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

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Jerommel
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Hey, i had one in a Astrolux S1 for a while, on a 8× 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. Thumbs Up

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.

2Q19

TBone
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Mouser and Digikey have the 6500K on stock.

Jerommel
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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.

2Q19

djozz
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I guess that I am lucky thusfar, I have used the Luxeon V in 4 builds sofar and they all do not show this. All on moonlight, left to right: E2L, D4, VG10, S8-clone. Btw, you can see PWM in three, they have a BLF-A6 driver, the D4 uses higher frequency PWM probably.

khas
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I bought some Luxeon V’s , I don’t have a lens to try with but here is a couple of photos through a welding glass :
X6 (left) D4 (center) Sofirn C8 (right)

It’s the best picture I could take by they seem uniformly lit when I check under the magnifying glass, they have not been spared in any way they are both used with a FET driver and a Sony VTC6’s.

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It looks like some blue light seeps through at the underside of your faulty led and that gets me to the following hypothesis: can it be that the dome had some sideways force and has party detached from the die? With the phosfor coming off with the dome (like with all new leds except the SST-40), the air in between die and phosfor prevents part of the light to enter the phosfor (various surface reflections) and escape back into the die or sideways. The phosfor above the detached part would appear darker then.

ImA4Wheelr
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Looks like the defect has not manifested in the 4 in my Q8 yet.   These poor guys got reflowed no less than 8 times.  I have 6 more that I'm trying to figure out what to use them for.  I'll report if any of them have the half dying issue.  I have to say it again.  I just love the tint and beam pattern with this emitter.  The below pic is bottom of Ramp Mode.

 

Flashy Mike
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Jerommel wrote:
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.

Same here: several Luxeon V damaged the same way, but they got higher currents. The typical appearance as can be seen in Jerommels photos: about the third part (rectangle shaped) at one side of the die is darker.
Note: this is not always visible in low moonlight level! It can better be seen at higher currents through some filter (I use a writable DVD for this purpose).

Edit:
My LEDs were only mounted in reflector lights, so a force to the side of the LED is unlikely.

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I will try the same picture tonight with the 4 lights on max. With some 10.500 lumen pointing at the ceiling I hope that no one will be disturbed Shocked

khas
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The pictures I posted is taken on max output, I have build two quads and two reflector lights, I can’t see any irregularity’s in the die output in any of them.

I have been running them all hard and hot with FET drivers and VTC6’s and VTC5A’s.

djozz
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Still trying to figure out if this is a random thing going on:
At what temperature do you reflow, Jerommel/Flashy Mike?

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I haven’t reflowed them by myself, got them mounted on MCPCB, just like Jerommel (I guess).

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Flashy Mike wrote:
I haven’t reflowed them by myself, got them mounted on MCPCB, just like Jerommel (I guess).

That should be very ok, I trust led4powers reflows way better than my own.
Jerommel
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I got them reflowed on 4040 boards too.
Very well done reflow indeed.

Flashy Mike wrote:
Jerommel wrote:
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.

Same here: several Luxeon V damaged the same way, but they got higher currents. The typical appearance as can be seen in Jerommels photos: about the third part (rectangle shaped) at one side of the die is darker.
Note: this is not always visible in low moonlight level!
That’s the weird thing.
When you test them with very low current, it looks fine.
Quote:
It can better be seen at higher currents through some filter (I use a writable DVD for this purpose).

Edit:
My LEDs were only mounted in reflector lights, so a force to the side of the LED is unlikely.

No mechanical damage on mine either.
The picture does show a small slightly blueish area, but that’s because of a sloppy, hastily put together aspheric test set up.

2Q19

Jerommel
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djozz wrote:
It looks like some blue light seeps through at the underside of your faulty led and that gets me to the following hypothesis: can it be that the dome had some sideways force and has party detached from the die?
No, it’s just a sloppy set up, the lens was at a slight angle. Prism like tint shift effect.

