LED Advantages And Industry Classification

LED is a light-emitting device made of light-emitting semiconductor materials. The material uses III-V chemical elements such as gallium phosphide (GaP), gallium arsenide (GaAs) and so on. The principle of luminescence is to convert electrical energy into light, that is, to apply the current to the compound semiconductor through the combination of electrons and holes, and the excess energy will exist in the form of light. Release, to achieve luminous effect, belongs to the cold light.

The biggest feature of LED is that it does not need warm light time (turning time), the reaction speed is fast (about 10 ^ -9 seconds), the volume is small, the power consumption is low, the pollution is small, it is suitable for production, the reliability is high, it is easy to match the application demand, and makes small or array components, such as automobile, communication industry, computer, traffic number and so on. Intelligent lamp, LCD panel backlight, LED screen and so on.

The LED industry can be divided into three categories: the upper part, the middle part and the downstream part. The upstream is single chip and its epitaxy, the middle is LED chip processing, and downstream is encapsulation testing and application. Among them, the upstream and middle reaches have high technology content and large capital investment. From upstream to downstream, the appearance of products varies greatly. The color and brightness of LED are determined by the epitaxial material. The cost of LED is about 70% of LED's manufacturing cost, which is very important for industry.

The epitaxial chip is formed upstream, and the diameter of the epitaxial chip can be 6 to 8cm, and has very thin thickness, such as flat metal. The common epitaxial methods include liquid phase epitaxy (LPE), gas phase epitaxy (VPE) and metal organic chemical vapor deposition (MOCVD), of which VPE and LPE technology are quite mature, which can be used for the growth of ordinary luminance LED. The MOCVD method must be used to generate a long high brightness LED. The upstream epitaxial process sequence is: single chip (III-V substrate), structure design, crystal growth, material properties / thickness measurement.

According to the performance requirements of LED, the middle reaches manufacturers have designed the device structure and technology. Through the diffusion of the epitaxial film, a metal coating is then formed, and then lithography, heat treatment and metal electrodes are formed, and then the substrate is cut and polished for cutting. According to the size of the chip, it can be cut into 20 thousand to 40 thousand chips. These chips, such as sand on the beach, are usually fixed with special tapes and sent to downstream manufacturers for packaging. The production technology of midstream chips is: chip, metal film evaporation, photomask, etching, heat treatment, cutting, cracking and measurement.

Downstream includes application packaging and testing as well as LED chips. LED encapsulation is to connect external lead to LED chip to form LED device, which encapsulates the function of protecting LED chip and improves the efficiency of light extraction. The processing sequence of downstream manufacturers is: chip, solid crystal, bonding, wire bonding, resin encapsulation, long baking, tin plating, shearing and testing.