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September 2017 • The PCB Design Magazine 41 hours or days later. Now the PCB designer must stop the new design, move several components, reconnect the design, and finally, return the fab- rication package to signoff with fingers crossed. Had the PCB designer started with the proper DFM rule set, such as copper-to-cutout checks, the designer would have recognized this issue much earlier, before starting interconnect, and avoided rework altogether. Enter Predictive Engineering A better approach is for the PCB CAD tools to identify DFM errors as they are made in real time, not after more work is done. Predictive engineering in-design, in real time. Feedback as you make edits, not later on. Not through an embedded batch engine that must be run after some amount of work is done. Most PCB CAD tools have accounted for DFM rules in their system, but they are usually a subset. If they were complete, you wouldn't need third-party manufacturing signoff tools and wouldn't have any iterations with the con- tract manufacturers that build your boards. Tools have evolved to focus more on electrical and physical rules to ensure the product will function as it is designed and will fit in the enclosure once it is assembled. Manufactur- ing processes have also evolved, and PCB CAD tools have not kept pace with new fabrication, assembly, inspection, and test methods. Rigid- flex, HDI, and embedded components are some examples of such new approaches that have re- cently been available to PCB designers. Detecting DFM issues as they are made allows designers to fix them in the shortest amount of time possible before moving forward with rest of the design. It is also important for designers to avoid spending weeks or months of time to set up the rules. DFM rules should be easy to set up and reuse across multiple designs. Having a real-time DFM arbiter during design ensures Figure 3: Connector pins are too close to the cutout in the board. It is much less time consuming to move this away from the cutout. AN OUNCE OF DFM ERROR PREVENTION IS WORTH A POUND OF CURE

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