Unformatted text preview: t is a mix-driven capacity constraint, find its capacity loading under the forecast scenario. Then calculate how far this is from 85%. Let’s say that Tool Group X turns out under the forecast scenario to have a capacity loading of 80.0%. Therefore this tool group’s capacity loading could be increased five percentage points before it would reach 85%, necessitating purchase of an additional tool. Calculate the number of wafers that would have to be shifted from the lightest- to the heaviest-loading product to bring this tool group to 85% loading. In this example, it’s (85-80)/.130 = 38 wafers. In the forecast product mix, shift the 38 wafers from the lightest- to the heaviest-loading product and recalculate the product-mix percentages (note: if you “run out of” the most lightly loading product, run the calculations for the next-most lightly loading product and remove any “overkill” wafers from that product). In our case, let’s say that the forecast called for 300 WGR divided among Products A/B/C 60/10/30%, or 180/30...
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- Spring '11
- Semiconductor device fabrication, Headway, tool group