Seoul P4 initial Evaluation- Production LEDs

NewBie,

Do you have any closer shots of this picture? The southeast corner of the semiconductor appears to be lifted (thinner amount of phosphor coating).

Newbie, could you please make a diagram which shows what part of the emitter is supplied by Cree? would this come from Cree like this or does this happen after SS get the "part ind install it into their package.

Is there a possibility that this effect was accelerated by the high current tests? Can you do the same to a "virgin" emitter?

There are just too many variables here to draw any kind of realistic conclusion. This could be a total aberration, a single bad unit or whole bad reel. Could it have been caused by high current testing?
Unfortunately this "issue" raises far more questions than it answers. Such is life.
I can't imagine a part like this having a realistic service life. Shirley large corporations who plan to use these parts by the 10's or 100's of 1000's are testing these emitters in the same way that you are. before committing to spending millions of dollars to implement these emitters into new LED fixtures in cars and boats and elsewhere.
As this Nation makes the switch to solid state lighting we will see a lot of companies spending lots of R&D $$ in order to design super efficient methods of lighting our homes while maintaining lumen output reducing heat increasing efficiency all while producing an acceptable "new" type of light for us to see at night by. There will be companies which do not make it. Lumileds will not be one of them. will Cree? what about SS? I do not know. I do see a lot of dust on the horizon obscuring a clear view of the future. the images of the die you show here adds to this obscured view. I am sure most agree.. I look forward to what the future holds. I almost can't wait for a practical solution to replacing the compact fluorescent globes in m home with LED based systems. Wouldn't you hate buying 20 globes for your house only to find out that a MUCH better technology has just hit the market?

I believe that it is important to keep in view the much bigger picture. the picture which shows us custom and semi custom flashlight nuts as the absolute bottom of the LED food chain. We are not the reason they are spending billions on developing these new solid state light light sources.
They aren't making these for us little flashlight users in mind!!!!
WE are very picky. Will this translate down the road to better lighting for peoples homes? Maybe. I think we are a small annoyance to these companies.
Did I drive this post off topic? sorry if I did.
NEWBIE can you tear apart a few more of those emitters? we need a large sample set. I am sorry I can not afford to contribute much to the Newbie R&D fund but I could send something if needed.
BTW I have not been able to get my hands on any of these emitters (outside of a flashlight). Not for lack of trying. I would like to have a few for space needle builds and for some of my own crude (by comparison ) testing. Have fun!!!
yaesumofo

Those of you who might want to better understand where this pulled apart at, please see pages 2-5 of this link:

http://www.lumileds.com/technology/tutorial/

or this:

http://www.lumen.com.ua/html/info.htm

I notice over in the group buy for this emitter, quite a few people are backing out.

Which leaves me wondering, is the "sky really falling?"

I see one part with a poor solder joint, and almost an entire thread of evaluation around that one defective component. (Am I right?)

NewBie, could you put this all into perspective?

yaesumofo said:

Newbie, could you please make a diagram which shows what part of the emitter is supplied by Cree? would this come from Cree like this or does this happen after SS get the "part ind install it into their package.

Click to expand...

No, it would be flat and very shinny on the backside from CREE.

CREE only supplies the little die part shown here:
http://www.cree.com/products/pdf/CPR3CR.-.pdf

yaesumofo said:

Is there a possibility that this effect was accelerated by the high current tests? Can you do the same to a "virgin" emitter?

Click to expand...

No, as I mentioned, this part showed the issue the very first time I applied power, as I slowly turned the current up, and it showed up at about 500mA. It has not gone over 1A. The part you are thinking about is another one of the same part.

yaesumofo said:

There are just too many variables here to draw any kind of realistic conclusion. This could be a total aberration, a single bad unit or whole bad reel. Could it have been caused by high current testing?
Unfortunately this "issue" raises far more questions than it answers. Such is life.

Click to expand...