2Q19

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Seem like the failures are most likely a manufacturing defect (as opposed to a design defect) as mine have been tortured with excessive handling and heat from reflows and high current.  Took a pic in Turbo mode under welding googles:

 

EDIT: I just reread the above posts at the problematic emitters.  I missed that one was working fine and then went bad.  Seems unlikely to be a manufacturing defect when that is considered.  Djozz's hypothesis makes a lot of sense.  Would be informative to see how evenly the failed emitters lighted up with the domes completely removed.

 

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If I remember right maximum current decreased also when the LED got damaged. Don’t have a flawless LED currently for comparison.

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^

When you look at that emitter from the sides that the thermal pads extend out to, do you see indication that there is adequate solder between the emitter's thermal pad and the base?

EDIT: That may not work.  The thermal pads don't extend all the way to the edge.  Probably the best that could be done is to unreflow the emitter and see if it appears there is an adequate amount of solder on the thermal pad.

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Checked 2 boards, there was no excessive solder on the visible ends of the center pad. So I unsoldered the LEDs and there is solder on the center pads of LED and board.

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^

Thanks for checking. We expected that based on who reflowed the emitter, but it would have explained the drop in current and damage to your emitter if you had found otherwise.

If you don't think you will ever use that emitter in its current state, you could try a hot dedome.  I would do it by reflowing it back onto a base.  Before it cools (but after solder locks up), lift off the dome with a pick.  The dome might break up.  If it does, just try to lift of as many pieces as you can while trying to not remove phosphor.  If you do remove phosphor, that is ok, but you will be left with a UV or Royal Blue emitter.  After the emitter cools and you hook it up, put on some UV/Blue eye protection (if you lost phosphor) and power the emitter up.  If the light is now evenly spread across the die, djozz's theory is correct (i.e. There was some separation of the dome from the phosphor) and you now have a dedomed Luxeon V.

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ImA4Wheelr wrote:

Seem like the failures are most likely a manufacturing defect (as opposed to a design defect) as mine have been tortured with excessive handling and heat from reflows and high current.  Took a pic in Turbo mode under welding googles:


 



EDIT: I just reread the above posts at the problematic emitters.  I missed that one was working fine and then went bad.  Seems unlikely to be a manufacturing defect when that is considered.

Because?
What if the chip wasn’t properly soldered to its 4040 base?
Quote:
  Djozz’s hypothesis makes a lot of sense.  Would be informative to see how evenly the failed emitters lighted up with the domes completely removed.

 

You can hypothesise all you wish, but the LEDs were not mechanically abused, only saw 3 Amperes max.
The blueishness is only there in the picture because i had the little aspheric a bit askew.
You can see on the opposite side the yellow sticks out.
(I thought i explained that already…)

2Q19

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@ImA4Wheelr:
I might try that when I find the time but that wouldn’t explain the lower maximum current after the damage, I guess. I don’t know how this LED is build but I rather suspect some broken electrical connection in the LED. My damaged LEDs look exactly like the one shown by Jerommel, and with a separated dome I would expect some variation.

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‘Expert’ is very relative here, everyone here is a good meaning amateur, just as you are. No one is claiming to know what really happened, and every one hopes that we will find out together how it can go wrong because this is one of the more interesting leds at the moment.

Edit: you re-phrased your post Wink

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I'm detecting a bit of frustration/anger Jerommel.  If I sounded like I was trying to say you're to blame for the damage to your emitters, I apologize.  I'm not.  I just really, really like this emitter and want to know what is causing these failures.  I wasn't counting the reflow as part of the manufacturing process of the emitter.  I completely agree that if the base's thermal pad is not adequately connected to the LED's thermal pad, bad things will result.

 

If I come across as trying to sound like I know what I'm doing, I again apologize.  I think I tend to write in a way that makes me come across as sounding authoritative.  I'll try to watch out for that more.

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djozz wrote:
‘Expert’ is very relative here,
I already deleted “experts”, it sounded too offended.
Quote:
everyone here is a good meaning amateur, just as you are. No one is claiming to know what really happened, and every one hopes that we will find out together how it can go wrong because this is one of the more interesting leds at the moment.
Both LEDs look like new, mechanical damage like you proposed would be visible to the naked eye.
Quote:

Edit: you re-phrased your post Wink

Yes.
My first reaction when i noticed a problem was: Jerommel, what did you do wrong this time…
Then i doubted the reflow on the 4040 PCB, so i desoldered it, only to find out it was reflowed perfectly by Neven.
I had a somewhat similar thing with the XP-G3 in the Manker E02, only that one was half lit on low current and fully lit on high current (by the way, i replaced that one with a 219C).

