To automate the placement of surface-mounted components on PCBs, a Centroid file must be created. In order for the machine to know exactly where and in what direction to mount components on a PCB, it uses a Centroid file. This is the content of a Centroid file:
1. Designator (RefDes)
2. Layer(top or bottom)
3. X location
4. Y location
5. Rotation
Designator (RefDes)
It will match your bill of materials and the markup on the PCB.
Layer
The term “layer” describes the top side, bottom side, or side of the PCB where the components are mounted. The top side and bottom side are frequently referred to as the component side and solder side, respectively, by PCB assemblers.
Location
X and Y Locations indicate the vertical and horizontal position of a PCB component relative to the board’s origin. The location is measured from the component’s origin to its center. The origin of the board is (0, 0) and is found in the lower left corner of the board when viewed from above. Even the flip side of the board references the lower left corner as its origin. The position values for X and Y are computed to the ten thousandth of an inch (0.000).
Rotation
An orientation of a electronic component’s placement is referred to as “rotation” if it is viewed from the top. 0 to 360 degrees is the range of the rotation. This perspective is used by all the upper and lower parts of the machine.
A Sample Centroid File
|
Designator |
Layer |
Location-X(mil) |
Location-Y(mil) |
Rotation |
|
R26 |
TopLayer |
784.252 |
-19.173 |
90 |
|
R29 |
TopLayer |
595.945 |
372.047 |
180 |
|
R28 |
TopLayer |
350.906 |
372.047 |
180 |
|
R22 |
TopLayer |
1028.347 |
-19.173 |
270 |
|
Q8 |
TopLayer |
1166.142 |
36.418 |
90 |
|
Z4 |
TopLayer |
845.276 |
-21.142 |
270 |
|
Z3 |
TopLayer |
967.323 |
-21.142 |
270 |
The following are procedures for producing a Centroid file using various software:
1.Eagle Software
1) To produce the Centroid file, run mountsmd.ulp.
By selecting the menu, you can view the file. Run ULP after choosing File from the drop-down menu. The program will create the.mnt (mount top) and.mnb files rapidly (mount reverse).
This file stores component locations and PCB origin coordinates. It’s a.txt file.
2.Altium Software
1) Create an outjob file. This creates an output generator.
2) Click File. Click Assembly Outputs, then Generates Pick and Place Files.
The output will appear in the Pick and Place Setup dialog box once you click OK.
Note: The output produced by the Pick and Place Setup dialog box and the Output Job Configuration file are two different things. When utilizing the Output Job Configuration file option, the settings are saved in the config file. The settings are kept in the project file when utilizing the Pick and Place Setup dialog, though.
3.ORCAD/ALLEGRO Software
Both Orcad and Allegra Centroil files can be created in the same way. Select File from the drop-down menu. Then select Export and Placement from the drop-down menu.
This approach is compatible with the most recent releases of Orcad and Allego. Versions from the past may have some differences. For more information, go to the user manual.
