Arctic Alumina epoxy?

What is used to bond the emitter to a heat sink. Is it Arctic Alumina, or AA epoxy? Also where would on find this type of product in a store? What type of store? Are there any other products that could be used? Can you use other types of epoxy like JB Weld?

You can use snot, but AA (acronym for arctic alumina) epoxy gives a better bond and is made to conduct heat.

Look at www.theledguy.com

Does anybody know if JB Weld conducts heat good? I can't find AA at the local stores like Radio Shack.

You can order arctic alumina from
http://www.anlighten.com/shop/default.php
cheers
Des

If JB Weld is electrically conductive, i wouldnt reccomend using it for securing luxeons in place. Its all too easy to short and fry a Luxeon.

Ailsnail, According to the study on theledguy.com that you pointed me to, regular epoxy worked just about as good as AA epoxy. (as far as thermal conduction) Are there other reasons to use AA ? Can you remove the emmitter from AA or is that permenant like regular epoxy? It seems to me that JB weld should conduct heat well... Does anyone have any further input on why AA is better. I want to use something that works good. I have access to many types of epoxy, and I have some JB weld. But I will buy some AA if it is indeed the best...?

AA is fairly permanent, but you can remove the emitter if you really want to. It's not easy, though. I blew an emitter and to replace it I had to bake the head for a bit to loosen the emitter, then remove it from the head with pliers. While removing it, the dome and black plastic casing seperated from the die, so be VERY careful if you're trying to salvage a working emitter. After removing the die, I still had to clean up the AA left behind so I could have a clean surface to mount the new emitter to. To get all the gunk out, I had to soak the head in alcohol (acetone supposedly works better) overnight and scrape a lot with a chisel.

AA is good because it electrically isolates whatever you're using it on. That's something you don't get with standard epoxy and certainly don't get with the somewhat conductive JBWeld. On the whole, though, the goal is the same as with CPU heatsinks: get the luxeon as close to the heatsink as possible. You want your layer of thermal stuff to be as thin as possible so that it conducts as well as possible.

I was advised to mix 50% grease (arctic silver grease in my case) in the AS to make the bond less permanent. I haven't tried to break the led loose yet.

I think the thickness of the layer is the most important. I have no idea what kind of epoxy or glue might conduct heat better or form a thinner join. I was told the slower curing glues would be thinner. AS cures fast.

As thin as possible isn't always the best idea. For CPU heat sinks, it's obviously the way to go, but there you usually have a clip or some other physical device that holds the sink to the CPU. For epoxy applications, you may need more than the thinnest layer possible in order to hold the emitter in place securely. Also note that a very thin layer will probably not do a very good job of electricly isolating the emitter from the head/sink if that is a requirement in your application.

Has anyone tried Loctite® 3873 Acrylic thermal conductive adhesive? It provides both mechanical attachment and heat transfer with a thermal conductivity of 1.65W/m-K.

Anyone tried Thermally Conductive, BLACK, Epoxy Encapsulating & Potting Compound ?

-Tim

I've got some stuff from epoxies, inc. that I'm also going to investigate as potting compount. I'll post on it once I have a chance to test it...

Did anyone try the loctite product?

TheFire: Any results with the above?

I have used AA and found that I get it thin by pressing the emitter down, and wiggleing it around a bit until I feel it seat, or drag on the metal heatsink. Of course it's not electrically isolated anymore, but will conduct heat the quickest!

Kakster said "JB Weld is electrically conductive, i wouldnt reccomend using it for securing luxeons in place. Its all too easy to short and fry a Luxeon."
I emailed JB Weld asking them what the thermal conductivity of the stuff is, also requesting an MSDS that I never got. The sales person told me that it is totally non-conductive (the literature indicates that JB Weld (standard, I didn'took at JB Quik) is non-conductive electrically. It's probably not productive to ask any of their sales staff this question, I figured someone would test it & post it.
Tyler, I did the same thing to an emitter while removing it from a star with pliers. My current approach is to use a razor blade or exacto knife after heating. Even then you need to be careful to get under the base of the emitter (not just the plastic) before using any upward force - it may break loose before that, but if its loose enough for that, apparently it doesn't hurt. I've broken one good one and two 'fried' ones learning to do this......

Personaly I would NOT use JB weld...It AS or AA for me...Although now that I'm about out of AS I'll have to switch to AA...Good thing though, because I'll be working with red and Red/orange emitters! JB weld is horrible at thermaly conducting heat. I doubt it will conduct...But it just plain sucks...

THe locktight stuff sounds interesting, i thought I was some benches on it before that said it was like 40 times better than As, but somehow I highly doubt it...It really is difficult to test thermal epoxies, because the application of the epoxy itself Has ALOT to do with the results. I knwo when seating HS's on CPUs you do NOT want to move the HS from side to side while installing, I have done that and done it without any movement and that always turns out better when you do NOT shift the HS, assuming you have the proper thin layer of thermal goop on the CPU... However, exposy is another story...

I have a BadBoy500 potted with JB Weld. So far with no ill effects. Also have an ILL PILL potted with JB weld also with no ill effects so far.
Just for fun I grabbed a DMM good to 10 meg O and give my pills a check and my meter shows open. So if it's conductive it's not very much so. I've also used it on mounting my emitter to the BB. The body of the flashlight gets quite warm. That heat is coming from somewhere. I understand that the BB's get warm themselves. Perhaps thats the heat I'm feeling??? I guess I won't know for sure for a while if my led is going to cook or not. I hope not. I'll certainly post if my emitter lets out all of its magic smoke. Untill then cross fingers.

cheers,
zwf

arctic alumina can usually be found at many computer stores or online computer stores. they are used on the cpu to make better contact with the heatsink.

Wayne had talked about AA epoxy before. The only problem with AA is that it gets soft when it heats up, which could become a problem....

If you've owned one of his sandwiches, you'll notice that he doesn't use AA to epoxy any of them. The epoxy is primarily for strength and some thermal conductivity...