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18 DESIGN007 MAGAZINE I MAY 2019 Timing is everything in life and complex PCBs. —Anonymous The following is an excerpt from Chapter 5 of The Print- ed Circuit Designer's Guide to… Executing Complex PCBs written by Scott Miller of Freedom CAD Services. It is a fact that complex electronic compo- nents will not function properly unless a spe- cific set of physical conditions is met. Active components and chipset performance require- ments are presently being pushed to the edge. Their capabilities are only limited by the physi- cal geometry and electromechanical properties of the materials that interface with them. We have come to the point where component chip makers are supplying 100-page user manuals describing not only what a chip can do, but also the layout, assembly manufacturing, and environmental operating criteria required for it to perform. Careful attention to these rules must be considered for the successful opera- tion of the individual component within a cir- cuit and the performance of the circuit in rela- tion to all circuits on the PCB. One designer said: "Signal and power integrity analysis is a key way to ensure that the board design will meet the performance requirements on the first pass. By using software to simulate the effects on signal and power integrity, our customers spend less time in the lab trying to find out why their design isn't performing as expect- ed. Performing in-process simulations enables problems to be identified and corrections to be made earlier in the design process, thus mini- mizing the collateral damage. The more items you have to move to address a problem, the more time this takes." Starting the Physical Design Process The next step is entering the execution phase of the board design process, which involves implementing all of the elaborate pre-planning that has already taken place. Layout Processes Many companies employ a number of spe- cialized layout processes. One senior project engineer explained his process for very com- plex boards that he has refined over many years: "I work with larger OEMs, and this is what I tell them. I go through their design and cre- ate libraries of templates to give us predictabil-

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