If a display manufacturer were to indiscriminately purchase a run of packaged diodes from a diode manufacturer without any thought to the variation of optical and electrical specifications between the diodes, the display product they eventually manufactured would exhibit inconsistent performance. To avoid the outsized impact on display performance differences between diodes can have, diode manufacturers, at the request of display manufacturers, sort newly created diodes through a classification process that groups together like diodes based on three separate metrics. Display manufacturers then purchase only those diodes that fit their parameters. This diode sorting process is referred to within the industry as “binning,” and the three metrics commonly used to “bin” diodes are brightness, color wavelength, and forward voltage. But what impact does strict binning actually have on performance? Do the differences between diodes really matter? What happens if you don’t bin? To answer these questions, we’ll first have to answer a few more.
Why Do Diodes Differ?
Though the diodes within an LED display can seem identical to the naked eye, every diode is not made equal, and one inconsistent diode can compromise an entire display. How is this possible when every diode used in a display is created using the same process? The answer to this question can be understood through a simple analogy. Imagine spraying a flat surface with spray paint, using a precise automated system that aims to coat the surface equally. Even though you may limit the number of variables and strictly control the operations of the system, you are still going to find small inconsistencies and variations. The same is true with the diode manufacturing process. Each diode made in a production run will exhibit tiny differences from the others on its silicon wafer, even though they were all created with the same materials, ostensibly under the same conditions. Variations between diodes on separate wafers will be even more prevalent. The diode manufacturer will then pick and place the diode from these wafers into their packaging, complete the wire bonding (or wireless bonding), seal the package, and then sell these completed LEDs to display manufacturers.
Why Bin Based on Lumosity, Wavelength, or Voltage?