# Production CREE XR-E Testing



## NewBie (Oct 26, 2006)

*Production CREE XR-E Testing (SLOW lots of pictures!)*

First off, CREE made a vast improvement in the Vf of their LEDs, and it holds quite well with increasing current. In fact, I know of no other power LED company producing LEDs with Vf's this low. Why does it matter? Power consumed is Current * Voltage. So, here is the first chart, compared with a Philips LumiLEDs Luxeon K2, their latest device:








Next, I measured the lumen output (I figure accuracy is +/-10%), vs. current:







This is also a vast improvement vs. any other LED I've tested to date, and pretty much, producing roughly 2x more light than other similar LEDs at the same current. Or looking at it another way, at the same light output, this part consumes about half the current, so your batteries will last 2x as long, and the LED will produce half the heat.

Due to the extra low Vf, and the outstanding amount of lumens comming out of the device at a given current, when you multiply these two together, the total power is often less than half, compared to most devices.

The extra high lumen output of this device, vs. power consumed, means it is more efficient, and more of you power leaves the device as light, instead of being converted to heat. Heat is the bane of LEDs and reduces both their expected lifetime and lumen output.

Yes, you can find the rare unobtainium bin of some whizbang Philips Luxeon, but they are rare, and still won't come close to matching the lumens vs. current of the CREE XR-E. CREE also makes some premium bins, this one tested here is just a run of the mill part.

For testing, the device was directly soldered to a 2" by 3" plate of 0.162" copper slab, and set on a table with no cooling air. Your results may be better, if you are more agressive in your heatsinking.


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## dat2zip (Oct 26, 2006)

Wow, that's totally impressive up to 2A. Amazing!

I can't recall, but, I'm wondering if the datasheet has any information of output vs heat? Just curious to know of the thermal degradation versus temperature is relative to the competition. I wonder if the Cree die is better or worse in this.

My question is this? Assuming you could drive it at say 2A and die temperature rises to 120C as an example. Would it be better to drive it at say 1.5A and have a lower temperature die rise. It's possible that the same light configuration might produce more lumens at the lower current since it doesn't get as hot. There might be a sweet spot that increasing current to LED might generate less lumens output when the light gets to thermal equilibrium.


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## x2x3x2 (Oct 26, 2006)

do u happen to have a shot showing the beam profile from the bare emitter?


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## Billson (Oct 26, 2006)

You don't gain much above 1400ma. 17% increase in lumens vs 43% increase in current.


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## McGizmo (Oct 26, 2006)

Nice graphs Newbie! I was told the die is rated at 2 amps but the lumen maintenance and packaging are not up to this current.

Some might falsely assume that twice the light means 1/2 the heat. Instead of lumens, it would probably make sense to measure the light in radiometric power and get a feel for the light output in watts and compare that to the input power of watts to get an idea of the actual power in heat generated. I suspect that in some cases, a light with the XR-E and a good MCPCB may deliver more heat to the flashlight host than a Luxeon driven at the same power level. The low thermal resistance of the Cree XR-E and MCPCB may be low enough to bring this about, relative to the Luxeon. Anyone soldering one of these LED's will appreciate how well the heat transfers throughout the package!

Any idea of Vf shift as a function of temp? I think that flat curve shows the difficulty for a DD set up. There is one DD composition though that I bet would be real viable and that would be on a single CR123.


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## dat2zip (Oct 26, 2006)

I found the thermal information on page 3 of the current data sheet.

-Wayne


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## davidefromitaly (Oct 26, 2006)

thanks jarhead!!!


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## cy (Oct 26, 2006)

WOW! what impressive gains!

2x performance increase from same power, seems the next paradigm shift for LED's has occurred.


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## light_emitting_dude (Oct 26, 2006)

Jarhead? Sounds like Marine Corps terminology! If so Semper Fidelis!! Will be interesting to see the new flashlights with this new LED!!


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## jch79 (Oct 26, 2006)

Thanks NewBie!! The testing begins!


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## CM (Oct 26, 2006)

Nice. Thanks for the data.

This is what I got with one sample. Bin WF-P2

Vf(V) ILed(A)
=========
2.7	0.01
2.75	0.02
2.8	0.04
2.85	0.05
2.9	0.07
2.95	0.09
3	0.11
3.05	0.14
3.1	0.16
3.15	0.2
3.2	0.22
3.25	0.24
3.3	0.27
3.35	0.29
3.4	0.33
3.45	0.39
3.5	0.45
3.55	0.52
3.6	0.59
3.65	0.64
3.7	0.7
3.75	0.8
3.8	0.88
3.85	0.95
3.9	1.03

Theta Jc for XR-E is 8 C/W and the K2 is 9 C/W. I think if everything else allows, these can be driven to 1.5A like the K2. I prefer moderation where the incremental increase in current results in a somewhat linear fashion with the output which is 700mA or less which incidentally is how Cree specs their part.


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## NewBie (Oct 26, 2006)

Did you measure those Vf's Kelvin connected at the emitter, or did you measure them at your power supply?

It makes a big difference.


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## ViReN (Oct 26, 2006)

Thanks *NewBie||Jarhead*...

It would be interesting to see the lumen's maintained over a period of time at lets say 1 A current.

Also, I do not feel there is much in overdriving the LED over 800 mA as the slope changes drastically after that current.

The Peak's Snow LED (5mm's based on Cree die) do not have good Lumen Maintenance record over 40 mA.

But I must say, Cree XR-E are an edge over any of the currently available LED's. Imagine 90 lumen's at 400 mA current... WOW 

MiniMag LED already has a deep reflector, now what we need is to mod it with a Cree LED and AR UCL, and we would see it putting out around 90 lumen's easily.


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## Pinter (Oct 26, 2006)

I also got higher values for Vf.

Cree XR-E, bin WC-P4, right out-of box, epoxied to heatsink. Measured on the emitter. Current source: nFlex.

20 mA - 2,71 V
58 mA - 2,84 V
100 mA - 2,94 V
175 mA - 3,05 V
350 mA - 3,24 V
500 mA - 3,34 V
700 mA - 3,49 V
1000 mA - 3,59 V

Last one is a little suspicous, I will check it later, maybe I was blind and missed a segment on my multimeter.


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## chimo (Oct 26, 2006)

Great data Newbie! 

Wow, this is more than an incremental improvement - more like a leap. Looks like Cree has a real winner here. The conformal phosphor coating is icing on the cake (no pun intended).

It's VI curve looks like it would resemble a UxxH LuxIII (but with a greater light output). Luxeon did not do themselves much of a favour in releasing the K2 with such high Vfs. It was a more of one step forward and two steps back.

Paul

Correction: Oops - I was looking at the wrong point (500mA instead of 700mA) binning for the Cree. Looks like a good VxxH instead of a good UxxH bin!!! Outstanding.


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## NewBie (Oct 26, 2006)

Pinter said:


> I also got higher values for Vf.
> 
> Cree XR-E, bin WC-P4, right out-of box, epoxied to heatsink. Measured on the emitter. Current source: nFlex.
> 
> ...




Vf's will typically vary from part to part, but your Vfs are much closer to what I measured.

The reason why they are closer, is that it may be because you measured at the emitter for the voltage, typically, when you have current going down a test lead, it causes a voltage drop, which means voltages measured at the power supply will be higher than normal.

But remember, Vf's will vary from part to part, just like the Luxeons do.

Luxeon III binning current is 700mA
Your sample looks like it would be a Philips Luxeon III bin J.
My sample looks like it would be a rare Philips Luxeon III bin H.

@ 701.5 mA and half the voltage of a Lux V (3.2716
Volts), I'm getting ~134.075 lumens and 2.2950274 Watts.
This would make it a VXOH bin, and a very upper end of the flux bin at that.


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## X Racer (Oct 26, 2006)

NewBie said:


> This would make it a VXOH bin, and a very upper end of the flux bin at that.


 
What a major jump forward. Can't wait to see what can be done with these...


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## hakstooy (Oct 26, 2006)

I got some LEDs in and have been testing them and this is what I've gotten. 

The ø data is output and is measured in an uncalibrated integrating sphere, so the units don't mean anything outside of relative comparison among the samples I've measured.

I'm using a current controlled source, and the voltage measurements are simply a rough estimate of the mean value measured during the spectral measurement. (Roughly 10 seconds to do)

Since I haven't built a real measurement setup, this is done simply by probing stars that are placed in air against the integrating sphere port.


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## Calina (Oct 26, 2006)

I put Newbie's data in an excel sheet, this is what I got.

Bear in mind that this is a graph interpretation since I didn't have the exact data so the results are aproximate.

V A W R Lm Lm/W

2,78 0,05 0,14 55,60 15 107,9
2,86 0,1 0,29 28,60 28 97,9
2,98 0,2 0,60 14,90 50 83,9
3,06 0,3 0,92 10,20 72 78,4
3,14 0,4 1,26 7,85 90 71,7
3,18 0,5 1,59 6,36 106 66,7
3,22 0,6 1,93 5,37 120 62,1
3,26 0,7 2,28 4,66 135 59,2
3,3 0,8 2,64 4,13 145 54,9
3,34 0,9 3,01 3,71 157 52,2
3,38 1 3,38 3,38 166 49,1
3,4 1,1 3,74 3,09 175 46,8
3,42 1,2 4,10 2,85 185 45,1
3,46 1,3 4,50 2,66 192 42,7
3,38 1,4 4,73 2,41 193 40,8
3,52 1,5 5,28 2,35 194 36,7


At 50 mA you have more than 100 Lm per watt, 5 mm LED don't do as well.
At .4 A you have about 70 Lm/W
At .6 A about 60 Lm/W
At 1 A it degrades to 50 Lm/W

You would need pretty agressive cooling to use the Cree above this level.
For a bicycle light it could still be useable since the air displacement is important but for a flashlight I would certainly not go above this level.

Thanks Newbie, great work



.


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## bombelman (Oct 26, 2006)

Nice find, ordering 2 leds for testing now


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## CaLux (Oct 26, 2006)

As my understanding, CREE doesn't allow user to choose Vf value. They said there has no bin code for forwading voltage.
So, if they can keep low working voltage is very good for user.
But, if they can't control well. It may be a challenge to engineer.


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## AlexGT (Oct 26, 2006)

Wow!!! or should I say Holy $hit!!!! That curve is incredible! Amazing! Now where can I get a Q3 bin? 

By the looks of it If you have stock invested on lumileds you should really think about selling it, Lumileds may go the path of the dinosaur very soon as word spreads to the high use manufacturers.

"The king has died!!! Long live the new King!!!

"Lumileds RIP"

AlexGT


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## AlexGT (Oct 26, 2006)

Newbie do you have beamshots compared to say a U bin Lux 3?, I am wondering if a Mcr-27L (long) can focus the light to a useful level.

Good work as always keep it up!

