Lumileds Luxeon V, test of a 4000K 70CRI emitter

Hey I just noticed this, but “a thermal resistance of 0.8 degC/W, which is 3 times as low as any existing high power led” is not really correct, the CFT-90 has a thermal resistance of .45C/W at the junction.
But this is probably because the LED chip itself is like 10mmx10mm or something huge like that :stuck_out_tongue:

Yes and no. :smiley:

0.8°C/W is by far the best value ever for a 4mm^2 LED (XM-L2, XP-L2 etc. => usually around 2.5°C/W).
Luminus has traditionally reached the lowest thermal resistances because they use larger DIEs and a special direct-to-copper mounting technique (notice that they have two sets of bond wires, the current doesn’t got out the bottom of the DIE).

Generally LEDs with large DIEs seem to have lower thermal resistances. I think it makes sense to compare thermal resistances relative to the Die size, so I multiply them (so lower values are still better):
XHP70.2: 0.9°C/W * 14.2mm^2 = 12.78
CFT-90: 0.45°C/W * 9mm^2 = 4.05
XHP50.2: 1.2°C/W * 8.24mm^2 = 9.89
XHP-35 HI: 1.8°C/W * 5.9mm^2 = 10.62
Luxeon V: 0.9°C/W * 4mm^2 = 3.2 (I had to guess here regarding the DIE size)
SST-40: 2.5°C/W * 3.994mm^2 = 9.99
XP-L2: 2.2°C/W * 3.55mm^2 = 7.81
XP-G3: 3°C/W * 2.06mm^2 = 6.18
Osram Black Flat Gen2: 4.3°C/W * 1,122mm^2 = 4.82

So it seems the Luxeon V and the CFT-90 are indeed very good, but the Osram Black Flat, XP-G3 and XP-L2 certainly hold their own.

I’m not sure theses theoretical values tell the whole story though or even have any meaning at all. I am completely ignoring the size of the LED package and thus of the center solder pad. The Luxeon V has a larger solder pad compared to the XP-L2 and the SST-40 is even larger than the Luxeon.

I’m using the D4 with Luxeon V’s everyday now during a short holiday on Schiermonnikoog. Despite the very small margins between the solder pads on the ledboard because of the non-fitting footprint the light holds up fine and proves to have a very good and pleasant tint for use in a natural environment. Actually in showing contrast and depth it does no worse than my E2L with 4000K R9080 219B’s.

But I still feel a bit lonely using this led, is there anyone else who has used the Luxeon V in a flashlight? Experiences?

I built S2+ with 9A LD-A4 (+ thermal enhancement kit) and Luxeon V on 16mm DTP, it works nicely,I'm seeing highest lumens from 4mm^2 die LED with absolutely great tint, it's pretty unbelievable this LED is only 70CRI,it has quite a bit of red in spectrum and beam is very uniform across emitting angle, also tint is very consistent over wide range of current. CREE XP-L V6 3D tint looks pretty crappy compared to Luxeon V, and it has less output too (fast drop due to high Vf).

Djozz, the same depth and contrast as 319b sounds great
Do you think it is a candidate for the FW3A?

Been trying to join you, but the footprint is frustrating me in my chosen target, the Q8. It looks doable. Sorry for the off angle of the picture. Seven reflow attempts so far. All seemed dead on. The last few reflows were just one emitter, the other 3 excluded. Always shorting the positive side. Even if I hold the emitter from where it wants to sit.

If I want to keep the stock mcpcb, I think I will have to modify the pads slightly.

I have many different XP boards in my spare box and the solder pad size and position vary a bit, to the point that on some the electrical pads are too far to the middle to fit the Luxeon V at all. Perhaps the Q8 board is one of those :slight_smile:

Just ordered 3 mounted on the 16 mm's from Led4power. That looks wayy too challenging even for me to mount on a XP board.

Just checked - these are 4.0 x 4.0 mm, bigger than XP's, smaller than XM's. Soooo, guess stock centering pieces won't work?

Rotating XM-L spacers should work .

XP-L V6 3D (EE X6) vs. Luxeon V 4000K (S2+) white wall

Luxeon V 4000K beam

Has anyone tried cutting away some of the center pad with an exacto knife?

Now that is proper led surgery! :smiley:
(no I have not tried that)

Interesting idea FmC. Sounds promising.

I modified the Q8's MCPCB to fit the Luxeon. Just used a utility knife to remove the solder resist on the outside of the pads out to the overflow tabs and to remove just a slight bit of the coper trace on the inside of the pads. It wasn't pretty, but it works. Measured about 8.5k lumens at start up which dropped down to 8K about 20-30 seconds (wasn't timing). I had also swapped out to the A20DP FET. The tint as has been reported by djozz and others above is so nice. As led4power stated, it's really hard to believe the CRI is only 70.

