CONWIP based control of a semiconductor end of line assembly

Abstract

Advancement of technology and trends in globalization has resulted in higher customer demands and expectations. Manufacturers now offer mass customization to stay competitive. In the semiconductor industry, where product mix and volume are high, production is further complicated by the different process routes and processing times for different product families. Coupled with rapid changeovers of products, it is essential to keep the work in process (WIP) low in order to reduce the inventory level on the shop floor. CONWIP is a production control strategy applicable in many manufacturing environment, that uses cards to control WIP level. In this paper, discrete event simulation models for processes at the End of Line (EOL) assembly in a semiconductor manufacturing company were developed. Experiments were conducted using these models to compare the current system with the single loop and multi loop CONWIP control mechanisms. Performance parameters of throughput, cycle time and WIP level were compared in all experiments. The result, firstly, shows that, generally, CONWIP production control is more effective to reduce WIP level compared to the current system. The reduction in WIP is accompanied by corresponding improvements of cycle times. Secondly, the multi-loop system performs better than the single loop system with higher cycle time reduction. Multi loop control is also more robust and provides a better control mechanism compared to the single loop system.