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November 2015 • SMT Magazine 81 process should be carried out in one place, on the design side, before handing the product to the manufacturers for production. But unless there is a formal common language for defin- ing the product-model and the rules to be ap- plied, the DFA process cannot be left-shifted from the manufacturing level into the design domain. Figure 3 shows a simple real-life example of what happens when the designer is looking at the product with the design library, and the manufacturer is looking at the product with the manufacturing library. The component is the same, but its modeling is different. On the design side, the library sizes the pin of the com- ponent according to the pad it is standing on, whereas the manufacturing library sizes the pin according to the actual pin that is part of the component that will actually be placed on the board. Any communication between the de- signer and the manufacturer about what is an acceptable pin-spacing is meaningless unless a common modeling of the component is sup- porting the discussion. The same applies to the DFA rules themselves, unless the rules have the same meaning at both ends of the DFA process, the process will bring incorrect results and be of no value. First requirement The previous examples have shown how the models of the components must be standard- ized across the DFA workflow. The first assump- tion is that existing formal standards such as EIA, IPC, or JEDEC would meet the need. As- suming a reliable source of content could be found to deliver component models according to the standards, all mapped to their commer- cially purchasable part numbers, the standards approach would have had obvious benefits. However, we discovered, when examining the master parts lists of major DFA practitioners, barriers to a scalable solution based purely on the formal standards. • There are PCB-mounted components that do not conform to a standard of any kind. Fig- ure 4 shows several examples of commercially available components that cannot be described by the JEDEC standard. STreAmLINING PCb ASSembLy AND TeST NPI WITH SHAreD ComPoNeNT LIbrArIeS arTIcLe figure 2: outsourcing separation between design responsibility and manufacturing-process responsibility.