| Summary: | 碩士 === 中華大學 === 科技管理研究所 === 90 === In the wafer foundry industry, due to high investment cost and fast depreciation in equipment, the fully use of equipment utilization and increasing the productivity are the major objectives of all foundries. As we know, the output of fab is limited by the bottleneck machine. If there is a discrepancy between planned and actual products mix, the new bottleneck machine will occur and the capacity will be short. In general, all famous foundries, such as TSMC, UMC,…etc., are taken the backup solution for this kind of problem. Unfortunately, the side effects will occur if the backup quantity can’t be well controlled.
Based on the above situation, a capacity backup determination model will be proposed. There are two parts in this model , one is Excess Capacity Determination Model (ECDM) ; the other is Performance Evaluation Model (PEM). The concept of protective capacity is applied to determine the excess capacity in ECDM. The determination of protective capacity is based on statistical fluctuation of factory which includes the machine downtime and unreasonable waiting time of WIP before machines. The queuing theory and Little’s Law are applied in PEM to evaluate the influences upon throughput、WIP and cycle time of backup fab when the requested backup capacity is over excess capacity which backup fab can support.
Based on the information provided by the capacity backup determination model, the decisions of capacity backup can be made accordingly.
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