# thermal epoxy -VS- thermal adhesive tapes...?



## kramer5150 (May 14, 2009)

What are the pros and cons of each?
Which is better at thermal conduction?

I get both at work, which should I use to adhere my Q5 emitters to the brass pill?

thanks!!

:thinking:


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## Justin Case (May 14, 2009)

I've never used thermal adhesive tape, but a Google search provided the following:

Arctic Silver epoxy looks to be better than thermal tape for computer video RAM, and also cheaper:
http://www.overclockercafe.com/Reviews/other_misc/Artic Silver Adhesive/artic silver.html

Arctic Alumina compound thermal conductivity is an order of magnitude higher than one brand of thermal tape:
http://www.arcticsilver.com/arctic_alumina.htm
http://vendor.parker.com/Groups/Seal/Divisions/Chomerics/Chomerics%20Product%20Library.nsf/24eb4985905ece34852569580074557a/a834a65321cdb0b8852569580073de67/$FILE/TB67a.pdf


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## kramer5150 (May 14, 2009)

Justin Case said:


> I've never used thermal adhesive tape, but a Google search provided the following:
> 
> Arctic Silver epoxy looks to be better than thermal tape for computer video RAM, and also cheaper:
> http://www.overclockercafe.com/Reviews/other_misc/Artic Silver Adhesive/artic silver.html
> ...





thanks so much!! Looks like I'm going to radio hack tomorrow to pick up some AA. I can't remember the last time I bought anything there LOL. The stuff at work is from 3M.

thanks


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## bshanahan14rulz (May 15, 2009)

kramer,
3m thermal tape is decent, their 9882 epoxy I haven't tried yet, but looks to be better than tape. 

Arctic _____ is usually the best performer, though. 

I have a DX/KD light, the star is just sitting on a ledge in the head. I applied 3m thermal tape, the thinnest and best that I could find, reassembled, and now the head gets much much warmer than it did before. For simplicity, reworkability, and nonpermanance, can't beat it!


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## Justin Case (May 15, 2009)

In reading more about thermal tapes, I think you have to also consider the application. If you are going to glue down a Seoul emitter to an unanodized heat sink, then you have to be very careful how the thermal tape is made. I read about one that uses metal particles impregnated into thin Kapton film. On the other hand, if you want to fill the gap between a P60 drop-in and the flashlight neck or a Mag heat sink and the Mag tube, then tape certainly seems like a cleaner, neater way to go (assuming you can fit the tape in the gap).


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## Mr_Light (May 15, 2009)

I highly recommend the following thermal glue:
http://www.dealextreme.com/details.dx/sku.4579
I have used this for over 200 led emmitters/stars and have had zero failures so far. Works great, simple to use, no mixing. It also makes it possible to disassemble things to change leds etc., which would be near impossible using epoxy.


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## bshanahan14rulz (May 15, 2009)

the 3m tape I have is non-conductive up to a certain point that wouldn't be reached with LEDs anyways, and is made with ceramic particles suspended in this tacky, thin, stretchy stuff. It is very glittery when viewed in the light, which I thought was interesting, even if it doesn't really affect anything. 

You need to be careful with anything you use, not just tape. Some epoxies have metal in them too. arctic silver 5 has silver in it, even though it isn't very conductive though...


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## IMSabbel (May 15, 2009)

The main difference is not the heat conductivity...

Its the effective thickness you can create.

With some pressure you can get thermal epoxy WAY thinner than even very thin thermal tape...


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## bshanahan14rulz (May 15, 2009)

but you risk creating shorts if your surfaces aren't perfectly level, flat, and clean. tape has ease of use and reworkability going for it, epoxy has performance/permanance going for it, compound has amazing performance. 

Tape has its merits, but if I were designing and not modifying, I'd always use compound or epoxy.


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## Justin Case (May 15, 2009)

IMO, the risk of shorts is mainly if you are using something like a Seoul P4 or P7 with the slug connected to the anode and you are using an unanodized substrate.

