i just desolder a XRE from the star and there are 3 metal pads underneath the emitter. i think the two pads on the side are the anode and cathode. but what about the big one in the middle? is it connected to the anode or cathode?
i want to put the emitter directly on a piece of copper. any tips from ppl who have done it b4?
The center pad on most (not all) emitters is a neutral thermal pad, it transfers the heat to the MCPCB.
I’m not sure but I think you can put an XR-E on a MT Noctigon. One question, why an XR-E? There’s not much reason to use it over an XP-E2 these days.
i am using XRE simply because i have a few spare and wanna have some fun with it 
. it’s the EZ1000 version. i direct drive it with 4 eneloops while it was still on a star and it drew 3.0A and the tint turned a little blue. so i wanna put it on copper to heatsink it better. i plan to put it in a light with a 50mm aspherical lens.
Xre’s are pretty nifty because they are so big you can grind the anode and cathode pads off the bottom of the led and solder it directly onto a copper heat sink of any size and solder the wires to the top of the led. Don’t even need a star.