Assembly accuracies of 0.05-0.1 mm, needed for electronic product manufacture, are attainable with current automated manufacturing equipment. Aggressive electronic system designs will require manufacturing accuracies in the range of 0.005-0.01 mm. A system and strategy is described here to fabricate circuit boards requiring alignment accuracies of 7.5 /spl mu/m using existing automation equipment with enhancements and typical manufacturing line fixtures. The system, configured as a pilot workcell, consisted of an IBM 7576 coarse positioning robot, a fine positioning manipulator, an optical sensing system and a unique bracing method to reduce environmental disturbances. The strategy was to use a coarse/fine placement technique with sensing to align, stack and bond individual test laminates with patterns of 100 /spl mu/m holes. The results showed that pairs of holes were consistently aligned to 2-5 /spl mu/m which surpasses the 7.5 /spl mu/m manufacturing requirement.>

The authors discuss design considerations and control issues of a fine-motion device which provides very high performance, precision, and speed (12-g acceleration, 0.2 mu m resolution). Coupled with a standard industrial robot and external sensing, improvements in precision up to two orders of magnitude can be achieved. Software enables it to be operated from a serial port of an IBM PC or PS/2. The moving element of the positioning head can be commanded to move over a +or-1 mm range in x and y, and rotated up to +or-1.75 degrees in theta about the z axis. The device provides variable compliance with compliance set by loop gain in a digital controller. It incorporates a novel three-degree-of-freedom motor, a pair of internal position sensors to enable controlled motion in the plane, and an air bearing to support the moving elements.>

Previous work on coarse-fine robots has emphasized improved positioning resolution or improved compliant behavior. The authors stress the use of the coarse-fine system's redundant degrees of freedom for bracing of either the coarse or the fine manipulator to execute an assembly task reliably. They refer to real bracing if the constraining forces and torques are supplied by mechanical means, and to virtual bracing if they are supplied by a control system. An application of the coarse-fine robot bracing approach to precision laminate registration and stacking for electronic packaging is presented. Results show that assembly errors of only a few microns can be readily obtained, approximately an order of magnitude improvement over the unbraced coarse-fine case, and nearly two orders of magnitude better than those attainable by coarse manipulation alone.>