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Design007-Jan2024

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50 DESIGN007 MAGAZINE I JANUARY 2024 If a copper plating thickness beyond IPC requirements is specified, that additional plat- ing can impact the drill diameter we choose. So, it's not as easy as using the IPC formula to calculate the minimum pad size. Unless you know what the fabricator will choose for a drill diameter, then you might be off on your pad size calculation, which is why partnering with a fabricator when you're beginning your design is very important. e last thing you want to do is complete your entire layout, release it, send it to get fabricated, and suddenly the fabrica- tor says, "You have to change the pad size." at can have a major impact on your layout, and you may have to allow exceptions to your annular ring requirements if you can't update your design. Another common DFM finding is copper spacing. Most people know how to design for half-ounce, one-ounce, or two- ounce copper on print-and-etch layers, but internal and external plated layers are not as simple. Plating and fabrication processes can vary when there are multiple hole structures like buried vias, microvias, plated through- holes, or epoxy-filled holes. ese features can impact the minimum spacing needed on the plated layers. Oentimes, internal and exter- nal plated layer design requirements are not straightforward because they depend on the way the board will be fabricated. Is it getting planarized? Is it getting button-plated? How much copper will end up on each plated layer aer processing? Not having enough spacing for fabrication can result in electrical shorts and low yield, so collaborating with the fabri- cator from the get-go is crucial. Frontloading this communication can prevent major hic- cups down the line. That's interesting. Even if the designers are following IPC specs, it's still possible to get things wrong if you don't work with your fabri- cator, because you may not be aware of their capabilities or limitations. Exactly. Boards are becoming so complex that you have to work with the fabricator now. On a simple single lamination, with only plated through-holes, the fabrication process is pretty straightforward. But when you start getting into multiple lamination cycles, inter- nal plated layers, and multiple-hole structures, it becomes more complex to fabricate. Fabricators joke about how designers get all the matched impedance stuff right, but they'll put a connector too close to an edge or a component in the bend zone of flex. It seems like these little board-level errors put many jobs on hold. Yes, there are many things that can put a board on hold. at's why having DFM up front is becoming so important. Many cus- tomers just expect it because they know that will catch most of the issues before they go into fabrication. So, we're trying to rise to that occasion and offer multiple solutions. Some customers just want a quick DFM, and that's good enough for them. Other customers want an in-depth review. By offering multiple solutions, we can provide that extra service. Laura, I saw you last year at PCB Carolina, and since then you've moved into a new job at a new company. Tell me about your past year. Shortly aer last year's show I transitioned to Summit Interconnect as director of applica- tions engineering. It's been an exciting jour- ney as I assumed the responsibility of leading a department focusing on recruiting and train- ing field application engineers. Our mission is to excel in technical support and customer ser- vice. Over the past year, I've enjoyed the pro- cess of establishing a department, introduc- ing new processes, and innovating the way we approach DFM for our customers. Traditionally, DFM has been a somewhat ambiguous concept in the industry. Design- Another common DFM finding is copper spacing.

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