AlexGT


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## CM (Oct 26, 2006)

NewBie said:


> Did you measure those Vf's Kelvin connected at the emitter, or did you measure them at your power supply?
> 
> It makes a big difference.



Measured with a voltmeter right at the LED. I know there's a huge IR drop thru the leads from the power supply especially at 1A. I realize my data shows higher Vf but I'm sticking to it. I see some incosistency in Vf since I have two other parts that I went ahead and measured and they're closer to what you got though still a bit on the higher side. I re-measured the data I posted again and got the same results. Maybe a single LED fluke?

EDITED TO ADD:

Two other leds measure 3.50V and 3.55V at 700mA. Still very happy with the output of these. I'm now looking at my S bin and U bins with contempt


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## goldserve (Oct 26, 2006)

I'm curious to know if there is any VF drop after burning in the leds or the heat from soldering the part enough to burn it in?


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## NewBie (Oct 27, 2006)

I don't have much time tonight.
Though, I took some photos that I thought you might enjoy:


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## x2x3x2 (Oct 27, 2006)

since u were already testing the input current vs output, didnt u take any beamshots?


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## NewBie (Oct 27, 2006)

Like this?







I stopped the picture way, way down, so you could see the CREE better:


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## havand (Oct 27, 2006)

Nice work. I'm starting to get excited  A little not so excited about the lack of hosts though  I won't be buying an aleph or a TI McCree so i'm kinda out in the cold on that one. Maybe a minimaglite and just put up with the beam pattern.


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## NewBie (Oct 27, 2006)

Okay, I poked around a bit and found that I did find a loose reflector from McGizmo handy, it is 45mm in diameter.

I know that this isn't a fair comparison, but what I happened to have that was portable is a circuit that delivered 450mA to the CREE XR-E. The exact wattage drawn by this CREE at this current is 1.423 Watts.


I do not know how many mA the Fenix P1 delivers to the emitter, but I had one with a fresh battery I put in earlier today, so I used that as a reference. I just checked the current draw from the cell, and it is measuring 625mA, with the cell voltage dropping to 3.05V. This is 1.91 Watts. I suspect the converter is ~80% efficient, so the power delivered to the Luxeon III in the P1 would be roughly 1.525 Watts- but this is not fact.


I held the reflector in my hand, over the CREE XR-E and thus it isn't centered, and the photo is at an angle, as the truck was in the way. So, we have the larger reflector I used (so please keep this in mind!), and this is what I saw:







Anyhow, I need to run off to bed, maybe I can put together something tomorrow that is a much more fair comparison.


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## Loomy (Oct 27, 2006)

The fact that you ran an XRE way past the recommended 750mA and into 1500mA territory makes me wonder how long it would take to explode in a U2.  

And considering how well the L6 mod turned out, I wonder if the U2 reflector is long enough to make a 200 lumen XRE beam look good... just before the LED melts down and your eyeballs are irradiated! Or a Gladius for that matter.


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## ViReN (Oct 27, 2006)

NewBie said:


> I don't have much time tonight.
> Though, I took some photos that I thought you might enjoy:



wow... from photos looks like there is a real thin layer magic phosper sprayed all over including the bond wires. I wonder, if Heat would cause any long term issues (if it's a thin layer).

the 100 Lumen figure at 350 mA is unbeatable as of now


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## ViReN (Oct 27, 2006)

also, why 3 bond wires?


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## x2x3x2 (Oct 27, 2006)

finally recieved my 0021 batch from cutter few mins ago.
so it should be 73.9-100.4 @ 350mA, just hope i get lucky with the tint.

also, what does the "U-bin" mean, they wrote that on the invoice. i thought the XR-E bins are refered to with "P" and "Q"?

so i have a question as this will be my first "mod".
am i right to guess that the top is where i solder -ve wire to and
buttom is where i solder +ve wire to? does is matter which side of the + i solder to?






cant wait to see how it goes in a FT-01


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## paxxus (Oct 27, 2006)

NewBie said:


>


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## 270winchester (Oct 27, 2006)

Thanks Newbie for the pics.


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## leukos (Oct 27, 2006)

I predict 2007 will be a whole new landscape for LED lights.


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## jtr1962 (Oct 27, 2006)

Amazing results and thanks for testing these NewBie!

To show how much less heat these make for a given lumen output let's say the design goal is 80 lumens. You can get that with a typical Luxeon III running at 700 mA. Typical Vf is roughly 3.7 volts so input power would be 2.59 watts. Efficiency is about 10% so you would have to deal with about 2.33 watts of heat.

Now let's do the same thing with a Cree XR-E. You only need about 350 mA. Vf would be around 3.1 volts so power input would be only 1.085 watts, a reduction of 58% compared to using the Lux III. The heat reduction is even more impressive. Since this part is about 25% efficient you would only be dealing with about 0.81 watts of heat, a reduction of 65% compared to the Lux III. In other words, _*one-third*_ the heat for the same lumen output. :rock: 

The good times are just beginning. A few years ago I was waiting patiently until LEDs finally reached or bettered fluorescent tube efficiency. That time has finally arrived. I can hardly wait to see what Cree has in store for us next year!


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## havand (Oct 27, 2006)

I'm not ready to count lumileds out yet....I'm ridiculously happy they now have performance (and pricing competition), but I'm sure they havn't just been sitting around on their hands.


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## milkyspit (Oct 27, 2006)

havand said:


> I'm not ready to count lumileds out yet....I'm ridiculously happy they now have performance (and pricing competition), but I'm sure they havn't just been sitting around on their hands.




Agreed! Competition for Lumileds can only benefit the consumer. Go Cree!
:thumbsup:

Newbie, keep on rockin'! Your testing is a BIG help to many of us. :bow:


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## milkyspit (Oct 27, 2006)

jtr1962 said:


> Amazing results and thanks for testing these NewBie!
> 
> To show how much less heat these make for a given lumen output let's say the design goal is 80 lumens. You can get that with a typical Luxeon III running at 700 mA. Typical Vf is roughly 3.7 volts so input power would be 2.59 watts. Efficiency is about 10% so you would have to deal with about 2.33 watts of heat.
> 
> ...




*Jtr, *how does one know the efficiency of a given LED? You cited 10% for your LuxIII scenario.

On a semi-related note, I've been building with LuxI S**H for a while now and have noted that there's a VERY noticeable reduction in heat... for example, my M180 builds even after two hours of continuous runtime, generate only lukewarm amounts of heat. As far as light, we're looking (ballpark) at 180 lumens out of the emitters with efficiency around 55 lumens per watt. But how efficient in percentage terms are these emitters as far as light vs. heat? The evidence suggests there must be a marked increase beyond that 10% figure, but how do I quantify?

As far as fluorescents, good riddance! I've long been of a strong ANTI-fluorescent mindset, given that EVERY FLUORESCENT TUBE CONTAINS MERCURY VAPOR! Nasty, nasty, NASTY stuff! And even if the manufacturers don't gloss over this fact (most do), we all know broken fluorescent tubes are most definitely NOT cleaned up in the manner one would treat release of a hazardous chemical... in school classrooms full of children, for example, nobody leaves, the janitor shows up with his dustpan and just sweeps up the glass. Not good!

If high-efficiency LEDs can put the final stake through the heart of fluorescent lighting, then God bless them.


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## MillerMods (Oct 27, 2006)

WOW! Those pics put it into perspective. These XR-E's ROCK!


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## DragonFlame (Oct 27, 2006)

OMG!
The visual difference in output is almost unbelievable !


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## WAVE_PARTICLE (Oct 27, 2006)

LOL! The spill of the CREE is actually brighter than the hotspot of the P1!


 WP


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## jtr1962 (Oct 27, 2006)

milkyspit said:


> *Jtr, *how does one know the efficiency of a given LED? You cited 10% for your LuxIII scenario.


I'm assuming a luminous efficacy of around 330 lm/W for the emitted spectrum. I read that this is about right for blue plus YAG phosphor LEDs. While my calculations may not be exact, they are at least in the ballpark.



> On a semi-related note, I've been building with LuxI S**H for a while now and have noted that there's a VERY noticeable reduction in heat... for example, my M180 builds even after two hours of continuous runtime, generate only lukewarm amounts of heat. As far as light, we're looking (ballpark) at 180 lumens out of the emitters with efficiency around 55 lumens per watt. But how efficient in percentage terms are these emitters as far as light vs. heat? The evidence suggests there must be a marked increase beyond that 10% figure, but how do I quantify?


55 lm/W would be roughly 17 or 18% efficient. The great thing about efficiency increases is first off you need less power for the same light output. That already means a reduction in heat. Since the LEDs are more efficient in terms of converting power to light, you get a smaller percentage of the power you put in coming out as heat so you win again. That's why your S-bin LuxI's make way less heat than, say, a Q-bin.



> As far as fluorescents, good riddance! I've long been of a strong ANTI-fluorescent mindset, given that EVERY FLUORESCENT TUBE CONTAINS MERCURY VAPOR! Nasty, nasty, NASTY stuff! And even if the manufacturers don't gloss over this fact (most do), we all know broken fluorescent tubes are most definitely NOT cleaned up in the manner one would treat release of a hazardous chemical... in school classrooms full of children, for example, nobody leaves, the janitor shows up with his dustpan and just sweeps up the glass. Not good!
> 
> If high-efficiency LEDs can put the final stake through the heart of fluorescent lighting, then God bless them.


Believe me, I share your sentiments which is exactly why developments like this make me happy. Although I love everything else about fluorescent lighting I've always hated the hazardous chemicals and the fact that the tubes can shatter just like incandescent bulbs. A highly efficient, unbreakable, pure white (I _really_ hate the yellowish light of incandescent lamps), and very long-lasting light source is what I have long wanted. Finally with the Cree it seems we have that, and it will only get better as time goes on! Now if only Lumileds can get off their collective rearends to release something competitive.


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## MillerMods (Oct 27, 2006)

I quote from here 

"The theoretical maximum for any light spectra is 683 lm/W (for 555 nm monochromatic radiation). For white light, the maximum is typically 300 to 350 lm/W (for a traditional fluorescent lamp spectrum).....It has been shown that it is theoretically possible for a RGB white LED to have a maximum of over 400 lm/W, which means that source efficacy of 200 lm/W can be achieved with 50% LED radiant efficiency. This is the rationale for the US Department of Energy’s solid-state lighting goal of 200 lm/W."

So 85-95 lm/W will be something close to 21-24% efficient for the Cree XR-E. About the same or better than a high quality flourescent lamp. 

I have a good feeling that Cree's development and pricing will generate a huge boost in LED's place in the lighting industry.


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## Nitroz (Oct 27, 2006)

NewBie said:


> I held the reflector in my hand, over the CREE XR-E and thus it isn't centered, and the photo is at an angle, as the truck was in the way. So, we have the larger reflector I used (so please keep this in mind!), and this is what I saw:
> 
> 
> 
> ...



@%$! *[email protected]# That is amazing. Looking forward to more reports. Nice Work Newb!


