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52 DESIGN007 MAGAZINE I JANUARY 2024 PCB designers fresh to the industry may think that once the schematic is loaded into CAD and routed out into XY data, the finished PCB is an "exact" copy of their XY data. at's not an unreasonable assumption for basic designs. Here, I'll outline some of a designer's considerations related to signal integrity as designs become more complex. A False Assumption? It may appear to the casual observer that PCB fabrication is "just" like PCB assembly. Even in casual language, when industry outsiders dis- cuss making printed circuit boards, nine times out of 10, they imagine the assembly process rather than the PCB fabrication process. It's New Designer's (Partial) Guide to Fabrication then a casual segue to consider that just as com- ponents are attached to a PCB with solder— but apart from that are unchanged from their raw form—the PCB itself is just that: a bonding of components unchanged by the manufactur- ing process. I've met many PCB designers and some EEs who slip into this assumption, espe- cially that they can create a stackup "exactly" from the base material datasheet. It's not a bad assumption on low layer count and simple low-speed boards, but as layer count and stack complexity increase in a design, it becomes increasingly necessary to know which layers are core or prepreg, which ones will press, and which layers the copper traces will press into. Experienced designers The Pulse Feature Column by Martyn Gaudion, POLAR INSTRUMENTS