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24 DESIGN007 MAGAZINE I DECEMBER 2020 Feature by Chris Young THE GOEBEL COMPANY PCB design is more than a short sprint to the finish line; it is a journey best suited for the prepared adventurer. According to a study by Lifecycle Insights, the average PCB design project requires 2.9 respins. These respins can cost anywhere from tens of thousands to mil- lions of dollars—each! As an engineer/business owner, I find re- spins frustrating because I would rather spend my time and money applying scientific prin- ciples inventing, improving technology, and solving problems. I am not an advocate for perfectionism, but rather I focus on becoming a better adventurer. Sometimes I get to taste the sweet wine that is a single spin PCB. As fellow adventurers, let's discuss some top- ics that influence unnecessary return trips on our PCB design journey: simulation, technical reviews, and interest in PCB design. I like to say, "A sim in time will save dimes, especially on the assembly line." Yes, it's true: Circuit simulation guides PCB design decisions and helps avoid costly mistakes. A customer of mine ran into a simple problem of misapply- ing design reuse, which could have been easily caught if a simple simulation had been per- formed. They were using a simple NPN tran- sistor to drive a 12V relay in a previous design and decided to use the circuit design for a new 5V design. The new product passed certifica- tion testing, and all design documents were locked down in configuration control with the regulatory authority. The first assembly run immediately began to see failures in production testing—many more failures than were allowed by the reg- ulatory authority. The transistor that worked well for the 12V design did not work for the new 5V design. A simple Spice simulation performed as part of the root cause analysis clearly showed the transistor did not have suf- Cutting Respins: Journey to the Single-spin PCB

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