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 ductileand 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 Van-Nhat Le 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.

Effect of cutting parameters on surface integrity of monocrystalline silicon sawn with an endless diamond wire saw

“…Considering a fixed range of diamond grain protrusion and that all diamond grains are in contact with the surface of the mono-Si specimen, an increase in v c would increase the engagement frequency of the diamond grains on the mono-Si specimen along the sawing line, leading to a decrease in h cu . As a result, more kinematic cutting edges will engage and contribute to the removal of ductile material, as reported by Liu et al (2017b) and Chung and Le (2015). This change from brittle to ductile mode in the material removal mechanism, resulting in surfaces with more regions that are free of fractures associated with the fragile mode.…”

Study on surface integrity and ductile cutting of PV polycrystalline silicon and wear mechanisms of electroplated diamond wire

“…On the other hand, on increasing v c , the h cu value is reduced considerably and this leads to a predominance of ductile material removal. However, as reported by Chung and Le [10], there is still a number of grits with high h cu , which leads to cutting in the brittle mode, resulting in a sawn surface with mixed brittle and ductile cutting modes.…”

“…Considering the ndings of Li et al [15] and Liu et al [36], around of 10% of the kinematics edges take the ductile mode cutting, affecting the sawn surface, and they are restricted to the position angle on the wire cross-section of θ ≤ 25º. Chung and Le [10] complement that the diamond grits on upper side of the wire cross-section (50º ≤ θ ≤ 90º) assume mainly the brittle cutting mode. Theoretically, it is possible that the collected silicon chips have been formed in the following regions of the wire cross-section: at upper region of the wire, in which the diamond grits assume predominantly the brittle cutting, there is the formation of fragmented chips (Fig.…”

“…Considering a random distribution of the characteristic abrasives, their position over the wire and brittle and ductile modes during the cutting, the model was able to predict the surface roughness value obtained on varying the cutting parameters. Chung and Le [10] studied the depth of cut per diamond grit in the diamond wire sawing process, based on polar coordinates to identify the grit position for the generation of a wire pro le. Different depths of cut were observed due to the random diamond distribution, which led to both brittle and ductile cutting modes.…”

Dynamic Force Modeling of Wire Saw Machining Processes

“…The density of diamond abrasive grains on the wire is determined by counting the number of abrasives on sections of wire. The ratio of active abrasives on the wire is taken to be 0.3 [21]. In the experiments conducted in this paper, Vx = 0.75 mm/min, the total wire length is 65 m and Qp = 0.2 MPa.…”