LED is a light-emitting semiconductor material made of light-emitting elements, materials using III-V chemical elements (such as: gallium phosphide (GaP), gallium arsenide (GaAs), etc.), the principle of light is converted to light , That is, the compound semiconductor current, through the combination of electrons and holes, the excess energy will be released in the form of light to achieve the effect of light, are cold light.
LED is the biggest feature: no need to warm time (idling time), the reaction speed is very fast (about 10 ^ -9 seconds), small size, electricity province, low pollution, suitable for mass production, with high reliability, easy to match Applications need to make a very small or array of components, the scope of application is quite wide, such as automotive, communications industry, computers, traffic lights, LCD panel backlight, LED screen.
LED industry can be divided into the upper, middle and lower reaches of the three categories. Upstream for a single chip and its extension, the middle of the LED chip processing, downstream for the packaging test and application. Among them, the upstream and middle reaches a higher technical content, capital investment density. From upstream to downstream, the product in the appearance of the gap is quite large. LED light color and brightness determined by the epitaxial material, and epitaxial LED manufacturing costs about 70% of the LED industry is extremely important.
The upstream is formed by the Lei chip, this Lei chip looks is about a diameter of six to eight cm wide round, the thickness is quite thin, like a flat metal. Common epitaxial methods are liquid phase epitaxy (LPE), vapor phase epitaxy (VPE) and metal organic chemical vapor deposition (MOCVD), etc., which VPE and LPE technology has been quite mature, can be used to grow the general brightness LED. The growth of high brightness LED must use MOCVD method. Upstream epitaxial process sequence: single chip (III-V substrate), structural design, crystal growth, material properties / thickness measurement.
Midstream manufacturers according to the performance requirements of the LED device structure and process design, through the epitaxial wafer diffusion, and then metal coating, and then photolithography, heat treatment, the formation of metal electrodes, followed by thinning the substrate after polishing. According to the size of the chip, you can cut to 20,000 to forty thousand chips. These chips look like sand on the beach, usually fixed with a special tape, and then sent to the downstream manufacturers for packaging processing. Midstream chip process sequence: Lei chip, metal film evaporation, mask, etching, heat treatment, cutting, cracking, measurement.
Downstream includes LED chip packaging testing and application. LED package refers to the external lead connected to the LED chip electrode, the formation of LED devices, packaging plays a protective LED chip and improve the efficiency of light extraction. Downstream manufacturers packaging processing order: chip, solid crystal, adhesive, wire, resin packaging, long roast, tin, cut feet, testing.