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## CM (Oct 27, 2006)

Let me contribute a white wall beam shot (sorry, it's all I got right now)

I built an Aleph 19 with a Wiz2 running the Cree at 690mA on the left. A modified HDS B42 with the brightest U bin I can find is on the right. I estimate the HDS is hitting the LED pretty hard since my runtime tests on it show about 12 minutes on high. It's also comparable to another HDS light that measured over 60 lumens at LSI so this particular light is my "calibrated" source.







The McR-19 in the Aleph is an excellent match to the XR-E. Lots of sidespill but the hot spot has enough intensity to be able to give the light some respectable throw.


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## MillerMods (Oct 27, 2006)

oops, double post.


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## MillerMods (Oct 27, 2006)

I like the 75 degree viewing angle of the Cree. It makes the spill much more useful. A really deep narrow reflector will make one of these XR-E's a real flame thrower! The new AA Mag LED reflector would be a good candidate.


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## CM (Oct 27, 2006)

Finally went ahead and did some quantitative measurements. I have a P2 bin Cree and comparing that to a U bin Lux III, it is 50% brighter. I wish I had access to a sphere but based on what I know about this particular U bin Lux III, the Cree is outputting over 90 lumens easily through the Aleph's sapphire lens which is pretty lossy.


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## p1fiend (Oct 28, 2006)

NewBie said:


> I held the reflector in my hand, over the CREE XR-E and thus it isn't centered, and the photo is at an angle, as the truck was in the way. So, we have the larger reflector I used (so please keep this in mind!), and this is what I saw:


:huh2: 
No Way! That P1 beam shot looks totally wrong. If this was taken at an angle, but close to a garage, the P1 beam should be much bigger and have at least SOME spill to it. What gives?


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## :)> (Oct 28, 2006)

Please tell me that the HD45 could be modded with the Cree's for 2 level light. The beamshot was tremendous even at 450 ma. From the looks of that beamshot, the output at 450 ma is greater than the output of my Lux III HD45 at 900 ma. 

Nice.!

-Goatee


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## AlexGT (Oct 28, 2006)

I think the only thing that "gives" is that the Cree is totally OWNING the U bin:goodjob: 






p1fiend said:


> :huh2:
> No Way! That P1 beam shot looks totally wrong. If this was taken at an angle, but close to a garage, the P1 beam should be much bigger and have at least SOME spill to it. What gives?


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## p1fiend (Oct 28, 2006)

AlexGT said:


> I think the only thing that "gives" is that the Cree is totally OWNING the U bin:goodjob:


 
There is no way that a P1 beam is a tiny < 1ft x 1ft spot with no spill. Something isn't right with that shot, yet everyone seems incredibly impressed with it.


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## grapplex (Oct 28, 2006)

...


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## NewBie (Oct 28, 2006)

The flood brightness in the CREE is tremendous. Instead of a really "contrasty" hotspot with a weak flood, it has easily as strong of a hotspot, and a very strong flood. It makes for a *very* useful light, that can throw and has a flood beam that is much closer to the hotspot, imagine flood that can be throw. I found it very useful for searching for things.


Anyhow, I got my A19 XR-E, which has a bit of an issue. Within two hours of receiving the package, dat2zip was all over things to get the problem rectified. So, this isn't a good comparision either, as it is, the XR-E is "crippled"

But it has bracketing of the photos, and the reflectors are so close in size, that it takes out the reflector factor-just remember the XR-E is now crippled:


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## AtomSphere (Oct 29, 2006)

P1 got owned! Thanks for the pictures!


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## Robocop (Oct 29, 2006)

Man this new stuff is really advancing pretty quickly.....pretty soon we will all be replacing our coveted U bins as outdated.

Ok not knowing much at all about dome characters and even less about reflectors is there a necessary reason for the actual design of this new Emitter? Would it be possible to place this new design inside the same dome shape as a standard Luxeon III design? I am wondering if this new emitter somehow has to be made into a more flood pattern by design?...Is it simply done because they do not wish to violate some form of copy write design of LumiLeds?

I am wondering if they will offer different viewing angles to better use existing reflectors while maintaining the same output as the new design. It seems a shame that we will have to start all over trying to find a custom made reflector for this new design however Don seems to be doing just that.

I sure do like the idea of using some of the ready available 17mm reflectors and a small host light for this new emitter. Imagine this beast coupled with an Orb NS and direct drive with the much improved efficiency levels.....now that is impressive to say the least.....or one of those slick MillerModded Arc hosts....the possibilities are sure interesting to think about.


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## BentHeadTX (Oct 29, 2006)

Robocop said:


> It seems a shame that we will have to start all over trying to find a custom made reflector for this new design however Don seems to be doing just that.
> 
> I sure do like the idea of using some of the ready available 17mm reflectors and a small host light for this new emitter. Imagine this beast coupled with an Orb NS and direct drive with the much improved efficiency levels.....now that is impressive to say the least.....or one of those slick MillerModded Arc hosts....the possibilities are sure interesting to think about.



The McR17XR reflector? Yeah, I think those will fit in my MillerMods 1.7 watt L1P with an XR-E sitting behind it. 100+ lumens with a basic and 125 lumens with a Q3 bin sounds rather tastey to me. 

Don has taken the lead with this so I eagerly await what kind of magic he has planed in the XR series.


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## paxxus (Oct 29, 2006)

I want an XR-E based high-end torch so badly it's not even funny. Gimme, gimme!


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## AlexGT (Oct 29, 2006)

What I would like is to have retrofit kits for popular and custom lights, like HDS's McGizmo's, Bulk's.

I am currently searching for a way to put one of this babies on a LH to have variable output, anyone have the physical dimensions of the CREE star? Is it the same size as the lumileds star? 

Why the hell did CREE come up with a stupid 75 degree angle? cant they see that almost all the current optics and reflectors are based on the radial pattern? That seems DUMB!!! bigtime, again there is no standarization, VHS vs Beta dilemma.


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## Chronos (Oct 29, 2006)

The cree looks so promising. I too thank you Newbie for the information! I bet this would be a great lightsource in a Gladius, my Minimag LED, and I'd love to see one retrofitted to my KL5 head. Hell, I bet this will be the LED to have in '07.


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## NewBie (Oct 29, 2006)

Chronos said:


> The cree looks so promising. I too thank you Newbie for the information! I bet this would be a great lightsource in a Gladius, my Minimag LED, and I'd love to see one retrofitted to my KL5 head. Hell, I bet this will be the LED to have in '07.




LOL!

It is the LED to have for 2006.

Next year will bring further improvements, trust me.


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## Anglepoise (Oct 29, 2006)

Don,NewBie and others. 
Thanks for all your hard work in bringing all this info to the membership.
Much appreciated. Thank you.


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## Archangel (Oct 29, 2006)

Any chance someone could do a comparison between a Lux III, V and XR-E using the same type reflector, preferably a 17 or 18mm? I'm curious how the beams compare.


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## KDOG3 (Oct 29, 2006)

Wow. Just wow. Sorry if my questioning is repititous, but I'm just dyin' for answers to some questions:

Where do we get them? How much are they?

Possibility of mounting one in a U2? Whats the U2s' current draw on high anyway?

Putting one in a MagLED - someone has GOT to try this. I would if I could get a hold of one!

There seems to be a HUGE spread as far as the output numbers, 74-100. Is it possible to know what a particular emitter puts out?


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## Mike Painter (Oct 29, 2006)

KDOG3 said:


> There seems to be a HUGE spread as far as the output numbers, 74-100. Is it possible to know what a particular emitter puts out?



This spread represents a big improvement over the 3 watt Luxion which has a range from 60 to 249.6 Note that the higher bins have equal or greater spread over a single bin. 
U.....87.4....113.6 = 26.2 
V...113.6....147.7 = 34.1
W..147.7....192.0 = 44.3
X...192.0....249.6 = 57.6


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## [email protected] Messenger (Oct 29, 2006)

you guys created my almost notorious habit of almost buying lights and hearing about the newest latest and greatest stuff.


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## NewBie (Oct 29, 2006)

[email protected] Messenger said:


> you guys created my almost notorious habit of almost buying lights and hearing about the newest latest and greatest stuff.




LOL!

Thats better than buying the latest high end flashlight, then the next day, before it arrives, having something killer, like the CREE XR-E hit the streets...


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## bombelman (Oct 29, 2006)

KDOG3 said:


> Where do we get them? How much are they?
> Is it possible to know what a particular emitter puts out?


Source: http://www.cutter.com.au/proddetail.php?prod=cut651

Info: https://www.candlepowerforums.com/threads/128311&page=1&pp=30

Lumens ? Bin P3 available at the moment. (P3= 73.9~80.6 lumens @ spec)


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## vetkaw63 (Oct 29, 2006)

There is a group buy going on now. Check it out.
Mike


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## lumapower (Oct 30, 2006)

woooooo....
great light,I love it!


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## NewBie (Oct 30, 2006)

I've been goofing around a bit with the XR-E, if anyone is interested in some beamshots:

http://candlepowerforums.com/vb/showthread.php?p=1664042#post1664042
http://candlepowerforums.com/vb/showthread.php?p=1664044#post1664044


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## Kryosphinx (Oct 30, 2006)

Would direct driving it on 1 li-ion overdrive it by a lot?


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## BentHeadTX (Oct 30, 2006)

Kryosphinx said:


> Would direct driving it on 1 li-ion overdrive it by a lot?



Not if it is a LiFePO4 based 3.2V Lithium-Ion. Punching the low voltage Cree with a 3.7V one would cook the thing as it will attempt to pull 2 amps.


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## NewBie (Nov 3, 2006)

Many folks have talked about how utterly ice cold the CREE looks, or how it is blue.

This is usually due to a monitor that is not calibrated, or a camera that was not white balanced "correctly".

To give folks an idea, here is my A19 CREE XR-E measurements. If you look at the block labeled T, you will see that it measured 6402, which works out to 6402K:


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## LEDninja (Nov 3, 2006)

Did sone efficiency calculations using Newbie's graphs from post 1:
mA ------- 20 ---- 80 ----- 350 ----- 700 --- 825
Volt ----- 2.7 --- 2.84 --- 3.1 ------ 3.27 --- 3.32
Watt ---- .054 - .2272 -- 1.085 -- 2.289 -- 2.739
Lumens - 6 ----- 23 ------ 80 ------ 134 ---- 152
Lm/W --- 111 -- 101 ----- 74 ------- 59 ----- 55

I picked mA based on the more common LED drive currents.
20mA >>5mm LEDs.
80mA >>my guess for Peak Pacific Baltic Fenix E1 L0P-SE default.
350mA >> Lux 1 nominal.
700mA >> Lux III nominal.
825mA >> The 1st production light from the Shoppe.

I do not have a working copy of Excel. Maybe someone with a copy can get the raw data off Newbie and plot a nice graph.


