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12 DESIGN007 MAGAZINE I OCTOBER 2018 your suppliers, you should have a basic understand- ing of IPC standards because that is how you're going to communicate your intent to your fabri- cator and assembler. At the same time, you need to fully comprehend what you are giving to your sup- pliers and what you are stating in your fabrication and assembly drawings. Are you correctly stating your fabrication or assem- bly notes? Do they make sense? Do you have all the required information listed to fabricate your PWB or assemble your PWA successfully? Do you have statements in your drawings that conflict with one another and could cause confusion? Worse yet—and I feel this is the root of the problem—do you understand your company's documentation details, or are you just "rubber stamping" your documentation because "that's how it's always been done?" These are some of the questions that come to mind when I think about bad data being handed off. Board design construction is key for success and getting the details correct is paramount. Many times, bad data is given because people are not paying attention to the details. Some designers simply don't know what they don't know and pass on bad data. In my experience, when you get into pro- duction runs with a top-tier supplier, they will not change or modify your data without per- mission. If you send a job over to them with issues, concerns, or missing data, chances are it's going to be put on hold. By the time you receive any feedback that your job has been put on hold, it could be five or more days lost in a schedule before you can address these issues flagged by the supplier. For many com- panies, that's a huge negative hit. The sad thing is that this usually stems from something that could have been easily mitigated up front in the beginning stages of your design with the supplier. Shaughnessy: Communication is the key, as we keep hearing. Chavez: Exactly. Let's discuss PWB classes, for example. If you don't have the requirements for Class III implemented in your design, but you ask the supplier to build to Class III, the sup- plier will kick your data back and say it's phys- ically impossible and your board isn't designed correctly for it. Then what do you do? Find a board shop somewhere that can build it once if you're lucky, or do you go back and redesign your board appropriately for a Class II design? That's why it's paramount that you understand IPC specifications and bring in your fabricator at the beginning stages of the design process. You should discuss stackups and all the details that make up your board depending on if it's a Class II or III design. This is one piece of infor- mation you need to know before starting—not something you find out afterward when your design is finished. By engaging your suppliers early in the design stage, you'll ensure that everything aligns, is cohesive, and meets the basic indus- try IPC standards to make the smoothest tran- sition from design to fabrication, assembly, and test. The transitions could be from you as a designer to the manufacturer, or from the fabricator to the assembler, with the least amount of resistance. Then everything is opti - mized. This is why three perspectives have been identified for a successful design that must be met: layout solvability, performance (routing solvability that includes signal and power integrity), and DFX (manufacturabil - ity). I refer to this as the "Designer's Trian- gle." The end result is making the first revision work! Shaughnessy: We keep hearing CAM depart- ments complain about receiving bad data— even from senior designers who know how to design a complex board. Chavez: Just because someone has a senior designer title doesn't mean they truly compre- hend what they are doing or are paying atten- tion to all the details. I've come across design- Steph Chavez

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