Using coarse/fine manipulation with vision to place fine pitch SMD components

An experimental system that can accurately align and place SMDs (surface mount devices) on a printed circuit board is described. Features of the system are fine positioning and endpoint sensing after an IBM 7576 robot coarsely aligns the SMD to its target. Fine positioning is done using a customer-designed micropositioning device. The endpoint sensor is a single camera vision system that by image analysis determines the alignment error of the SMD to the board. System performance was evaluated by placing SMDs of 100 leads with 25 mil lead spacing on a board. The alignment error is less than 0.5 mil and 0.015°, independent of feeder and board position error or robot repeatability. The average cycle time is less than 10 s.