Issue link: https://iconnect007.uberflip.com/i/1537475
JULY 2025 I DESIGN007 MAGAZINE 27 » Plan your layer structure logically. This will depend on the design requirements. Once a PCB stackup is dialed in, validated, and agreed upon between user and supplier, lock it and don't change it. » Know the electrical and physical per- formance requirements that must be addressed, such as SI, EMI, PI, EMC, and thermal. The stackup will dictate which sig- nals go where within the stackup. Route signals adjacent to or between their appro- priate reference (GND) plane. Having and implementing a good strategy is key. » Keep power and ground planes tightly coupled together throughout the PCB stack and where they make sense. A good PDN is a must. Physical Rules These are considered the "city ordinance" rules: • Traces are like roads in a city. They need to be defined by their width and spacing per the requirements. Keep your traces from get- ting too close to one another and be mindful of trace parallelism. Every design is different; therefore, trace width and spacing will vary from design to design, depending on the requirements. • Components are like buildings in a city. They require real estate. Give components some breathing room. Don't crowd or congest component placement, making assembly dif- ficult or nearly impossible. DFM (MDD) must not be an afterthought when it comes to component placement. Do the analysis. • Keep components away from the board edges. Enclosures can drive rules as well. Again, DFM is key. Electrical Rules These are the "road and highway" rules: • Critical signals are like critical roads in a city that require specific attention and must be addressed first in the routing stage. Parame- ters such as trace impedance requirements, matched lengths, matched timing, custom topologies, and routing topologies must be prioritized and addressed first. • Regular signals are like secondary roads in a city. They are typically lower in priority when it comes to routing and addressed after all critical signals are routed and locked down. ▼ F i g u re 2 : E xa m p l e of a 1 6- l aye r P C B st a c k u p i n t h e c o n st ra i nt m a n a g e r.