A MAIC approach to TFT-LCD panel quality improvement

The liquid crystal displays (LCDs) possess the most mature technology and best consuming competitiveness in the flat panel display (FPD) industries. Of all the LCDs, thin film transistor-liquid crystal display (TFT-LCD) keeps some real advantages. It is thinner, smaller and lighter than other displays and has low power consumption, low-radiation, high-contrast and high-dpi at the same time. Hence, the TFT-LCD panel is widely applied in daily electronic products, and the demand for the TFT-LCD panel increases. The product life cycle of the TFT-LCD panel is gradually getting into the mature stage, and meanwhile, Taiwan’s firms face fierce competition from South Korea and Japan. Thus, at present, continual cost reduction is an all-out pursuing topic for Taiwan’s panel manufacturers. If the quality and yield of the TFT-LCD panel can be effectively enhanced, the non-conforming rate and the cost of the TFT-LCD panel will be reduced. In this study, TFT-LCD panel manufacturing process is discussed, and then five critical-to-quality (CTQ) characteristics (or sub-processes) are identified and summarized. At the early stages, the assessing model of process quality index (Cpm) and the MAIC (i.e., measure-analyze-improve-control) approach of Six Sigma are used to measure and analyze the CTQ characteristics that make TFT-LCD panel unqualified and incapable. During the later stages, Hartley’s homogeneity test and joint confidence intervals were conducted to determine the optimal parameter setting of the critical factor in TFT-LCD panel manufacturing process. By using these optimal settings, Six Sigma quality level can be achieved.