It is important to have a thin layer since the conductivity of any of these products is poor in comparison to metal or solder. They are good only in comparison to an air gap or other thermal insulator.

My concern with tape would be its adhesive permanence. I haven't checked any of the datasheets on that aspect yet.


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## Sub_Umbra (May 15, 2009)

Hi Justin- 

Is there any chance that you could shorten that hidiously long link in *this post* so everyone won't have to scroll back and forth for ever more?

You could use *BB code* or just go to www.tinyurl.com and feed it to them. It would then post up like this:

http://tinyurl.com/q96q94

You'd be a hero.

Thanks in advance.


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## Lighthouse one (May 15, 2009)

The thermal glues that Mr light recommended are excellent. I too have made several dozen home made lights using p4, Q2,Q5 and seoul emmiters. AS he mentioned, you can later cut through the glue if you need to undo a job. Not too easy with the epozy..


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## spencer (Sep 29, 2009)

Just went to Luxeon Star's website and found that they have precut, thermally and electrically isolating tape. Link. It seems to be reasonably priced. 0.86C in^2/Watt. But at 100psi. That seems to be pretty good. Any thoughts?


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## Black Rose (Sep 29, 2009)

I was looking at those as well for mounting some Seoul P4s.

I wonder how they would work on the bottom of a reflector to keep the reflector from shorting out cree emitters...


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## samuelcpaul (Feb 12, 2010)

Hey all,

Generic Thermal Paste has been around for quite some time and up until not too terrible long ago silicon paste was your only real choice. Along came the increased availability of Thermal Tape (aka Frag Tape.) 

Sam.

.

safe adhesive tape


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## Justin Case (Feb 13, 2010)

Let's look at this Luxeon thermal tape. The thermal resistance is given as 0.86 C-in^2/W. that converts to 0.00055 C-m^2/W. Thus, thermal conductance is 1800 W/m^2-K. Pad thickness is given as 0.005". Thus, thermal conductivity calculates to 0.23 W/m-K (at 100psi). Pad size is listed as 0.28" sq. I assume that means 0.28" x 0.28" (0.0784 sq in). Thus, 100psi pressure means you have to exert about 7.8 pounds.

Plain epoxy thermal conductivity is about 0.2 W/m-K. Air is about 0.026 W/m-K.

Arctic Alumina compound thermal conductivity is advertised as >4 W/m-K.

Arctic Silver 5 compound thermal conductance is advertised as 350000 W/m^2-C for an 0.001 inch thick layer. That calculates to 8.89 W/m-K thermal conductivity.

Ceramique compound thermal conductance is advertised as >200000 W/m^2-C for an 0.001 inch thick layer. That calculates to >5.08 W/m-K thermal conductivity.

Arctic Silver adhesive thermal conductivity is advertised as >7.5 W/m-K.

There is no stated thermal conductivity or conductance data for Arctic Alumina adhesive. However, I would think it is safe to assume that the upper bound has to be the thermal conductivity of AA compound, which is >4 W/m-K. Various references in the literature list the thermal conductivity of epoxy-alumina composites at about 0.5-2.7 W/m-K depending on filler loading.

This Luxeon thermal adhesive looks to be about 10X better than air as a thermal conductor and comparable to plain epoxy.

AA adhesive is probably about 75X-100X better than air as a thermal conductor. Arctic Silver adhesive may be about 300X better than air. AA compound is about >150X better. Arctic Silver 5 compound is about >340X better. Ceramique is about 200X better.


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## HarryN (Feb 14, 2010)

Hi Justin,

Thanks for running the numbers for us. It is easy to forget the basic assumptions about all of these products - thin and under pressure. Take the pressure off, and they degrade to "poor" fast.


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## Black Rose (Feb 15, 2010)

Oh well.

I was looking at the tape from Luxeonstar as an easy way to isolate the annoying positive slug on SSC P4s as well as installing them in P60 pills without permanently bonding them to the pills.

