Pretty much. I would suggest you re-examine your diode mounting strategy though.
First off, AS5 conducts at about 10 (maybe) where the worst of solders (50/50) conduct at 20. 97/3 conducts in the low 60's and indium in the 70's. But let's not put the cart before the horse.
AS5 won't give me a bond by itself. I was considering using the thermal adhesive:
http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm
I don't have values for conductivity of the adhesive, but it would have the advantage of being able to mount to the (more conductive) non-anodized aluminum. If it's the same as AS5 (~10), then I suppose that would be the bottleneck.
Are you saying that the worst solders conduct at 20, and this would be the effective bottleneck before the anodized aluminum layer (at 30)?
You need to look at your thermal path as a part of your overall design.
You've been more than willing to put a ton of effort in your responses, so I can at least clue you into my design.
I'm going for a tiny palm sized rectangular light, custom CNC cut from aluminum plates. It will house 2 XML-2 U2 emitters and a single XPG-2 R5. It will have adjustable brightness and can turn on the XML pair and XPG thrower independently. The battery will be a newer lithium polymer cell with a C rating capable of reliably running all 3 emitters at max current if I want, which is a potential of 7.5A. Blasting all three at max power would only net a ~7-10 minute run time at 100% DOD, at a serious >2000 Lumen. That is worst case, but in daily situations would probably do 0.5A to each XML for a nice flood and >1 hr run time. The heat transfer issue is of concern to me because the better I design it, the longer I can run at higher power levels.
I realize a (classic) radial design is best for heat dispersal, but I want this to be a low profile pocket light. The power output, body thickness I cut, and driver efficiency are all going to play a huge role in this. If I must, I'm willing to put in micro-fans and maybe some heat pipes/fins if the body saturates quickly. Should I bother anodizing the exterior? I don't care about waterproofing.
I have the CNC machine, aluminum, small optics, the batteries, diodes, etc. It's
slowly coming together.
The smaller the die, the smaller the amount of energy flow. The warmer the diode, the less light it emits and the more input energy is turned into heat. You will eventually reach the point where the diode won't go any further. But getting there, the additional energy is simply going to waste. That's why when you put a 1000 lumen and an 1100 lumen flashlight side by side, you're hard pressed to identify which is which.
Yeah I know that perceived brightness is pretty much logarithmic, and brightness of a LED is somewhat inversely related to the temperature. We're always fighting the law of diminishing returns. I have read anecdotal claims of 3% brightness lost for every 10C temp increase. Basically, I will be considering fan cooling if power consumption lost via fan more than makes up for efficiency lost from warm LED's. I have a strong inclination that the mass limitation alone will necessitate active cooling. I'm probably not going to run the LED's much higher than their defined max ratings, so I suppose I should focus more of my attention on convecting away the heat from the body. Thoughts?
PS: thanks for the info on the copper cored MCPCB's, I always like options!