On Sep 21, 2005, at 11:02 PM, Chen Xiao Fan wrote:

> Just curious, how big can this one watt LED die be?
> How big can an LED die be (I think it will not
> be 12inch/300mm).
>
> Isn't the single chip LED also cut from a bigger die?
>
I think we have a word definition issue.

A "die" is the smallest piece of circuit that exhibits the desired
circuit behavior.  I think you're thinking of a "wafer", which is a
whole bunch of individual circuit dice laid out on a thin disk of
semiconductor.  "die" == "chip", and a single chip LED has a single
die from the wafer mounted to some sort of lead frame and embedded in
plastic.  I have no idea how big a wafer full of LED dice is; remember
that it's NOT silicon, so it's probably not 300mm either.

It's vaguely interesting that you don't hear about anyone doing
"waferscale" power LED emitters (where "waferscale" implies a single
piece of wafer containing multiple individual devices.)  You'd think
the sort of parallelism that I gather works for power mosfets would
work good for LEDs, too.  Maybe not.  Or maybe that's how they DO work.

High power LEDs in general consist of unusually large LED dice on a
substrate aimed at dissipating a lot of power.  The 5W LEDs out there
seem to have 4 individual LED dice/chips...

BillW
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