Fiducial marks

The peripheral contours of pcb are subject to large tolerances. But for the setup of the pick-and-place systems and for the alignment of the stencil of the printer to the pads of the pcb for the printing sequence, these tolerances are too large. To overcome this tolerance issue, and in order to be able to exactly align the systems with the tracks and pads of the board, special marks, called fiducials, are added to be board layout. These fiducials have always the same position in relation to the pads for the components. With camera systems active prior to starting the process sequence, an exact alignment of the pick-and-place head or the stencil can be established. The excessive tolerances are therefore compensated for.