Improvement of the process of monitoring tester performance by applying the six sigma method

Abstract

In this thesis, a process of monitoring tester performance is developed by using manufacturing tested data to replace the current process that is running three standard parts across a group of testers. Six sigma method is used as a guideline to provide techniques and tools to help the thesis accomplish effectively. The current process of monitoring tester performance has low effectiveness in detecting tester performance. Tester availability loses due to unnecessary corrective actions when out of control of SPC is indicated. Frequent causes of out of control condition that indicates testerproblem occurred are mostly from standard parts used. Only 30% that witnesses effectiveness was from the testing system. To overcome the problem occurred, manufacturing tested data is used. The process of monitoring is changed by using the new system that six sigma is followed to reach the objective of the thesis. By using six sigma, the problems and causes are elaborately identified by cause and effect diagram, Pareto diagram, and FMEA in measurement phase. Problems are found from part degradation causing low repeatability of part's performance. Other disadvantages of using the current process are also identified. For example, measurement is only based on three standard parts, and operators are lack of understanding in monitoring process. Then, in analysis phase, manufacturing tested data is analysed for its same wafer quad relation. It is found that parts made of same wafer quad have performance correlation that provides no significantly difference in means of the populations. Therefore, in improvement phase same wafer quad relation has been used to detect the shift of out of control on SPC. When that shift causes significant difference in means based on same wafer quads matching comparing to same tester at different time, different testers at same time, or different testers at different time, tester is considered to be taken the actions for the problems occurred. This analysis is shown on the company's internal webside which provides the information for making decision about tester performance. Finally, control phase is implemented by periodically reviewing the system, studying weekly report, following up the actions taken, implementing the control plan, and so on. Since the new system has been used for tester condition monitoring, a lot of benefits could be obtained that are saving from yield improved, decrease of tester downtime, lower consumer's risks, cost reduction such as cost of standard parts, cost of generating standard parts, cost of performing by operators. Furthermore, the objective is met by increasing the effectiveness in detecting tester performance up to 78%.