1、附录 A Research&Fabrication of Packaging Technology for High Power White LED Comparing with the traditional incandescent and fluorescent lighting, the high Power white LED has many significant incomparable advantages such as energy saving, envirorunental protection, long life and so on. It represents
2、the development direction of green lighting, and is moving into the field of lighting rapidly. From the packaging technology of 1 W high-bower white LED, the cost and performance of several methods were analyzed and compared for white light LED. Based on this, using the“blue chip&YAG phosphor for pr
3、oducing white light LED is the final selection with its good perfounance and proper price. The results show that in improving the light emitting efficiency, unilounity and stability of high-power white LED, it needs further development of new materials and new technology. Introduction LED use semico
4、nductor chips of solid as light emitting materials, the use of electric light-emitting. As a light source, LEDs advantages is in energy saving, environmental protection and long-lived three aspects. LED does not depend on heating filament to light-emitting, energy conversion efficiency is very high,
5、 in theory only 10% of the energy consumption of incandescent. compared with fluorescent, LED can be up to 50% of the energy saving effect. Special survey showed that the annual electricity consumption of Chinas lighting is more than 300 billion, to replace all incandescent lamps with LED or in part
6、 or to replace the fluorescent lamp, can save 1 / 3 of the lighting electricity, means that the saving of 1 000 billion kwh, representing the full-years generating capacity of Three Gorges Project which investment of more than 200 billion. Using LED to replace fluorescent lamps, bamboo lamps to avoi
7、d the breakdown of a spill of mercury pollution, moreover waste and manufacturing backplane LED (Copper Clad Aluminum) reuse can be recycled. LED by solid package, the structure is deep-set , life expectancy can be up to 510 h. In addition, LED also has a low operating voltage, power consumption in
8、small, high luminous efficiency, response time is very short (ns-grade), pure light color, light weight, small size, such as a series of characteristics of rapid development, especially high-power high-brightness white light LED of the invention, by the insider as the lighting the area of the third
9、revolution.following make fire lighting, after Edison invented the lamp . White LED production method At present, the way to product white light with LED chips show in the table1. Tab.1 Preparation principle of“blue chip&YAG phosphor The way of The white light production method Advantages Disadvanta
10、ges CaN single grain Blue light LED +fluorescent material Single grain production method, low cost, electronic circuit, designed is simple Luminous efficiency is low； of poor color； fluorescent material is not easy to find； limited phosphor coating, so thewhite light is not even UV LED (375nm) + flu
11、orescent material Phosphor material is not easy to find, will enable the conversion efficiency higher than the YAG fluorescent material, light-emitting efficiency of space； good color Luminous efficiency is low； packaging materials are easy to produce ultra-violet by UV light ； limited phosphor coat
12、ing, so thewhite light is not even ZnSe single grain Blue LED + ZnSe substrate Single grain product white light, low cost； low drive voltage (2.7)； without the use of phosphor Luminous efficiency is 50% lower than CaN, about 8lM / W； short life, only 8000h Dual- wave single grain white light Single
13、grain product white light,Other to be done to be done Multi-grain Green, blue & red, green and blue multi-color combinations High luminous efficiency； can be dynamically adjusted color-temperature； of good color； natural color The needs of three grains, the grain of the need for individual electroni
14、c circuit design, high cost； poor of the close-up color； multi-color LED light-emitting efficiency is not even As a result of blue light chips + YAG phosphor have a white LED production method of the lowest cost, practicalitys characteristic has become the mainstream products on the market. Therefor
15、e, the experiment chosen this method to product white LED. Key processes and technical measures Compared with the ordinary white-light LED, the high-power (W-class power) white LED has a higher power and more heat, therefore, in the packaging process, be considered light, electricity, heat and other
16、 factors. Flip-chip technology Installed in the traditional way of LED chip package, because of P-type doped GaN difficulties, the current widely used in the preparation of P-type GaN metal transparent electrodes on the ways in which even the spread of current in order to achieve the purpose of ligh
17、t-emitting uniformity. P-type GaN on the transparent electrode metal to absorb 30% to 40% of a light, while n-type electrode and the lead will block some of the revealing light, which severely affect the chip LED light efficiency. In the manufacturing process, in order to improve light efficiency, g
18、enerally transparent electrode metal thinning methods, so that in turn limits the current in the h-GaN surface evenly spread the impact of the products reliability, constraint of the LED chip operating current . At the same time, such a structure is installed through the PN junction calories derived
19、 sapphire substrates, sapphire is the thermal conductivity 35 W / (mK) (worse than the metal layers), a larger thermal resistance, resulting in bamboo core temperature rise, thus affecting the device the performance. This experiment, to take advanced flip chip (flip-chip) technology, through the P-c
20、hip and n very very bottom of the production of ultrasonic gold wire leads to solder joint as the electrode structure and the outside of the Si chip on the production floor gold lead, to overcome the above-mentioned LED chips are mounted in a light efficiency and the shortcomings of current constrai
21、nts； chip PN junction from the heat generated by gold wire solder through a direct transfer to the Si substrate and heat sink, the heat transfer is far superior to the effect of Sapphire is mounted cooling structure； flip chip solder ball structure of the gold wire to shorten the path, avoiding the
22、chips installed in the traditional structure is a result of a long wire path phenomenon resulting from high fever； At the same time, the production of Si substrate reverse bias the PN junction, the realization of Si substrate and the Cu heat sink electrical isolation between； thus Increased product
23、life LED, so that package greatly enhance the reliability. Optical design techniques 1. To improve the refractive index High-power white light LED chip refractive index of n = 2-4, much higher than the lens plays a role in the refractive index of packaging materials (generally of the refractive inde
24、x of epoxy resin at about 1.4-1.5). Therefore, when the light after the chip packaging materials, in a total reflection from the interface effect occurred, resulting in about 50% of the light reflection back to the chip itself, can not be effectively exported to become ultra-high brightness LED chips from low light efficiency underlying causes. How different materials will be among the internal refraction, reflection of light energy to be consumed in use, the design of optical systems is the key.
