairing and so on has a thermal conductivity of about 0.25W/mK

Thanks everyone. Some good ideas and thoughts to ponder.

I ordered some of the thermal pads linked to by RaceR86 because they look good to have on hand.

I really like Comfy's JB Weld idea and will try it when if will fit my app. My current app has too many obstacles for it.

I may try leftye's idea (Post 27) in my current app as I have a copper pill that can be soldered to, but I really like the idea of just injecting silicone or something into the pill once I feel the light if finalized. The above thermal pads are silicone and are white. That indicates they probably contain alumina. I will search to see if their are any non-corrosive silicone products out there like that. I wonder how much alumina power can be mixed in silicone before it begins to become electrically conductive?

Alumina powder shouldn’t become conductive as it’s ceramic based. Unless you meant to say aluminum powder. That would be entirely different.

Since ceramic is an insulator, it shouldn’t ever produce a short. Just like in the good ole days where home wiring was exposed, without insulation of any type, and run in parallel rows through white ceramic insulators to the rotary switch.

Any RTV marked as 'oxygen sensor safe' is what you're looking for. Go to the auto parts store, not Lowe's/HD.

Now we are getting somewhere. Combining alumina powder and RTV marked as 'oxygen sensor safe' sounds like the solution I'm looking for. Thank you DBCstm and Comfychair!

Comfy, in your experience, does that RTV stuff peel/crumble off driver type surfaces fairly easily? If its like other gasket maker stuff like I have used in cars and bikes, I imagine it does.

Permatex Ultra Grey. It still sticks like hell, but it's not gooey/slippery/slimy like clear RTV when you have to scrape it off. It's much stiffer when cured.