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## milkyspit (Nov 3, 2006)

*Newbie, *I wouldn't mind a copy of the raw data I'd need for lumens/watt efficiency testing. Any chance I could snag a copy of your raw data? PM if so... if not, no biggie! Just wanted to ask.


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## davidefromitaly (Nov 3, 2006)

NewBie said:


> Many folks have talked about how utterly ice cold the CREE looks, or how it is blue.
> 
> This is usually due to a monitor that is not calibrated, or a camera that was not white balanced "correctly".
> 
> To give folks an idea, here is my A19 CREE XR-E measurements. If you look at the block labeled T, you will see that it measured 6402, which works out to 6402K:



x:0.3136 and y:0.3378 mean a WF bin, if you is sure that yours are WC bin this mean that with overdrive the tint shift (just for comparison WF is like lumileds X1)


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## NewBie (Nov 3, 2006)

Dave,

The one used in my A19 is clearly a different bin than the raw CREE LEDs I have received. Yes, it is an X1 bin, but barely in that bin, and doesn't appear green to my eyes. I however, have plenty of luxeons that are X1 bins, and are very clearly green in comparison. I have another A19 light engine that is cooler in color temperature. I hope to measure it soon.

Yes, driving an LED at other currents than what it was binned at, will cause a tint shift from what it was binned at.

Also keep in mind, that reflectors also change the tint of an LED.


Plot of lm/W vs. Current on one of my samples, directly soldered to copper 2" by 3" by 0.165", no MCPCB:


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## havand (Nov 3, 2006)

You wouldn't happen to have a U-bin luxIII that you could overlay on that efficiency graph? I think it would be pretty interesting to see. If not, don't worry about it. Thanks Newbie, your info is really helping put these leds into perspective.


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## hotbeam (Nov 3, 2006)

You're a legend!


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## NewBie (Nov 4, 2006)

Okay, I have a second A19 XR-E light engine to check out, and obtained the following information:







Note the color temperature on this one, 7207K.


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## xochi (Nov 4, 2006)

Damn Jarhead, What the hell do you have against Lumileds? You didn't think we'd notice that all this praise of the Cree XR-E is just a veiled assault on Lumileds luxeons and their K2? Sheesh, and in such bad taste! :scowl:

I mean , so what , the cree is a little brighter than the luxeon . I'd be much happier with my slightly dimmer luxeons than have to put up with all this evil luxeon trashing. :thumbsdow















Just kidding , Jar ! I'd hate for you to get soft with these threads that can't help but evoke giddy luminous joy in even the most jaded LED junkies out there !!!! :laughing:

I noticed that the P2 VF's posted earlier in the thread are lower than the P3's you posted and given that Cree isn't binning based on VF, perhaps we can count on a trend of rising VF's relative to flux bins? Certainly some XR-E's are more efficient than others but with the luxeons it seemed that higher flux bins were at least partially the result of higher input power . I mean when T**J's were the mainstay the U binners were mostly K's and then T**H's started percolating out and U**J's weren't too far behind. 

I suppose that if rising VF relative to flux bin is an appreciable factor then application becomes a more relevant influence in pursuing bins and we won't be plotting and schemeing to acquire holy grail bins. To be honest, the flux bin lust surrounding luxeons was a little over the top at times and it would be nice to see the "man behind the curtain" early in the game (if he exists). 

Feel free to correct me where I'm clueless since I'm really just pretending to know something about this stuff. 

Thanks for the great information , Jarhead. :goodjob:

Oh, one more question, do Cree LEDs us Silcon Carbide semiconductors? It'd be kinda cool to talk about space diamond LEDs :laughing:. It might be easier to explain to normal people why our lights are so expensive.


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## davidefromitaly (Nov 4, 2006)

NewBie said:


> Dave,
> 
> The one used in my A19 is clearly a different bin than the raw CREE LEDs I have received. Yes, it is an X1 bin, but barely in that bin, and doesn't appear green to my eyes. I however, have plenty of luxeons that are X1 bins, and are very clearly green in comparison. I have another A19 light engine that is cooler in color temperature. I hope to measure it soon.
> 
> ...



a yeah sorry, i haven't noticed that is another led  is a X1 but really near the X0.

just for fun your second led is a WE tint but near the WB, translated in lumiled mean full Y0 tint 

and thanks for the efficiency graph


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## NewBie (Nov 4, 2006)

Okay, a few folks have asked me about the drawbacks of MCPCB.

There are high end and low end MCPCBs on the market, and just like the difference between a 5mm LED and a CREE XR-E, they are not created equal.

A common low cost MCPCB that is used by some of the folks selling the CREE XR-E is shown in the thermal photo below.

When doing the same test with a copper plate, there is a whole world of difference, maybe I'll show you if I have a chance.


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## chimo (Nov 4, 2006)

Newbie, which MCPCB is that:

One of these?











Paul


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## NewBie (Nov 4, 2006)

Very similar.


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## Anglepoise (Nov 6, 2006)

From what I am reading, it seems the only use of a MCPCP
in this application is to allow re flow soldering. 

With the poor thermal qualities in these MCPCP's as indicated by Newbie
it would seem to me that we would be better off 
using AA epoxy if we had to fit the XR-E directly to a solid aluminum 
heatsink within the light.


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## McGizmo (Nov 6, 2006)

Hi guys,

I falsely assumed that MCPCB's were MCPCB's. I have heard of more exotic materials used for thermal PCB's but I was surprised at the thermal resistance noted by Newbie on he XR MPCB that Wayne and I are currently using. Grant it, I am not overly concerned as my current uses for these are at lower than max drive levels and steady state temps will be more governed by the overall relief of heat, beyond the light engine. We do have a query now into the vendor for possible and better alternatives to the present MCPCB material and composition. Again, I am satisfied with the performance of the present MCPCB's but if better is available, why not.

I am always at a loss when it comes to the thermal issues of the big picture let alone under a microscope but unless I am completely off base, realistically and pragmatically, I know I won't achieve the thermal conditions of a large copper plate in a small 1 cell flashlight; nor do I need to consider this a must do on the design goal list. If you are after a throw monster of max brightness, stick one of these XR-E's on a large plate and put it behind a 2.5" optic lens. If you are interested in a small light with say 60 lumens of real output, then you can underdrive the XR-E and get a cool runing proposition where some loss due to heat is not that great or of real concern. The beauty of the XR-E is its potential and ability to meet the needs of various light design goals! :thumbsup:


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## chimo (Nov 6, 2006)

I just checked - the center block is insulated from the Aluminum heatsink below. It is very, very thin - but I guess it must not have the best thermal properties.



chimo said:


> Paul


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## NewBie (Nov 9, 2006)

I took a known Binned WC CREE XR-E emitter and ran a color test on it.

Measurement Guaranteed Chromaticity Accuracy: x: ± 0.0015, y: ± 0.001
Repeatability: Chromaticity: ± 0.0002


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## LEDninja (Nov 9, 2006)

What bins and what amps were the XR-Es run at in the spectrographs on posts 77 & 84? Not at all familiar with the binning - colour temperature relationship, but my guess is 7207 degrees would be outside the 'XO' bin box.
I am guessing daylight=~5500 degree=~WO bin.


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## NewBie (Nov 9, 2006)

LEDninja said:


> What bins and what amps were the XR-Es run at in the spectrographs on posts 77 & 84? Not at all familiar with the binning - colour temperature relationship, but my guess is 7207 degrees would be outside the 'XO' bin box.
> I am guessing daylight=~5500 degree=~WO bin.




No, 5500K is V0 bin towards the center of it, on the left side, which is not very popular. The X0 bin runs up to 7000K


Typically, XO (6300K-7000K), X1 (7000-5650K on the green side), and WO (6300K-5650K) are the most popular "killer" bins. A few of the outdoor types like the X1 bin, which is a green tint of white, as they feel it offers better color rendering outdoors.


A great way to understand K temperatures, is to simply take your monitor and push the settings button, and you will typically find settings for 9300K white, 6500K white, and 5600K white.


The producers of the A19 will not specify which bin is used in their lights. On one of them the current at the LED itself was 800mA.


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## davidefromitaly (Nov 9, 2006)

NewBie said:


> I took a known Binned WC CREE XR-E emitter and ran a color test on it.
> 
> Measurement Guaranteed Chromaticity Accuracy: x: ± 0.0015, y: ± 0.001
> Repeatability: Chromaticity: ± 0.0002




you rule man!!!!!!!!! thanks!!!!!!! this explain well how shift the tint with overdrive. another led that don't start in the "X1" region can easily shift in the "Y0" region with overdrive.

is too much to ask to try a osram halogen lamp? curious to see how many IR are trapped in the IRC bulbs...


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## NewBie (Nov 9, 2006)

Keep in mind, if things heat up more, there will be additional shift in the color.

So, if you mount it on the MCPCBs that are common for the CREE at the moment, you will see additional tint shift. Also, if you hold the temperature more constant than my copper plate, such as having more surface area to get rid of the heat, better thermal transfer, etc, the shift will be less.

Heating is also cause by converters, which produce their own heat. Some converters will produce one third of the heat in the flashlight, causing extra tint shift, where as higher efficiency converters will cause under 2% of the overall heat. Resistors also produce heat, which heats everything up.

You also have heat produced by the power source, such as batteries, which contributes to flashlight heat and tint shift.


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## IsaacHayes (Nov 10, 2006)

yeah convertors (especially boost) will produce a lot of heat.


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## NewBie (Nov 10, 2006)

IsaacHayes said:


> yeah convertors (especially boost) will produce a lot of heat.



Most especially Buck-Boost, which produce the most heat of all, as they are in fact, the least efficient.

However, with very careful design, you can achieve 90% with a buck-boost, but not likely in the form factor of a dime, especially at 1 Amp of output current.

A boost or a buck, has one-half of the switches of a buck-boost, and this is easier to get effcient. They can hit 90% in this form factor, and with a bit more room, 96-98% efficiency is not at all impossible.

With an efficient coverter, you will produce less heat from the converter, you will pull less power from the cells which creates less heat from the cells, each of which will help keep the LED cooler, and raise the LED efficiency. If the LED is cooler, and running more efficiently, it will produce less heat, and in turn will load the converter less and make it more efficient making it also run cooler, and the converter will pull even less power from the cell which reduces the heat produced by the cell, helping the LED to be more efficient.

On top of all this, your cells end up lasting longer, due to the reduced load, and you can get more power out of the cells, with less going up as heat.

Eventually, you reach equilibrium.


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## vetkaw63 (Nov 11, 2006)

Hi,
Can somebody explain the difference between Buck, Boost, Buck-Boost, and flupic boards?
The search engine sucks here.
Mike


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## IsaacHayes (Nov 11, 2006)

Boost. used for:
battery voltage is lower than needed for the LED to pull your desired current. Vin < Vf. 

