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F E AT U R E A RT I C L E by S te p h e n V. C h a vez , S i e m e n s E DA Setting Design Constraints Effectively PCB design requires controlling energy within the medium of a PCB. We control the chaos of energy by implementing and utilizing physical and electri- cal rules, known as constraints, along with a specific struc- ture and material(s) that make up what is known as the foundation of the design. These rules govern everything within the PCB structure and generally fall into two camps: performance and manufacturability. Setting this foundation correctly is extremely important and the key to success. At times, especially with very complex designs, it's no easy task to make sense of these rules while creating and implementing these design constraints. It can be daunt- ing and time-consuming. How many times during the ini- tial phase of the design process have we heard project management ask, "What is taking so long? Why haven't you started placing components and routing? Why do you even need constraints?" I'm sure you can relate to such questions. The goal for any PCB design is to be "correct by construction," where you have the highest potential for first-pass success. This means that revision 1 works with no res- pins required, and there are no interrup- tions in the process of getting the prod- uct to market as fast as possible. This is accomplished by implementing and utiliz- ing design constraints along with indus- try best practices, which are vital toward achieving PCB design success. Design constraints are typically derived from customer requirements. Depending on the intended function of the end prod- uct, how it needs to function, and under what conditions it needs to operate are the keys to deriving the specific details of the actual constraints to be implemented in your design. Make sure you work closely with your manufacturers (both fabrication and assembly) from the very beginning of the project and throughout the design pro- cess. I cannot stress enough that close col- laboration with your manufacturers, also known as your external stakeholders, is key to downstream success. I have always stated that PCB design is like creating a small city. In every city, there are rules that everything must follow or be governed by so that the city functions prop- erly. So, let's talk about something that can make or break your PCB design: setting up your design constraints. I know, I know, it sounds boring, but trust me, getting this right will save you tons of headaches and potentially reduce the need for respins later. Think of design constraints as your PCB's rulebook. They're like the guardrails that keep your design from going off a cliff. Get them right, and your board will work great and be manufacturable. Get them wrong, and your wallet won't be happy, your schedule will be blown, and you'll be required to respin your design. How Do Design Constraints Come About? Design constraints are derived from the customer (project) requirements and should be created early in the project, 24 DESIGN007 MAGAZINE I JULY 2025