Tried my hand at reflowing for the first time with an XM-L2 U2 emitter on a 16mm board. Not sure if I did it right, but it seems to work fine so I guess it’s good enough. (I put a 60w soldering iron point up in a vise, then used long-nosed pliers with cloth tape wrapped around the tips to hold the star while I held its bottom to the iron. I was waiting for the soldering paste to turn silver. That didn’t happen, but it did get hard and the emitter seems secure and hasn’t fallen off yet)
I put the new star into my modded SK58 zoomie with 2.8 amp driver on IMR 14500 and then placed it side-by-side with a different modded SK58 with the same driver that still had the older XM-L U2 emitter. At full zoom, I was able to see a clear picture of each die. My observations:
1. The stock XM-L emitter has the customary square die shape with 3 cut-outs for the wires. Visible dark lines in a series of stacked rectangles cover the top of the emitter.
2. The XM-L2 emitter’s surface looks different. When powered up there are 2 cutouts at the side for the wires. There is no third wire, however there was a slightly darker patch roughly corresponding to where the middle wire is on the XM-L. The top of the XM-L2 die has no visible lines at all. However, there is a grid of very small dark dots not present on the XM-L. These dark dots are much smaller than the lines on the XM-L.
3. The light output from the XM-L2 is remarkably uniform across the entire surface of the die. Much less variance than the XM-L.
4. Very unscientific, But looking at the die images side-by-side, it did seem to me that the XM-L2 really does look around 20% brighter.