LED die size limitation?

I have worked in the semiconductor field for awhile, I am familiar with the process of IC production ie plasma etchers and the CVD process. That being said, What are the limitation factors in the production of LARGE LED substrates? I mean, wouldent it be REALLY cool to have an LED die round at about 10mm with a spiral pattern? Aside from the obvious problem of thermal management and higher cost, is anything else limiting it?.

Jeff

Extraction efficiency (the ratio of produced photons vs. photons that actually exit the substrate) goes down significantly with larger die sizes. Maintaining equal current distribution also becomes more difficult, so current spread contacts must increase in area as well.

In addition, as we've experienced with the Luxeon V and red/orange/amber Luxeon IIIs, optical systems become more difficult, especially when trying to produce a narrow beam spread. A large light source is a beast that is difficult to tame.

Technically, there is nothing stopping manufacturers from making LED dice large, but when that is done, all of the things evan9162 said will come into play. Extraction efficiency goes down, current management becomes a bear, and optical systems for collecting light from such large dice will become rather difficult.

I was just tossing around the idea for large scale lighting, ie office and outdoor geleral lighting as well as for can style drop lighting. No optics would be needed, and the large die area would actually cut down on sharp shadows.
ehh, just wondering.

Jeff

i think a LINE emitter would be cool for general lighting.
a DOMEd pour would still work well on a line (cap).
and it seems like it would still be able to be run off on MACHINES that could pump them out.

that way the heat could be removed easily.
also Quad lines, with like RGB+ would blend well too.

Hi Wildrice,

I can't comment on the semiconductor issues, but was interested in your interest in large scale lighting.

You're probably better off with large arrays of LEDs rather than LEDs with big die sizes....or big modules like the lamina with lots of small LED dies. Even the lamina at a distance gives a sharp shadow.

One thing I've noticed is that the diffuser is very important, even if it may cut some of the light...because of the soft shadows. On a purely subjective level I think not having sharp dark shadows helps your eyes think that the light is brighter than it actually is. Presumably its a psychological perception...the eyes are used to soft shadows in daylight and household settings, and so assume they're in the same situation even if you've only got LEDs lighting the place.

Here's a pic containing three of my upcomming boards:

(actually, it's the prototype model. My production board has 66% more LEDs.

This will nicely light up a room, probably around the level of a 25W globe, or a big TV set. Enough to see by, eat munchies while watching a video and read the TV guide and locate your beer. Certainly a nice mood light, but I wouldn't read Lord of the Rings by one of these lights.

Oh and with large scale lighting, you won't need much blue, it's hard on the eyes. You can get by with mostly red, a little green and even smaller amounts of blue to get a nice warm white.

phli

There's no such thing as a nice warm white. 5500K OR BUST! /ubbthreads/images/graemlins/grin.gif