To drive rotation of a workpiece and efficiently machine it without providing a workpiece driving device in a sheet type double face machining device lapping and grinding the thin discoidal workpiece such as a silicon wafer.
Two tool discs 24 and 34 are mutually rotated in the same direction, and they are pressed against both faces of the rotatably supported work piece W. By providing outer diameters of the two tool discs within a range of 53-83% of an outer diameter of the workpiece, and a distance between a workpiece rotation axis of the workpiece and a tool rotation axis of the two tool discs within a range of 46-50% of an outer diameter of the tool discs, the workpiece is corotated at a desired rotating speed by rotations of the rotating tool discs.
ABE MORITOSHI
IWAI HIDEKI
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