On the use of yielded cost in modeling electronic assembly processes

Yielded cost is defined as cost divided by yield and can be used as a metric for representing an effective cost per good (nondefective) assembly for a manufacturing process. Although yielded cost is not a new concept, it has no consistent definition in engineering literature, and several different formulations and interpretations exist in the context of manufacturing and assembly. In manufacturing, yield is the probability that an assembly is nondefective. To find the effective cost per good assembly that is invested in the manufacturing or assembly process, cost is accumulated and divided by the yield at the end of the process. This paper reviews and correlates existing yielded cost formulations and presents a new approach that enables consistent measurement of sequential process flows. This new approach defines the yielded cost associated with an individual process step (step yielded cost) as the change in the process's yielded cost when the step is removed from the process. This approach is preferred because it incorporates upstream and downstream information and because it provides a prediction of a specific process step's effective cost per good assembly that is independent of step order between steps that scrap defective product.