Troubleshooting from Your Design to Your Manufacturer - Building Open Source Hardware - page 233

File Types for Effective Communication
Once you've made sure your design uses widely available parts, you need to confirm that
you can generate files for your design in a format that's compatible with your potential
manufacturers. This is really part of the process of selecting a manufacturer, so we'll dis-
cuss it more later. If your manufacturer is also assembling parts on the PCB, it will gener-
ally need a file that contains centroid data. I cannot stress how important this file is. The
centroid file information gives the location of each component to be placed on the circuit
board. This file is commonly a .CSV spreadsheet file that specifies the X,Y coordinates of
each part in relation to one corner of the PCB. A typical centroid file includes the coordin-
ates shown in Table 13.1 .
Source: Centroid Data for PC Board: “SensorMoteSMT_V1.1.brd” as of: 4/19/13 3:45
P.M .
Table 13.1 A Centroid File
Any decent circuit board layout software should be able to automatically generate the
centroid data. The file should also include the coordinates of the fiducial marks that you
included on the PCB. The fiducial marks are critical for assembly. They give the auto-
mated assembly equipment a reference point to orient the robotic part placement device in
regard to the circuit board ( Figure 13.2 ).