With some manufacturers they don't have the tight controls of other manufacturers. I often test parts before I will consider utilizing them in a design, even from industry leaders. If you don't, you risk being burned. When I get a production part that has issues like this, where a manufacturer could have worked more on dialing their process in, or if they can't, or hasn't put in tests to prevent process problem parts from getting out the door, it is concerning for me. If it was just one of five, that would be one thing. As it stands, I see significant variations in the production parts I purchased, and have seen things that do concern me. IMHO, if I was to consider trying to use this part in a product for a production run, I'd definitely have to do a lot more testing, and I'd definitely need to obtain parts from multiple batches, and I'd want to make sure the supplier wasn't cherry picking parts for me.

yaesumofo said:

I can't imagine a part like this having a realistic service life. Shirley large corporations who plan to use these parts by the 10's or 100's of 1000's are testing these emitters in the same way that you are. before committing to spending millions of dollars to implement these emitters into new LED fixtures in cars and boats and elsewhere.

Click to expand...

It is hard to say much, without more testing. If a bad batch did get out the door, what is to prevent that from happening, and why did the QA department not catch it, and what is wrong with the manufacturing process that was put in place, or is it a design issue from the get go?

With some suppliers you have lots of variations, it is the nature of the beast. Luckily, not too many people count on their flashlights, and most flashlights don't see much use, but some people use their flashlights like crazy.

yaesumofo said:

As this Nation makes the switch to solid state lighting we will see a lot of companies spending lots of R&D $$ in order to design super efficient methods of lighting our homes while maintaining lumen output reducing heat increasing efficiency all while producing an acceptable "new" type of light for us to see at night by. There will be companies which do not make it. Lumileds will not be one of them. will Cree? what about SS? I do not know. I do see a lot of dust on the horizon obscuring a clear view of the future. the images of the die you show here adds to this obscured view. I am sure most agree.. I look forward to what the future holds. I almost can't wait for a practical solution to replacing the compact fluorescent globes in m home with LED based systems. Wouldn't you hate buying 20 globes for your house only to find out that a MUCH better technology has just hit the market?

Click to expand...

There is a city in California that purchased LED traffic lights for the power savings and for the reliability and reduced maintenance. Unfortunately, they went with the lowest bidder. To hit the cost target, the LED traffic lights manufacturer used LEDs from a Far East (non-Japan) company. Within the next two years, every single one of the lights failed, with many of them going dim in as little as six months, and they had much higher maintenance than they had with incandescent bulbs. Unfortunately for the city, they did not put anything in the contract to hold the LED Traffic Light maker accountable. The city had to eat the whole thing. However, there are several other cities that went with quality LED Traffic Lights, and the power savings, reliability, and reduce maintenance held true and they have had an outstanding experience with them.

yaesumofo said:

I believe that it is important to keep in view the much bigger picture. the picture which shows us custom and semi custom flashlight nuts as the absolute bottom of the LED food chain. We are not the reason they are spending billions on developing these new solid state light light sources.
They aren't making these for us little flashlight users in mind!!!!
WE are very picky. Will this translate down the road to better lighting for peoples homes? Maybe. I think we are a small annoyance to these companies.
Did I drive this post off topic? sorry if I did.

Click to expand...

Right, but due to demands, companies like LumiLEDs have gone from CCT Kelvin binning, then under customer demand on to binning like XO/WO, that everyone knows, and under even more pressure and demand, many of those bins have now been sub-divided even further.

If you haven't taken a look at the new binning structure that came out the middle of last year you should. They sub-divided all the bins around white much further yet. Its like wow, nice (page 5):
http://www.lumileds.com/pdfs/AB21.pdf

yaesumofo said:

NEWBIE can you tear apart a few more of those emitters? we need a large sample set. I am sorry I can not afford to contribute much to the Newbie R&D fund but I could send something if needed.
BTW I have not been able to get my hands on any of these emitters (outside of a flashlight). Not for lack of trying. I would like to have a few for space needle builds and for some of my own crude (by comparison ) testing. Have fun!!!
yaesumofo

Click to expand...

These are super simple for even you to purchase. TTI, a large distributor, owns Mouser, who is a catalog house, which is very similar to DigiKey. They have been available there for at least ?two weeks? You could have them in your hot hands tomorrow if you wanted.

Direct link:
http://www.mouser.com/search/ProductDetail.aspx?R=W42180-Tvirtualkey61510000virtualkey889-W42180T


Anyhow, I did discover a few more things about these LEDs that I will go into later.

EngrPaul said:

I notice over in the group buy for this emitter, quite a few people are backing out.

Which leaves me wondering, is the "sky really falling?"

I see one part with a poor solder joint, and almost an entire thread of evaluation around that one defective component. (Am I right?)

NewBie, could you put this all into perspective?

