# Super Glue for Thermal Adhesive



## Tekno_Cowboy (Jul 31, 2010)

Just a thought: would super glue work well as a thermal adhesive?


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## A380 (Jul 31, 2010)

I'm not sure but I think no. Super-glue (cyanocrylate) is flammable.


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## Tekno_Cowboy (Jul 31, 2010)

Even dry?


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## kramer5150 (Jul 31, 2010)

I tried it once and the fumes made one of my XRE domes foggy. well... I used AS-5 in the middle and placed 3 dabs of superglue gel around the heatsink disk, and pressed it flat. Another member later told me I should have placed it infront of a fan to circulate the air around it.


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## A380 (Jul 31, 2010)

Tekno_Cowboy said:


> Even dry?


 
Yes, even dry. Just try it; put some drops on a non flammable material (stone for example), let it dry and put a flame on it.


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## Foxx510 (Jul 31, 2010)

I found one reference to it's thermal conductivity being 0.1W(m.K). Not great compared to copper ~400 or aluminium ~180. I've used it to secure a luxeon emitter sitting on thermal grease, reinforced with microspheres. It's holding up fine in a minimag with heaps of use.


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## kaptain_zero (Jul 31, 2010)

For all intents and purposes, CA or Super Glue, once cured, is simply Acrylic Plastic. 

For a more in depth article on CA glues, do a google search for "cyanoacrylates.html" which takes you to a wood turning site where the author has done some serious research on the topic. 

Regards

Christian


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## IMSabbel (Jul 31, 2010)

Its not that much worse than most of the typical cheap "white goo" thermal paste.

The main point is: If you are used to it, and using superglue helps you make a very thin interface layer, no problem with it.

The glue being flammable is of no convern for its heatsinking capabilities. In case of a thermal rundown, PVC wires are just as flammable and much more toxic.
Plus, if you use it correctly, you will only have a very tiny amount of the glue in use, without contact to any air.


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## Foxx510 (Jul 31, 2010)

If you go on the numbers, CA could be many hundreds times worse than a basic thermal transfer paste. How that translates in real world performance is hard to say. The unknown factor is the thickness of the layer, which depends on the thickness of the CA used and the pressure applied. "Thin" grade CA is really really thin, but the downside is you'd have pretty much no positioning time as it goes off really quickly.


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## Light Sabre (Jul 31, 2010)

One problem with super glue is that when it dries, it becomes brittle and susceptable to breaking apart. Dropping your flashlight and cracking the super glue would then separate the 2 pieces and then you would have a gap and loss of any kind of thermal properties. Super glue will also out gas when heated up and then get deposited on anything nearby. :thumbsdow

At work we use epoxies for the most part. And not the 5 minute kind either. Most of the epoxies we use, don't become brittle when dry. They are more like the tread on your car tires. If you use your finger nail and press into it, you will see the impression in the epoxy. We do use a thermal epoxy that does get rock hard, but it is not brittle at all.


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## Justin Case (Jul 31, 2010)

Cree datasheets explicitly warn against exposing the Cree dome to super glue fumes, which can cloud it as Kramer discovered. Don't know about other LED domes, but I personally would not take the chance.

In addition, the bond strength at elevated temp is poor, especially in the presence of a humid environment.

Finally, thermal conductivity is low, probably at least a factor of 10X lower than AA epoxy.

Thus, super glue seems to me to be a poor choice for a thermal adhesive. It's not much of an adhesive when things get warm and humid, and it doesn't transfer heat well, which will help get things warm. And it can damage your LED as well.


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## Tekno_Cowboy (Aug 1, 2010)

Looks like a big old fat "no" is the answer. Perhaps someone knows of a fast setting non heat-curing thermal adhesive other than Arctic Alumina adhesive. I'm looking for something that comes in larger quantities than the AAA, or in lieu of that, easier to find locally.


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## 65535 (Aug 1, 2010)

Tekno_Cowboy said:


> Perhaps someone knows of a fast setting non heat-curing thermal adhesive other than Arctic Alumina adhesive..



