The very best compounds are probably used when you have to pump hundreds of watts through one square inch, like on a monster MOSFET in a wind generator or something like that. We are trying to move tens of watts through the bottom of a 16mm or 20mm star.
As for the emitter-star interface, the direct bonded copper star addresses that better and cleaner than any TIM will ever do. A few microns of bonded solder is going to be tough to improve upon.
Tens of watts through a 16mm star is in the same thermal density as the heating element on an electric stove…
Not sure what point that makes, and it might depend on a lot of variables (element type, power rating, etc). In any case, pertaining to electronics where we want things to stay cool, the perspective that we are moving around 10-30W per star, where a large power inverter MOSFET block might need to move 200W through a similar surface area. I’m just trying to use that example to point out where using a really good TIM could make a difference. For our use in flashlights, probably not that effective.
I lul’ed
Not exactly MOSFET, but normally IGBT (sorry for the useless datum)
Me too, this was a good one!
Actually, I'm pretty sure that most brands of jalapeno cheddar cheese dip are better thermal compounds than the commonly used Fujik :) (I'm only half joking, by the way).
As for Wakefield 155 being more conductive than copper - that's just absurd, unfortunately. I'm not sure where that datapoint came from.. Wakefield 155 is about the best thermal EPOXY/GLUE you're ever going to find (without, perhaps, mixing up your own out of diamond dust and ground up unicorns), but compared to Copper, it just doesn't compare...
The trick with ANY thermal epoxy or thermal compound is to absolutely minimize the bond thickness. The thinner you can make the junction, the less thermal resistance you introduce.
To summarize, Wakefield 155 is AWESOME.. For what it is. You can't go wrong with it, and I'm sure you'll be very pleased with the results. Keep your bonds as thin as possible while still providing full coverage of the junction.
I actually have a copy of a study done by one of the biggest Jet Engine manufacturer's in the world showing that in practice, Wakefield 15X provides a lower resistance junction than even the best thermal greases/pastes. The reason isn't because it's less resistive than the best greases/pastes, it's because of the fact that it doesn't require continued pressure to maintain the bond. Paste/Grease requires that something apply pressure to keep the two materials FIRMLY pressed against each other since even microscopic air bubbles severely retard the junction's ability to conduct heat. Deltabond 15X does not suffer from that problem and as long as pressure is maintained during the cure process (dry time), it will maintain the same thermal properties essentially forever.
And in regards to shelf life, as long as you keep the two parts separated, it will last a LONG time. Keeping it cool (toss it in the refrigerator) will make it last even longer. Sure, it may expire based upon the date printed on the label, but it will still work just fine, I promise.
PPtk
Killer, thanks for the info. I found your post on it around here someplace. That started me down the road searching out information. A lot of what I read was over my head. (hence the confusion about comparing it to copper I’m sure I got something backwards there) But I was convinced that is was the best. Mostly what convinced me was that the people who said so are experts and used it for a living when it really mattered the most.
Granted, it could be overkill for many applications but I don’t see anything wrong with using the best especially as I’m going to be trying to really push some emitters hard.
Thanks for the info on how to get the most out of it too.
I think I will order some 3cc oral syringes and offer some smaller amounts for sale. I searched and searched but obviously nobody is selling small amounts. I’m sure there are some people who would like to know they are using the best and not have to pay $40. Even 6cc’s would be enough for a bundle of emitters if used properly. I’m sure it will end up saving the lives of a bunch of emitters too.
I'm just about willing to bet there's no measurable difference in light output, longevity, or current-carrying capacity between this stuff and regular JBWeld in a like-for-like test using actual flashlight parts.
I'm not trying to rain on your parade, I'm glad you're happy with it. Just don't let your mind fool itself into seeing things that aren't really there (like the 'audiophiles' who swear they can hear a difference in a $600 power cord and a $1.39 power cord, but strangely only when it's not a true double-blind test and they know which one is being used).
So I won’t be putting you down for a couple of syringes full? 
Heh, well I did qualify that with a 'just about'. If it manages to do the things you're expecting then $40 is cheap.
The biggest problem with thermal adhesives (particularly epoxies) is that they tend to be permanent and rather future mod-unfriendly.
Ya got any in a snortable/smokeable form? :party:
Mix it, let it harden, then chop it up with a razor blade. You can then smoke/snort it right up! May I suggest something a little less toxic though?
Awww, where’s the fun in that? If it doesn’t kill you, it only makes you stronger.
Well, there are other things that can possibly kill you that I guarantee will be more fun...
I have reflowed LEDs with the board still glued into the pill with JBWeld with no ill effects, using hot air on the bottom of the pill. JBWeld survived just fine and didn't take any longer to melt the solder than doing a bare board.
Come on PPTK, we rely on you for accurate information. Everyone knows mayonaise makes an excellent thermal grease.
(Tested for CPU cooling)
Source: http://www.hardwaresecrets.com/printpage/Thermal-Compound-Roundup-October-2011/1396
It could be a special glue. Gold-plated designed by a famed glue designer (if there is any). :bigsmile:
Scaru. Is one brand or type better than another? Maybe low fat would be better. Please help.
I am wondering if light mayonnaise will work better than the regular one