SCREEN PRINTING APPARATUS

摘要

A screen printing apparatus for and method of printing deposits of material onto a workpiece (3), the apparatus comprising: an inspection station (1) for determining a positional relationship of features on upper and lower surfaces of the workpiece, the inspection station comprising: an imaging system for determining a positional relationship of features on upper and lower surfaces of the workpiece, the imaging system comprising at least two spaced imaging units (15, 17) for imaging features on an upper surface of the workpiece, at least two spaced imaging units (19, 21) for imaging features on a lower surface of the workpiece, and a processing unit for determining a positional relationship of the imaged features on the upper and lower surfaces of the workpiece ; and a printing station (5) for printing deposits of material onto the workpiece, the printing station comprising: a workpiece support assembly (41) comprising a workpiece support member (43) for supporting the workpiece at a printing zone; a printing screen (5) disposed above the workpiece support member; a transport mechanism (27) for transporting the workpiece to the printing zone; and an alignment system for aligning the upper surface of the supported workpiece and the printing screen in relation to one another, the alignment system comprising at least two spaced workpiece imaging units (49, 51) for imaging features on a lower surface of the workpiece, and an alignment stage for moving the workpiece support member and the printing screen in relation to one another such as to align the upper surface of the workpiece and the printing screen in relation to one another by reference to positions of the imaged features on the lower surface of the workpiece as imaged at the printing zone and the positional relationship of the imaged features on the upper and lower surfaces of the workpiece as determined at the inspection zone.