Click to expand...

Sky falling? Looked up at the moon and stars, and they are still up there, so no.

I do wonder why of the five LEDs I've starts shifting color at a different current level. Right now, it may have to do with the method that Seoul Semiconductor is bonding the die to the slug, the materials used, the process, the design, process variation, poor batch to batch control, or whatever- who knows? Possibly they discovered it and corrected it already, but didn't post a public advisory on thier website, nor sent out thru the distributors? Maybe they just didn't catch it because testing wasn't good enough? It is all idle speculation. McGizmo assured me that the parts are extremely consistent and stellar performers from his experience, and thats why I went out and purchased production parts. Now I've been hearing there is the typical variation, and personally, with the ones I purchased, I've not had the same experience.

Will others have a great experience or an okay experience, a mediocre experience, or a bleh experience? I do not have a clue, only time will tell. I most certainly hope that things end up more like what McGizmo talked about, where the tint is consistent, doesn't change with drive current, and are extremely robust.

I definitely was quite amazed by the level of abuse the CREE EZ1000 die, that is deep in core of the Seoul P4, was able to take, without heatsinking under a whole portion of the die. At least this holds much promise.

Don't forget, the LumiLEDs Luxeon V when it first came out. It was out at for a while, and folks were reporting it was going south in a matter of a couple of days, and I saw the same type of issue myself. It was denied that there was any issue, and it was the fault of the customer causing the problem. This went on for some time, until LumiLEDs fessed up to the problem. Then you couldn't get them for awhile, while they were looking into things. Some changes were made, which definitely improved the lifetime, and the specification was revised to a 500 hour lifetime. Since then, a more specific specification has come out, which gives you a guide on how long they are expected to last, depending on how well they are heatsink, and the drive levels.

To this day you still find the following statement on LumiLEDs White Luxeon V page:

Features
Superior lumen maintenance
Luxeon V Portable LEDs lasts longer than any incandescent bulb

The datasheet was revised back in 2004, and you will find this on page 9, even though they just revised it in August 2006:

Heat sink temperature: 85°C
Current: 600 mA
Average Lumen Maintenance After 500 Hours of Operation65%

"LUXEON V Portable is designed primarily for portable lighting and other applications requiring operating lifetimes of 500 hours and less. While the device will operate past 500 hours, its lumen maintenance cannot yet be characterized. Longer life versions of white LUXEON V will become available in the future."
http://www.lumileds.com/pdfs/DS40.pdf


The whole point here is even the market leaders make an oops on occassion, and we could go into the K2 for more examples...

Consider things and comments in this one post here, all pure speculation, and no more.

Okay, I need to get the other camera out to get a better picture, but here is what I see:



At the moment, the best I can tell right now, this looks like many of the low silver content thermal epoxies that I have used and have a number of samples of. This technique has been used with very low power 5mm LEDs, due to their low heat levels. It is possible it could be some odd solder, but from what I can see, it looks like globules held together in a matrix (I guess it could possibly be solder paste that wasn't fully heated up to the melting point). I'll know a little more when I get a chance to look at things more tomorrow night.

Thermal epoxies have a much higher thermal resistance than solder and are rarely as durable as solder. You will find that LumiLEDs, OSRAM, CREE, and others actually solder their die. I see that CREE put a 0.00012" AuSn (gold tin) layer on the backside of the die.




I'll need to get in at a much higher magnification level to tell more, and poke and prod it- for the moment, consider things and comments in this one post here, all pure speculation, and no more.


BTW, EngrPaul regarding your earlier comments- I found nothing at all between what appears to be a delaminated die area and what appears to be "die bonding material" on the slug.


.
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That is far from a cree so the only cree in their is the PCB well I won't be buying a Seoul chip thanks newbie.

NewBie,

Thanks for (re?)stating the total number of parts in your evaluation.

Let me restate the failure I'm observing. On the picture above, marked "Thermal Epoxy?", the bottom right corner of the joint was never soldered/bonded correctly, metal to metal. The chip was never seated planar against it's mating face, instead a corner was lifted during this attach. This caused a gap at the high side. Some of that liquid seeped into the air gap during process stages after this soldering/bonding.

