A fiducial mark is typically a circular pad or other shapes of exposed copper that is surrounded by a clearance area. It acts as a reference point for automated machines, such as pick-and-place machines, and also for PCB stencil alignment to ensure that components are accurately placed on the board. During the assembly process, these machines use computer vision systems that scan for the fiducial marks and use their locations to align the PCB and components. Fiducial marks are particularly useful for surface-mount technology components, and it’s advisable to put a mark near the packages with small pitches like BGA, QFN, and QFP.