Study On The Light Efficiency And Color Temperature Of High-power White Leds Based On The Packaging Technology

Comparing with the convenient light source, the high-power LEDs have many highlighted performances, such as conserving energy, long service life, environmental protection, less volume, quick response, high reliability, convenient control and etc. LEDs are now becoming more and more popular as a new-type light source. However, there are certain bottlenecks for development of the high-power LEDs, i.e. low luminous efficiency and higher color temperature. Phosphor compound films with different parameters were prepared, light reflectors with different material were designed and LEDs were packaged with two packaging structures that the Phosphor is isolated from the chip in this dissertation. XRD, optical microscope, confocal raman microscope, Integrating Sphere and PMS-50 high accuracy test system were used for phosphor, phosphor compound film and LED characterization.During the process of making the phosphor compound film, two problems must be considered: the phosphor sedimentation and agglomeration. It was found that ultrasonic oscillation can improve the dispersion uniformity of phosphor obviously by phosphor compound film microstructure observation. The ultrasonic stirring and vacuum defoaming method are used in the experiment to reduce air bubbles in phosphor compound film and improve the optical property and uniformity of light.Through Raman spectrum analysis on the phosphor compound film, it was showed that: when it was being excited by 325nm UV-light, the luminous flux of yellow light shall increase with the thickness of phosphor compound film; while adding a certain percentage of red phosphor in the yellow phosphor, it would make the light efficiency of white LEDs drop and color temperature increase.The finished phosphor compound films were packaged with two packaging structures that the phosphor is isolated from the chip. For the measurement on the luminous flux, color temperature and color coordinate of each apparatus, it used the PMS-50 comprehensive light, color and electricity measurement system. The measurement results showed that structure that the phosphor is isolated from the chip can improve the lumen efficiency of white LEDs, as well as reduce its color temperature. When concentration of yellow phosphor is 15.0%, thickness of phosphor compound film is 300μm, the optical property of LEDs are well. Its light efficiency can obtain 60.86lm/W and color temperature is 6187.The improvement on the light efficiency and color temperature of high-power LEDs is an important content of the high-power LEDs'development career, especially the commercialized process. Since the optical property of LED is dominated by the package effect, this work has practical value on the high-power LEDs packaging.