Another point: Seoul's T bin is significantly lower than their U bin. Aren't T-bins are components that "didn't quite" meet the output target due to flaws in materials and workmanship, but are good enough for certain applications that don't need flawless performance? If we put them through rigorous performance tests, we're only going to find out more details about those flaws. It doesn't necessarily mean that the part doesn't meet specifications. I look forward to some U-bin evaluation.

P.S. I'm not trying to stick up for Seoul, just continue to justify my $ order for more than a dozen U-bins

lots of good info as usual!

EngrPaul said:

NewBie,

Thanks for (re?)stating the total number of parts in your evaluation.

Let me restate the failure I'm observing. On the picture above, marked "Thermal Epoxy?", the bottom right corner of the joint was never soldered/bonded correctly, metal to metal. The chip was never seated planar against it's mating face, instead a corner was lifted during this attach. This caused a gap at the high side. Some of that liquid seeped into the air gap during process stages after this soldering/bonding.

Click to expand...

This area as I said, is where the thermal transfer was not occuring.

If you read, there was no material found under that area.

EngrPaul said:

Another point: Seoul's T bin is significantly lower than their U bin. Aren't T-bins are components that "didn't quite" meet the output target due to flaws in materials and workmanship, but are good enough for certain applications that don't need flawless performance? If we put them through rigorous performance tests, we're only going to find out more details about those flaws. It doesn't necessarily mean that the part doesn't meet specifications. I look forward to some U-bin evaluation.

P.S. I'm not trying to stick up for Seoul, just continue to justify my $ order for more than a dozen U-bins

Click to expand...

IMHO, that is really pulling things out of .... ...

Oh, did I say that? I meant stretching things beyond the breaking point.

The Seoul T bins are the ones that are easy to get your hands on, their normal parts. The U bins are the rare ones, and for many, they have been waiting to get their hands on them. It is expected that by February, they should be more plentiful.

There is a significant difference? Humm. I remember checking out some premium priced Luxeon U bins, and comparing them to a number of T bins, in an integrating sphere, and the difference between them was easily within the measurement error of the equipment. I took over another older T bin set I had purchased, and the difference was 5%, which made me feel a little better about the purchase, but not by much.

I don't know if I'd really put that much emphasis on the difference between them, unless I had a set from the same Vf, Tint, but the U and the T lumen bins, and one was seeing a very clear difference. This would be more prone to better performing die, and if you look at the die datasheet, you will see there are five bins for brightness, and twelve bins for wavelength in each brightness range measured @ 350mA on page 3 and 4:
http://www.cree.com/products/pdf/CPR3CR.-.pdf


The wavelength also comes into play, as most YAG phosphors have a narrow wavelength range for their peak conversion of blue light to broad band yellow.

This very tight wavelength binning helps, in that it makes it much easier to hit the target of the phosphor. Each bin wavelength range is only 2.5nm wide!

With five die brightness bins, starting out at 200mW and going to 380mW, one at least gets to start out knowing the amount of light output the particular binned die makes, fairly precisely to boot.

65535 said:

That is far from a cree so the only cree in their is the PCB well I won't be buying a Seoul chip thanks newbie.

Click to expand...

I don't know if I'd put it that way, but so far, I'm not too happy with my purchase from this batch. I'm really hoping that I'll get some better batches in the future.

I am now much more leary about the parts, after looking at the construction and the materials it looks like they used, but I need to look much closer at the die bonding method they used.

NewBie said:

If you read, there was no material found under that area.

Click to expand...

The picture says there is

no, it doesn't

Look at the picture of the backside of the die. The shiny part is the die, the black part, the overspill of phosphor. The top left section of the outline of the backside die shot is missing and broken off. It matches the shape of the phosphor left on the slug.

If you look at the shot of the intact LED, you will see that the phosphor layer is larger than the die, and creates a border around it. That's the border around the shiny part in the backside die shot.

Man, my brain hurts trying to read this thread! From what I gather the Seoul Crees' aren't as great as we'd hoped?

Going by the pictures only, the metal square is the solder joint. It should be fully shiny through the square, with the exception of some air pockets. Instead, it's dark in the lower left corner where solder didn't join, and liquid (phosphor, whatever) wicked in later. If a cross-section at 45 degrees (a cutting line from NW to SE) was done, it should reveal there is solid material on the surface of the metal at that corner of the solder joint. This is why it pulled apart so readily. Good, complete solder joints should not come apart like that.

