Centroid is the special file for assembly used for quickly programming the assembly machines. This is also known as aka Insertion, Pick-N-Place, or XY Data. Some of the CAD tools will automatically generate this file and some not, but you may need to modify the file and then generate the Centroid file. The Centroid file describes the position and orientation of all the surface mount parts, which includes the reference designator, X and Y position, rotation and side of Board (Top or Bottom). Only surface mounting parts are listed in the Centroid.
A FEW HINTS OF THE CENTROID FILE
Every now and then, we get questions on the centroid file (AKA Pick and place file or SMT locations file). Most CAD applications will create one for you.
If you want to poke around and need some hints on what’s what you can download our Understanding the Centroid file. Here are a couple of illustrations from the guide. Fist, the point of origin needs to be centered in the part.
It should be centered in a box that contains the outline of the pins as well as the body of the part. The chips on the left are easy. The connector, to the right, is a little more ambiguous, but as you can see, it’s centered around the imaginary box containing the area.
That would place the cathode left for diodes and the positive side left for electrolytics and other polarized two lead parts.