The Impact Of Led Packaging On Direct Type Backlight Module Design

Large-size LED-backlit LCD TV has become the mainstream TV. However, with the increasing size of the backlight, the light guide plate for the light injection cannot achieve our requirements. The LED backlight of large-size backlight module, which is convenient and low-cost, will be the future. Instead of using light guide plate, we choose lens to spread light of LED to illuminate the entire module. This way helps us reduce the distance between the LED source and the target surface. So the thickness of backlight module is reduced too. The spot on the target surface is related to both lens material and the characteristics of LED source. They decide the brightness, uniformity contrast and other core parameters of backlight module. We also know chip and packaging technology are the most important things for LED devices. With the development of LED packaging technology, new LED devices, which called “Chip-scale package” LED has been found. They are small, high efficiency and simple packaging, such as CSP,PFC,Po D and so on. Whether these LED can be used as backlight source is worth for us to exploring.This paper presents a novel idea of using new LED devices as a backlight source. We analyze from light angle, size, brightness, uniformity of color and thermal performance of CSP and PFC. Then compare these parameters with conventional LED backlight source 3528. After simulating and practicing, we verify the feasibility of “Chip-scale package” LED as a backlight source.The main contents are as below:1. We briefly overview the development of LED backlight technology and LED packaging, the advantages of LED backlight as well as the purpose and significance of the research.2. Describe the direct-type LED backlight module structure, LED light principle and three methods to realize white LED. Then analyze photometry, colorimetry and thermal of LED, introduce the “Chip-scale package” LED.3. Researching how the packaging impacts on the thermal properties of LED backlight. We use Ansys software to simulate the thermal performance of three LED devices. Comparing the thermal performance of one traditional 3528 LED with two “Chip-scale package” LEDs. Draw a conclusion that “Chip-scale package” LEDs have advantages in terms of thermal performance.4. Researching how the packaging impacts on the optical properties of backlight module. First we do the near-field optical test for both 3528 LED and “Chip-scale package” LED. Then we use Light-tools to simulate the illuminance distribution on the target surface. Two backlight lens are used to help spread LED light, the light mixing distance of lens are 15 mm and 25 mm. After analyze the illuminance distribution of three different LEDs, we find that “Chip-scale package” LED is easier to get large area and uniform illumination spot than tradition LED.5. Researching how the packaging impacts on the color uniformity of backlight module. We use the color near-field optical file to simulate the color uniformity on the target surface. That makes a contradistinction of 3528 LED and “Chip-scale package” LED in the color uniformity side.6. Comparison of theory with practice. Verification the simulation results and show “Chip-scale package” LED can be used as backlight source and has its potential.