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February 2016 • The PCB Design Magazine 65 measuring and manually reconstructing the drill data from it, in a laborious and error-prone process. Don't do this—have mercy on the poor CAM engineer! Note that the considerations in this chapter apply whether the drill files in your fabrication data sets are in NC or Gerber format. (In Chapter 4 in this series, we argue that Gerber is by far the best choice). Whatever format you choose, the bare minimum is that you create a separate file for each span, and for plated and non-plated holes, and that you clearly indicate which is which. These requirements for drill data also hold true for rout data. Even though drilling and routing are very different fabrication processes, the difference between them is largely irrelevant when they are viewed as fabrication image data: both simply indicate where material is removed. Indeed, the fabricator may very well nibble a slot in a rout file, or rout a large hole. In conclusion, the fabrication data must specify what the fabricator must fabricate. The fabricator will decide how to fabricate it. And remember: Put plated and non-plated holes in separate files. This column has been excerpted from the Guide to PCB Fabrication Data: Design to Fabri- cation Data Transfer. Karel Tavernier is managing direc- tor of Ucamco. Karel has 30 years' experience in software and imaging equipment for the PCB and electro- nic printed packaging industry, in- cluding sales, service and R&D. Figure 1: A drill map. It may be useful, but it's not a substitute for drill data. the gerBer guide, chapter 6