The last batch of the Arctic Alumina I bought went bad and I don't use enough of the stuff to warrant buying more of it.


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## ma_sha1 (Feb 16, 2010)

I use all 3 types depends on situations, it feels to me that thermo conductivity is in this order: 

Dx Thermo grease > Arctic Silver > 3M Thermal Tape

I don't know the specs, just based on experience from practical use. 
But each has it's own limitations too:

*Thermo Grease*: Reversible, Great heat conductivity, never failed me, drawback is Not adhesive, suitable for large contact surface only, otherwise won't stay. (Add a drop of super glue can help it to stay)
*
Arctic Silver*: Some times tricky to use, If you press too hard, it may become super thin & become conductive. I had a P7 press down too hard glue down & it become conductive, had to reverse battery as I can't take the led off off once glue down. 

*3 M thermo tape*: Easy to use & reversible, but limit to low power led
only, I used it for XPE/XPG up to 0.7Amp/10mm board. 
I think should be fine on 20mm Star driven to 1 Amp. 
But not good enough for P7/MCE/SST-50, 90 etc. 
expect angry blue.


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## PMM (Feb 16, 2010)

arctic silver epoxy

I've used it for years with my computers on ram chips & northbridges etc etc

there website quotes negligible electrical conductivity in their blurb.

Its only really e-conductive under alot of compression, been in the situation of applying too much and getting between pins but never suffered a short to date.

It is men't to be slightly capacitive hence why you should avoid where possible getting it on any IC pins.

Darn good stuff in my book.

Also if you want to create a weaker bond but keep the thermal conductivity get some arctic silver 5 as well and do a 1 to 1 to 1 mix or slight higher on the artic silver 5.

That potentially then gets you the option to break the bond via cooling in a freezer to -20 or lower for a few hours.

Thats what I used to do to pop heatsink off gfx card chips after modding and using AS epoxy to bond with.


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## Black Rose (Mar 2, 2010)

I decided to get some of the termal tape from luxeonstar to try out.

I also have a Neutral White Rebel mounted on a 10mm square base on the way.

I am building a P60 drop-in that will use the Rebel and the thermal tape. 
Rebel will be driven at 800mA.

I didn't want to use AS themal epoxy to permanently attach the LED to the brass pill, so we'll see how well/poor this tape does.


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## Justin Case (Mar 2, 2010)

PMM said:


> arctic silver epoxy
> 
> I've used it for years with my computers on ram chips & northbridges etc etc
> 
> ...


 
Since Arctic Silver 5 is advertised as non-conductive, I have to assume that the silver particles are not in a concentration above the percolation threshold, which would result in electrical conductivity. Definitely squeezing the Arctic Silver 5 can put the silver particles into a path of continuous contact, producing electrical conductivity.


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## Justin Case (Mar 2, 2010)

Black Rose said:


> I decided to get some of the termal tape from luxeonstar to try out.
> 
> I also have a Neutral White Rebel mounted on a 10mm square base on the way.
> 
> ...


 
Estimated thermal conductivity of the thermal tape is 0.23 W/m-K. Pad thickness is 0.005". I mic'ed my old style round 6P neck at 0.872" ID. I mic'ed the OD of a DX11836 at 0.855". A DX6090 mic'ed at 0.856". So it looks like you need to add two layers of this Luxeon thermal pad material. There will be some compression of the pad (I suppose this is good since the thermal specs are for 100psi applied pressure) to fit the drop-in into the flashlight neck. Bond line is thus about 0.008", or about 0.0002m. Contact area is a cylindrical surface about 1cm tall and 0.856" diam, or pi * (0.011m)^2 * 0.01m = 3.7e-6 m^2.

