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58 The PCB Design Magazine • October 2015 The Gerber Guide chapter 3 by Karel Tavernier uCAMCO It is possible to fabricate PCBs from the fa- brication data sets currently being used; it's being done innumerable times every day all over the globe. But is it being done in an efficient, reliable, automated and standardized manner? At this moment in time, the honest answer is no, because there is plenty of room for improvement in the way in which PCB fabrication data is currently transferred from design to fabrication. This is not about the Gerber format, which is used for more than 90% of the world's PCB production. There are very rarely problems with Gerber files themselves; they allow images to be transferred without a hitch. In fact, the Gerber format is part of the solution, given that it is the most reliable option in this field. The problems actually lie in which images are transferred, how the format is used and, more often, in how it is not used. In this monthly series, I will explain in detail how to use the newly revised Gerber data format to communicate with your fabrication partners clearly and simply, using an unequivocal yet ver- satile language that enables you and them to get the very best out of your design data. Each month we'll look at a different aspect of the design to fa- brication data transfer process. This month we'll look at the PCB profile, or outline. Chapter 3: The PCB Profile (or Outline) The profile defines the extent of the PCB. It separates the PCB from what is not the PCB and is an essential part of PCB fabrication data. Without the profile, the PCB simply cannot be fabricated. The profile must be properly and precisely defined. The profile defines a simple region in the 2D plane. The proper way to do this is to speci- fy a closed contour: The inside of the contour is the PCB, and the outside is not. It is that simple. Note that such a simple region is solid, wi- thout holes. By definition then, a profile cannot have holes intentionally placed within it. These are superfluous and represent an unnecessary and complicated duplication given that drill holes are well defined in the drill/rout file. One can view cut-outs in a PCB as still part of the PCB, just as much as the drill holes are. A contour is defined by the Gerber spec as follows: "A contour is a sequence of connected draw or arc segments. A pair of segments is said to connect only if they are defined consecutively, with the second segment starting where the fi rst article

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