Design And Optimize Of LED Packaging Process

The fourth generation light sourceLight-emitting diode(short for LED)has abroad future due to its development and vitality. LED is one of the high technologies with social and economicalvalueandwill greatly effected on energy saving and emission reduction in the next decades. LED packaging is one critical step ofLED industry chain. It's a complex technology relates to various fields including the optics, thermalmanagement,electronics,materials, mechanics and so on.A lot of problems of LED packaging need to be solved such as the optical performance,reliability costand so on,which has seriouslyhampered the development of general lighting.This dissertation mainly focuseson design and optimization of surface mounted devices (LED) packaging process,elaboratescurrent situation of LED packaging industry and technology,explores the optimal optical parameters, and finds out low cost manufacturing processes. The mainly research works are summarized asfollowing:1.The packaging processes for SMD LED are standardized and optimizated.Plasma cleaning process is supposed to the LED wire bonding,which improves the surface quality of silver layer on the LED holder.The results show that the tensile strength increases 24.6%,the reliability increases andcostdecreases.2.For the new improved phosphor coating method increases color uniformity by use of phosphor deposition form a convex hemispherical structure of the phosphor layer which. Fortradition phosphor coating method, phosphor power with particle size 8μm and silicone with the medium viscosity have a good performance based onconsistency, brightness andother factors.3.The matching character of the spectra between blue LED chip and yellow phosphor affects the conversionefficiencyandtheoutputlightquality. Blue chip LED with peak wavelength of 450-452.5nm, half-wavelength of 20nm matching 4 kinds of YAG phosphor is measured,. The result shows that YAG03has a good performance when the LED color temperature is 5700K.4. Thefactors that affect LED optical performance arewellanalyzedby experimental.Thecolor rendering index increases with the color temperature in a certain rangewhen the LEDs use the same blue chip and YAG phosphor. LEDs with higher peak wavelength have good color rendering index when coated with the same phosphor at the same color temperature. Red phosphor has a significant effecton adding LED's red spectrum, the color rendering index increases from 70 to more than 80 when the red phosphor contents of 10%. Thelumen efficiency will be reduced significantlydue to low Red phosphor quantum efficiency.How the current and junction temperatureaffect on LED optical properties are also discussed.5. Discuss the influencing factorsof SMD LED light attenuation and find that the blue chip is the main factor that influents the white LEDattenuation, whilethe YAG phosphor plays the main part in warm white LED attenuation.