| 摘要 |
PURPOSE:To allow different-sized wafers to be attracted and held on a pneumatic table without adjusting suction values by automatically opening only the air inlet valves for suction when the wafer is set on the table, while closing the valves of all the other air inlet pipes. CONSTITUTION:Air pressure sensors 2a and 2b of air inlet pipes 1a and 1b, which are communicated to air inlet holes covered with a wafer 9 sense the pressure difference between the insides of the air inlet pipes 1a and 1b and atmospheric pressure. After a specified period from the time when the wafer 9 is set, signals are sent to a control unit 7. Only valves 3a and 3b of the air inlet pipes 1a and 1b required for suction are kept under the automatically opened state. Other valves 3c and 3d are closed on the other hand. Therefore, the vacuum degree in an air sucking device 16 is increased, and the wafer 9 is sucked to a work stage 12. Therefore, the opening and closing works of the valves 3a-3d in correspondence with the size of the wafers 9 are not required. |
