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How many Fiducials on PCB for best placement

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#65518

How many Fiducials on PCB for best placement | 23 November, 2011

What is the Industry standard for number of fiducials on PCB. Is it just 2,3 or 4 for good placement.Any reference to IPC or any other standards to support your suggestion.

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#65529

How many Fiducials on PCB for best placement | 25 November, 2011

"IPC-2221 - Generic Standard On Printed Board Design" talks to fiducials. Anther take on fiducials says they shall meet the following requirements. * Make fiducials 1 - 1.5 mm diameter circle. * Cover fiducials with tin. * Keep solder mask opening at least 1mm greater diameter than fiducial. * Keep the distance from any fiducial to any land, trace or hole a minimum of 1mm. * Keep silk screen markings a minimum distance of 1.5mm from any fiducial. * Keep a minimum of 4 mm distance from fiducials to any board edge. * Place fiducials on each side of board that contains SMT components. * Ideally, use 3 fiducials for each side of the board with SMT. * Place 3 fiducials to lie on two lines that intersect at a right angle. * Use a minimum of 2 fiducials for each side of the board with SMT. * Locate fiducials as far apart as possible within all restrictions stated above. * Place fiducials on each individual board, rather than side rails or panel break-aways. * Further, place a set of fiducials on each panel array in the break-aways using above restrictions.

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