Purpose: To ensure a minimal number of global fiducials for proper alignment of the board inside the assembly mac
Purpose: To ensure that fine pitch devices have local fiducials placed in the center of the component, or in two opposite corners, to allow fine alignment of the assembly equipment.
Fiducials should be placed equally distant from a component. If this is not the case, it may indicate a design mistake.
Purpose: To ensure the area adjacent to fiducials is free of exposed copper which may mislead the optical alignment equipment and cause inaccuracies.
Purpose: To ensure the area adjacent to fiducials is free of holes which may mislead the optical alignment equipment and cause inaccuracies.
Purpose: To ensure global fiducials are not too close so as to provide the optical alignment equipment sufficient accuracy to account for shift/rotation errors.
Purpose: To ensure global fiducials are not too far apart. This is considered bad design practice.
Purpose: To ensure fiducials are a minimal distance from board edge so as to provide a sufficiently contrasted area for the optical alignment equipment.
Purpose: To detect features, similar in size and shape but are not fiducials, which may possibly confuse the optical system in identifying fiducials.
Purpose: To ensure fiducials maintain a minimal distance from the conveyed edge of the board.
Purpose: To ensure fiducials maintain a minimal distance from the non-conveyed edge of the board.
Purpose: To ensure that fiducials are found on a uniform background - either all copper or all laminate - as required by the optical equipment identifying them.
Purpose: To ensure that fiducials are not covered by components and are, therefore, accessible to optical inspection systems. This category applies to global fiducials only.
Purpose: To ensure that each fiducial has a large enough gap between it and the surrounding solder mask to provide reliable recognition by optical alignment equipment.
Purpose: To detect silk screen features which may confuse the optical fiducial identification system.
Purpose: To ensure that fine pitch components, requiring a local fiducial at their center, have it. This is in addition to the board global fiducials.
Purpose: To ensure that fine pitch components, requiring two local fiducials placed in their corners, have them. This is in addition to the board global fiducials.
Purpose: To ensure that each component has at least one global fiducial close to it. A component, far from any fiducial (e.g. more than 4”), may be statistically vulnerable to placement accuracy errors.