IC設計公司在交期可調情境下的晶圓採購決策

Abstract

IC設計公司指專注於IC設計而將製造全部外包的公司。整個IC產業的供需變動幅度大，需求預測經常不準確，加上從晶圓製造到IC成品出貨的生產週期很長，因此IC設計公司需備較高的安全存量來因應需求的變動，以避免缺貨造成商機的損失，但同時也容易造成高額的庫存而降低獲利。本研究提出一個可調整晶圓交期的機制，假設下單後可依預測需求的變動，在晶圓製造的凍結期之外要求晶圓廠提前或是延後交貨，期望能降低存貨或是減少缺貨的發生。經過模擬驗證後，本研究可調整交期的機制，在滾動式排程下的利潤會顯著優於固定交期的模式。

IC (integrated circuit) design houses, by definition, concentrate on design while leaving production to wafer foundry companies. They place orders based on a rolling demand forecast, and receive the ordered deliveries after a constant production lead time. Due to volatile demand, IC design houses commonly reserve a high level inventory. This research proposed and examined an idea of adjustable lead time for reducing inventory level. The adjustability means that IC design houses are eligible to change the lead time of a particular order, at some time (say, the next period) after they has placed the order. That is, the quantity placed in the order cannot be changed but part of the order can be delivered one week earlier or later than the originally designated due. Under such a trading scenario, in addition to the decision of determining safety stock level, IC design houses have one more decision to make--how to make the lead time adjustment. This research formulates the two decisions and uses a simulation approach to justify the idea. Simulation experiment results indicate that adopting the idea of adjustable lead time could effectively increase the profit of IC design houses.