Luxeon K2

xpitxbullx

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Looking at the pictures, it looks like a single die Luxeon. Probably a new 3W design. Also, When comparing the output in the factsheet to the the Lux-I and the Lux-III, it was still showing about 100 lumens. This is under the 5W output. Seeing that and the single die picture, I say, its the new 3W design.

Jeff
 

IsaacHayes

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Jeff, take a look at the link above, I talked about the efficiencies, etc of it. It probably has better thermal contact and lower Vf. Funny thing is the new 5W Seoul led has the same input voltage and current draw as the luxeon K2 yet it produces 178lumens instead of 130....
 

SemiMan

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Yes, but the K2 is a single die device and the Seoul is a multi-die. You can get better efficiencies at lower current (per die at least) or lower current densities. However, have you seen the thermals on the Seoul? Realistically, if you ran it at the rated current, unless you have a huge heat sink, the life of the things is likely to be pretty short. 5W * Rthj-a + ambient will likely be over 100C at room temperature. I would like to see some lifetime versus heat plots from Seoul as well on this unit. Being multi-die, you also have the issue of focusing though it should be ok in a reflector.
 

IsaacHayes

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ya didn't know it was multi die. I'd heatsink them, not sure how they'd do with HS'ing still though.
 

evan9162

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If that datasheet is to be believed, then the "warm" (red/orange/amber) Luxeon K2s are not as bright as the new warm Luxeon IIIs. I bet the K2 versions are still using the smaller TIP structure, rather than the larger one found in the Lux III version.

The K2 versions have the same Vf and dynamic resistance as the original Luxeon versions, just a bit lower thermal resistance, and the ability to run at higher current.

Interesting - the K2 red/orange/amber would seem to be a bit of a step backwards from the Luxeon III counterparts.
 
L

LITEmania

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i heard K2 is using copper for the slug. but just a little improvement for thermal handling ? /ubbthreads/images/graemlins/confused.gif
 

evan9162

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Luxeons, Luxeon V, and Luxeon IIIs already use a silver coated copper slug.

However, it looks to me like the slug was redesigned. The current slug is a ~2mm diameter pedistal about 3-4mm tall sitting on top of a thin base, so the profile looks like an inverted T. That leaked datasheet shows the bottom of the slug, and press photos have shown the top - it looks like it's the same size on top and bottom, so it would be a single chunk of metal the same profile the whole way. That would help the thermal path a bit.
 

IsaacHayes

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evan, I was just thinking of that today, that the K2 Red/ambers would be smaller luxeonI size and a little brigther but not as much as luxIII ones. This is because I saw the picture of the k2 demo with a red that had the small die. I figured that they wouldn't revert back to a smaller die AND have more output than a luxIII...

But the green/blue/white/etc would be brighter though...
 

IsaacHayes

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Very interesting data sheet. Seems there will be 2 versions 12 and 14. A 12 S flux 60lumens @ 350ma seems like fun! The lri proton needs that!

So guys that make HS's start making them to accept the new package and use the new case size/shape to make an alignment thing...

Sorry in advance if I don't make much sense I've drank near a 12 pack and I'm really tired. Actually I'm gonna go to bed now.. darn CPF always eats up my time! /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/happy23.gif
 

evan9162

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Issac,

The new K2 R/O would definitely produce a brighter spot with a Mag reflector, since it's rated at 100 lumens, but would be 1/4 the volume of the Lux III R/O, so it would focus tighter.

However, since the main point of the R/O seems to be signalling applications, it would make more sense to keep the brightest output instead. So I'm not sure what Lumiled's motivation is for using the smaller die.
 

IsaacHayes

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Evan, true. I guess with the K2 it's suppsodly a "new generation" of luxeons. Meant to be almost a replacement for luxeonI. You got 350ma parts that can be "over-driven" to 700ma, and then 700ma/1000ma parts that can go to 1500ma.. All with improving exsisting die's and interfaces... I'm wondering if some of the current LuxeonI's will be phased out eventually by the K2...
 

evan9162

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The "warms" can only go to 700mA. Their thermal resistance (I think it said 12C/W) is way higher than the Lux III warms (at 6C/W) - so the maximum current is definitely thermally limited.
 

IsaacHayes

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Hmm, wonder why it's so high? It would do good to be lower and still only drive them at 700ma to be brigther... /ubbthreads/images/graemlins/icon3.gif

The LuxIII R/O is driven at 4x luxeon1. Which it has 4x the size of dies. It's like a 5W luxeon only all in parallel and one die. The K2 is the same size as luxI but overdriven x2.

