Editing Gerber format (section)

==PCB fabrication data==
[[File:Openbiosprog-spi PCB Kicad 0.1 (4935009830).png|thumb|View of a Gerber format file]]
PCBs are designed on a specialized [[electronic design automation]] (EDA) or a [[Printed circuit board#Design|computer-aided design]] (CAD) system.<ref name="EDA: Where Electronics Begins"/> The CAD systems then outputs [[#Guide|PCB fabrication data]] to allow fabrication of the board.<ref name=":0"/> Fabrication data contains a Gerber file for each image layer and drill span (copper layers, solder mask, [[Printed circuit board#Legend printing|legend or silk]]...) (For historic reasons drill data is also transferred in [[PCB NC formats|NC formats]] although Gerber files are often of better quality.)<ref>{{Cite web|url=http://www.wellpcb.com/news/creating-gerber-files-and-excellon-files-eagle-355.html|title=Creating Gerber Files and Excellon Files with EAGLE 3.55|website=www.wellpcb.com|access-date=2017-04-11}}</ref> Typically, all these files are "[[zip (file format)|zipped]]" into a single archive that is sent to the PCB bare board fabrication shop. The  fabricator loads them into a [[Printed circuit board#Manufacturing|computer-aided manufacturing]] (CAM) system to prepare data for each step of the [[Printed circuit board#Manufacturing|PCB production process]].<ref name="PCB layout data">{{cite web |url=http://www.eurocircuits.com/pcb-layout-data |title=PCB Layout Data |publisher=Eurocircuits |access-date=2011-11-26}}</ref>

The .FileFunction attribute is the standardized method to link each layer in the PCB with its corresponding Gerber file in the fabrication data.<ref name="OffWebsite"/>{{rp|Section 5.6.3 of the 202308 release of the Gerber Layer Format Specification}} 

If attributes are not supported, then only informal methods are available. A simple informal method is to express the file function clearly in the file name. Sometimes the file extension is abused to indicate the file function - e.g. .BOT for the bottom layer rather than the standard extension .GBR.<ref name="tavernier"/><ref>{{cite web |url=http://techdocs.altium.com |title=Altium TechDocs - Online Documentation for Altium Products |access-date=2019-12-27 |archive-url=https://web.archive.org/web/20190914073343/https://techdocs.altium.com/ |archive-date=2019-09-14 |url-status=dead }}</ref> In industry this is considered poor practice and engineers should use the appropriate X2 attribute instead.

PCB Fabrication Data must comply with a number of rules: all layers must be aligned, a profile layer must be included, etc.<ref name=PCBFabricationGuide/><ref name="EC 10 rules">{{cite web |url=http://www.eurocircuits.com/10-Rules-for-better-data |title=10 rules for better data |publisher=Eurocircuits |access-date=2016-01-06}}</ref>

The CAD netlist can be embedded in the Gerber files.<ref name="OffWebsite"/><ref name="Netlist KiCad">{{cite web |url=http://design.iconnect007.com/article/100982/ucamcos-gerber-netlist-goes-live-with-kicad |title=Ucamco's Gerber Netlist Goes Live with KiCad |publisher=PCB007 |date=2016-11-09 |access-date=2016-11-12}}</ref> However, for historic reasons, netlists often are described in a separate file in IPC-D-356A, an electrical test format.<ref name="IPC-D-356">{{cite web |url=http://www.artwork.com/gerber/netex-g/ipc356/index.htm |title=Using IPC-D-356 for Importing Net and Node |access-date=2011-10-16}}</ref>

The material stack up, components and finishes are typically provided in informal text files or drawings.<ref>{{citation |title=IPC-2524 PWB Fabrication Data Quality Rating System |date=February 1999}}</ref> In 2018 Ucamco has published a specification for an extension of the Gerber format to cover this fabrication documentation.<ref name="Fab doc final 007"/>