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84 SMT Magazine • November 2015 designer, such an idea has obvious attractions. But the design library fails the suitability test for four reasons. Firstly, design library content is not systematically constructed according to any level of standardization that is recognizable outside the boundaries of a specific design orga- nization. The rules and meaning of the design library content is defined and owned by the li- brarian, and it is highly likely to be inconsistent with the library content from a library in an- other organization that is under the control of a different librarian. Secondly, the design library usually does not model the physical pin of the component at all, focusing instead on the component body outline and the related pad stacks; yet it is the relationship of the physical pin to the pads and solder mask openings that mainly determines the quality of the soldered joints that will be created in the manufacturing process. Thirdly, the design library component mod- el is usually an approximation based on all al- ternative purchasable parts that may be placed there (according to the master parts list or AVL), thus it cannot be said to support the DFA analy- sis of any specific part that may be used in pro- duction. Fourthly, many design libraries contain multiple outlines for the component bodies, representing anything from the actual outline, to a "keep-out" box that will be used to enforce component spacing design rules. As a conse- quence, when the product model is output to manufacturing and especially in an outsourced manufacturing environment, it is not always clear what the component body outlines actu- ally represent and thus which DFA rule-values to apply. Therefore, and as part of developing a porta- ble DFA process, a dedicated library format was defined that provides a shared standard for the participants in the DFA workflow. The approach taken was to use the JEDEC classification sys- tem, but with extensions to give the granularity required to support the full range of DFA rules to be applied. The essential structure of the library is shown in Figure 6, showing how the linking of the component manufacturer and purchas- able part number(s) to the component model comprises a classified name linked to the graph- ics of that particular model. Examples of com- ponent models are shown; the principle being that, whenever a different graphical model is required to fully represent the detail published in the component manufacturer's datasheet, a new unique classified name is generated. But it is not only the definition of the library structure and format that is essential to the so- lution, but also the availability of the content, as a service to the DFA engineers; the greater the extent to which the library can deliver the content for any particular PCB bill of materi- als (BOM), the greater the comprehensiveness of the DFA analysis that can be performed. Af- ter 15 years of building the content on behalf of DFA engineers around the world, there are now approximately 100,000 uniquely classified graphical models in the library mapped to up- figure 5a: according to JeDec Mo-236c, minimum component body height is 0.45 mm. figure 5b: a commercial part, claiming to conform to JeDec Mo-236c, but actually does not conform. STreAmLINING PCb ASSembLy AND TeST NPI WITH SHAreD ComPoNeNT LIbrArIeS arTIcLe