Best Practices: Footprint Design and CAD Library Management


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The I-Connect team spoke with Altium’s John Watson about the hurdles surrounding footprints and footprint design. John talks about how being proactive and improving the CAD library can better QC processes and help protect against footprint difficulties.

Andy Shaughnessy: I’m here today with John Watson from Altium to discuss footprints, footprint design, and what can be done to achieve best practices. This came about because we recently conducted surveys asking for design problems. The results came mainly from designers, and around a quarter of them said footprint issues were a big problem.

John Watson: There’s a real conflict in a lot of companies. They want to get their product to market. So, I think that the first issue that comes in with anything in a design is this conflict between the management schedule and the design schedule. If you’re creating a new component, for example, number one is that component needs to be put into quarantine. It’s not used in new designs. It needs to be put into quarantine and checked. There’s such a rush to say, “We’ve got to get this done and get it out.” And there’s just too much going on in a design to catch things that are wrong like that.

Barry Matties: How long should it be in quarantine?

Watson: It stays in quarantine until a couple of processes are completed. Number one, there is a QC process that’s done on that component, and that QC process is actually multi-level. There will be different steps involved. For example, if you have a new component, you bring that component in or that footprint in, and you verify that footprint to the datasheet. On this first level of QC, you want to set up your verification documents to that footprint. What are we going to be looking at? We’re going to be comparing this footprint to the datasheet, we’re going to be looking at IPC standards, whatever the standards are that you’re going to be lining this footprint up with. That’s going to be your first level of QC, but I’ve actually seen where there’s a second level of QC that’s done. Once that part has been verified to the datasheet, that part then goes into what’s called the prototype status; what it does is that component is then put onto a PCB, kind of a live test.

When that board comes back with the component on it, you look at it under the scope to see if there are any issues with the soldering. It’s like a real-world environment. Those are the two levels of QC. Number one, you compare it to the documentation, and then you have a real-world environment that you take it through. That step and those processes are what you go through. That way, you’ve actually had both sides of it: You have your side of it, and then also the assembler’s side of it. I’ve found that a lot of times, believe it or not—I know it’s a shocking comment I’m about to make—but datasheets have been known to be wrong. VPs have no understanding of what it takes to put a PCB design out—the steps, the checks that you have to do, all these different things. Often, that’s lost in this whole process.

To read this entire conversation, which appeared in the February 2021 issue of Design007 Magazine, click here.

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