Buck: Battery voltage is higher than led Vf. 

boost-buck: used when you have multiple battery voltages (primary and recharable) or the battery voltage is very close to the Vf of the led. Like starting it it's too high, then partially drained it's too low. The circuit keeps it at the right level to the led the whole time.

FluPIC is used with a higher voltage in than Vf, and IIRC it's not as efficeint as buck (which converts extra voltage into current, thus drawing less from the batteries than the led actually sees.). I believe it's called LDO which is kind of like a varible resitor if I'm correct in that it just turns extra voltage into heat inside itself.


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## Calina (Nov 11, 2006)

What does LDO stand for? Same for IIRC ?

Is there a post somewhere, or a sticky, or something, that translates all those abreviations acronyms etc into proper english?

Is Flupic just a name or is it also an abreviation, if so what does it mean?

Thanks.


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## IsaacHayes (Nov 11, 2006)

IIRC= if i recall correctly. LDO i think is limited drop out. flupic is a name of a driver.


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## Calina (Nov 11, 2006)

Wow, that was fast!

Thank you very much.


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## Pinter (Nov 17, 2006)

[Parallel operation]
There will be serious issues when operating several XR-E in parallel.
Vf vs I curve is so flat that even a small difference in Vf results in big difference in current.

I do not know how consistent the Vf-I curve is within a production batch, but even 0,1V difference yields 100-150mA difference in current below 700mA.


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## glire (Nov 17, 2006)

Calina said:


> What does LDO stand for? Same for IIRC ?
> 
> Is there a post somewhere, or a sticky, or something, that translates all those abreviations acronyms etc into proper english?
> 
> ...


http://www.cygwin.com/acronyms/


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## chimo (Nov 17, 2006)

I did a *very* quick check of a P2 XR-E. WOW!

The Vf at 700mA was in the range of a very low H bin or a high G bin!

If the output was mid-point within the bin range, at 700mA the output would have been equivalent to a V-bin Lux!

These things are incredible - the excitement is justified!


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## glire (Nov 17, 2006)

Crazy CPF influence !
Instead of simply speaking in "volts" or "lumens" they speak in "bins" 
So you got a LuxIII like VX1G bin, great !


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## MillerMods (Nov 17, 2006)

chimo said:


> I did a *very* quick check of a P2 XR-E. WOW!
> 
> The Vf at 700mA was in the range of a very low H bin or a high G bin!
> 
> ...



I wonder if the Vf will be even lower if they are burned in.


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## Anglepoise (Nov 17, 2006)

I must have a bad P2 as the one I tested at 750 ma was Vf 3.67.
Fkuke meter.


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## MillerMods (Nov 17, 2006)

Anglepoise said:


> I must have a bad P2 as the one I tested at 750 ma was Vf 3.67.
> Fkuke meter.



No binning for Vf... yea, that's a bit of a problem. I guess one could buy lots of these and bin them by Vf and sell them at a premium though.


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## milkyspit (Nov 17, 2006)

MillerMods said:


> No binning for Vf... yea, that's a bit of a problem. I guess one could buy lots of these and bin them by Vf and sell them at a premium though.



I've tested a couple 10-packs of P3 bin at 350mA on my regulated PSU... from a single 10-pack I'm typically seeing a low Vf around 3.11V and high Vf around 3.48V. IMHO that's a pretty broad range! oo:


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## Archangel (Nov 17, 2006)

milkyspit said:


> I've tested a couple 10-packs of P3 bin at 350mA on my regulated PSU... from a single 10-pack I'm typically seeing a low Vf around 3.11V and high Vf around 3.48V. IMHO that's a pretty broad range! oo:


Is that "worse" than you'd get if you grabbed ten random luxeon that were binned only by output?


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## Christexan (Nov 17, 2006)

I don't know the details on what kind of circuit a "flupic" is, but my understanding is it's more of a complete "circuit" regulator (parts mounted on a board), rather than a discrete single part such as the linear regulators below (one single package). Could be wrong, but that's my understanding, you could build a flupic from separate parts, a linear regulator IS a single part (externally, internally there are several transistors, protection diodes, resistors, etc, but on a "microchip" level, not a discrete component level).

LDO is "Low dropout", a term used in comparison to a standard voltage regulator. Most commonly...
LM317 (adjustable)/LM78XX family (and many others) - these are standard "linear" regulators (basically work by throwing out excess voltage/current to achieve the desired voltage/current output, kind of a "brute force" "buck" method (cannot boost either number above what the source puts out). Typically drops about 1.5V internally (1.2-2.0V neighborhood depending on output) in operation (regardless of output desired), in addition to whatever additional drop is needed to achieve desired output.

LM108x family - does exactly the same thing as the LM78xx/317 family, however uses a different internal transistor configuration to achieve around 0.5V drop (therefore "dropping out of regulation" one volt lower than the previous models, hence an "LDO") in voltage (0.2 to 1.0 neighborhood depending on output levels). This gives you a "free" volt on average to play with in your design (3.3Vf LED with 4 NIMH batteries (4.8V nominal) leaves 1.5V to deal with... an LM317 would use all that out of the box (well, not exactly, but "nominally"), so you'd get little benefit over using it over just dropping another 1.5V with another type of diode. But put an LM1086 in there, and it leaves you one extra volt, now you get some runtime before the regulator becomes extraneous.

LM78 family runs around $0.32 at mouser.com per unit, LM108X runs around $0.98, so that's why someone with a high volume usage and modest power considerations could save money with the more wasteful version, however for any battery operation like CPF users would be concerned with, the extra 66-cents is worth the extra usable volt from the source.


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## LightBright (Nov 17, 2006)

Pinter said:


> [Parallel operation]
> There will be serious issues when operating several XR-E in parallel.
> Vf vs I curve is so flat that even a small difference in Vf results in big difference in current.
> 
> I do not know how consistent the Vf-I curve is within a production batch, but even 0,1V difference yields 100-150mA difference in current below 700mA.



You're right about the situation being bad if you run them in parallel - SO DON'T DO IT!! Run them in Series. Yes, you will need a high voltage supply.

I just got some P2's. Wow- I am impressed by the relative lack of heat buildup yet the very good light output! At 1 amp the Vf was about 3.6ish


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## IsaacHayes (Nov 17, 2006)

Christexan, thanks for the most excellent explanation!!
LightBright, or if you can't do series, have a resistor/circuit for each single led.


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## LightBright (Nov 17, 2006)

Yep, but resistors in a flashlight circuit - not so great for overall efficiency, especially as the power driven through the LED (Luxeon 1, 3, 5 watt or Cree XR- E) increases.


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## Christexan (Nov 17, 2006)

Isaac - Your welcome. 
Parallel isn't so bad, so long as it's CURRENT regulated (not voltage), and the Vf and current specs of each LED at the operating current is well within max limits (not overdriving any of them outside of ratings or thermal envelope). 
You might however see visible output differences in that scenario. Adding low ohm resistors would help even it out some, yes it's wasteful, but high series voltage may not be an option, and small resistors (say 1 ohm or less) won't waste much power, but will definitely stabilize things. 
If your LEDs individually at 500mA range from Vf of 3.3 to 3.6, and the LOWEST one (say the 3.3 in this case) runs at 700mA at 3.6Vf, then you are still within spec so long as you can keep the heat from escalating. Brightness will DEFINITELY vary however in this scenario. 
In other words, choose the current you wish to operate at, and you have a few choices.. 
Option 1 (riskiest but reasonable): Find the LEDs voltage range at the desired current (say 500mA)... ranked from high to low (use 3.3 low to 3.5V high as an example). Take the highest Vf LED rating (at test current).. for example, 3.5V... now run the lowest Vf LED at 3.5V (ramp up to avoid burning it out) and see what current it pulls. If it's still within safe margins (say 600mA), then you can run them in parallel, so long as you are current regulated. (Pushing lower LEDs to match highest while keeping in rated specifications, brightness COULD vary significantly) 

Option 2 (very safe): Find the range, and test the highest Vf (3.5Vat 500mA) LED, but test it at the voltage of the lowest rated LED's Vf at 500mA (3.3V)... Set the current to whatever current makes the highest rated Vf LED equal to the Vf of the lowest rated, and almost no chance of problems (Limiting the circuit to the lowest end denominator, dimmer performance likely in this case, and varying brightness of LEDs)

Option 3 (best safe performance) : Test LEDs Vf range, put resistors on all LEDs ("resistor match" them), adjusting resistance to match current levels at a given voltage (I'd choose a tiny bit more voltage output than the the top Vf, and work back from there). So put say a 0.2 ohm resistor on the top LED (just to be safe, all the LEDs should have some resistance, or none, otherwise you might have problems (the non-resisted ones would have a nonlinear resistance curve to the rest of the set)). This gives a regulator output of 3.6V to drive the top LED at 3.5Vf. The 3.3Vf LED should have a resistor of 3.6-3.3 = 0.3/.5A = 0.6 ohms
Losses to resistance (in this 2-LED case for example) would be small if you start with small enough resistance. In this example, if it were just these 2, you'od have .1*.5=.05 watts (tiny) plus .3*.5 = .15 watts. Total loss of 0.2 watts, plus maybe a little more loss from driving the regulator 0.1V higher. Anyhow, you can use smaller resistors to reduce this further assuming you can find them smaller (or make your own).


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## win67 (Nov 17, 2006)

Received my sample from Cree today.
The sheet says it is Bin number: xr7090WT-U1-WG-P3-0-0001.
Looks a little bit on the greenish side compared to my hds xrgt.
Put two crocodile clamps to it and powered it with a used duracell cr123.
Lights up the isnide of my wardrobe very well (broad beam) and doesn't get hot at all (no heatsink used)
Thank You, Cree!

Jens


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## srvctec (Nov 17, 2006)

Christexan said:


> Parallel isn't so bad, so long as it's CURRENT regulated...(edited to save space)



:goodjob:

Thanks for the detailed info!! I've learned a lot from your posts in this thread. It's easy to understand and well explained. :rock:


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## NewBie (Nov 17, 2006)

Christexan said:


> Isaac - Your welcome.
> Parallel isn't so bad, so long as it's CURRENT regulated (not voltage), and the Vf and current specs of each LED at the operating current is well within max limits (not overdriving any of them outside of ratings or thermal envelope).
> You might however see visible output differences in that scenario. Adding low ohm resistors would help even it out some, yes it's wasteful, but high series voltage may not be an option, and small resistors (say 1 ohm or less) won't waste much power, but will definitely stabilize things.
> If your LEDs individually at 500mA range from Vf of 3.3 to 3.6, and the LOWEST one (say the 3.3 in this case) runs at 700mA at 3.6Vf, then you are still within spec so long as you can keep the heat from escalating. Brightness will DEFINITELY vary however in this scenario.
> ...




Actually it is one of the worst ideas I have heard since AWR started suggesting it for someone that was doing a headlight.

One major factor you have neglected to think about.

