Alternative to thermal epoxy?

Does anybody know of a less-permanent alternative to using thermal epoxy to electrically isolate a ssc p4 slug? Silicone adhesive would problably do, but I want to make sure the heatsinking will be good as I'm going to be running 3 emitters at 700ma, and may end up driving them even harder at some point.


:thinking:

I've used this thermal adhesive for over 100 stars/emitters without any problems so far.
http://www.dealextreme.com/details.dx/sku.4579

^ That's also what I use, although I have had a Cree burn out. I maybe didn't glue enough heatsinking on for that one.

hmmm... any morereliable place to pick this up? Just bought a cateye triple shot and will be converting to ssc p4 ASAP so the DX ship time is a big draw back (as is the QC varible).

Buck91 said:

Does anybody know of a less-permanent alternative to using thermal epoxy to electrically isolate a ssc p4 slug? Silicone adhesive would problably do, but I want to make sure the heatsinking will be good as I'm going to be running 3 emitters at 700ma, and may end up driving them even harder at some point.

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I'm not sure if this is in the direction you want to go. Arctic Silver used to say in the directions to both types of epoxies they sell, if you mixed 25% of the regular thermal compound and 75% epoxy would make whatever you were gluing optionally removable. The fact that they no longer say that I'm guessing is as a result of failure complaints. LED's and stars are generally smaller than heat sinks and should be OK.

Here is a trick posted a while back somewhere in the forums. Use two hairs, that's right - growing out of you or some other mammal, one at each side of the emitter slug to maintain a small distance for electrical isolation along with con-conductive thermal paste for heat transfer. Once you get it set, apply a drop of super glue to each side to hold it in place.

DX has an option to pay for shipping. I hear its faster but I've never done it.

mudman cj said:

Here is a trick posted a while back somewhere in the forums. Use two hairs, that's right - growing out of you or some other mammal, one at each side of the emitter slug to maintain a small distance for electrical isolation along with con-conductive thermal paste for heat transfer. Once you get it set, apply a drop of super glue to each side to hold it in place.

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Yes I remember that one. I thought to myself at the time it would probably be easier to use something like a small piece of a nylon stocking for isolation. More porous and thinner than cloth. Someone in the same thread suggested tissue paper and thermal compound. That would probably be the best. Also you need a continuous ring of epoxy to encapsulate the thermal paste you are using. Otherwise as the thermal paste bleeds away it forms a gap while your LED remains suspended by its glue "legs".

The hairs was a novel idea I never heard of before. If the heat sink was large enough you could use tape to hold the hairs in place. But if not, how do you hold them? It must be a little touchy to work with.
https://www.candlepowerforums.com/posts/2474628#post2474628

What about applying a liberal layer of epoxy to the slug, waiting for it to dry and using some thermal grease between that and the heatsink/body? Or would that introduce considerable thermal resistance?


hmm... I need to check to see if the light body is even energized now that I think about it. Good chance that there is no harm in lacking to provide electrical insulation to the slug.

If you need electrical isolation, you can achieve it with only a thin but uniform layer of epoxy applied to the slug. This can be accomplished by drawing a new razor blade's edge over the epoxy or by pressing the slug against a non-stick surface that the epoxy will not bond to. Somewhere in the forums is an account of what type of plastic to use...:thinking: I would think a siliconized mylar would work, but I recall the solution being more common than that.

I'm using a mixture of 66%-75% thermal paste and epoxy. It works good and it is still possible to dismount the led

Buck91 said:

What about applying a liberal layer of epoxy to the slug, waiting for it to dry and using some thermal grease between that and the heatsink/body? Or would that introduce considerable thermal resistance?

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You would want to use a very thin layer. About as thin as you can spread it.

hmm... I need to check to see if the light body is even energized now that I think about it. Good chance that there is no harm in lacking to provide electrical insulation to the slug.

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That is very unlikely. In most cases the body is ground the slug is positive. That equals no light and a shorted driver.

Well, this is a cateye tripleshot. AFAIK the body isn't a primary electrical contact, though it may be incidentally.

Buck91 said:

Well, this is a cateye tripleshot. AFAIK the body isn't a primary electrical contact, though it may be incidentally.

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If the body is metal, chances are very good that it's the primary method of connecting V- on the battery to V- on the board.

Yeah after some more online research, the body is indeed v-...

Anyways, I agree with stereodude that the thinner the layer of pre-cured epoxy the better, but what does everybody think; will it work well?

Buck91 said:

Yeah after some more online research, the body is indeed v-...

Anyways, I agree with stereodude that the thinner the layer of pre-cured epoxy the better, but what does everybody think; will it work well?

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That will work, so will a thin coat of paint/lacquer (i.e. sub .001 in, which isn't difficult).

Will it provide adequate thermal transfer? Initially (and maybe only) I will be running stock driver (700ma) but I've love to upgrade to a multimode driver with 400-500ma, 1000ma and strobe functions and don't want to burn out the u2's.

Buck91 said:

Will it provide adequate thermal transfer? Initially (and maybe only) I will be running stock driver (700ma) but I've love to upgrade to a multimode driver with 400-500ma, 1000ma and strobe functions and don't want to burn out the u2's.

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I built a light that runs 3 emitters at 700ma, insulated by a thin layer of clear lacquer and DX goo, and it warms up.