Flat lapping machine with sizing mechanism

摘要

A flat lapping machine with an ultrasonic sizing mechanism for automatically lapping the work, such as a semiconductor wafer and a magnetic disk substrate, to the present desired thickness. The flat lapping machine permits high-precision thickness measurement or sizing and uniform work lapping by assuring stable propagation of ultrasonic waves by eliminating such noise-induced waveform disturbance as might occur when slurried abrasive is used as the propagation medium and such localized dilution of slurried abrasive as might occur when water is used as the propagation medium. The flat lapping machine may have a sizing mechanism for automatically lapping the work to the preset desired thickness based on the difference between the preset and measured thicknesses of the work. The machine comprises top and bottom rotatable lapping surface plates and a transducer attached to the top surface plate in a position opposite to the work to send out ultrasonic waves to the work to determine its thickness. An ultrasonic-wave propagation medium of such solid material as metal, glass or plastic is interposed between the transducer and the work.