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How to Describe Data Formats
Gerber data and other XY languages use a standard method for describing the data format. Two examples include:
"2,3 leading inch" or "3,3 trailing metric". The first number specifies the whole digits used. The second parameter states the precision. "Leading" and "trailing" pertain to the zero suppression. And the last part of the description indicates the units. Refer to the above sections if these concepts seem unclear.
When designing CAD data for Gerber output, it is important to keep the following in mind:
All pads should be flash as opposed to draw data. This serves to minimize file size, reducing computer processing time and allows us to extract net list information for electrical test. If drawn data is supplied we must convert it which again leads to the potential of human error.
Create polygon fills ,i.e. plane areas, using the largest aperture possible to provide the required resolution. Do not use a cross hatch fill pattern when producing a solid fill, and do not overlap fill segments by more than 1mil. Failing to observe this will create exceedingly large files. We have received files which, after the step and repeat process, are so large that they require an entire shift just to photoplot.
Remove any text, targets and company logos from outside of the board area. While these may be useful if you print copies of each layer for your files, they must be removed for the step & repeat process and do nothing more that add extra work at the CAM stage.
Board Outline Data Standards Guide ©Copyright 1995, FASTechnologies, Inc.
PURPOSE
The standards herein are intended to guide the PCB designer in defining PCB profiles in a manner consistent with the needs of the manufacturing process. CAD design files created in accordance with these recommendations are directly usable by CAM systems, thus aiding manufacturers in accurately making the designer's PCB.
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