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Design007-Sept2019

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100 DESIGN007 MAGAZINE I SEPTEMBER 2019 en wrong by someone who does it successful- ly! Overall, I think IPC has done a good job of being a "fast follower" with specifications. Members can be quite anxious to get a new re- vision out to reflect new needs, and IPC itself is pushing hard to turn revisions more quickly to keep up with the pace of change. Shaughnessy: You're also a flex instructor at various industry conferences. What are some of the biggest challenges that your attendees are facing with flex and rigid-flex? Koop: The biggest challenges we see are pack- aging and component related. As products get smaller and denser, making boards thin enough, and being able to bend or fold them into the final assembly can be a challenge. This leads to making material selections to make the parts very thin and flexible. BGAs are another challenge. The sub-0.8-mm BGAs are driving smaller pads and holes and mi- crovias. Large form factor BGAs have so many I/O points, which creates big challenges for de- signers to fan out the entire pattern. This often drives very fine lines and extra circuit layers. Shaughnessy: Is there anything you'd like to add? Koop: This is a great industry to be a part of. We get to see all of the latest and greatest technology advances because circuit boards are what makes them happen. I would also encourage more young engineers to get involved. We are seeing the exit of many very experienced and talented designers as they retire. New designers are tak - ing their places but have not had the opportunity to learn from their senior counterparts. The key to success for new designers will be to reach out both internally and externally to learn. Take advantage of the opportunities to mim- ic other successes and avoid previous failures. There are lots of resources out there to help. Shaughnessy: I appreciate your time. Thank you. Koop: Thanks, Andy. FLEX007 mon. Flex provides a lot of advantages over a rigid board and discrete wiring. My initial ad- vice would be to gain an understanding of the similarities and differences. The key differences are unique materials and a variation in material movement, which can impact alignment. I often hear comments like, "But you did it on one of our rigid boards…" This is when we talk about how to adjust the design for flex. And as you noted, talking with a flex fabricator is key. Attending flex seminars can give you a quick head start as well. A good designer understands that flexibility brings advantages, but also some design considerations. Shaughnessy: Some design teams say that they almost always exceed certain flex standard rec- ommendations, such as for bend radii in 2223. Do you think IPC flex standards will ever "catch up" to where the industry is now or is that not necessarily the standards organization's role? Koop: Bend radii is probably one of the most commonly exceeded guidelines. The guide- lines are intentionally set very conservatively to stimulate a discussion. Every situation is dif- ferent; in some cases, a very tight bend radius can be very successful, but it may lead to prob- lems in others. Understanding the environment and specifics of the design are key. I don't know that the standards will ever "catch up," as you mentioned. While we do our best, technology continues to advance quickly. As early adopters, some designers are willing to take risks, but others are not. As new tech - niques are more widely adopted, they get in- corporated into a specification. It is a balanc- ing act, as we do not want to "legitimize" a questionable technique by including it in the specification before we know it is viable. Some- times, the fabricators are developing process techniques to accommodate designer's needs; some work out, but others do not. We want to see these processes reaching acceptable man - ufacturing or production readiness levels, and then we incorporate them. There are times where we hear comments to the effect of, "That will never be done," which tends to be a red flag for me. We are often prov -

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