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FEBRUARY 2024 I DESIGN007 MAGAZINE 63 Avoiding Parts-Related Manufacturability Pitfalls 2 Issues with parts fit are one of the most fre- quent causes of delay and cost overruns. ese are five methods to avoid common, parts- related manufacturability issues. • Pay close attention to pinhole size. It's important to check component physical dimensions, take dimension tolerances into consideration, and account for varia- tion that can impact fit. In addition to watching part sizes, pay close attention to the minimum, nominal, and maximum material conditions for the original part. • What to do when the land pattern differs from pin size. One of the most frustrating mismatches with alternate through-hole parts is when the land pattern matches, but the pin size is off. When designing the land pattern, the pin size and tolerance range for components can be found in the product datasheet. Use that information to plan the proper hole size. • Datasheets can disagree with CAD software. Third-party CAD libraries can contain millions of different parts, so dis- crepancies are inevitable. When the data- sheet and the library part don't match up, address the delta before submitting the design. Always check any library part for accuracy before using it the first time. • Pay attention to pinouts when using alternate vendor parts. Even if pin size and through-hole size are a con-firmed match, and even if solder joints appear sound, a part can still not work as expected. Similar parts with the same footprint might look like they should act identically, but they won't always have the same pinout. Each transistor has a gate, drain, and source, but different manufac- turers can differ in what goes where. • Be aware of mechanical fit. Physical size of a component can keep parts from fitting into designated spaces. MMC body size should be the rule, so pay close attention to the tolerance range. As parts get larger or are sourced from multiple vendors, footprint size may need to expand consid- erably to accommodate all dimension and tolerance variables. Designing for Efficient Drilling 3 Drilling is one of the most fundamental steps in printed circuit board manufacturing. Designers can take several steps to improve the efficiency of drilling and help cut down on errors: • Reduce the variety of through-hole sizes from the PCB design, allowing fewer tool changes. • Avoid unnecessary design elements that can increase the chances for burring. Among these are higher copper weights and anything that can keep layered boards from sitting flat against each other. • Minimize hole sizes to reduce the amount of material that needs to be drilled and removed from a board. In addition, a clever design can optimize spacing between the holes, which reduces the amount of motion a drill needs between drilling. ese design optimizations might seem minimal, but their savings can add up for large manufacturing runs. • Optimize the through-hole and pad sizes to facilitate the drilling process and ensure high-quality PCB manufacturing. Accurate drilling is key to a reliable and effi- cient board, and by focusing on these essential elements, designers can produce PCBs with fewer errors and failure rates. Choosing the Right CAD Tool 4 Each designer has different needs from a CAD tool, and needs can vary by project. We recommend evaluating CAD soware using the following criteria: • Price: When evaluating tools, make sure they are actively maintained and have an