Issue link: https://iconnect007.uberflip.com/i/1500943
34 DESIGN007 MAGAZINE I JUNE 2023 How Tolerant is Your PCB Design Layout? Have you ever been to traffic school? Years ago, I sat in a room with other offenders lis- tening to rules about driving that I thought I already knew. It all seemed quite boring until we got to the slideshow of actual images of accident scenes. ese images depicted the potential cost of operating a vehicle system outside of the acceptable limits. Similarly, PCB designers cause accidents caused every day by operating their layout tools on cruise control. PCB designers are being given the "keys" to PCB layout tools with default settings they do not understand, producing data output to be supplied to PCB manufacturing stakeholders whose capabili- ties are off their map. Fabrication and assem- bly stakeholders see the real-world cost of operating outside your EDA tool's limits in the form of shorted connections, hole break- out, non-wetted leads, poor solder fillets, and tombstoned components. You can see some of these non-conforming images for yourself in the PCB acceptability standards IPC-A-600 and IPC-A-610. e current buzz about using artificial intel- ligence for PCB layout could compound the issue of PCB designers not understanding global limitations, and could drive the PCB layout process autonomously. From what I gather, these visionaries do not appear to be partnering with global manufacturing supplier constraints in mind. Some are partnering with costly, smaller scale, onshore fabrication and assembly services which specialize in proto- type quantities. We in volume production oen hear from our customer's project management team leaders who want to scale their assem- blies without loosening design constraints: "Well, our proto shop never complained. Why are your suppliers seeing issues now?" 'Traffic School' for PCB Design Engineers Have you ever attended a traditional dra- ing school? Surprisingly, it is possible to earn a four-year electronics engineering degree with- out ever taking a design draing course. Our brilliant EEs, young and old, seem to know everything about "design automation," elec- tromagnetic fields, physics, and how to make electrons flow. But expecting them to pick up a CAD tool and create a manufacturable PCB design is like giving an inexperienced driver the keys to an autonomous vehicle not set up for busy traffic. Without any training, they are led to believe the intuitive settings will fin- ish the job with little understanding of what's really required behind the scenes. A meaningful, thorough understanding of manufacturing tolerance specification is required to create a successful PCB design. A PCB is a component which must perform by interfacing with hundreds or thousands of other mechanical component part features, all while supporting the electrical requirements of the design. Remember, nothing is perfect; everything has a tolerance. It is the job of the PCB designer to consider cost and perfor- mance constraints from all the project stake- holders for the design to achieve success. Yes, Figure 4: Three examples of data "car crashes."