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82 SMT Magazine • April 2014 to confirm that the product is fit for their opera- tion and to get the processes set up. Industry standard formats such as ODB++ create a com- plete and detailed product model such that the need for data reconstruction is avoided. The assembly process does not usually have the luxury of being able to negotiate design respins. The physical PCBs are already made in quantity. Again, however, tools are used to as- sess the data from design, and again, assump- tions and adjustments are made to make sure that the product fits to the assembly platforms to be used. Each assembler will again have simi- lar issues and is likely to resolve them in differ- ent ways. These manufacturing engineers have a lot of responsibility on their shoulders. They are on the front line, preparing complex manufactur- ing processes that will produce quality prod- ucts. The manufacturing process, however, is often significantly separated from the PCB lay- out process, even though this is their key source of data through the NPI flow. There has been a lot of frustration historically among manufac- turing engineers about why the designers make the same mistakes time after time. Issues occur with fabrication, assembly, test access, fiducials, pads, tracks, component spacing, and many more. All of these issues happen over and over again, which could simply be avoided. In OEMs, neers who understand their processes and spe- cialist technologies. They are also likely to have one or more software tools, to assist them with the interpretation of the data they receive from design, which they need to check, and in many cases to reconstruct so that their process will work efficiently with the required yield. It is most often the case that issues from the design that could cause serious problems during the manufacturing setup will be picked up. In the best case for PCB fabrication, there is usu- ally the scope to request that the PCB design is changed to accommodate issues or limita- tions of the manufacturing process. This can trigger whole repeated cycles of layout design refinement, testing, output generation and re- engineering for manufacturing, but it solves the problem. More risky, however, is when it is agreed that the fabricators can change the PCB design locally by themselves to avoid this cy- cle. The problem is again solved, although with many issues going through this process, the designer has lost a great deal of control of the consistency of his product. This is compounded when multiple fabricators are used, together with inevitable differences in ways that each apply their solutions Obviously, the greater the level of detail and completeness of the product model coming out of design, the easier it is for process engineering The eSSenTiAl Pioneer'S SurViVAl guide EXpaNDiNG YOUr COMFOrT ZONE continues figure 1: The traditional nPI flow from design to manufacturing for new PCbs.