Depth of cut per abrasive in fixed diamond wire sawing

Abstract

Because of the high requirement for quality, the surfaces of prime wafers have to be flat and without damages. During the first machining process in wafer manufacturing, the defects introduced by wire sawing must be removed by the subsequent lapping, grinding, and polishing processes. Therefore, the quality of sliced wafer is very important. Fixed diamond wire saw, on which the diamond grains are coated as abrasives, has become the major tool to slice ingot into wafers. Ductile-regime machining is an attractive process to achieve crack free surface on brittle materials in abrasive machining process. The depth of cut of the abrasive is a hint for the transition between ductile- and brittle-regime machining. In order to understand the cutting behavior in fixed diamond wire sawing, this paper presents an investigation of depth of cut per abrasive based on the wire profile model developed by the authors. The simulation results show that the larger depths of cut are unavoidable in fixed diamond wire sawing because of the random position and size distribution of diamond grains on the wire. Although the number of active abrasives and the depths of cut at the bottom of slicing groove are larger than those at the side of the groove, few larger diamond grains may introduce larger depths of cut and cracks on the side, which is the sliced wafer surface. Effects of process parameters to the depth of cut distributions are also analyzed. The variation in number of active abrasives in cutting zone as well as their depth of cut shows the possibility to increase process productivity without increasing the depths of cut of the diamond grains. Consequently, the surface quality could be remained without further deterioration.