Fiducial Mark Structure – PCB DFM 11
11.2.1 Panel Fiducial Marks and Image Fiducial Marks
[97] Size/Shape: a solid filled circle with a diameter of 1.0 mm.
Solder mask opening: 2.00mm in diameter and concentric with the Fiducial.
Covering copper: an octagonal copper ring 3.00mm in diameter concentric with the Fiducial and clearance
Area.
Figure 60: Structure of Panel and Image Fiducials.
11.2.2 Local Fiducial
[98] Size/Shape: a solid filled circle with a diameter of 1.0mm.
Solder mask opening: 2.00mm in diameter and concentric with the Fiducial.
Covering Copper: not needed.
Figure 61: Structure of local Fiducials.
11.3 Position of Fiducials
[99] In General: PCBs which require SMT automated assembly must have Fiducial marks on the necessary
layers. PCBs which only require manual soldering do not require Fiducial marks.
For single-sided boards, Fiducial marks are only required on the side where the SMD components are to be
soldered.
For double-sided boards, both sides must have Fiducial marks. The position of the Fiducial marks must be
generally consistent (except for mirror panels).
Figure 62: Both sides of a double sided PCB should generally be consistent with each other.
11.3.1 Panel Fiducial Marks
[100] Panel Fiducials and image Fiducials should be located on the panel margins and on individual
sub-boards respectively. There should be three panel Fiducials per board and three local Fiducials per
sub-board, arranged in an ‘L’ shape as far from each other as possible, as shown in Fig. 63:
Figure 63: Fiducial positioning requirements on the panel margins and individual boards.
When using mirrored panelization, the panel Fiducial marks must be consistent after flipping.
11.3.2 Image Fiducial Marks
[101] There must be three Fiducial marks per sub-board, arranged in an ‘L’ shape, located as far as possible
from each other. The distance from the origin of the Fiducial mark and the edge of the sub-board should be
greater than 6.00mm. If it is not possible to ensure that the four edges satisfy this requirement, then the
requirement must be satisfied for the primary side at least.
12.3.3 Local Fiducial Marks
[102] For devices with gullwing pins and a pin pitch of 0.4mm, and surface array packaged devices with a
pin pitch of 0.8mm, local Fiducial points are required.
Two local Fiducial marks are required per component and must be symmetrical on both sides of the origin of
the component.
Figure 64: Local Fiducials must be symmetrical about the component’s origin.
If you already know about the design rules, then turn to Seeed Fusion for pcb manufacturing and assembly now!
More Chapters:
1. Brief Introduction
2. Seeed Fusion PCB Specification
3. Panelization and Bridge Design
4. Component Layout Considerations
5. PCB Hole design
6. Solder Mask Design
7. Copper Trace Design
8. Silkscreen Design
9. PCB Lamination Structure
10. PCB Dimensions Specification
12. Surface Treatment
13. Files for Manufacture Requirements
14. Appendix
About Author
