Issue link: https://iconnect007.uberflip.com/i/1511130
48 DESIGN007 MAGAZINE I NOVEMBER 2023 prise to make a clean getaway. e scene ends with Scotty's sarcastic comment about the overly complicated computer on the other ship, "e more they overthink the plumbing, the easier it is to stop up the drain." I've always liked Scotty more than anyone else on that show because, let's face it, he was an engineer. But with this movie, I really came to appreciate his common sense and, if I'm being honest, the sarcasm he used to describe it. Even in a universe where transporter beams and deflector shields are as common as the Keurig on my kitchen counter, Scotty still knew when something was too com- plex to be practical. Wise words, and a lesson here for everyone. In our industry, we design and manufacture amazingly complex elec- tronics. I've laid out circuit boards for everything from large computer systems to small wearable devices, and even though they have had different degrees of design dif- ficulty, they all had the same common objec- tive: ey all had to work correctly once they were built. To accomplish this, circuit boards are designed according to several standards to ensure they can be manufactured and work as intended. If you are in the design and layout part of this business, you are no doubt already familiar with many of these different standards. But once you go beyond the industry standards and into the realm of rules, processes, and pro- cedures, the water can get murky. Take, for instance, the rules and constraints we use in the CAD system to design the board. ese are wonderful tools and an essential lifeline for both design and manufacturing, but they can work against you if you aren't careful. Let's look at a couple of ways this can happen: • Too many rules: Our design databases can become afflicted with the same problem that Scotty alluded to, where overthinking the plumbing can stop up the drain. For example, instead of defining a unique rule for each net and thereby managing thou- sands of rules, group your nets together according to their needs and assign them all to a single net class. is will save you time and system resources. • Lack of understanding: It is important to be very familiar with what your PCB design CAD system will do with the rules you feed it. I've seen some databases where rules have clashed with each other, like keep-out areas that block a cop- per pour that is supposed to connect to a specific net in that area. If you don't rethink and redefine the rule, you have to either break it or turn check- ing off. • Old data: Sometimes CAD databases get inun- dated with rules they simply don't need. is can happen when people read in stock rules from their corporate library, fail to clean out older rules already in their databases, or both. I've opened up some designs that have rules not even intended for that design but reside in the database, taking up additional resources. Mismanaged design rules can overload your system as well as generate unexpected results. I'll summarize here by saying it is imperative that PCB designers know what rules are loaded into their systems and optimize those rules for the best performance of their design tools. But design rules are just part of the murky waters I described earlier. Now, let's look at processes and procedures for a moment. Processes and procedures are an essential part of any design department. ey organize the workflow, ensure that the proper steps, checks, and balances are in place, and serve as a guide to the users in the department. How- Mismanaged design rules can overload your system as well as generate unexpected results.