Patent ID: 7824245

Claim:
Polishing apparatus, comprising: a base; a polishing platen mounted on the base and having an upper surface for receiving a workpiece to be polished; a jig shaft having a lower end, a workpiece mount affixed to the lower end of the jig shaft for suspending a workpiece above the upper surface of the platen, the jig shaft supporting a first weight prior to the contact of the workpiece with the platen, the first weight including the weight of the workpiece, the jig shaft and the workpiece mount; means for supporting and for raising and lowering the jig shaft, workpiece mount and workpiece relative to the platen, said means operable to lower the workpiece until the workpiece comes into contact with the platen; a sensor for determining how much of the first weight is being supported by said means for raising and lowering; and control circuitry for controlling the raising and lowering of the workpiece as a function of the amount of the first weight which is being supported by said means for supporting, raising and lowering.