A preventive maintenance forecast method for interval triggers

There are two methods to schedule PMs: periodic trigger and interval trigger. Periodic trigger is based on working days, and can be predicted rather easily. Interval trigger is based on a certain measurement, such as the accumulated RF hours, accumulated thickness, number of wafers processed, etc. However, predicting the next PM date by interval trigger is not as easy. To solve this issue, we devised a new forecast method for interval triggered PMs. It can cope with exceptional events and plan accurate PM schedules.