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.
MZ explains it - details, details...
What's your definition 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.
This PCB w/out LEDs is in the “MCPCBs - ALUMINUM” part of the shop. And there’s no copper mentioned anywhere. And weight is low for copper.
Yep, I know all that for the bare alum board, but for the pre-mounted quad in the listing I linked -- nothing about alum, copper or weight.
It's confusing without reading every post on BLF about this stuff...
Actually weight is available under “Additional Information”.
But I agree, these could have been clearer.
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.
Ouch, no fun.
Thanks djozz! That’s very interesting.
Is that definitely the die failing and not the dome separating from the die?
Multiple dies would explain the very low Vf of these LEDs. It’s much easier that way.
I have had more than a few doing this, and the shadow over the led was always the same size: about half the led not lighted.
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.
edit: see here, same plane as the ESD diode pads
Cool! Thanks for posting this.
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.
Thanks djozz! Ok - now I gotta take a closer look at mine - it's bug'n me now...
This is a good look'n V:
This is a bad one in my modded OTR M3:
Up closer:
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.
I certainly didn’t. It’s good to know as I have a few of them I haven’t yet put to use.
Luxeon V has extremely low Vf so I will presume that direct drive is the culprit, and that such degradation might not occur even when overdriven as long as the LED does not see unregulated high voltages.
But from my experience, the failing Luxeon V’s is not a one-to-one result from overcurrent. The failing Luxeon V in my C8S was already the third one failing, after three reflows (on the challenging triple 3535 board 
) and again a failing led I called it a day. And from the output (a bit over 4000 lumen when all 3 leds still worked) it is drawing under 15A (I could measure actual current again) so not really extreme for the V. On the other hand I have one Luxeon V in a VG10 with BLF-A6 driver and all bypasses doing over 2000 lumen, and still going strong!
I have wondered if, for super low Vf LEDS, high cell voltages may induce damage even if the continuously delivered current is not excessive. Also, LEDs are sensitive to reflow temps and duration, maybe some more than others, and possibly even moisture content as per the datasheets.