Potting Drivers - Budget reversable option?

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ImA4Wheelr
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Potting Drivers - Budget reversable option?

 

Update:

So here are the 2 recipes that have been developed.  They have not been tested for safety or effectiveness.  They are very cheap way to reversibly pot your driver or what ever:

Very easy, low cost, no wait recipe:

  • Ground Silicon Carbide (Both Medium and Fine Grit) - Suggested by TexasPyro
  • Duct Seal - Suggested by Leaftye

Complete removal after being in a light for an extended period is not an easy task.  Pull off what you can by hand and then us an alcohol to clean off the residue.  For all the little nooks and crannies, I use plenty of alcohol and a tooth brush.  I recommend you don't press this potting mix into all the nooks and crannies if you think you may be removing it later.

Silicone Recipe (Haven't tried yet):

 Mix to desired consistency.  For duct seal recipe, I like to mix as much silicon carbide in as I feel the it can take and still stick together.  If I want it more pliable, I use less silicon carbide.

Original Post:

I want to pot a couple drivers, but I want it to be reversible. Does anyone have anything they recommend? 

Would silicone work?  It seems to crumble off stuff fairly cleanly.  If yes, what type would be best to conduct heat and not cause shorts?

Edited by: ImA4Wheelr on 07/02/2014 - 23:42
Helios-
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If you try silicone be sure its neutral (non-corrosive).


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ohaya
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There’s “thermal pads”, which are thermally conductive, and more like “putty”. I think that IOS provides that with some of the drivers that they sell, e.g., the 3.5/4.5 amp driver (see pic):

http://intl-outdoor.com/xml-multicell-circuit-board-45a-ouput-55126v-p-5...

RaceR86
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Here are small pieces like that:

https://www.fasttech.com/p/1285500

I would not consider them a good a option to potting..Better than nothing though.

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garrybunk
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You should easily be able to remove the drivers cleanly from this type of potting:

1

Sorry,
-Garry

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RaceR86
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^

LOL!

haha... Big Smile

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ImA4Wheelr
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Garry, you're banned from posting to my threads.

 

ok, it was kind of funny.

 

Thanks for the ideas guys (except for Garry Wink).   I would like to use something that fully surrounds all the components.  I could use thermal paste, but I really don't like the invisible residue it leaves.  Very hard to completely get rid of and it interferes with future soldering.

Any other ideas out there!

Werner
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Plastidip is removable…

comfychair
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Carnuba wax and JB Weld.

http://75.65.123.78/jb/Dsc06019.jpg

http://75.65.123.78/jb/Dsc06020.jpg

ImA4Wheelr
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Does Plastidip transfer heat better than air?

 

Not sure I could use JB Weld for my apps, but that is cool Comfy.  Did you wax the driver so that it was a release agent for the JB Weld?

DB Custom
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I love that, excellent idea Comfy! When I first saw the question JB Weld came straight to my mind, but I didn’t think about the wax to make it easily removable. Good stuff! Wink

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Yep, it's just a release agent. Cool thing about it is that you can lay it on thick where you want to prevent the epoxy from getting into, like under the corners of chips or under exposed leads, etc. It doesn't affect the epoxy curing, either. Just scrub everything clean with an old toothbrush and shampoo afterwards and it's all gone.

I'm planning to use that method for the difficult IOS 9A driver in a big Maglite pill. Works neat for boards where the hot things aren't on the same level, this gives them all a common surface that will have a nice flat surface for contact to the ID of the pill, and even has good contact to the PCB. Any pinch points that make it fit too tight can be opened up with a tiny engraving bit in a Dremel, I haven't found JB Weld to do anything strange electrically, but it really only needs to make good contact with the flat areas on top of chip packages and whatever.

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ImA4Wheelr wrote:
Does Plastidip transfer heat better than air?

Nearly anything is better then air.


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comfychair
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Helios- wrote:
ImA4Wheelr wrote:
Does Plastidip transfer heat better than air?
Nearly anything is better then air.

How about a wool blanket?

Reminds me of the arguments many years ago about aluminum 'heat spreaders' glued to PC DDR RAM. RAMBUS needed them, as the first chip was worked harder than the others, and thus ran hotter, and spreading the heat from a hot area to a cooler area actually did some good. Then somebody had the bright idea to stick them onto regular DDR RAM which ran all the chips in parallel and so they were all the same temp, with no thought put into it other than 'they look neat so they must work', and all the little aluminum shields did was to keep everything insulated and away from any airflow that might do some actual good.

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Only thing that insulates better then air... many pockets of air1. Try to think of a material that doesn't rely on pockets of air. Best insulator in the world? Aerogel, 99.98% air by volume, record lowest-density solid.

1. Ignoring vacuum.


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comfychair
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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.

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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.

Flashlight designers should look at lighthouses and pottery.
这些谁设计的手电筒应该看灯塔,以及在陶器。

Helios-
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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. Silly Beer


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comfychair
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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'?

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

I was never arguing against JB weld.

Helios- wrote:
ImA4Wheelr wrote:
Does Plastidip transfer heat better than air?
Nearly anything is better then air.

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


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DB Custom
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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.

comfychair
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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:

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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 low mode should be lower.

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Fritz t. Cat
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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.)

Flashlight designers should look at lighthouses and pottery.
这些谁设计的手电筒应该看灯塔,以及在陶器。

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

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

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comfychair wrote:
I think JB Weld is, possibly, better thermally than Arctic _____ epoxy.

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.

comfychair wrote:
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 happens? Silly

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NightCrawl wrote:

comfychair wrote:
I think JB Weld is, possibly, better thermally than Arctic _____ epoxy.

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.

'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.

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NightCrawl wrote:
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.

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.

The low mode should be lower.

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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.

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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

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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?

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