Gentlemen,
Here are my results from testing a Cree XM-L T6 that I directly soldered to a pure copper slug. Other than eliminating the star, this test was performed much like my other emitter tests.
And without further ado, here are the results:
I have super-imposed the new data on top of my previous xm-l star mounted data for an easy comparison.
To say the least, I found the data shocking! I knew these pcb's were holding emitters back, but never thought it would be to this extent. Also, I only expected to see a noticable divergence above @3 amps, but the data shows there is a difference even as low as 1.2 amps.
Not only that, but the emitter keeps chugging along all the way up until it maxed out my test bench power supply.
All datapoints are lumen snapshots 30sec after power on. Once the test was complete, out of curiosity I set the power supply to 5 amps and let it run. After 5 minutes, lumens dropped from 1367 to 1357 for a 10 lumen drop... in a word - Wow!
Now, how pratical is this for flashlight use? Having used my modded 1C mag with a very similar set-up as this I can say it definately has its merits. True, the body and head of a typical maglite will get heatsoaked well before the 25lb block of aluminum used in this test, but still the difference is dramatic. One could now have a true turbo mode to be used for brief periods and actually get the increased output from the power spent.
Update
Hopefully the info below will help answer some of the questions I've seen pop up in the comments.
* The procedure I used to create the copper/emitter bond is exactly as shown here.
* The dimensions of the above copper slug are 21.5mm diameter and 5mm thick. This in turn was lapped to the aluminum test block and secured.
* At 6.4 amps, initial turn-on was a bit higher than the 30sec snapshot, and continued to drop slowly after 30sec. With the current test set-up, I'm not sure how much more power could be supplied without running into issues such as the bond wires melting. (Yes, active cooling such as dry ice or TEC modules would help :) ).
* Both the emitter and copper heatsink were pre-tinned then sanded before reflow to ensure a very thin solder layer.
* Despite some places now offering copper pcb's, I'm not sure that they would mimic my results. The reason being that even though the pcb is copper, there is still a very thin layer of high dielectric bonding ply under the emitter that limits optimum heat transfer.
-Match