Placing surface mount components using coarse/fine positioning and vision

An experimental system that can accurately align and place SMDs (surface mount devices) on a PCB (printed circuit board) using a coarse/fine positioning component placement strategy and end-point sensing to measure the alignment error is described. Coarse positioning is done with an IBM 7576 robot, and fine positioning is done using a custom-designed precision micropositioning device attached to the end of the IBM 7576 robot. The end-point 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 0.63-mm (25 mil) lead spacing on a board. An alignment error of less than 12 mu m (0.5 mil) and 0.015 degrees was obtained independent of feeder and board position error or robot repeatability. The average cycle time was less than 10 seconds.<
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