| Development of thin-film transistor liquid crystal displays(TFT-LCDs) has brought great impact to the human’s life. The application market of TFT-LCDs keeps increasing. There are several companies set up for producing TFT-LCD panels and modules in China mainland. With increased competition in the market, the price of TFT-LCD products decreases gradually, and the profit margin for the companies becomes lower and lower, especially for the TFT-LCD module plants. Due to the labor-intensive feature, labor cost at least 60% of the total production cost in a TFT-LCD module plant. Therefore, it’s particularly important for the module companies to reduce labor cost, increase production capacity and accelerate production cycles. At the same time, the companies should actively improve the quality of production in order to reduce material consumption and wastes, which can also reduce production cost on the other way. This thesis studies the methods for improving productivity and production quality of TFT-LCD modules.In this thesis, firstly the structure, operation mechnisms and key components of a TFT-LCD module are introduced, followed by description of the production processes. These form the basis for the further studies in the thesis.In order to improve the production efficiency in module plants, the traditional approach is to use industrial engineering techniques. The line balancing and "ECRS" methods are described in this thesis. They contribute significantly into the early production improvement in the module plants. Taking the backlight assembly station for example, the efficiency is increased by 47% by hanging the original line-style production into the cell-style production. The second example is that by optimizing and combining the final display and visual stations as the final inspection to simply the procedure, the efficiency is increased by 50%. However, the two methods are not suitable to solve the technical-level problems related to the module. Therefore, in order to address the bottleneck of traditional approaches, this thesis focuses on the following technical approaches to improve the module processing efficiency.1) During manufacturing TFT-LCD modules, if the subsequent process is started right after the dispensing process, the formed structures could be damaged, and some undesired surface dirties could be caused. Therefore, waiting for 5-6 minutes to make the surface dry is required before starting the subsequent process. As a result, to improve the production efficiency, the drying time should be shorten. The TRIZ method is used in this thesis to improve the drying process. By analyzing the tradeoff between the ideal result and the technology, ways to reduce the required time for drying are found, and are verified by experiment results.2) Before shipment of the display modules, aging test at high temperature is needed to find out the unqualified products at the early stage. This thesis shortens the required aging time to improve the production efficiency by drawing the bathtub curve from the experimental failure rate results, as well as considering the customers’ requirements.3) At the final visual inspection station, the workers need to check the defects through continuously changing the test images, which can result in serious visual fatigue after one day work. Based on the fundamental properties of human visual system, this thesis uses a method of sorting the different test images according the brightness through the Weber-Fechner law. As verified by experiments, the method can shorten the time required by human eyes to adapt to the change of picture brightness, and therefore improve the inspection speed and production efficiency, as well as reduce the visual fatigue.4) Additionally, this thesis also presents two other technologies, including the anisotropic conductive film(ACF) of rapid main bonding and automatic backlight assembly, to improve the production efficiency.The other focus of this thesis is to explore ways to enhance the production quality. Based on the 6-sigma theory and other quality control techniques, the quality problems during bonding particles in the JI(JISO in Japanese) module process are solved through the procedure of definition, measurement, analysis, improvement and control. This scheme is also universal.This thesis presents new methods for process improvement when the module plant meets the bottleneck of improving production efficiency and quality. TRIZ and 6-sigma are applicable to different improvement approaches. The benefits of these methods might not be very significant, but even a tiny improvement may have a profound impact on the products in the fierce competition market in the long term. |
PDF Full Text Request