How does an LED emit light? The most common type of LED is the "shell-type," in which an LED chip is bonded to a leadframe crown and protected with a shell-shaped epoxy cover (Figure 1). Another common type is the "surface-mount (chip)" LED, in which a chip is mounted on a flat substrate, and this type is becoming the mainstream in recent years.
Light is emitted from the LED chip built into the LED lump. As indicated by the name "light-emitting diode," an LED chip is a semiconductor that emits light when energized.