IPC International Community magazine an association member publication
Issue link: https://iconnect007.uberflip.com/i/1543955
80 I-CONNECT007 MAGAZINE I MARCH 2026 PCB manufacturing supplier stakeholders. So, in essence, how we flood a layer matters just as much as why we do. Positive vs. Negative Artwork Once CAD/CAM was adopted for PCB design and artwork generation, planes on PCB layers were mostly created in a negative context, meaning that power plane artwork used to etch the PCB layer was created in reverse of "what you see is what you get" (WYSIWYG). Much of this was a carry-over from the tape-up days; considering the ease of ap- plying black, spoked pad thermal relief to a clear sheet of Mylar, anything appearing black would result in etched copper, including dusty, stray tape we'd call boogers. CAD tools evolved to create artwork this same way: pads and thermal relief spokes were quickly "flashed" onto the artwork film to create the pho- totooling. Back then, our FIRE9000 photoplotters were fed from files recorded on large magnetic tape reels, which had to be hand-carried to the PCB fabricator. Sometime in the 1990s, CAD tool creators must have had a collective thought: "Why are designers thinking in negative imagery? Let's simplify their lives and let them design copper with WYSIWYG graphic data." At this point, designers could truly "see" the copper they were designing, modify colors, and check for shorts more easily. I loved this transition, but our CAD tool output routines and suppliers hated it. The term "pouring copper" was created; it seemed simple enough and was very pleas- ing to the eye, but the size of design databases exploded. We were creating positive copper pour outlines, and when we thought we had them ready to flood, we hit "pour all," and our software began constructing tool paths to fill the outlines. The time it took for the software to accomplish this seemed endless. I remember finishing a design late one evening, hitting "pour all," and setting my alarm for 2 a.m. to wake up and check its progress. If something went wrong, it had to be corrected, and the flood routine had to be restarted. Hours were spent creating TA RG E T C O N D I T I O N