For electronic products, most of the defects will be generated in the PCBs, as discussed in Chapter 4. The final product might consist of many other mechanical and electrical parts, including sheet metal, plastics, and connections to other electronic boxes, signal inputs, and display units. For new product introduction, the total defects expected from all of the product components could be tallied using the design and manufacturing quality analysis, and then a plan for removing them could be implemented. A test strategy could be developed to have the proper balance between investing in improving the PCB assembly process capability or performing additional tests and troubleshooting to remove defects generated. Cost modifiers such as equipment investment and volume adjustment would certainly affect this balance.
An overall example of a product test strategy is shown in Figure 8.11, based on the sample new PCBs outlined in Table 8.5. The choice of removing these defects could be decided by the test strategy: which PCBs will undergo in-circuit tests, and what type of functional or system tests should be performed. The example system is made up of 10 PCBs and 240 mechanical parts and assemblies. Figure 8.11 shown an optimized defect removal scheme based on six sigma quality analysis of defects generated by design and manufacturing.
The application of quality and cost improvement techniques to the de- sign process requires an assessment of design quality as well manufacturing process capability of the product creation life cycle. Six sig， ma design quality analysis can be performed at all levels including systems, modules, and printed circuit board designs as well as part selection and specifications. Examples of using quality-based analysis at each level of mechanical and electrical products and systems were shown. This statistically based analysis contrasts with the traditional worst-case analysis of design, and is shown to be compatible with six sigma design for quality techniques. In addition, special considerations such as synchronized designs, emergency shutoffs, and software modules can be examined at the system level where a six sigma analysis could be performed using the system architecture. Finally, the use of six sigma tools such as DoEs can be performed to improve multidisciplinary trade-offs in the design and analysis for high quality and low defects in new products and systems.