Matching models to real life for defect reduction

This paper describes a method for quantitatively linking easily measurable parameters [defectivity in parts per million (PPM), test effectiveness (TE), failures in time rates (FIT)] with both customer and producer valued metrics. It describes a process by which test data derived from assembled printed circuit board (PCB) test and the determination of process capability are quantitatively linked. How these derived values relate to continuous improvement activities in PCB assembly, test, component supply and design quality is also discussed, as is the use of this data as a feed forward to the design of future products. Typical examples of our experiences at Tandem Computers are included to illustrate the implementation of the techniques.