Arctic Alumina, or Arctic Silver you may be able to find larger quantities, I think some have in the past and did a group buy. The stuff doesn't have much of a shelf life so having large quantities really isn't idea.


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## precisionworks (Aug 1, 2010)

Devcon Tru-Bond 215 might work:

http://www.devcon.com/techinfo/Tru-Bond_215.PDF

Thermal Conductivity is listed at 0.98 W/m-K


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## Tekno_Cowboy (Aug 1, 2010)

There's a similar product to AAA, but you have to have a business license to buy it, which I do not.
Since I mod a quite a few lights, and I've been using AAA to pot some of my lights, it goes pretty fast. I go through a 5g set of AAA in about 3 weeks...

The Devcon will not work because it is electrically conductive.


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## spc (Aug 1, 2010)

Ive heard of others mixing regular 2-part devcon epoxy with some kind of AL powder. I would like to know what kind of powder and what mixture. This may be alot easier to get in large quantities..


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## saltytri (Aug 1, 2010)

Very fine aluminum oxide powder:

http://mamasminerals.com/products/Pro%252dPolish-%280.5-Micron-Aluminum-Oxide%29-Rock-Polishing-Powder,-1-Lb..html

Don't sneeze anywhere near it. Try a search. This has been extensively covered.


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## spc (Aug 1, 2010)

thanks saltytri :thumbsup:
looks like a 50/50 mix of the aluminum oxide powder and devcon epoxy works well + a 1lb bag like the one saltytri linked would last a while!


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## saltytri (Aug 1, 2010)

My memory ain't what it used to be but I'm thinking that it was darkzero who has said that he uses this method successfully. Will?


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## Tekno_Cowboy (Aug 1, 2010)

I suppose the simpler thing to do would be to just get some potting compound and use the AAA for only mounting LEDs.

If you do use this Will, what is your method for mixing it?


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## precisionworks (Aug 1, 2010)

> Devcon will not work because it is electrically conductive.


Try again ...

Loctite 3860 http://www.wentite.com/jscs/nj/Product_3860.pdf

Deltabond 155 http://www.newark.com/jsp/level5/module.jsp?moduleId=en_US/4479.xml


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## darkzero (Aug 2, 2010)

Tekno_Cowboy said:


> If you do use this Will, what is your method for mixing it?


 
Yes I do. I can't even remember the last time I used AATA except on the TaskLightII LEs.

I don't have a science on what is the best method for mixing it. Over the years I've got accustomed to what seems to work best for me for certain applications. I would say I don't see any drawbacks in mixing in too much powder aside from the mix getting too thick. I also stay away from not mixing in "enough" where the mix still appears to be transparent.

As you know alumina oxide is the main ingredient in AATA to give it it's thermal properties. I'm sure the AO/epoxy mix may not have as good as thermal conductivity as AATA but it I feel it's good enough for flashlight applications & never had an issue with any of my builds since I started using this method in 2004. Even with SST-50s, have not tried any SST-90s at full power though. I wish someone could do a comparison of the two with a method of being able to show some real numbers.

The main reason I started using it is I hated how AATA expires over time, gets too thick to use. When I first started to modify lights it was only a few here & there & my tubes of AATA would go to waste. When I returned to CPF & started offering modding services, having the product expire would no longer have been an issue. But AATA is expensive IMO, the AO/epoxy mix is very very economical compared to AATA.

I do not use thermal epoxy excessively to attach emitters. IMO if you have thermal epoxy oozing out the sides of the emitter that is too much & it defeats the purpose. Generally I cautiously use the thinnest layer possible of thermal epoxy. Depending on my mix I can apply a layer much thinner than I could with AATA. This alone makes a big impact on thermal conductivity. I would bet using a very thin layer of just plain epoxy would perform better than using a very thick layer of AATA.

I would say this might be a good solution for you. Some say it's too much of a hassle & time consuming having to mix in the powder for every application. When I used to work on builds everyday, I never once felt this way.

