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FEBRUARY 2021 I DESIGN007 MAGAZINE 67 models (schematic symbol, footprint, and 3D model) to speed up their design process. Makers come to Octopart to find ideas for projects, conduct research, compare parts, and find the most economical way to acquire parts in small quantities. is includes using our BOM tool, which makes it easy to consoli- date your BOM into your preferred distribu- tors, thus reducing shipping costs. Hackers like our API because you can use it on projects for free. Makers also use our ECAD models a lot to save time and effort. Shaughnessy: What are your customers' big- gest issues related to footprints and ECAD? Lipman: Although there are a number of com- panies that promise high-quality ECAD mod- els in their marketing materials, engineers with money and careers on the line cannot trust the majority of free ECAD models. Engi- neers understand that symbols must be of high quality. Schematic diagrams exist to transmit understanding, and so engineers have devised symbols that have been in use for nearly 100 years to convey this understanding. ECAD symbols need to comply with this tradition, and with sensible standards in the field. Footprints should follow the manufacturer's recommendations. For standard package type parts, IPC-7351 standard footprints should also be provided. 3D models should follow a simple rule. ey should look like—and be the same size as—the actual part. And the best 3D part is "photorealistic," or at least has the right colors and shapes. Every part we build comes with a schematic symbol, PCB footprint, and 3D model. Every schematic symbol looks like it should, follow- ing the guidelines of IEEE 315-1975 and IEC 60617. We provide footprints that follow the manufacturer's guidelines, and when standard packages are used, we also supply three IPC- 7351-compliant footprints for different PCB densities. Every part is checked three times by electrical engineers before we release it as a "verified" model. And we do not release unver- ified models. Shaughnessy: Do you have any advice for designers who are having trouble with foot- prints? Lipman: Sure. Your best resources for help with footprints are: 1. The manufacturer's datasheet or land pattern drawing. In most cases, a manufacturer will have tested their parts with the land patterns in their tech- nical documentation. at makes this a pri- mary starting point for any footprint design. If you have a specialized use that involves tight geometries, close component spacings, or challenging thermal aspects, check with the manufacturer for literature or other advice about how to optimize your footprint for your application. 2. IPC-7351B. is IPC standard lays out equations for land pattern geometries that are optimized for man- ufacturing. is can be especially helpful if you cannot find any documentation for a part. In most cases, the manufacturer's recommenda- tions and the IPC recommended footprint are very similar. 3. Your PCBA assembly provider. Your PCBA assembly professionals are experts in their machines and processes. It is common to submit designs to the assem- bly house before production so that they can discover any issues and recommend remedia- tions. Similarly, during design, you should be able to reach out to them to get recommenda- tions for particular parts. Shaughnessy: Sounds good, Geof. anks for your time. Lipman: ank you, Andy. DESIGN007

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