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Design007-June2019

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JUNE 2019 I DESIGN007 MAGAZINE 31 of "Seinfeld" in 1994. But since 1994, the un- foreseen challenges presented by industrial de- signer's shrinking packages and its effect on IPC levels of manufacturing producibility has only made PCB design packaging and layout more perplexing. With package shrinkage, the typical product design iteration cycle goes something like this: 1. Product invention requires competitive advantage in capability, size and cost shrinkage 2. Product idea goes to industrial design to be aesthetically and ergonomically conceived 3. Product renderings go to mechanical engineers to create enclosure tooling 4. Product specifications go to Electronics engineers to locate electronic parts 5. Electronic parts are placed into schematic and BOM 6. PCB designer begins layout with PCB outline and keep-outs from ME and BOM and schematic from EE 7. Only 50% of parts will fit on PCB outline. 8. EE must shrink parts and consider two-sided assembly 9. PCB designer manages to fit parts within PCB outline though part-to-board outline spacing is compromised. Some clearance issues are mitigated by shrinking some land pattern geometry though solder joint reliability is now compromised 10. Another problem arises: limited board surface real estate on board surfaces for routing 11. PCB design must go to multilayer stackup to allow routing and power distribution Now, the PCB cost quotation exceeds the tar- get cost model for the project. It is only at this point, far downstream from the concept ren- derings phase, that the entire product must be re-evaluated for feasibility. Rinse and repeat the entire process. Or we can try to change this process. After all, we'll never get back this wasted time and resources. Design For the Unknown As PCB designers in this early, critical stage of design, we served as the project team's reali- ty checker. We didn't really get to design much at all. Too many critical PCBA design attributes and constraints were unforeseen by the up- stream stakeholders, rendering the concept un- feasible in this configuration. So now that the project is a prime candidate for DFU (or a rede- sign), how can a design team do a better job? Project teams must embrace the concept of designing with the end in mind. From proj- ect conception on, everything will flow down- stream. After all, what river raft guide would float a team of tourists down an unknown, un- navigated river? While the design is still in the earliest stages, check in with all of the knowledgeable folks downstream—the PCB designers and all of the process stakeholders who reside downstream— and gain their design feedback. When you're in DFU mode, you will avoid the perils of the unforeseen. Design and, if necessary, redesign with the end in mind and try leaving a little bit of extra space to make any future DFU efforts more navigable. I hope that by working with Design007 on this idea, we can start an industry-wide discus- sion about DFU, and how this can help all of the stakeholders involved in developing elec- tronic products. Feel free to drop me a line, and let's get this conversation going! DESIGN007 Kelly Dack is an IPC CID instructor with EPTAC. He has over 30 years of experience in PCB design. To contact him, click here.

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