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22 DESIGN007 MAGAZINE I JUNE 2018 the system level. In current-generation tools, the signal verification process for a multi-board design involves exporting pin lists that include net names for each board connector and cor- relating the net names to the master list of net names. In many cases, it's also necessary to manually verify each board connector's signal name. With mechanical engineers and board designers working with disconnected systems it's difficult, if not impossible, to intelligently manage connectivity and changes between boards. Using a spreadsheet or some other dis- connected document to manage the large num- ber of interconnects between the PCBs in the system is time-consuming and prone to error. When mechanical engineers have inaccu- rate information on the electrical design or electrical engineers have inaccurate informa- tion on the mechanical design, the result in many cases is that batteries don't fit, mount- ing screws create shorts against PCBs, and connectors don't mate with packaging open- ings. Improper management can easily result in wasted product development time, scrapped boards and slipped schedules. The combination of increasing capabilities, shrinking size and more complex external shapes means that electronics must increas- ingly consider the shape of the package while the mechanical design is more dependent than ever on the physical aspects of the internal electronics. Multi-board designs make ECAD- to-MCAD translation more difficult because of the need to communicate the position of con- nectors and other common points between the boards. Yet in the current generation of tools, the collision-checking process involves exporting placement information, usually in IDF format, for each PCB to a mechanical engineer for assembly analysis. PCB design tools have con- tinued to focus on working in 2D on one PCB at a time, with the electrical work done in 2D and then the 2D design being exported into 3D mechanical design software where the boards are positioned and checked for interference. The PCB designer is unable to, for example, position two boards on top of each other to see how they fit together. This is normally done after the board design has been exported to the mechanical design tool. Interdependencies between interlocking boards and their enclo- sure in complex products are critical. The limitation of this approach is that if a problem such as an interference is identified, it's necessary to go back and forth between two different environments—PCB and mechanical design—to try and solve it. The other option is for a PCB designer to use a non-native viewer to conduct their own analysis. It is estimated that 50% of complex products require at least one additional PCB fabrication to address elec- tro-mechanical issues. It is also very awkward to perform a high-level design study, such as Figure 2: Today's products are competing on style, size, weight, cost, and function. A product-centric design process should be optimized for competitive factors.

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