TL;DR: If your PCB fiducials are poorly designed or placed, your pick-and-place accuracy will suffer. This guide explains the essentials of fiducial design so your assembly partners deliver consistent, high-quality results.
Why Fiducials Matter
Fiducials are the reference points SMT assembly equipment use to align the PCB during pick-and-place. Without accurate fiducials, even the best machines will place components off-pad, leading to rework, scrap, and production delays.
Common Fiducial Design Mistakes
- Too Small or Too Large: Recommended diameter: 1.0–2.0 mm copper pad, no solder mask.
- Insufficient Clearance: Keep at least 2 mm clearance from other copper features.
- Inconsistent Shapes: Use the same shape for all fiducials; circles are standard.
- Poor Placement: Place at least two global fiducials diagonally opposite; add local fiducials for fine-pitch or BGA areas.
- Lack of Mask Relief: Always remove solder mask over the fiducial to ensure optical recognition.
Best Practices for Fiducial Design
Follow these guidelines to ensure consistent assembly results:
- Use at least two global fiducials placed diagonally across the board for scaling and rotation correction.
- Add local fiducials near fine-pitch or high-density areas.
- Maintain 5 mm distance from PCB edges for global fiducials.
- Ensure fiducials have a high contrast with the PCB surface for optical recognition.
Key Takeaway: Fiducials are not an afterthought—they are the foundation for accurate PCB assembly. A few minutes of careful design can save hours of troubleshooting later.