So if the bond wires on the LuxIII can survive and not fuse open, you'd think you could over-drive it too espcially with the lower thermal resistance as long as you can get the heat away better.

Per surface area, the LuxIII R/O and LuxeonI R/O have the same brightness as they have same current per surface area. That's why the LuxIII doesn't out throw the LuxeonI.

The K2 will because it will have 2x the current per surface...
 

evan9162

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Issac,

With increased area, you also get a decreased thermal resistance. That's why the Luxeon V thermal resistance is lower than the Luxeon III. Likewise, for the warm Luxeons vs warm Luxeon IIIs.

Some time ago, I used the thermal resistances of the Luxeon V and III to calculate what the die->submount thermal resistance is for each Luxeon III die, and the thermal resistance from the submount -> slug.

Lemme see if I can dig that up:

Here are snippits from that post:
[ QUOTE ]

However, the thermal resistance (j-s) of an L5 is only about 1/2 of a 1W...why?

Theoretically, it should be 1/4.

It's possible that there is some base thermal resistance for the submount, based on the thermal resistance of the submount, plus thermal resistance for each die (junction -> submount)

This base thermal resistance would be nearly identical between the 1W and 5W (actually, a little worse for the 5W), since the submount area is the same between the two.

For a Luxeon III, if we say we can go from 13C/W to 8C/W, but some part has to be divided by 4 (because of the junction area/number of solder blobs being
multiplied by 4), then that's Rj-s = Rbase + (Rj-sub)/(# of dies)




[/ QUOTE ]


so using the Lux V and III for the above (the good ole system of equations):

8 = rbase + (Rj-sub)/4 <--- L5

13 = rbase + (Rj-sub) <--- L3




Then Rj-sub = 6.7 C/W

Rbase (sub-slug) = 6.3 C/W


Likewise, we apply the same forumla to the warm Lux I/III - there isn't a silicon submount, but we'll say that Rj-sub is the thermal resistance from the junction to the joint between the die and slug.


17 = rbase + (Rj-sub) <--- L1 warm
6 = rbase + (Rj-sub)/4 <--- L3 warm

Then,
rbase = 2.3C/W
and
Rj-slug joint = 14.7C/W

by quadrupling the size of the die, that Rj-slug gets reduced to 3.7C/W, for 6C/W total.

That 14.7C/W also includes the die attach method, so any thermal resistance in that gets reduced to 1/4 as well when the die size increases. This is not true for the "cold" luxeons, because the silicon submount->slug is the same size/attachement method between the Luxeon III and V.

So, one way that Lumileds could reduce the warm K2 thermal resistance to 12C/W is through improving the die attach method, and also improving the slug thermal resistance (with a beefier slug). But, there is still a ton of thermal resistance in the junction->die attach path that looks like it's simply a result of the materials/structure themselves.

Notice that the cold K2s thermal resistance is only reduced to 9C/W. That could have been accomplished mostly by improving the submount->slug and slug thermal resistances (which is probably easier than improving the junction-> submount thermal resistance), but I'm sure improvements in the junction->submount path have been made as well.
 

lamperich

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@ Evan


What do yo mean with cold an warm?
i hope you dont mean the Color temp :)

R/O is red orange?


Im quite impressed

35 lm @ 350mA are possible
and round about 55 @ 700mA

above that in my eyes led´s get to inefficient for small flashlights. but still /ubbthreads/images/graemlins/ooo.gif
 

IsaacHayes

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Evan, ah makes sense you have larger die touching the slug you have more area for heat to escape.
 

evan9162

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[ QUOTE ]
lamperich said:
@ Evan


What do yo mean with cold an warm?
i hope you dont mean the Color temp :)

R/O is red orange?


Im quite impressed

35 lm @ 350mA are possible
and round about 55 @ 700mA

above that in my eyes led´s get to inefficient for small flashlights. but still /ubbthreads/images/graemlins/ooo.gif

[/ QUOTE ]


With "warm" luxeons, I'm talking about red/orange/amber Luxeons which use a different material mix: AlInGaP, and physical structure: truncated inverted pyrimodal, than the blue/green/white Luxeons ("cold") which are InGaN based, and are a flat plane structure. So it's in reference to the color family, since there are differences within the product lines based on the color of light they produce.

It's not meant to distinguish the warm white luxeons (2900K) from the cool white (5500K) luxeons.
 

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