2Q19

Jerommel
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ImA4Wheelr wrote:

I’m detecting a bit of frustration/anger Jerommel.  If I sounded like I was trying to say you’re to blame for the damage to your emitters, I apologize.  I’m not.  I just really, really like this emitter and want to know what is causing these failures.  I wasn’t counting the reflow as part of the manufacturing process of the emitter.  I completely agree that if the base’s thermal pad is not adequately connected to the LED’s thermal pad, bad things will result.


 


If I come across as trying to sound like I know what I’m doing, I again apologize.  I think I tend to write in a way that makes me come across as sounding authoritative.  I’ll try to watch out for that more.

I’m over it already, don’t worry.
Yeah, i was a little annoyed..
I would never claim something to be a faulty product if i wasn’t certain i didn’t damage it myself in any way.

I can understand you don’t want this product to have problems.
Neither do i.

2Q19

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Flashy Mike wrote:
@ImA4Wheelr: I might try that when I find the time but that wouldn't explain the lower maximum current after the damage, I guess. I don't know how this LED is build but I rather suspect some broken electrical connection in the LED. My damaged LEDs look exactly like the one shown by Jerommel, and with a separated dome I would expect some variation.

 

Your suspicion sounds quite plausible, but lack of variation does not seem to rule out separation.  If there is some defect in the dome adhesion process, it could result in similar looking failures.

 EDIT: Fixed typo.  Didn't include the word "not".

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Jerommel wrote:
ImA4Wheelr wrote:

I'm detecting a bit of frustration/anger Jerommel.  If I sounded like I was trying to say you're to blame for the damage to your emitters, I apologize.  I'm not.  I just really, really like this emitter and want to know what is causing these failures.  I wasn't counting the reflow as part of the manufacturing process of the emitter.  I completely agree that if the base's thermal pad is not adequately connected to the LED's thermal pad, bad things will result.

 

If I come across as trying to sound like I know what I'm doing, I again apologize.  I think I tend to write in a way that makes me come across as sounding authoritative.  I'll try to watch out for that more.

I'm over it already, don't worry. Yeah, i was a little annoyed.. I would never claim something to be a faulty product if i wasn't certain i didn't damage it myself in any way. I can understand you don't want this product to have problems. Neither do i.

Cool.  I don't think djozz was trying to say you caused the damage.  I thought he was just asking a reasonable question to gain data.  I imagine dome separation could be caused by a defect in the manufacturing process.  That could explain how I could beat the hell out of mine with no failures, while other emitters failed for no apparent cause.

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Ok, I was impatient (as mostly) and “cold” dedomed the LED including phosphor using my fingernails and tweezers.
Was hard to take close pictures with my low end smartphone but finally I put it on top of the lens of my 3rd hand which also (hopefully) helped to keep my eyes undamaged since I don’t have UV protection glasses. This is the (still ugly) result:

The orientation of the 2 pictures might be different since I moved the MCPCB after taking the first picture.
It’s only the inner square of the LED surface which is lit and I can only see a small difference between the halfes. But I powered the LED with a couple of milli amps only since otherwise my smartphone camera had been blasted. Might be there is a bigger difference at higher currents.

Edit: in the 1st picture the LED is not powered and the inner square doesn’t look patterned as seen in the picture, it’s even.

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Actually the inner square is not completely even. Take a look at my first picture, you see a vertical line, a tiny bit left from the middle of the inner square. You don’t see it clearly with naked eyes, but with my tiny microscope there is very narrow line visible. It doesn’t appear to be a crack, more like the remaining kink in a paper sheet which has been folded and unfolded again, somewhat elevated. Don’t know at all the meaning of this, perhaps a conductive trace underneath the kink has been blown.

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