How LEDs are made (2014)

Man, I miss photo articles like this that I can read at my leisure, without sound. Nowadays this would likely be a (probably frantic) video.

Back at Caltech, one of the students realized that the only thing limiting the brightness of an LED was heat dissipation. So, he dipped an LED into liquid nitrogen, and cranked up the current. It got pretty bright before it melted.

Naturally, he realized that the clear plastic blob it was inside was an insulator. How to fix - he filed it down to the bare minimum that would hold it together. This time, it would light up a whole room!

Liquid nitrogen is all one needs to make bright LEDs.

1. Fascinating overall

2. "they can align over 80 per minute or about 40,000 per day." - terrifying, as I assume this is a metric workers are held against :O

80 per minute is less than a second for what sounds like several movements - move the die over, align, push down, move it out. While your eye is stuck to the microscope.

Neat article.

I'd love to know more about how candle-flicker LEDs are assembled, because that source of [apparent] randomness is very interesting to me. I'm not sure if it's an LFSR or true HRNG, and I'm sure there are lots of different designs out there for the simulcrum of natural candle light.

You can get a better sense of their operation if you wire up the LED to an audio circuit where they'll make a pleasingly happy beep boop sound.

(Edit: There was an article somewhere that explored the entropy and concluded that their component operated on a LFSR, as they binned all the brightness outputs into integer values and waves hands did fancy math to conclude that the brightness it was likely modulated by a LFSR. I'll see if I can find it.)

(Edit 2: https://cpldcpu.com/2013/12/08/hacking-a-candleflicker-led/ here's that article for those interested. https://news.ycombinator.com/item?id=25530895 was the original submission to HN.)

De-doming these things (as discussed in another comment) is quite a chore; I de-domed 30 LEDs (candle-flicker, of course) in order to diffuse the light and fit under the keys of a small 3x10 keyboard I was building. But the effect is neat when the backlight is on as it almost looks like a shadow is randomly typing away as the entire array flickers.

I guess I had read this article 12-13 years back. I think it was this same article.

One of the things I vaguely remember was reading somewhere that working on this LED manufacturing severely damages the workers' eyes. I don't know how much of it is true and if it is, whether that is still the case.

So every LED die is manually aligned?

Surely 10 years on that isn't true anymore??

China has improved a lot in commerical, high power LED. 10 years ago, they could not even touch the performance of CREE or Luxeon or Osram LEDs, now thay are on par in term of performace, and much cheaper.

Neat, I was expecting more about how the semiconductor part is made. I toured the Lumileds/Phillips fab that closed in San Jose but you can't really see much.

This was a lot lower-tech than I was expecting. Very cool!

I wonder why some leds have a high TDP and if even that it is efficienty and how it could be fixed...

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