There are many types of LED package, and patch LED is one of them. Light-emitting principle of patch LED beads: the terminal voltage of PN junction forms a certain barrier. When the forward bias voltage is applied, the barrier decreases and most carriers in P and N regions diffuse to each other. Because the electron mobility is much larger than the hole mobility, a large number of electrons will diffuse into the P region, forming the injection of a few carriers into the P region. These electrons recombine with the holes in the valence band, and the energy obtained by recombination is released in the form of light energy. This is the principle of PN junction luminescence.
There are many types of LED packaging. LED packaging is very important for the quality of patch LED beads.
I. Necessity of LED package
The LED chip is only a small solid. Its two electrodes can only be seen under a microscope, and it will not emit light until the current is added. In the manufacturing process, besides welding the two electrodes of the LED chip, which leads to the positive and negative electrodes, it also needs to protect the patch LED beads and the two electrodes.
II. The role of LED package
Research and development of packaging technology with low thermal resistance, excellent optical properties and high reliability is the only way for new LED to be practical and market-oriented industrialization. Most of the patch LED bead technology is developed and evolved on the basis of semiconductor separation device packaging technology. The core of ordinary light-emitting diode is sealed in the package, which protects the chip and completes the electrical interconnection.
Choice of packaging mode for patch LED beads with different LED package types
The photons emitted from the PN junction of the patch LED beads are non-directional, i.e. they emit the same probability in all directions, so not all the light generated by the chip can be emitted. How much light can be emitted depends on the quality of semiconductor materials, chip structure, geometry, internal packaging materials and packaging materials.