Are You On Pot????? (potting and heatsinking with epoxy and silicon carbide)

Flashlight Modding and DIY Parts
10

Nah. But I´ve used it before but based on ordinary silicone from the hardware store and mixed in lots of the silicon carbide dust you also use.

Gives you a few hours to work with it. And it mixes quite well. I put a few drops of silicone oil in it to make the mixing better. Also seemed to keep the air out of it better.

This compound can be remowed btw. If you know you might remove it later you can spray the driver and cavity in a thin film of silicone oil before applying it. Then it is quite easy to get out.

11

try “depleted fujik”. spread it thinly on paper and let the paper absorb the silicone oil. scrape it off then spread again on another sheet. the consistency of putty

well there’s still convection and radiation of heat. so styrofoam is worse than air

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Ledsmoke wrote:

Nah. But I´ve used it before but based on ordinary silicone from the hardware store and mixed in lots of the silicon carbide dust you also use.

Gives you a few hours to work with it. And it mixes quite well. I put a few drops of silicone oil in it to make the mixing better. Also seemed to keep the air out of it better.

This compound can be remowed btw. If you know you might remove it later you can spray the driver and cavity in a thin film of silicone oil before applying it. Then it is quite easy to get out.

Great tip. I will be trying this. I've just been using my potting recipe that I have a thread on. It's great because there is not curing time, but it's a hassle to remove.
14

Thanks for sharing.

Do you, or anyone know of a good place to buy suitable silicon carbide with free shipping?

15

Here in the USA it's almost always available domestically on ebay. Hopefully, you will have the same there in Norway.

16

I compacted a pure copper scrubber in my 15 led light. It does seem to help.

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What grit of silicon carbide powder do you guys use?

19

I use one that is a mix of like 220 and 4xx. I have some 1500, but I don't use it because it goes airborne easily and I don't want to inhale it.

20

I noticed reading up on Arctic silver 5 that they actually use different grits in their mix. I’ll be ordering more silicon carbide soon in various grits. Makes sense to mix the smaller particles with some larger depending on what you are using it for.

21

Then there is this……http://www.pflexpro.com/ At the top of his page Flashlight 101, then to the left the list “Potting”

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http://www.pflexpro.com/

23

Crazy question…would sensor safe RTV or silicon and the above silicon carbide make a softer easier to remove potting for say drivers in case you needed to “peel it off”

24

That is cool and they are right on about the potting. I also like the copper ring they use for the outside of the drop in. That is exactly what I do and it works. I can’t remember who it was on here that suggested that instead of the aluminum foil trick but they were sure right. Easy to take on and off and works perfectly. I have thought about going the extra yard and even filling that in more with potting compound but then it would no longer be a drop in at all. Still it would have some advantages depending on how hard you want to push it. I built a couple 502B’s with 5 amp dimming drivers and was tempted to pot the drop ins so they would bet even better thermal transfer. But like I said, they would no longer be drop in’s then. I did of course pot the drivers anyway.

25

I didn’t know silicon carbide, a mineral, was such a good thermal transfer material.

26

any material other than air is much better at moving/absorbing heat, especially stagnant air inside a pill that isn’t moving…air does “ok” if it is moving, but if it is just sitting there it really does no good at moving heat away from an object

http://www.ioffe.ru/SVA/NSM/Semicond/SiC/thermal.html

with mixing epoxy and silicon carbide, it still averages out much better than stagnant air

I actually put a blob of silicon over the chip on my TP4056 charger module…what I noticed was that instead of the chip getting so hot you can’t touch it at 1A draw, the entire board is now quite warm but not crazy “burn your fingertip hot” when air was the only medium to move the heat from the chip (sure if they had it soldered to a surface mount vias or whatever it would be better but the IC in that package pretty much just sits above the board and doesn’t transfer heat very efficiently), sure there is the issue of it maybe keeping the heat in, but when it diffuses the heat over a larger area, and allows the heat to soak away into the board it lowered the temperature (I’m sure there is a laundry list of calculations and maths involved…but it breaks my brain)…all fine and dandy until you put the daggum battery in backwards (no reverse polarity protection = kaput IC…dangit)
That is pretty much my real world experience with conformal coating/potting/heatsinking…

27

It’s actually really interesting stuff. It’s man made now and it’s considered a ceramic. It has very high thermal conductivity. On the chart I was looking at it was the best of the ceramics by quite a bit. I can’t find the chart right now but this site is pretty good shows it’s properties. Really neat stuff.

28

It probably would, Also I know that you can coat the emitter first with wax so that it will peal off. Comfychair does that I think. I would do that if I had an application where I was going to be messing with the driver later. But for me, I’m done once I finish. Some people of course want to be able to flash the driver later to change modes and stuff like that.

29

Great idea thanks for sharing. I’ve got two drivers I’ve held back on.
This also looks like a solution to a too thin LED shelf. Straws to protect the shelf holes then pot the under side to a more desirable thickness. Maybe cap off the underside with an Aluminum or Copper plate.