*Temperature.*

One of the LEDs will start to pull more power than the other. The result is the LED starts to heat up. This causes that LED's Vf to drop, which causes it to pull more power. 

As the first LED starts to pull more current, the one next to it will begin to pull less current, and it will cool down, and it's Vf will rise. This causes the current in that LED to drop, which then diverts more current to the other LED, which makes that one get hotter.

Pretty soon, you end up with a radical difference in current between the LEDs.

A person *might* possibly be able to get by with this half baked idea, if the temperature was held constant, and the LEDs were somewhat matched, and also had resistors on them.

The situation becomes worse with these high power LEDs, as compared to the lower power LEDs.

Here are the basics on what you are attempting to do, but done with a low power LED:
http://www.lumileds.com/pdfs/AB20-3.pdf

An addendum if you have more interest in the subject:
http://www.lumileds.com/pdfs/AB20-3A.PDF


Of course, I've seen plenty of examples where designers have used your technique, and sections of road signal lamps as well as automotive rear lamp arrays, have sections burned out. No surprise here.


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## milkyspit (Nov 18, 2006)

Archangel said:


> Is that "worse" than you'd get if you grabbed ten random luxeon that were binned only by output?



Good question, and I don't know the answer... but I do know that with ten Luxeon I SWOH stars, for example, I'll typically see a low Vf around 3.12V and a high Vf around 3.23V... much tighter variance.


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## NewBie (Nov 18, 2006)

Archangel said:


> Is that "worse" than you'd get if you grabbed ten random luxeon that were binned only by output?






milkyspit said:


> Good question, and I don't know the answer... but I do know that with ten Luxeon I SWOH stars, for example, I'll typically see a low Vf around 3.12V and a high Vf around 3.23V... much tighter variance.



When you grab 10 random Luxeon SWOH stars, the H indicates the voltage bin, which can range from 3.03-3.27, with a die temperature of 25C. You are grabbing 10 random Luxeon parts from the same Vf bin. This variation will change as the die temperature heats up, since the die doesn't sit at 25C, once power is applied.

I have received Luxeon III with Vf bins of G (as binned low as 2.79V), and Luxeon III Vf bins of L, (which is binned as high as 3.99V).

Not only does the Vf shift with temperature, with some LEDs it also shifts further with time.

And the amount of Vf shift is different between two otherwise apparently similar parts. I've seen this Vf shift as much as 0.3V.

I have not had a chance to test the new XR-E that much yet.

But, the previous 3XL7090 series, and the one before it, had very little Vf shift. Here are my test results for the 3XL7090:








Here is an example of the new Luxeon K2:


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## Anglepoise (Nov 18, 2006)

I have only received a few XR-E's and the first on I tested had a very high Vf.
Also its steady state temp was a good bit higher than expected.

However this one sample turned out to be a bit of a dud as others have tested lower. I was a bit worried for a time.


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## AilSnail (Nov 18, 2006)

could they please put the useable vf outside li-ion range soon so we don't have to use buck-boost with singlecells? 

Maybe it is already feasible, with a low vf cree xr-e, if there is a buck with a bypass or Vin(almost)=Vo function? normal Li-ion are pretty much wasted at [email protected] right? 2c for a 123 is like .9a x 2 = 1.8A; wouldn't want a higher maximum drive for a 1x123 light even accounting for the converter losses.

Is there a suitable buck chip like this?


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## AilSnail (Nov 19, 2006)

like the tps62040 maybe? its got 100pct duty cycle but maybe the current buck-boost units aren't that far behind in efficiency to bother.


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## AilSnail (Nov 19, 2006)

like the tps63000 buck-boost. from the sheet, over 90pct over a lot of the useable li-ion and output range.


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## ViReN (Nov 19, 2006)

NewBie said:


> <snip>
> 
> But, the previous 3XL7090 series, and the one before it, had very little Vf shift. Here are my test results for the 3XL7090:
> 
> ...



NewBie, just a request, It would be great if you could put same scales for both the graphs. it would make understanding easier. also will it be possible for you to start with same Y axsis crossing zero of X axis in both the graphs.


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## NewBie (Nov 19, 2006)

I've got one somewhere, thats the older 3XRE7090 part there. I'll keep that in mind when I do the XR-E one.


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## Christexan (Nov 20, 2006)

I didn't neglect temperature, in fact I specifically stated that if temperature was handled properly... "So long as you can keep the heat from escalating" and "not overdriving any of them outside of ratings or thermal envelope" were both mentioned in my suggestions. All aspects of such designs naturally have to be considered, as you pointed out, many traffic lights and other light units have burnt out zones because of lack of these considerations. A robust design takes all considerations into account, and designs around limitations such as these as deemed critical for the application, which is why I said there are riskier and safer designs, limiting all the LEDs with resistors is the "safe" way to go, and in a traffic light, car signal, etc, is probably the design that SHOULD be used, but for a floodlight lighting up a flowerbed or a $5 flashlight, "safest" design isn't always worth the expense and space of preventing the random failure that might occur for a unit that is out of average enough to fail. 

I've very aware that if you allow these to heat up, they can and will go into runaway as their resistances drop, hence the 2 caveats that I put into my post, that if you keep them away from their limits and keep in mind thermal issues, then you can consider these options. I don't mind valid critiques of my posts and fully admit when I'm wrong (the PWM post where I meant SMPS, a perfect example), however please consider all caveats that I list in my post, before saying I've neglected such issues. (You quoted the very parts that I just re-quoted, that you have to consider the thermal (temperature) issues as part of it).


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## chimo (Nov 20, 2006)

I did a quick test on the three XR-Es I have on hand. They were cut consecutively from the same strip. 

Here's a quick list of their Vfs at 350 and 700mA:

XR-E #1 
2.91V @350mA
3.03V @700mA

XR-E #2 
3.03V @350mA
3.18V @700mA

XR-E #3 
3.18V @350mA
3.53V @700mA

Paul


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## McGizmo (Nov 20, 2006)

#1 is ideal candidate for DD on CR123 cell!  It is also obvious that these LED's need to be in a constant current control environment, in general!


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## jar3ds (Nov 20, 2006)

chimo said:


> I did a quick test on the three XR-Es I have on hand. They were cut consecutively from the same strip.
> 
> Here's a quick list of their Vfs at 350 and 700mA:
> 
> ...


 how much do you want for #1?


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## hotbeam (Nov 20, 2006)

It's great to see low Vf LEDs these days.


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## IsaacHayes (Nov 20, 2006)

Chimo: wow, 2.12 watts @ ~130 lumens! That's amazing! Talk about high output with a super long runtime!


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## Pinter (Nov 20, 2006)

But it's not so great that these are consecutive leds within one batch. Variation is too big.

I also thinking paralleling XR-E-s, but if I used e.g. sample #1 and #3 and drive 1000 mA through them, probably #1 gets 850mA while #3 only 150mA. Not acceptable.

How can we make sure that brightness and color does not have such a variation??? Based on Lumileds experience, low Vf samples statistically are on the lower side of brightness. Cree do not test each and every led, maybe this very low Vf sample should have been binned one brightness rank lower.


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## IsaacHayes (Nov 21, 2006)

Pinter, true, but remember Cree does not bin Vf. So they don't sort them at all. It would be like lumileds taking some TX0* leds and putting them all on a reel. They could be TX0H, TX0K, etc but as long as they are X0 tint and T flux that's all that is required to match them up.

Kind of a bummer I know, but at least they bin flux and tint, and not just flux. It does make it a little tricky if you are going with a simple resistor setup or crucial low Vf for super high drive from a low voltage cell... But those are "specialized" applications...


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## NewBie (Nov 23, 2006)

NewBie said:


> Here is the setup with no emissivity coating, the temperatures are **HIGHLY INACCURATE**
> 
> 
> 
> ...




Ran at a different current, but used for illustration, without emissivity coating:


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## glire (Nov 24, 2006)

NewBie said:


> I've got one somewhere, thats the older 3XRE7090 part there. I'll keep that in mind when I do the XR-E one.


Please, check also brightness variation overtime.


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## NewBie (Jan 6, 2007)

Okay, when I get a chance...


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## NewBie (Jan 14, 2007)

I just noticed Fraen has optics available for the XR-E, and the older Seoul P3 an P5 parts:

http://www.fraensrl.com/prodinfo.html


Other companies offering optical solutions for the XR-E are G&L, Fraen, LEDIL, Carclo, Khatod, Polymer Optics:
http://www.cree.com/products/xlamp_part.asp

NIST (National Institute of Standards and Technology), tested the CREE XR-E for color and Luminous Flux (lumens), and lm/W, back in October last year:
http://www.cree.com/products/pdf/NIST XLamp LED Document.pdf


Triad Flashlights has chosen the CREE XR-E for their product:
http://www.cree.com/press/press_detail.asp?i=1168609850571


Surefire has also chosen the CREE XR-E for use in several of their flashlights:
http://www.cree.com/press/press_detail.asp?i=1167920349046


One of the largest distributors in North America is now carrying the CREE LED line, Arrow Electronics:
http://www.cree.com/press/press_detail.asp?i=1162560893953

The parts, and the pricing for the CREE LEDs is shown at the Arrow North America website, just type in XR7090 in the search block on the left, there are three pages of parts already:
http://www.arrownac.com/


There are plenty of other distributors all over the world, you can find them listed here:
http://www.cree.com/products/xlamp_dist.htm


CREE was chosen as one of the of 300 companies chosen for the new Ocean Tomo 300 Patent Index, the first equity index based on the value of corporate intellectual property: 
http://www.cree.com/investor/patent_index.htm


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## chris_m (Jan 14, 2007)

You've got to be careful making the distinction between Cree XLamp, Cree XR series and Cree XR-E as they're not the same thing as the beam patterns of the LEDs vary. For instance, that Fraen page only mentions Cree XR (which isn't the same as XR-E), and that page on Cree's site only mentions XLamp, which could mean any of 3 different LED series (XL, XR and XR-E). Notably Khatod who do claim to have optics for the XR-E http://www.khatod.com/k52_lens_xlamp.htm only list medium and wide beam versions, whereas they have a narrow beam option for the original XR.


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## FloggedSynapse (Jan 14, 2007)

chris_m said:


> You've got to be careful making the distinction between Cree XLamp, Cree XR series and Cree XR-E as they're not the same thing as the beam patterns of the LEDs vary. For instance, that Fraen page only mentions Cree XR (which isn't the same as XR-E), and that page on Cree's site only mentions XLamp, which could mean any of 3 different LED series (XL, XR and XR-E). Notably Khatod who do claim to have optics for the XR-E http://www.khatod.com/k52_lens_xlamp.htm only list medium and wide beam versions, whereas they have a narrow beam option for the original XR.



Hopefully they're all of higher caliber than the common 5 mm LEDs out there. Apparently the XR-E uses the latest (EZBright1000) core, while the XLamp uses the older (XB9000?) core.