Thus, thermal resistance could be about 0.0002/(0.23*3.7e-6) = 235 C/W. That doesn't seem to good. The wide bond line and low thermal conductivity of the pad are problems. Can't do much about the wide gap. If you had a pad with a thermal conductivity of about 2 W/m-K, you'd cut the thermal resistance by a factor of about 10. That would be better, but still high. An 8 mil gap is rather large. If it were 2 mils wide, then you'd reduce the thermal resistance by another factor of four (total of a factor of 40 reduction). That could give you a thermal resistance of about 6 C/W.

A small gap is definitely doable. My Moddoo triple heat sink mics at 0.8715" diam. My FiveMega host neck measures 0.872", same as my 6P.

The Ferrishield TGF120 thermal pad material that TaskLED uses has a thermal conductivity of 1.2 W/M-K. But that stuff is also 1mm thick.


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## Black Rose (Mar 2, 2010)

Thanks for the info Justin. I'll try it with 2 pads and see how it goes.


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## Black Rose (Mar 5, 2010)

I'll have to wait to try the tape out.

Luxeonstar shipped a Neutral Rebel tri-star instead of a single Neutral Rebel on a 10mm base


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## richardcpf (Mar 7, 2010)

ma_sha1 said:


> *Thermo Grease*: Reversible, Great heat conductivity, never failed me, drawback is Not adhesive, suitable for large contact surface only, otherwise won't stay. (Add a drop of super glue can help it to stay)


 
Is this the thermo grease you are referrring to? I want to glue many 20mm stars to a 3.6" heatsink... 

Thanks for the super glue tip, will try it right away


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## Justin Case (Mar 7, 2010)

Super glue is the wrong adhesive to use near an LED, at least a Cree. The vapors can attack the dome, clouding it.


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## ti-force (Mar 7, 2010)

richardcpf said:


> Is this the thermo grease you are referrring to? I want to glue many 20mm stars to a 3.6" heatsink...
> 
> Thanks for the super glue tip, will try it right away


 
I can't speak for ma sha1, but that's a thermal adhesive you linked to. It's the same product that Mr Light recommended in post #6, and then, Lighthouse one shared his experience with that product in post #12, and now I'm going to say that I have also had very great results with that product. Some people don't like it, but it's worked very well for me.


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## ma_sha1 (Mar 8, 2010)

richardcpf said:


> Is this the thermo grease you are referrring to? I want to glue many 20mm stars to a 3.6" heatsink...
> 
> Thanks for the super glue tip, will try it right away



Yes, that's what I use. Good enough for just about any LED on Star
(Including SSR-50).

However, you you are doing bare emitter with very high power,
then you may want to use Arctic Silver, which is about 2x better for heat transfer, the bare SST-50 & -90 has very small contact patch, I would not use anything else but arctic silver. I just don't like working with AS as much, it's not sticky until it's dry, so you need to hold the led down with somthing for a couple hours. 

I usually use a tooth pick to dip a tiny bit of super glue, it helps to hold
things in place until thermo glue or AS drys.


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## degarb (Feb 26, 2014)

Justin Case said:


> There is no stated thermal conductivity or conductance data for Arctic Alumina adhesive. However, I would think it is safe to assume that the upper bound has to be the thermal conductivity of AA compound, which is >4 W/m-K. Various references in the literature list the thermal conductivity of epoxy-alumina composites at about 0.5-2.7 W/m-K depending on filler loading.
> 
> AA adhesive is probably about 75X-100X better than air as a thermal conductor. Arctic Silver adhesive may be about 300X better than air. AA compound is about >150X better. Arctic Silver 5 compound is about >340X better. Ceramique is about 200X better.



So, what you are saying is Arctic Alumina might raise the led temp by 1 degree C thinly applied per watt driven? Up to 2.5 degree per watt heavy. While Arctic silver will be 1/3 of this. Correct?

The states specs on AA is very poor.


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## chainrash (Jun 24, 2016)

Arctic Silver Thermally conductive epoxies and compounds seem to do pretty well. Here is an in depth review with test numbers and directions: http://www.ledsupply.com/blog/arcti...s-adhesives-are-crucial-in-led-heat-transfer/


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