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Design007-Mar2025

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14 DESIGN007 MAGAZINE I MARCH 2025 it doesn't cost you anything to add these dif- ferent via structures in your layout tool, like these functions are magically there for you to use. en, when the customer gets a fab quote, they ask, "Why do I have a five-lamination- cycle board?" A big area for us is educating designers to help them understand how fabri- cation works, and that offshore they use very different processes than onshore. Funny you mention magic. A designer told me recently that PCB design was almost a magi- cal world, like Hogwarts, compared to manu- facturing, which is the real world. Dack: I wish I had that magical power. I teach the CID courses, and they include some IPC standards criteria. e IPC-2221 series design standard is oen misinterpreted by designers. ey start their first fab note with, "Manufac- ture for IPC-2221 or 2222." If we understand the specs, we can design for the 2221 series, and then manufacture to IPC-6012. Jen, would you agree that this standard covers a big part of the communication required to get a board designed and built? Kolar: Yes, those are helpful. But still, it must be translated to the manufacturer that, "Yes, I want it built to this, and by the way, designer, that means that you have to do this and this." What about all the other details that get screwed up in the fab notes? ere are common ones that people leave in their fab notes when cutting and pasting from other projects or previous ver- sions. When you're getting earlier stackups and iterating with the fab vendor, you have many possible controlled impedance options. If they all get le in the final notes, it confuses the fab- ricator. Or you have boilerplate notes intended for production versions that may want OSP vs. ENIG, but you're doing a proto run where it doesn't apply. ere are a lot of details in the fab notes that aren't necessarily covered by stan- dards, which can cause more confusion. What about my spacing requirements and any aspect ratio requirements? So, even if you're following the standards, there's still a lot of wiggle room and you can get into trouble? Kolar: Absolutely. As you go to really fine designs or rigid-flex, where you have incom- patible materials that expand and contract dif- ferently that you're trying to line up, it comes back to the fact that theory is only so good. ere's also what happens with actual mole- cules in chemistry. Dack: Yes, sometimes impossible constraints are inflicted upon the manufacturer. Kolar: Exactly. I do all our signal integrity and power integrity analysis work and spend a lot of time helping them fine-tune some tiny sig- nal that will never be manufactured anywhere near a tolerance that what we're modeling will matter. But doing that analysis helps you feel more confident that, because of the slop that will be there in manufacturing, it's more likely it will work. It's so easy for us to talk about customer chal- lenges. How do we communicate better? How can suppliers communicate their require- ments to designers better? How can design- ers better communicate to suppliers or any other stakeholder in the process? Kolar: It helps to have standardized design kick- off checklists that you can hand to the customer. You can review and ask questions that may trig- ger things they forgot to tell you to trigger: "By the way, there are mounting holes here, or we will need the test to fit in this enclosure, or this has 500 volts." You cover all the things that you otherwise might not learn until a month into the design process. Going over a detailed kickoff checklist with your customer helps both sides and makes sure that they're both communicat- ing all of the important parts. Similarly, you should have a fab readiness checklist for your fab vendor so you can find out what their capabilities are, and then verify that with provisional DFM. It is very easy to

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