During fabrication, LEDs grow in the form of a crystal wafer. A 2-inch diameter wafer can carry more than 20,000 LED chips. Color and intensity variations are common across a wafer. LEDs can be â€œbinnedâ€ into various groups by wavelength, luminous intensity, voltage drops, and other characteristics.
Classifying chips by their performance (usually speed)--the analogy is to physically drop things into different bins. This happens at the final test. Once the chips have been packaged, they are tested one more time to see if they work and how well they perform.