Elimination of incoming test based upon in-process failure and repair costs

An economic model was developed that challenges traditional statistical quality-control methods in the factory. Incoming inspection levels can be determined as a function of both the PPM (parts per million) quality level and the lot-to-lot stability. When incoming quality levels fall to below 100 PPM, the model can be used to reevaluate conventional test strategies in high volume manufacturing operations. Process variability as measured by statistical process control methods can be monitored as lot stability and incoming inspection levels adjusted accordingly