Why are LED dies squared?
- Thread starter yliu
- Start date
Th232
Flashlight Enthusiast
The dies are all cut from a big wafer. They're square because it's easier to cut in a straight line than a curve. From memory they use fine diamond saws to cut the wafers, but I might be mistaken on that.
Also because it's more efficient to make squares than circles, you'd waste a lot of material making circular ones.
Also because it's more efficient to make squares than circles, you'd waste a lot of material making circular ones.
Lightfoot98
Newly Enlightened
After dopeing the wafers, the dies are separated by score-and break, sawing using a dicing saw (yes, diamond), or using laser cutter.
Laser cut is the most efficient because of the small kerf.
Laser kerf is about 10micron (.00039 inch) compared to about .008-.009 inch with saw or scoreing.
You get more dice (multiple dies) using laser compared to
saw or score-and-break.
Laser cut is the most efficient because of the small kerf.
Laser kerf is about 10micron (.00039 inch) compared to about .008-.009 inch with saw or scoreing.
You get more dice (multiple dies) using laser compared to
saw or score-and-break.
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So the real question is: how much would they have to charge for a low volume, circular die LED specifically for use in aspheric flashlights so that the final projected image could be round? My guess would be lots.
LEDAdd1ct
Flashlight Enthusiast
Walterk
Enlightened
Dividing current is easier with rectangular shapes then round ones, that way more lumen per led for the bucks.
idleprocess
Flashaholic
Rectangular/square is easiest to make - divide your die up into X by Y dice with simple rectangular dimensions cut using whatever methodology you desire. Your waste consists of kerf and the edges of the (presumably circular) die.
Hexagonal could be potentially done with a laser with a bit less waste per die. I suspect this approach would present numerous practical challenges ... laser control would need to be very precise (no continuous cut lines), the corners would likely require near-zero "dwell" time as the laser makes a 60 degree turn (lest it burn a notch in the corner of every die), and the cutting pattern itself is more complex (seems to me that the laser either would need to travel "cut" paths about a third of the time or run at two-third duty cycle and precisely re-engage at the apex).
Hexagonal could be potentially done with a laser with a bit less waste per die. I suspect this approach would present numerous practical challenges ... laser control would need to be very precise (no continuous cut lines), the corners would likely require near-zero "dwell" time as the laser makes a 60 degree turn (lest it burn a notch in the corner of every die), and the cutting pattern itself is more complex (seems to me that the laser either would need to travel "cut" paths about a third of the time or run at two-third duty cycle and precisely re-engage at the apex).
DIWdiver
Flashlight Enthusiast
To give you an idea what "low volume" means...
A former customer of mine offered to buy 1,000,000 units of an LED that Phillips was discontinuing (i.e. they had already made it). They wouldn't even respond to the inquiries. They offered Cree the same volume for a specific wavelength (that Phillips discontinued). Cree was more polite, but the answer was still no. Harvatek finally came through. They seem to cater to low volume orders. But they didn't make a custom die, they made a custom phosphor mix to put on an existing die.
If you want a round LED, de-dome a square LED, punch a round hole in something opaque, and lay it on top of the LED...
D