In addition to mcpcb's, we are going to need new isolator rings. I ended up using some xml isolators and drilled out the Q8 reflector some. Unfortunately, I was impatient and used a dull bit. Messed up some of the reflective coating at the enlarged emitter holes. Luckily, the beam pattern seems unharmed. Just not so pretty right now.

Thanks djozz for bringing this emitter to our attention. I think this may be my new favorite emitter.

EDIT: I should note that the Luxeon V's measured above went though at least 8 reflows until I got them all properly connected. I don't know yet if all the heat hurt their performance. But at a minimum, these are tough emitters. If I get a chance tonight, I'll get a couple beam shots.

EDIT: Sorry folks. It was raining last night. Looks like it will continue to rain with the tropical storm that is moving up the coast.

That is great and perseverent work ImA4Wheelr, and some bravery is required to attack the nice Q8 board with an exacto knife, I know how wrong it can go when you cross the dielectric layer when going too deep.

For clean reaming reflector openings for fitting centering rings I succesfully use a hand reamer. Mine was a really expensive one (the brand is PB) but I never regretted buying it, I use it often in modding.

The numbers that you get are as expected exactly 4 times the numbers of my VG10 with the LV.

^

Thanks for the tip on the reamer. I haven't ever used one. Will look into them.

I installed one of the 4000K/16mm MCPCB Lumileds L1V1 from Led4Power in a BLF KRONOS X6 SS/cu light - it has spring bypasses and looks like the stock 22 AWG LED wires.

With a VTC6 at 4.21V, measured 8.7A at the tail w/clamp meter, 2285 at start, 2135 at 30 secs, 42 kcd throw measured at 5 m. The tint is one of the best I've seen, as LED4Power said earlier. It's amazing what this LED can do, plus the drop over the first 30 secs is pretty low. I can only describe the tint as a milky white, no trace of yellow - nothing like the XP-L2's. It does appear very much like a 5B or 5D that used to be my favorite.

Arrow now has 5700K L1V1's in stock, but only in qty 1000: https://www.arrow.com/en/products/search?q=lumileds+l1v1

I'm now working on modding a Lumintop SD Mini with a full FET+1 or triple channel driver and another 4000K L1 V1.

Finally got one of these in a light. Convoy M1 with a MTN-17dd driver. The beam is gorgeous. Probably my favorite 4000k tint without tint mixing. Very hard to believe it is only CRI R7000. If they make a CRI 90 version this will be one of the best emitters out there IMO. No tint shift at all like with XPL2.

I tried out a 6500K version, and the cold white looks good too! Not as nice to me as SST40 for 6500K, but that’s because I kind of like the purple tinge SST40 has. Luxeon V is a more pure 6500K white.

Hey, i had one in a Astrolux S1 for a while, on a 8x 7135 driver with a pebbled 30° TIR optic.
Was not particularly impressing, but it turned out one of the 2 Luxeon V i bought was faulty:


(projection with a small aspheric lens)
I didn’t even notice this with the pebbled TIR.

Neven will send me a new one with my next order though. :+1:

Today i put the other one in my black C8, with a LD25 driver (3 Amperes).
It’s in a smooth reflector, and the tint shift (yellow corona, cool spill) is not worse than an XM-L2, in fact, i think there’s less tint shift than with an XM-L2 actually.

Of course it’s tempting to put in a 6 Ampere driver, but with the stock LD25 i have current regulation almost to the end of the battery charge, depending on the battery internal resistance (voltage sag).
Before this LED the C8 had an XP-L HI, which obviously gives a nice tight spot, but i have surely gained light output, and with the XP-L HI pretty soon there was little difference between medium and high…

I wish i had a cooler tint Luxeon V though.
This 4000K is quite warm, so the deep red lags behind the orangey red and yellow, making some things, also skin tones, look unnatural.
Since cooler white low CRI LEDs have less orangey red also, colours usually look more natural with cooler white low CRI LED light (well, it does to me anyway).
My Lumapower MRV (classic C8 sized cheapo with the fake brass ‘engine’) is still king in low CRI goodness, with it’s XM-L2 in 4D tint, but it’s not as bright and will not draw 3 Amperes on a low battery charge.

Mouser and Digikey have the 6500K on stock.

Dang, dang, dang…
The other one went bad too…

Both never saw more than 3 Amperes and never ran hot, but both are bad now, same problem… (see picture in my previous post)
I was about to order a couple more, but i’m not going to now.

So i want to ask you who have a Luxeon V in use to check out how it looks on a white wall focussed with a lens.