I think Kevin is talking about Luxeon MZ, which is quad 4x2mm2 die LED. Luxeon V is single 4mm2 die LED.
MosX boards more than good enough for triples, quads etc. because no one run LEDs at absolute max. in those setups - difference between DTP and mosX is marginal when you run LEDs like XPL, Luxeon V at 50-70% of max. current.
Are all MosX boards aluminum? Guess so... From this listing on a Luxeon V quad, I had no idea a MosX board is alum - would have fooled me for sure...
I'm surprised in triple and quads you are saying alum is no worse than copper - think about it, quads have 4 times as much heat, though amps per LED is lower, but the heat is not reduced.
Here is a quick picture of my C8F with Luxeon V’s . You can see that one is only lighted half. I did not know that one-quarter and three-quarter were also possible. You can not see individual dies though, I do not know how the led is built up.
That’s fair enough. It’s just that as i was unknowingly tearing the dome off an XHP50.2 it looked like one quadrant was failing, then that three were failing with a similarity to your picture.
Physically it’s clearly one die (see page 5) but it seems internally / electrically it’s 4. This is from the STEP file provided by Lumileds, you can’t see it in this projection but these pads are on the top plane of the substrate.
I hadn't read through this whole thread, but I just skimmed most of it. I'll definitely limit my remaining Luxeon Vs to below 6A (assumed in the case of the D4) to prevent killing them. None have seen one-on-one time with a FET yet, so they should all be fine.
So out of 4 lights, 2 look like the lower one and 2 look like the first one. But one of the LEDs that look good is reading much lower amps then it used to.