I've also heard people at work metioning thermal epoxies by MasterBond & Omega. Don't know anything about them though. And of course the larger manufactuers like 3M, Loctite, MG Chemicals, Chemtronics, Dow Corning, etc all make thermal epoxies but I would doubt them to be cost friendly and/or available in small quantities.




Tekno_Cowboy said:


> I suppose the simpler thing to do would be to just get some potting compound and use the AAA for only mounting LEDs.


 
Potting compound for electronics, like the common premium black stuff, should not be used for mounting LEDs as an alternative to thermal epoxy. Many of them have slow cure times & some need to be baked to cure. Their main purpose is to protect the electronic components from shock & moisture. (*EDIT*: Oops, misinterpreted your post, thought you were saying to use potting compound for mounting LEDs)

I also use AO/epoxy for potting electronics. May be a bit excessive but it's cheap enough. Potting compounds are very expensive & again have long cure times. Potting compounds are also much more harder to remove without damaging components. AO/epoxy is much more easier to remove. For potting electronics I use Devcon 2-Ton epoxy rather than the 5min that I normally use. The datasheet also states that one of it's uses can be for potting electronics. 

Speaking of which, I've heard people recommending to use thermal grease for the emitter & keeping it in place by applying CA or epoxy to the emitters case. I don't agree with this either as thermal grease degrades & thins out over a long period of time, it also doesn't look pretty. Not an issue if you are able to reapply the thermal grease periodically like you would in a PC. Perhaps in a flashlight, it's service life as determined by the owner, this would also may not be an issue. This is why you tend to see a dense thermal compound used in OEM applications when thermal epoxy is not suitable.

Some even mix epoxy with thermal grease. I wonder how this works as well?



Tekno_Cowboy said:


> There's a similar product to AAA, but you have to have a business license to buy it


 
If you are refering to Arctic Sliver's product called QCCE, a simple business license may not be all that is needed. Quick Cure Ceramic Epoxy is not be resold for retail. The retail product is AATA. QCCE is intended to be used in OEM & labratory applications. As far as I know, Fred (PhotonFanatic) was not able to get it for this reason.

QCCE is offered in three sizes. 60 grams is the largest size & is very cheap compared to the retail AATA product. We purchase the 60G size by the case directly from AS. But we are a large repair depot for many OEMs in the US & Canada. I use QCCE often at work & to be honest I don't think it's any different than AATA. Just the large tube sizes & lower cost ($27ea for the 60g) is much more convienent.

Like many of the Loctite adhesives we use that are recommended to be refridgerated when not in use to prolong their shelf life, we were told the same for QCCE. BTW, this also works for Norland too. Having such a large quantity of it may not be beneficial unless you are constantly using it. I still have 1 or 2 pairs of the 60G left in my supplies cabinent. It's been about over a year now & I suspect they are pretty much going to waste.

Now that I have retired from CPF, I still don't have to worry about my "thermal epoxy" going to waste as AATA would.


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## olephart (Aug 2, 2010)

There is a 1 part, liquid, ceramic adhesive called Rocksett. I use it as a high temp thread locker. Good up to 1,100 degrees. It electrically insulates up to 20 Radio units, whatever that means. I'm not sure about thermal transfer properties, but the term ceramic in the description holds promise.

Maybe one of you technical types could google the specs and let us know if it could be useful.


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## fyrstormer (Aug 2, 2010)

Superglue fumes can usually be wiped off with a dry paper towel. They don't set very hard onto whatever surface they come in contact with.

That being said, thermal epoxy is inexpensive enough, and easy enough to work with, that there's no point in bothering with anything else. It gets the job done just fine.


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## kramer5150 (Aug 2, 2010)

fyrstormer said:


> Superglue fumes can usually be wiped off with a dry paper towel. They don't set very hard onto whatever surface they come in contact with.



Yeah... I just used a polishing wheel on my dremel and _gently _buffed the fumes off the dome. It looks fine, but given the fragility of the XRE dome, its not something that I would recommend.


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