Asked before, and I'll ask again now: does anyone have any additional information on these cores? Considering the XRE is new, has set an efficiency record, and considering the competition it's not surprising there's a paucity of information on the geometry and functional layout of the die. Still curious though.


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## chris_m (Jan 14, 2007)

FloggedSynapse said:


> Hopefully they're all of higher caliber than the common 5 mm LEDs out there. Apparently the XR-E uses the latest (EZBright1000) core, while the XLamp uses the older (XB9000?) core.



Yes, but the point is they don't all work with the same optics (and it's only really the XR-E anybody's getting excited about).


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## NewBie (Jan 15, 2007)

Well, I'd refer you to CREE's datasheet for CREE's EZ1000 die for starters:
http://www.cree.com/products/pdf/CPR3CR.-.pdf

If you look at the die, you will notice it is one of the thin InGaN active layer types, with a metalization layer right underneath the active area. On the top surface, you will find a rough patterned surface to also help extract light from the thin active layer.







In the XR-E, you will find the very robust and highly thermally conductive SiC ESD diode underneath the die, and then this is also soldered to the package substrate.

Then if I was you, for further information, I'd be looking around on the various patent search engines.


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## NewBie (Jan 16, 2007)

FloggedSynapse said:


> Hopefully they're all of higher caliber than the common 5 mm LEDs out there. Apparently the XR-E uses the latest (EZBright1000) core, while the XLamp uses the older (XB9000?) core.
> 
> Asked before, and I'll ask again now: does anyone have any additional information on these cores? Considering the XRE is new, has set an efficiency record, and considering the competition it's not surprising there's a paucity of information on the geometry and functional layout of the die. Still curious though.




Since you asked, I thought I'd also enclose some additional photos for you. This should help several things to become more clear.

CREE and LumiLEDs use metalurgical and solder bonds at several points in the contruction of their LEDs which helps the resulting part to be robust from the die and thermal standpoint. Others do also, but fyi, the Seoul P4 does not. LumiLEDs and CREE both utilize a robust ESD diode, with CREE utilizing an extremely robust and highly thermally conductive Silicon Carbide ESD diode.

Here is the top side of the Luxeon III:







Here is the underside of the Luxeon III die that I unsoldered from LumiLED's ESD diode, the round and oblong bumps are the solder points and thermal transfer points:







This is the ESD Diode that the Luxeon III die is soldered to:







Cree takes a bit of a different approach, which results in better thermal transfer than the Luxeon III and better than even the new Luxeon K2. Cree uses metalurgical bonding as well as solder bonding. Try as I might, to the point of melting the gold bond wires, I have not managed to get CREE's EZ1000 die off of their SiC ESD diode. Later in the series of pictures, you'll see where the part is soldered at, as well as a demonstration.

MODERATORS-
I'll be posting these photos across three posts, due to the sheer size of each post, and the plentiful pictures. If there is an issue, please contact me, so I can abide by your wishes.

































































































First series.


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## NewBie (Jan 16, 2007)

Unsoldering the highly thermally conductive Silicon Carbide (SiC) ESD diode from the substrate:
























































Unsoldering series


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## NewBie (Jan 16, 2007)

Third in series of photos, light extraction coating on Thin active layer of InGaN:


















































Coating series


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## jtice (Jan 16, 2007)

VERY cool !!!!!
I have always loved macros, really another world once you get a good look at tiny things like that.
Lot of good info there, gives a better understanding of what goes into these,
and how they are actually built.

~John


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## NewBie (Jan 16, 2007)

Thanks Jtice!

I just noticed that around midnight last night, before bed, I was in a hurry to get these finished up, and I got a few labels on some of the photos wrong.

I'll fix them tonight.

For now, this one is correct:


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## PEU (Jan 16, 2007)

waaaay cool photos!!


Pablo


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## Doug S (Jan 16, 2007)

PEU said:


> waaaay cool photos!!
> 
> 
> Pablo



I'll second that!! Great stuff, Jar. 
I note that you have identified the surface texturing as a coating. Does this in fact appear to you to be a coating as opposed to the result of an etching operation? 
Also, the die is not centered on the SiC diode so as to accommodate the bond wires. Some of your photos make it appear that there is also an angular rotation of the die relative to the SiC. Is this for real or is it just an artifact of how the photo was taken? If for real, it would seem to indicate a bit of slop in the die placement step of assembly.


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## PEU (Jan 16, 2007)

waaay cool photos, THANKS!


Pablo


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## PEU (Jan 16, 2007)

waaay cool photos, THANKS!


Pablo


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## LumenHound (Jan 16, 2007)

Wow. Amazing pictures NewBie. 

Glad I'm on not dial-up though, there's close to 12 meg worth of pics between post #121 and #150. One pic alone was over 700Kb.


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## MillerMods (Jan 16, 2007)

Awesome info Newbie! I was curious about what goes into the construction of these guys


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## Gryloc (Jan 16, 2007)

Newbie, 

That is some very nice work there! Good job with getting up close.

How difficult was it to desolder the carrier? Do you think that you could remove the ESD carrier and die from the substrate without mutilating the phosphor and permanently damage the die (decrease its output and such)? If I would heat it quickly then take away the heat, will there still be some damage? The XR-E was made to be re-flow soldered.

What did you mean by "metalurgical bonding". Where was this applied, versus the solder bonding?

I was thinking that I can carefully cut the bond wires at the board, then de-solder the whole die and carrier. I would have to use an exacto knife to lightly press on the carrier to push it aside, of course.

Did the phosphor coating melt in your first pictures? I understand if you cannot remove the die from the carrier. Thats quite alright.

I was wondering this because maybe I can sacrifice 4 P2 pr P3 binned XR-Es and fulfill my desires with making a mini cluster (as Newbie understands). Then I can attempt to re-solder them. Then a tiny dab of solder can attach the bond wires, too. It would be tricky to do this, but that would be awesome! This thread has made my day and helped get a better understanding of the Cree innards. Keep up the crazy work...


-Tony


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## NewBie (Jan 16, 2007)

Doug S said:


> I'll second that!! Great stuff, Jar.
> I note that you have identified the surface texturing as a coating. Does this in fact appear to you to be a coating as opposed to the result of an etching operation?
> Also, the die is not centered on the SiC diode so as to accommodate the bond wires. Some of your photos make it appear that there is also an angular rotation of the die relative to the SiC. Is this for real or is it just an artifact of how the photo was taken? If for real, it would seem to indicate a bit of slop in the die placement step of assembly.




Yes, it is a coating that is both over the die and over the negative current spreader.

Yes, the off center placement of the LED die on the SiC ESD diode is in fact to accomodate the positive bond wire connections.

Part of the apparent magnitude of rotation is due to how the shot was taken, but there is actual rotation. The rotation doesn't hurt anything, and it does not actually extend beyond the Silicon Carbide ESD diode edge (such as the die hanging over the edge of the SiC ESD diode- I have never seen that actually happen). I've seen an occasional very slight sliver of the underlayment area where the metalurgical bond is, caused angular rotation as you see here. Remember, we are at pretty extreme magnifications here, in some cases exceeding 1000x





Gryloc said:


> Newbie,
> 
> That is some very nice work there! Good job with getting up close.



Thank you.



Gryloc said:


> How difficult was it to desolder the carrier? Do you think that you could remove the ESD carrier and die from the substrate without mutilating the phosphor and permanently damage the die (decrease its output and such)? If I would heat it quickly then take away the heat, will there still be some damage? The XR-E was made to be re-flow soldered.



If you are used to working with stuff this small it can be done. Re-attaching the gold bond wires (assuming you sever from the substrate) is tricky, as gold dissolves into solder. You can solder to the gold bond wire, but you have to be hella fast about it. Just take your time, and maybe buy some lower cost red ones just to practice techique. Don't apply force to anything, the die will chip and usually be destroyed. Also, if you get any solder up the side of the SiC or the LED die (say like you used the CREE EZ1000 die from a Seoul- its silicone is hard and makes doing the phosphor intact thing much harder) then you will often end up with a short. I'd utilize non-metallic handling tools, lowers chance of chipping the die. I know in fact it can be done, been there, done that. Also, the gel will need to be re-protected. With the Seoul P4, you risk a pretty good chance of severing bond wires due to the hard silicone they utilize, fyi.




Gryloc said:


> What did you mean by "metalurgical bonding". Where was this applied, versus the solder bonding?



Essentially it is a metal to metal bond, that can be accomplished a number of ways. No solder, no epoxy, and in this case, extremely robust and rugged.




Gryloc said:


> I was thinking that I can carefully cut the bond wires at the board, then de-solder the whole die and carrier. I would have to use an exacto knife to lightly press on the carrier to push it aside, of course.



See my comment on non-metallic above. Once you are in there, you'll soon realize how small things actually are. The LED die itself is just under 1mm by 1mm, pretty close to the size of the Luxeon and OSRAM die. The lens magnifies the apparent size dramatically.




Gryloc said:


> Did the phosphor coating melt in your first pictures? I understand if you cannot remove the die from the carrier. Thats quite alright.



No melt. That is the remaining gel over the phosphor.




Gryloc said:


> I was wondering this because maybe I can sacrifice 4 P2 pr P3 binned XR-Es and fulfill my desires with making a mini cluster (as Newbie understands). Then I can attempt to re-solder them. Then a tiny dab of solder can attach the bond wires, too. It would be tricky to do this, but that would be awesome! This thread has made my day and helped get a better understanding of the Cree innards. Keep up the crazy work...
> -Tony




I'm very glad you liked the photos and found them useful. It makes the effort needed to format them for posting on cpf worth it.

It can be done, but how well things will hold up, thats more up to your soldering skills.

Oh, and chill out before you do all this, and make sure you have plenty of time so that nothing is rushed. You might want to skip your morning coffee/tea/coke before attempting the "surgery"

Good Luck!


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## ViReN (Jan 16, 2007)

awesome Macro World.... Great Pictures NewBie.... wonderful to know interiors of Cree LED's


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## srvctec (Jan 16, 2007)

Simply amazing photos, Newbie! Macro is my favorite kind of photography.

What in the world did you use to capture all of those macro shots? Almost looks like it was done with a microscope!


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## NewBie (Jan 17, 2007)

Some are just with a Canon S3 IS camera, some are done holding the S3 IS looking into the microscope eyepiece.

Updated the naming errors I noticed.

Thanks, my pleasure.


If you'd like to see the Seoul P4 that uses the CREE EZ1000 die, here is the direct link to the photo posts:
http://candlepowerforums.com/vb/showpost.php?p=1769585&postcount=94
http://candlepowerforums.com/vb/showpost.php?p=1771587&postcount=106
http://candlepowerforums.com/vb/showpost.php?p=1773282&postcount=132


Here is the link for the thread:
http://candlepowerforums.com/vb/showthread.php?t=146607&page=3&pp=40


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## FloggedSynapse (Jan 17, 2007)

NewBie, cxcellent! Thanks for taking the time to throw those images out. I don't think most people realize the scale of the die.. I mean it's less than a mm square (right?). The LED looks, and operaties, like a solar (PV) cell in reverse. 

