Why not use larger single dies?

[Th232]

Maybe I'm just not using the right search terms, but I didn't find the answer to this, so if there's a thread I've missed (probably blindingly obvious), could a mod please lock this?

With multiple dies being put into one package, I'm just wondering, why not put a bigger single die in there? To my untrained mind, it seems as though while you'd still have the same issues of focussing because of the larger overall size, you wouldn't have that dark cross in the middle, thus simplifying some of the reflector/optics problem. Not to mention, no wasted space between the dies would result in the overall output increasing.

I've seen the links to the several thousand lumen LEDs with much larger dies, so I'm pretty sure it's possible, but I'm also pretty sure the big LED companies have thought of this and have a good reason to not do so. Hence, is the reason to do with manufacturing the dies, heat issues, or something completely different?

 

[taschenlampe]

Look at the links at these threads: 1 …. 2

tl

 

[BillyNoMates]

Isn't it all about manufacturability?

Multiple die in a single package doesn't require any semiconductor developement - just use existing die from the current process line.

Larger die means a new developement. Also consider the impact of yeild; a larger die has a greater chance of a defect, hence lower yield (or increased cost). For some applications, say architecural or street lighting the requirement for high-intensity outputs may out weigh the cost - hence the existence of some large output arrays.

 

[Marduke]

Isn't it all about manufacturability?

Multiple die in a single package doesn't require any semiconductor developement - just use existing die from the current process line.

Larger die means a new developement. Also consider the impact of yeild; a larger die has a greater chance of a defect, hence lower yield (or increased cost). For some applications, say architecural or street lighting the requirement for high-intensity outputs may out weigh the cost - hence the existence of some large output arrays.

It's more complicated than that. There are some basic laws of physics at work here which prevent you from making large single die LED's with our current technology.

 

[2xTrinity]

Maybe I'm just not using the right search terms, but I didn't find the answer to this, so if there's a thread I've missed (probably blindingly obvious), could a mod please lock this?

With multiple dies being put into one package, I'm just wondering, why not put a bigger single die in there? To my untrained mind, it seems as though while you'd still have the same issues of focussing because of the larger overall size, you wouldn't have that dark cross in the middle, thus simplifying some of the reflector/optics problem. Not to mention, no wasted space between the dies would result in the overall output increasing.

I've seen the links to the several thousand lumen LEDs with much larger dies, so I'm pretty sure it's possible, but I'm also pretty sure the big LED companies have thought of this and have a good reason to not do so. Hence, is the reason to do with manufacturing the dies, heat issues, or something completely different?

Those several thousand lumen LEDs have typically 100 dice in a 10x10 grid, or some similar combination of a large number of 1mm-square dice. They just deposit the phosphor over them all, such that the "seams" between them are not apparent when the light is off. The method Cree uses of only depositing the phosphor JUST over the surface of the die will give more consistent color (with lights that have excess phosphor you'll get yellow "blobs" along the edges of the beam profile, as the light will be passing through more phosphor into those angles)

 

[65535]

It doesn't hurt that it's easier to manufacture 1 die and use it for your single die LED packages as well as larger multi die LED packages.

 

[Th232]

Thanks for the info, especially about the several thousand lumen dies being made of the usual 1x1s, that's a new bit for me!

 

[NeSSuS-GTE]

Thanks for the info, especially about the several thousand lumen dies being made of the usual 1x1s, that's a new bit for me!

If you want to see that in action... LOOK HERE!
I just posted my review of BridgeLux multi-die arrays.

Trinity has made some applicable points that hold true. Multiple dies with a phosphor layer poured over them is exactly what you'll see in the above link.

 

[PsychoBunny]

Sorry for going slightly off topic, but what exactly is a "die"?
Is it the little board that the LED is mounted on?

I want to understand what the heck you guys are talking about!

 

[NeSSuS-GTE]

A die in the context of integrated circuits is a small block of semiconducter on which a circuit is fabricated.
The die of an LED is the actual light generating component.
Check my link. You'll see exactly what we're talking about.

 

[concept0]

Sorry for going slightly off topic, but what exactly is a "die"?
Is it the little board that the LED is mounted on?

I want to understand what the heck you guys are talking about!

The die is the little square of phosphor that actually emits light. In CREE emitters, it typically looks like a little yellow square in the middle of the emitter. In multiple die emitters, such as the MC-E or P7, you will see four dice in middle of the emitter...

 

[Th232]

If you want to see that in action... LOOK HERE!
I just posted my review of BridgeLux multi-die arrays.

Trinity has made some applicable points that hold true. Multiple dies with a phosphor layer poured over them is exactly what you'll see in the above link.

Posted in the thread, but it bears repeating here:



:bow::bow::bow:

Those pics are great!

 

[monkeyboy]

The upcoming Phlatlight SST-90 has a single 3x3mm die. Discussed here. As you pointed out, the benefit of a single die is better collimation and beam pattern as there are no gaps in the emitting surface. The only drawback is the large max drive current of 9A.

There's also the Osram diamond dragon die (~1.4 x 1.4 mm).

 

[PsychoBunny]

A die in the context of integrated circuits is a small block of semiconducter on which a circuit is fabricated.
The die of an LED is the actual light generating component.
Check my link. You'll see exactly what we're talking about.

Thanks

I dont see a link in your post though!
Maybe it's really there, and I just cant see it on my stupid
work PC!?

 

[PsychoBunny]

The die is the little square of phosphor that actually emits light. In CREE emitters, it typically looks like a little yellow square in the middle of the emitter. In multiple die emitters, such as the MC-E or P7, you will see four dice in middle of the emitter...

Got it, thank you.

Learned something new today :thumbsup:

 

[PsychoBunny]

I noticed on DealExtreme website, the R2 emitters they sell are
mounted to a rather large board that does not look like it would
fit in a flashlight. Could the LED be removed from that board?

Sorry for the slightly OT

 

[SemiMan]

Not sure I saw the answer in the thread. It all comes down to defect density. Defect density is consistent on an area basis hence, as the area of the LED increases, the odds of it having a failure go up considerably..... so compare 4 1*1mm dies with a single 2*2mm die. Imagine having a single defect in a 4mm square area. In one case, you may get 3 good dies and 1 bad one.... in the other one, you just get a bad one.

Semiman

 

[Ryanrpm]

There may be a trade off though. For a larger single die you could justify having a higher price because of manufacturing costs.

Look at the Diamond Dragons.....they are 2mmx2mm and cost a lot.