A geometric feature incorporated into the artwork of a printed wiring board or into a stencil. At fabrication, fiducials are etched on the outside surface of a circuit board or a panel at the same time as the conductive pattern is formed, and provide an optically measurable reference point for subsequent manufacturing and assembly processes, to confirm proper artwork registration and orientation. At assembly, fiducials are used as an optical target by the machine vision system to identify its exact location and orientation. These reference points serve to align and position boards and stencils both for printing and SMT component placement. Fiducial marks are particularly necessary for the accurate placement of fine pitch components.
A mark in the artwork that is etched in the stencil along with the apertures. It is used by the machine vision system to align the stencil to the PCB and to verify artwork orientation and location. Fiducials can be fully-etched or half-etched either on the top (squeegee side) or bottom (board side) of the stencil. Sometimes the fiducials are filled with black epoxy to provide contrast between the stencil and the fiducial for visual systems. "Global" fiducials are located outside the aperture footprint while "local" fiducials are placed within the image itself, usually in close proximity to an integrated circuit.