It's good the see CREE is serious about trying to keep the actual p/n junction cool. It's very difficult to measure the junction temperature directly. So I imagine a cheaper implementation might _appear_ to run cooler, but that would only be because the design does not let as much heat flow out of the working junction. So the CREE parts may apprear to run hotter, but that's simply because they have better thermal management, while the cheaper die actually has a warmer working junction. Very very important for the reliability of these devices - they must stay cool as possible for long life and reliability.

Does the SiC ESD serve two purposes - static protection and heatsink/thermal path? I'm curious what CREE did to improve the efficiency of the XRE - was the actual quantum efficiency of the junction improved, or is it more a matter of changing the die construction so more light can escape? Don't imagine anyone can shed some light on this (bad pun intended)?

You might find this interview of interest. Shuji Nakamura was one of the pioneers in the development of high powered blue LEDs and violet laser diodes:
http://www.sciencewatch.com/jan-feb2000/sw_jan-feb2000_page3.htm


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## FloggedSynapse (Jan 17, 2007)

NewBie, cxcellent! Thanks for taking the time to throw those images out. I don't think most people realize the scale of the die.. I mean it's less than a mm square (right?). The LED looks, and operates, like a solar (PV) cell in reverse. 

It's good the see CREE is serious about trying to keep the actual p/n junction cool. It's very difficult to measure the junction temperature directly. So I imagine a cheaper implementation might _appear_ to run cooler, but that would only be because the design does not let as much heat flow out of the working junction. So the CREE parts may apprear to run hotter, but that's simply because they have better thermal management, while the cheaper die actually has a warmer working junction. Very very important for the reliability of these devices - they must stay cool as possible for long life and reliability.

Does the SiC ESD serve two purposes - static protection and heatsink/thermal path? I'm curious what CREE did to improve the efficiency of the XRE - was the actual quantum efficiency of the junction improved, or is it more a matter of changing the die construction so more light can escape? Don't imagine anyone can shed some light on this (bad pun intended)?

You might find this interview of interest. Shuji Nakamura was one of the pioneers in the development of high powered blue LEDs and violet laser diodes:
http://www.sciencewatch.com/jan-feb2000/sw_jan-feb2000_page3.htm


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## NewBie (Jan 17, 2007)

Yes, the LED die is 0.98mm by 0.98mm and the high thermal conductivity and robust Silicon Carbide ESD diode is slightly larger.


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## Gryloc (Jan 17, 2007)

Newbie, 

I have a few questions for you. I hope that you understand what I am talking about...

I didnt think of this before, but how is the ESD carrier wired? I know the top of the die has two negative contacts, and the bottom side of the die, that is metallurgically bonded to the carrier, is the positive side. What about the carrier? There is a bond wire on the top of the carrier that goes to the positive copper pad, so is that entire side electrically connected to the bottom (+) side of the die? Then what about the bottom side that is soldered to the same positive copper pad? Is this soldered joint just for thermal conductivity? Is the carrier of the XR-E similar to Lumiled's carrier? I mean, is both the positive and negative contacts of the ESD diode on the very top side? Like this:




NewBie said:


>




The reason I ask is because if the very bottom side of the ESD carrier is electrically neutral or attached to the positive side, I now know how to design the solder pads. 

If they are neutral, I can have one larger pad for all four dies to be soldered to, with the bond wires going off to the side to their own pads.

If the bottom of the ESD carrier is the exact same as the positive (like after the actual ESD diode part), then I could really do away with the single little positive bond wire. With this, I can create four separate pads that attach to the negative side of the next series connected LED, and only have two bond wires to have to attach instead of three. This is how I designed the first LED module. With that drawing, I didn't have to worry about the ESD carrier and I just had to solder the positive side of the die to the pad for electrical contact.

If the bottom of the ESD diode is not neutral, but it also is not the main positive contact for the LED and ESD diode, then things will be more difficult.


Finally, do you know how the SSC P4 is wired? I see the negative wires disappearing to the side to connect to the negative lead. The bottom side of the die is attached to the aluminum slug, which is attached to the bottom side of the little diode cube. Then the top of that diode has a bond wire disappears and is attached to the positive lead. So does that mean if you attach the positive power wire (from the circuit or battery) to the aluminum slug, it bypasses the ESD diode and the whole LED is susceptible to damage?

This is interesting stuff. I always liked thinking and working on the micro scale of things. Thanks...


-Tony


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## NewBie (Jan 18, 2007)

The bottom side of the ESD diode in the XR-E is minus. Topside of the Silicon Carbide ESD diode is positive as is the bottom of the die. 

Wire runs from common junction to + substrate pad.

Two minus wires run from top side of die to minus substrate pad.

Seoul P4 has die epoxied to slug. A tiny ESD diode that sits off to the side is attached to the same slug. This is why the slug is the + connection.

Three wires, two from the Seoul P4 CREE EZ1000 die minus, as well as one from the ESD diode run to the minus lead. 

Then if you look carefully, there is yet another wire, the fourth one, which runs from the positive lead to the slug. If you happen to blow this wire, you can still power it by attaching your + wire to the slug.

No bypassing of the ESD diode, unless you cut into the dome and cut the ESD diode wire, but these die are rather static sensitive, so I'd not recommend doing that.

Be careful with the Seoul P4, don't push or load the dome, you can sever the bond wires on accident by the sheer forces, since a hard silicone instead of a gel was used inside you don't get much relief from the forces.


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## Gryloc (Jan 18, 2007)

Ahh, thanks. That makes perfect sense. I forgot that the ESD diode was in parallel with the die. It never looked like they were parallel just by looking at the internals of the package. Interesting setup...

Great. Now I see how to wire this thing up. This will be tough because I have to deal with three bond wires and the designs of the module will be far more complex.

I know the ESD diode made of Silicon Carbide has great thermal conductivity, but I wonder why Cree doesn't solder the dies straight to the pad. It appears to have plenty of real-estate on the board under the dome, compared to Lumileds parts that have very limited space. I was just thinking.

I see that fourth bond wire in one of your closeup pictures. Interesting! What is the power handling of a single, average length bond wire? It is nice knowing that if the fourth bond wire fails, I have a way to power it back up.


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## NewBie (Jan 19, 2007)

My understanding...

Different materials have different co-efficients of thermal expansion (CTE). So, when to items of differing material change temperature (lets say raise), they actually expand. But materials made from different "matter", expand at different rates. So, when you bond two items with different expansion rates or different CTE's, you get a lot of stress between them. Usually the bond fails, but sometimes you can get failure of the materials near the interface, or you cause enough stress to fracture it in other areas.

The SiC matches the CTE of the InGaN fairly well, and falls between the solder/substrate, and the InGaN, so it reduces the stresses at each interface.

There are also some additional advantages for crystal structure, or lattice, and growing the InGaN on SiC substrate, instead of sapphire.

In reality, the bulk material is Silicon, but is also Silicon Carbide. An example is the diagram at the bottom of page 1:
http://www.cree.com/products/pdf/CPR3CC.00c.pdf

Another example:
http://www.creelighting.com/products/pdf/CPR3DC.000.pdf


"Based on Cree's EZBright 1000 LED chip, the XLamp 7090 XR-E is produced on a silicon-carbide (SiC) substrate that has an indium-gallium-nitride (InGaN) epitaxial layer grown on it (Fig. 1). "
http://www.elecdesign.com/Articles/ArticleID/13982/13982.html


Take a look at the patent here:
http://www.freepatentsonline.com/6630690.html


They can directly grow the InGaN right on the SiC.

I don't think the high thermal conductivity of the rather thin SiC ESD diode that CREE uses in the XR-E is much of the equation as far as overall thermal resistance. See my comments later, about comparision to metal.

One would want to look in other areas like the ceramic substrate, which can be made from a variety of fillers.







Notice the low thermal conductivity is silica (silicon) and Alumina.

http://en.wikipedia.org/wiki/Alumina


Notice how the chemical formula is Al2O3. Turns out, that sapphire (mineral glass) is also aluminum oxide. In the crystal form, thermal conductivity of sapphire is only 33% of Silicon Carbide. Silicon Carbide also has 2x the thermal conductivity of pure Silicon.

At room temperature, Silicon Carbide has higher thermal conductivity than any metal.
http://www.cree.com/products/sic_sub_prop.asp

CREE is a leading producer of Silicon Carbide, and Silicon Carbide components, so it makes sense that they'd make their own ESD diodes in house. It is a very tough, and thermally conductive material, and is one of the hardest substances out there, and also performs quite well at elevated temperatures. SiC also has a very high electric field breakdown strength, and a very high maximum current density. It also has a low CTE.

There is a grade of SiC that CREE makes, that is colorless, and is used as a diamond replacement, even in jewelry. I forget the trade name for it off-hand...ah, here it is, Moissanite. It is produced by the C3 division of CREE, the only source of gem grade Moissanite. Even the thermal probe test, used to detect cubic Zirconia, is often fooled by Moissanite. One of the neat things about this material, that differs from diamond, is that it creates double refraction, and demonstrates birefringence. This causes a doubling of the facets cut in it then you look into it. It also has a dispersive power that is 2.5x greater than diamond and creates extra live "fire" than many feel is more beautiful. They are still expensive though, at 569.00 per carot or so.

With diamond at a hardness of 10, SiC at 9.5 Mohs is pretty darn close. The Mohs scale is a non-linear scale.


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## Gryloc (Jan 19, 2007)

Ahh, thanks Newbie. That is very cool. That would make sense for Cree to use it when the advantages are that great. I seen a presentation somewhere and it shows some advantages of SiC, but it didn't explain it fully. That "Moissanite" you mentioned is really cool> I have seen them before. I think one company that uses them calls them "Diamonds on Fire" or something close. They are so brilliant. As always, you are awesome for going out and researching even more into these topics. Keep that up!


-Tony


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## Doug S (Jan 19, 2007)

NewBie said:


> At room temperature, Silicon Carbide has higher thermal conductivity than any metal.
> http://www.cree.com/products/sic_sub_prop.asp


Or at least pretty darn close. Their marketing folks may have had a hand in the above statement. The linked reference lists a range of 3.0-3.8 W/cm-K. Using these same units, some high purity coppers range upwards to 3.85 and silver to 4.18.


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## NewBie (Jan 19, 2007)

Yeah, I know, I just quoted them.

I've need to look up the thermal conductivity of silver and copper @ 25C sometime. It varies a bit depending on temperature, and I'm not sure what pure copper and pure silver's numbers are. Anyhow, it isn't too often that you find the high purity metal in actual application, usually being alloyed with something to improve one performance criteria or another.

Gryloc, most this stuff I already know about, I just like to provide associated references for folks to read, if they care to learn more, or want to see it in "writing".


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