Incoming test strategy based upon in-process failure and repair costs

An economic model is developed that challenges traditional statistical quality control methods in the factory. Incoming inspection levels can be determined as a function of both the PPM failure rates and the lot-to-lot stability. Since current incoming failure rates have fallen two orders of magnitude to below 100 PPM, the model can be used to re-evaluate conventional test strategies in high-volume manufacturing operations. Process variability as measured by statistical process control methods can now be monitored as lot stability and incoming inspection levels are adjusted accordingly.<>