Wright Williams & Kelly
TECHNICAL ALERT #16
Double Counting Parametric Yield Loss
This tech alert only applies to v2.1.3 for Assembly & Packaging and Mask Manufacturing models where Parametric Limited Yield Loss is greater than zero.
TWO COOL® v2.1.3 for Assembly & Packaging and Mask Manufacturing use calculations for determining composite yield that were modified from the Wafer Fab model. Composite yield may be reported correctly in the Management Report but the modified equations double count parametric limited yield loss when calculating scrap cost. This error has been corrected in version 2.2 and greater.
Solutions to the problem are to reduce parametric limited yield loss entry by 50% or upgrade to v2.3.