Capability Assessment for Weibull In-Cell Touch Panel Manufacturing Processes With Variance Change

Abstract

Since touch panels can provide natural user-interface, including fluent multipoint touch or advance gesture recognition, recently they have been extensively applied in various portable devices, such as smart phones and tablet PCs. In-cell touch panel is the highest integration touch technology as compared to the on-cell and typical touch panel manufacturing technologies for the thinnest and lightest structure. In in-cell manufacturing processes, manufacturing yield assessment is an essential issue. However, inevitable process variance changes could arise from equipment, material, and operation, and may not be detected within a short time. In addition, the process output usually has a Weibull distribution. To circumvent the undetected variance change causing the inaccurate manufacturing yield calculation, we provide a yield measure index to avoid overestimating when the underlying distribution is Weibull with variance change. We also show that the accommodation of the process capability index would not be affected by the scale parameter of Weibull distribution. Applying this method, the magnitudes of the undetected variance change are incorporated into the evaluation of manufacturing yield. For illustration purposes, a real application in an in-cell manufacturing factory, which is located in the Science-based Industrial Park in Hsinchu, Taiwan, is presented.