Online information source for semiconductor professionals

DONALD P. MARTIN, IBM Microelectronics Division, Vermont, USA

ABSTRACT

Over the past two decades continuous flow manufacturing (CFM) has been the principal operational tool to help manage and improve the utilization of manufacturing assets. As the name connotes, the key focus of CFM is to measure and manage the throughput of tools/toolsets that comprise the manufacturing line. To this end, t h e re have been a variety of systems proposed to help manage throughput (e.g. PUSH, PULL, theory of constraints) with their attendant control methodologies (e.g. MRP, KANBAN, drum - buffer- rope, etc.). This paper explores how the X-factor (normalized cycle time) rather than throughput is used as the prime line control and line analysis parameter; hence, the name short cycle time manufacturing (SCM). Because manufacturing lines have both throughput and X-factor commitments, it is essential to understand the fundamental relationships between throughput, capacity and X-factor. This paper also demonstrates that X-factor is a much more sensitive indicator of capacity problems than throughput, because X-factor increases rapidly as the throughput approaches the effective capacity. This sensitivity in X-factor can be used as a powerful diagnostic tool to uncover unanticipated capacity issues. Short cycle time manufacturing (SCM) allows each tool/toolset to be analysed depending on its demonstrated X-factor and capacity versus target to determine which tools/toolsets need improvement, since the overall X-factor of the line is just the weighted sums of the component toolset X-factors. In addition, this paper analyses the impact of mix and volume with a cycle time constraint on the capacity of tools that are affected by batch or train size. Thus, SCM provides significant advantages over CFM in helping to manage and improve manufacturing asset utilization.