I think the group-buy dynamics may be changing for multiple reasons, possible quality control issues being one, but probably not even the primary one, as they've been tested, the physical dimensions and electrical characteristics are both different than Luxeons, and I think that has as much to do with it as anything else, people were hoping pre-release that they'd be similar enough to "drop-in" replace Luxeons, now that it's clearly not the case, people are getting second thoughts...
And then to find that there MIGHT be QC issues, just adds to the hesitation or reconsideration of the XR-E, a "known" quantity now in the wild, even with it's issues.

It seems to me that these are very similar teething problems to the initial Luxeon emitters.
I believe that a little patience is required. Give these manufactures some time to figure out these and other new technologies out. Remember these companies are not making parts designed for the close scrutiny that crazy flashlight freaks give to beams and tints. If you look at where the typical LUX III emitter is today compared to what was available when they first came out you will see major improvements.
Give 'em time guys.
I never read anywhere that luxeon drop in compatibility was a requirement for success. The idea that the Seoul emitters aren't ant good because they will not directly replace a Luxeon is silly.
If I were a large manufacture of semi conductors I would do what ever it took to differentiate my product from the others on the market.
Do you think that AMD should make CPU's that drop in on motherboards made for AMD chips or visa-versa? Amd and Intel do not work so that hardware (cpus) are directly compatible, They will use the same power supplies and cases, run the same software. but they use different sockets. Why should the Light Emitting Diode business be any different? Except for selfish reasons I can't think of any good reasons. We need to remember that we are talking about BIG BUSINESS. A big business which doesn't give a hoot about a couple thousand crazy flashlight freaks.
BTW I am quite happy with the flashlights I have with Cree emitters so far.
I look forward to further developments.
Thanks for the Link NewBie. I will wait for a while for their current stock to rotate before ordering some.
Yaesumofo

So basically... Cree is still King? For now anyway?

Fair enough, yaesumofo.

I've seen some pictures of defective Crees from group buys... everybody has to troubleshoot defects out of their production lines.

Take time to get it right? There is serious manufacturing problem here that is unacceptable. They need to get their die bonding down better, and hopefully that will take care of the blue shift issue. Having a part shift that much blue is unacceptable, especially when they advertise 240lumens at 1amp! Notice how the cree doesn't drop off in lumens when driven all the way to 2amps! The SSC ZLED P4 drops at 1300ma or so, which you would not think to be the case, since the die is on metal and not ceramic like the cree. You'd expect the thermal transfer to be superior.

Clearly they've gotta get their assembly process fixed as it's not performing to spec if you ask me. If they fix it then it could be a great part. I think Newbie has found out the main cause of it. This may even be why the tint is uneven in the beam coming out of the LED. The phosphor and application may not be the problem but the uneven temperature of the die.

Do you think that AMD should make CPU's that drop in on motherboards made for AMD chips or visa-versa? Amd and Intel do not work so that hardware (cpus) are directly compatible, They will use the same power supplies and cases, run the same software. but they use different sockets. Why should the Light Emitting Diode business be any different?

Click to expand...

You are forgetting the past. In the past, all AMD chips were 100% drop-in pin compatible with intel chips. That was the only way they could get into the market. It's only in recent years that AMD has been able to blaze new trails and require a new socket and mobo to use their CPUs. They only did that after gaining some marketshare, mindshare, and customer confidence by producing chips that were drop-in replacements for intel CPUs. AMD chips were this way from the 286 (early 1980s) through Socket 7 systems (pentium MMX / AMD K62, etc). So AMD had to conform to intel's interfaces for almost 20 years before being able to call the shots.

It's extremely arrogant (and fatal) for a tiny company to try to break into a market by requiring new tooling or a completely new interface when competing with a very large, well known, and entrenched competitor.

Right now, it's in the best interest for Seoul to make their power LEDs completely drop-in compatible with luxeons. I mean, they went to the effort of making their power LEDs look exactly like a luxoen, they should just make them optically and electrically compatible as well. They are a newcomer to the market, and for them to get a good enough foothold to actually start calling the shots, they need to get a large customer base. They are going up against lumileds right now, and the best way to do that and be successful is to offer a fully drop-in replacement for Luxeon LEDs that require no (or very tiny) change(s) mechanically, optically, and electrically.

To do otherwise would be to repeat mistakes of the past (hint - read up on NextGen CPUs)