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Research Of The Key Packaging Technology Of High Power LED Blue Light To White Light Conversion

Posted on:2015-02-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q W GuoFull Text:PDF
GTID:1262330422981520Subject:Control theory and control engineering
Abstract/Summary:PDF Full Text Request
With the development of LED (light‐emitting diode) lighting industry, chipmanufacturing, LED encapsulation and application products has formed a high technicalcontent industry chain with bright market prospect, especially the high power and highbrightness LED module has become a international research hotspot in the field ofsemiconductor lighting and display. The common Light-emitting principle of high powerwhite LED is to stimulate YAG(yttrium aluminum garnet) phosphor by a blue LED chipbonded on silicon carbide or sapphire substrate. As the matter of fact, the key technology ofthe phosphor coating has become the industry development barriers. So far, the domestic highpower white LED phosphor coating technology mainly is dependent on the method ofdispensing. The excessive use of this traditional coating technology and lack of research andinvestment in the new type of high efficiency coating technology determines that the statusquo of domestic light LED manufacturing enterprise can’t produce high quality white LEDindustry. Therefore, the control of phosphor layer thickness and uniformity and precisephosphor spraying technology has become the current hot research topic. This article mainlybase on the high power LED packaging phosphor coating technology and some key problemswith the design of coating equipment, and the research focuses on the following sections:1. Based on the research and design principle of piezoelectric coating phosphor actuatorfor phosphor coating equipment, structure of the piezoelectric coating actuator coatingprocess is analyzed and summarized; In order to improve the system response speed, stabilityand accuracy of coating, the structure of phosphor actuator and the mathematical model of thephosphor coating process were established. Through the simplification of internal phosphorglue fluid motion of piezoelectric coating phosphor actuator, the mathematical criterion offorming phosphor droplets was deduced, and the key performance indicators of piezoelectricactuator are put forward.2. This chapter aims at the base studying and qualitative analysis of the high-power LEDphosphor coating process, especially in the atomizing phosphor flow field distribution and itsdroplets transportation. A CFD (Computational Fluid Dynamics) research and the numerical simulation of the coating process are presented in this paper. Mathematical models of thevelocity distribution of the phosphor gel flow and3-D models of the EFD-781and EFD-787spray guns are set up. A reasonable coating distance downstream from the phosphor coatinggun nozzle exit to the LED chip surface is found out in this research. In addition, thisnumerical simulation can also predict the droplets trajectories, and its velocity distributionwill highly match with experimentally observations.3. This chapter aims at the application of vision technologies for high power LEDfluorescent powder coating process. First of all, vision positioning method of the phosphorcoating equipment is introduced; Then after completion of the current coating process, we gotthe edges image of phosphor layer by using CCD to grab a two-dimensional gray image of thephosphor glue points, filtering image noise through the median filtering, and by using themathematical method of phosphor layer edge detection; Meanwhile, Through acquisition ofphosphor layer image after coating phosphor, compared with standard coating image template,so as to detect the surface defects of the phosphor layer such as irregular, glue stained andforeign bodies, the phosphor layer defect detection is realized. Then, the triangulationmulti-point laser measurement method is given to detect the thickness of the phosphor layer,to detect the defects and such as thick, thin and uneven thickness; Finally, the height of eachpoint on the surface of the phosphor layer inside the edge of the glue point can be measured tocalculate the approximate glue point volume.4. For control process of phosphor coating, open loop control has been used in thetraditional phosphor dispensing process, however, due to the large quantities of LEDs incoating process, the phosphor coating quantity of single one LED phosphor will increase asthe number of coating grows, and its quantity will have plenty of drifting, which willseriously affects the white LED light quality. As the matter of fact, this charpter focus on thecontrol strategy of eliminating this drift phenomenon. In the process of practical production,most of the process variables affecting the quality of glue incapable or inconvenience tomeasure, so the choice of control method and controller is limited. This charpter, we used anew method of quality control (statistical process control, SPC) to regulate the amount of glueout size and to promotive and enhance adhesive performance consistency, based on the established phosphor coating process model.5. The overall framework of phosphor coating equipment and its control system aredesigned, according to the vision detection techniques and the SPC control strategy, and therelative experiment is the designed and validated. These experiments show that the phosphorcoating equipment and control strategy we used can complete the phosphor coating process ofPhilips Lumens1W high power LED chips encapsulation, one of the commonly used1whigh power LED packaging form, precisely and efficiently. And we also run the SPC controlstrategy experiment for a variety of COB encapsulation, SMD encapsulation LEDs, and alsoobtained the very good effect, which demonstrated this control strategy and the design of thephosphor coating equipment can be widely used in the most of LED phosphor coatingprocess.Finally, on the basis of summarizing the existing research results, this article puts forwardsome problems worthy of thinking and exploration, and made some prospects for t theproblem of phosphor coating technology.This project is supported by the National high technology research and developmentprogram (863program)(Grant No.2012AA041312) and the Key Research CooperationProject of Guangdong Province and the Ministry of Education “High power LED moduleproduction technology and complete set of equipments”(Grant No.2010A081002007)...
Keywords/Search Tags:LED packaging technology, LED phosphor coating equipment, Phosphorcoating thickness measurement, Modeling of coating principle, SPC control strategy
PDF Full Text Request
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