How LEDs are Made
learn.sparkfun.com
learn.sparkfun.com
Years ago I answered a "for sale" newspaper ad for used office desks and some test equipment. I showed up at the address and it was a small dingy old building and most of the employees seemed to be 55+ year-old women. When I asked what they did and was told they made diodes, you could have knocked me over with a feather. Like he did, I assumed that all electronics parts manufacturing was high-tech, cleanroom work, etc. But here were little old ladies putting pieces together.
I had a similar epiphany years later when a friend told me he was buying a thermocouple manufacturing business for $20,000!!! The business consisted of two senior citizens who wanted to retire. No high-speed pick&place robots working in inert argon atmospheres, just two old people putting wire in jigs and spot-welding them together (probably in an inert atmosphere, though).
The same thing repeats itself over and over: a huge amount of what we think of as sophisticated technology is being done by hand, or by ancient machinery, in dirty, poorly lit corners of the US.
It was a terrible time of my life and it informs a lot of my opinion about poor management and inefficient working and about ISO900x quality assurance systems.
I wouldn't make leds at home, but that's because of the chemistry, not because it can't be done...
Then you have the actual crystal growth portion where you shove all those wafers into an evacuated chamber, heat them to a thousand degrees, spin them around, and spray them toxic pyrophoric gases. This process takes multiple hours to grow just a few microns of light producing crystals.
Then you have to grind the wafers down to the appropriate die thickness, go through multiple stages of etching, add a phosphor for white LEDs, deposit gold and ITO for electrical contacts, and use lasers to cut them into individual die. Then, finally, you can ship them to the people in the linked article. Honestly, this article is the most boring part of the whole process.
Source: I used to work in R&D for an LED manufacturer.
and a lab to get a better feel for how band gaps affect the spectrum: http://electron6.phys.utk.edu/phys250/Laboratories/Light%20e...
That would mean the manufacturer would be spending half the cost of the finished product on a single step of the manufacturing process. I'd be surprised if that's economically viable.
so i think the costs per led are even lower...
Ridiculous URL: http://uk.farnell.com/jsp/search/browse.jsp?N=2031+202618&Nt...
Even the USB microscope cameras are garbage. Much better pictures just holding a digital pocket camera up to the eyepiece.
Also amazing how small the components (LED dies) are.
(says me who just bought 200 for a small prod run). So that's £10 or £50 out of the budget. Thanks to cheap LED guys, I can take my family out for that extra £40 :)
> 0402 (1005 metric): 1.0 mm × 0.5 mm (0.039 in × 0.020 in).
There was a reason I did it before I had any coffee!
The pick and place machine needed blank strip of about ten components (just for lead-in on the cassete).
Transfering components from one tape to another was really annoying. And one of the bosses just did not understand that the fractions of a penny saved were obliterated by time wasted moving components over.
And until you've had to do something like that you can't really understand the benefit of $60 Swedish tweezers.
The lady I have hand building my boards can place 0201 all day. Pretty amazing.
I am sure if I thought about it I would have realized that it is just support for the silicon. I guess I never thought about it that much until today.
I'd be very curious to see how this process differs from the high-power lighting LED manufacturing process (e.g. CREE), which is a more modern technology by several decades. I would guess there is much more of the automation people are expecting...
Every HP common slot server PSU has one of those round through hole LEDs on it. I have an HP server sitting here (DL580) that has two 7 segment displays on its motherboard. These things are definitely still used in modern products.
Remember folks, there is a world outside of Silicon Valley.
At work yesterday, at a microwave communications equipment manufacturer. Through-hole LEDs are the easiest kind to mount on the front panel of rack mount equipment. And there are 7-segment displays on two of our adjustable power supplies.
Don't forget: yield goes up when the die shrinks because the defects are typically small spots. The smaller the die the better you pixelate the defects.
The wafers are only 2 inch diameter to avoid yield loss due to edge effects: at the edge of the wafer you have lowest quality components (optical ring effects)
Secondly, upgrading your Fab to switch your process to larger wafer size has a 10-figure $ price tag. It's not trivial for digital, let alone opto electronics. LEDs are special in that they deviate severely from the standard mos process. When Monsanto first produced them they almost dumped the idea for LEDs because of all the issues to deal with the exotic materials.
I don't understand this. Given a fixed size die, the number of dies near the edge would go up linearly as the wafer size goes up. The number of interior dies would go up quadratically.
Here's a teardown with cost estimates for a recent 800 lumen Cree 60W equivalent, where they come up with an $8 Bill of Materials for a bulb that retails for $13: http://electronics360.globalspec.com/article/3212/cree-ba19-...
My only complaint, and it's a tiny one, is that they only dim to about 10% before cutting off entirely. There's also a small dark spot on the spot of the bulb opposite the socket, but in practice that's been a non-issue for all my use cases.
Now, I'd like to see someone do something like this for solar panels.
The book referenced as the first source on the "die" wikipedia link claims:
> The plural of die is dice. However, it has become standard practice in the industry to use "die" as the plural.
As a native speaker of English, I'd find any of "die", "dies", or "dice" to be pretty reasonable as long as it's clear what's referred to from context. (I'd prefer "dies" over "dice" if it's not immediately clear that you're not talking about playing dice, for example.)
A die is either a regular polyhedron with numbers on it, used in games, or a device for cutting/molding metal into a specific shape.