Gerber format-PCB fabrication data-Circuit
Board Electronic Pcb
PCB fabrication data
PCBs are designed on a specialized electronic design automation (EDA) or a computer-aided design (CAD) system. The CAD systems PCB fabrication data to allow fabrication. Fabrication data contains a Gerber file for each image layer (copper layers, solder mask, legend or silk...). Drilled hole information is also transferred in Gerber but for historic reasons the Excellon format is often used. (Using Excellon rather than Gerber usually leads to copper-drill registration problems.) Typically, all these files are "zipped" into a single archive that is sent to the PCB bare board fabrication shop. The fabricator loads them into a computer-aided manufacturing (CAM) system to prepare data for each step of the PCB production process.
The .FileFunction attribute is the standardized method to do link each layer in the PCB with its corresponding Gerber file in the fabrication data. If attributes are not supported 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. This is very impractical as the customary link between format and extension is lost.
PCB Fabrication Data must comply with a number of rules: all layers must be aligned, a profile layer must be included, etc.
The CAD netlist can be embedded in the Gerber files. However, for historic reasons, netlists often are described in a separate file in IPC-D-356A, an electrical test format.
The material stack up, components and finishes are typically provided in informal text files or drawings. Ucamco recommends using a subset of IPC-2581 for this non-image information.
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