LED, an abbreviation for Light Emitting Diode, translated as the light emitting diode in Chinese, is a semiconductor device that converts electrical energy into light energy. The core of the LED is a chip composed of p-type semiconductor and n-type semiconductor, and there is a p-n between p-type semiconductor and n-type semiconductor. 　　　

1. Basic introduction of LED  

LED, an abbreviation for Light Emitting Diode, translated as the light emitting diode in Chinese, is a semiconductor device that converts electrical energy into light energy. The core of the LED is a chip composed of p-type semiconductor and n-type semiconductor. There is a p-n junction between p-type semiconductor and n-type semiconductor. When the minority carrier and the majority carrier are combined, the excess energy will be released in the form of light, thus converting electrical energy into light energy. Chips made of different materials can emit light in different colors, such as red, orange, yellow, green, blue and purple, hence, the light emitting diode is named. 　

Compared with traditional lighting, LED has obvious advantages in energy conservation and is the world's advanced lighting technology. It is regarded as one of the great inventions by the industry after Edison invented the incandescent light bulb.  　　

Another feature of LED is environmental protection. LED is a solid-state luminescent device that does not contain mercury and will not cause toxic metal environmental pollution due to cracking during production and use.  

 

2. LED application field and its classification  

In the context of the global energy crisis, energy-saving, environmentally friendly, colorful, safe, long-life, and miniaturized semiconductor LED lighting has been recognized by the world as the third lighting revolution in the history of human lighting. With the improvement of LED technology, its application fields are expanding and extending, and it is widely used in LCD backlights, general lighting, signal display, signaling lamps, and automotive lamps.   

3. LED package and its product classification  

LED packaging refers to the process of encapsulating LED chips and brackets with materials such as epoxy resin or silicone. Specifically, it is a process of arranging, fixing, and connecting the LED chip and other components on the bracket or the baseplate, taking out the terminal, and encapsulating and fixing the plastic transparent insulating medium to form an overall three-dimensional structure, which provides protection and heat dissipation for the normal operation of the chip.   　

At present, the types of LED devices are mainly direct-embedded type (Lamp) and surface mounted type (SMD). Among them, SMD type products have many unique excellent characteristics compared with the Lamp type products. Such as the high assembly density, small size of electronic products, light-weight, saving materials, energy, equipment, manpower, time and so on. Specifically embodied as:  

(1) Low welding spot defect rate, good high-frequency characteristics, and reduced electromagnetic interference and radio-frequency interference;   

(2) High reliability and strong anti-vibration capability;  　　　

(3) Easy to automate, improve production efficiency, reduce the cost by 30% and 50%; 　　

(4) The size and weight of the SMD components are only about 1/10 of that of the conventional plug-in mounting components. Normally after SMT is used, the volume of electronic products is reduced by 40% - 60%, and weight is reduced by 60% - 80%.  　

At present, the SMD LED is mainly applied in those areas such as backlight and lighting, etc. 　

Classified by different packaging modes, SMD LED products consist of Chip Category, Top Category, Sideview Category and HD (Heavy Duty) Category, of which TOP, Sideview and HD categories are mainly white light and high light-based, and mainly applied in the backlight field (such as mobile phones and computers, etc.) and lighting field (such as interior and exterior lighting, etc.). Therefore, the specific products using SMD high-end packaging technology are usually those products under the TOP, Sideview and HD categories, i.e. those white light and high light-based products. The domestic market of the direct plug-in device has been essentially saturated with profit declining year by year. The market competition of the SMD low-end device has become increasingly intense, meanwhile, as the manufacturing capacity of the SMD medium and high-end device is gradually increasing , the product pricing has been experiencing fairly great changes.  　 

　　4. LED Classifications and its Applications by Colors of Emitted Light  

LED falls into the category of semiconductor photoelectrical appliance, which can be classified into monochrome LED, full-color LED and white light LED by the colors of the their emitted light. At present, the white light LED, which is mainly used in the back-light and lighting areas, has been widely applied. With the improvement of the luminous efficiency of white light LED, the semiconductor lighting has been widely used in various areas such as mobile phones, back-light, and special lighting, etc., and is driving its way to the common lighting area.