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1、AResearch of poor color; fluorescent material is not easy to find; limited phosphor coating, so thewhite light is not evenCaN single grainUV LED (375nm) + fluorescent materialPhosphor material is not easy to find, will enable the conversion efficiency higher than the YAG fluorescent material, light-
2、emitting efficiency of space; good colorLuminous efficiency is low; packaging materials are easy to produce ultra-violet by UV light ; limited phosphor coating, so thewhite light is not evenZnSe single grainBlue LED + ZnSe substrateSingle grain product white light, low cost; low drive voltage (2.7);
3、 without the use of phosphorLuminous efficiency is 50% lower than CaN, about 8lM / W; short life, only 8000hDual- wave single grainwhite lightSingle grain product white light,Other to be doneto be doneMulti- grainGreen, blue can be dynamically adjusted color-temperature; of good color; natural color
4、The needs of three grains, the grain of the need for individual electronic circuit design, high cost; poor of the close-up color; multi-color LED light- emitting efficiency is not evenAs a result of “blue light chips + YAG phosphor “ have a white LED production method of the lowest cost, practicalit
5、ys characteristic has become the mainstream products on the market. Therefore, the experiment chosen this method to product white LED. Key processes and technical measuresCompared with the ordinary white-light LED, the high-power (W-class power) white LED has a higher power and more heat, therefore,
6、 in the packaging process, be considered light, electricity, heat and other factors. Flip-chip technologyInstalled 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 i
7、n which even the spread of current in order to achieve the purpose of light-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 efficie
8、ncy. In the manufacturing process, in order to improve light efficiency, generally 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 tim
9、e, such a structure is installed through the PN junction calories derived 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 exper
10、iment, to take advanced flip chip (flip-chip) technology, through the P- chip 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
11、are mounted in a light efficiency and the shortcomings of current constraints; 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
12、 solder ball structure of the gold wire to shorten the path, avoiding the 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
13、and the Cu heat sink electrical isolation between; thus Increased product 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
14、 refractive index of packaging materials (generally of the refractive index 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
15、, 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.Therefore, taking flip-ch
16、ip technology to enhance the efficiency of the light at the same time, through on-chip light-emitting layer and Si increase the reflective layer between the bottom of the chip to heat sink side mirror processing methods, the rate of increase in light-emitting devices. In addition, flip-chip in the sapphire substrate surface and between the combination of epoxy resin to increase the Si layer of plastic mate
