Issue link: https://iconnect007.uberflip.com/i/1537388
54 DESIGN007 MAGAZINE I JULY 2025 When? Time is a Constraint Too Design constraints don't live in a vacuum. Tim- ing pressures often dictate how conservative or aggressive you need to be. Got a quick-turn pro- totype due in three days? You might need to relax certain constraints and communicate that to your team. Working on a Class 3 aerospace board? Bet- ter plan extra time for reviews and validation. A timeline is a constraint in itself. It can force compromises or call for tighter controls. Early clar- ity around the project schedule lets you tune your design rules appropriately. Where? Know Your Environment This question has two environmental facets: fab- rication and assembly environment and operating environment. Where will this board be built? Will it be a low-volume lab or a high-volume production line? Manufacturing constraint settings will differ drastically based on manufacturing capabilities. Where will it be used? In a cleanroom, a car engine bay, or maybe outer space? Some condi- tions require thermal constraint considerations, mechanical support, solder mask clearances, and more. A good rule of thumb: If the environ- ment can affect the board, it should influence the design constraints. Why? The Purpose Behind the Parameters This is perhaps the most important W. Why are you defining these constraints at all? The answer TA RG E T C O N D I T I O N isn't "because the tool requires it." It's because constraints protect the intent of your design. They enforce boundaries that ensure your layout matches the electrical, thermal, and mechanical goals of your project. Addressing this question can be an education for newer PCB designers. When you know why a differential pair needs 100-ohm impedance or why a 20-mil clearance is critical for 600-volt isolation, you don't just follow the rule—you understand it. That's how good designers become great. Summary: Constraint Context Must Match End-Use Requirements Setting up design constraints in your layout should feel like a handshake between you and your proj- ect team stakeholder. It should be a fulfilling con- versation—between design and manufacturing, and between function and feasibility. When you start defining rules with the 5 Ws in mind, you will begin to see constraints not as obstacles but as enablers of quality. DESIGN007 Kelly Dack, CIT, CID+, provides DFx centered PCB design and manufacturing liaison expertise for a dynamic EMS provider in the Pacific Northwest while also serving as an IPC design certification instructor (CID) for EPTAC. To read past columns, click here.