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Design007-Jan2020

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36 DESIGN007 MAGAZINE I JANUARY 2020 As a PCB manufacturer, we receive hundreds of PCB layouts represented in Gerber format every week. As you might expect, they're not all created equal. Some of the layouts check every box and roll straight into manufactur- ing, while others need work before they can be sent to the production floor. We affectionately refer to these layouts on occasion as Etch-A-Sketch designs, meaning that they did not adhere to best practices nor pay close attention to detail during the layout phase. And yes, sometimes these designs really do look like they were created on a toy from the '70s and not in a CAD tool. We recognize there are many good reasons for not-quite-ready-for- primetime designs to be submitted, such as: • A designer lacking layout experience • Looming deadlines and rushed design processes • A lack of attention to the details • A need for something to test in a hurry Often, these issues create delays and issues with yield or reliability. They can be avoided before they cause problems with your budget and production schedule. Here are some best practices for doing so. Use the Tools in Your CAD Program You can represent a feature in your design by almost any means you'd like, but adhering to a few best practices leveraging the many useful functions in your CAD design tools can help eliminate confusion for your PCB manufac- turer. For example, you can represent slots as overlapping drilled holes in your design. It is a common practice, but it creates two potential issues for the manufacturer: 1. If left as is, it can create broken drill bits impacting yields and quality of the product. 2. The other possibility is that the tooler corrects the issue during manufacturing, which is a very inefficient process. Most software for PCB layout offers the capa- bility to make a slot and have it contained on the drill layer of the Gerber files. Another common design issue comes in the form of circles drawn on a layer to rep- resent non-plated mounting holes. Your manufacturer may easily interpret this representation to mean you want cop- per circles on your PCB. Creating the mounting holes in your design tool and assigning them the plating type that you need is a much bet- ter approach. This will ensure you receive the non-plated mounting holes you want, not copper circles, and it doesn't take any more time. Design Tips for Layout Connect the Dots by Bob Tise and Matt Stevenson, SUNSTONE CIRCUITS

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