METHOD AND APPARATUS FOR ALIGNING FLAT AND THIN WORKPIECES

摘要

A method and apparatus permitting accurate and repeatable steps of location and alignment of flimsy sheets during their transfer. A preferred embodiment comprises a sheet handler and method for aligning unfired ceramic green sheets used in multi-layer ceramic semiconductor packages. The thin flexible sheets are square or rectangular in shape and are provided with holes accurately punched in each corner thereof for alignment purposes. The sheets are moved by a vacuum input transfer head into orientation with a porous registration surface of an alignment fixture. The sheet is then trapped between opposed pressure zones emanating from the input transfer head and through the porous registration surface, respectively. With the sheet stabilized between the pressure zones four bullet-nosed alignment pins are raised from the registration surface into contact with the holes in the corners of the green sheet, thereby accurately aligning the sheet with respect to the alignment fixture. The input transfer head is then withdrawn and an output transfer head picks up the aligned sheet via vacuum means and transfers it to other processing locations. In an alternate embodiment the pressure zones are created between the output transfer head and the registration surface of the alignment fixture.