Experimental Research On Sapphire Surface Quality Sliced By Multi-wire Rocking Sawing With Reciprocating Motion Of Diamond Wires

Sapphire has superior physical and chemical properties, and has been widely used for electronic, optical, and medical applications. As a result, the manufacture process of sapphire has attended constantly increasing research attention. During the manufacturing of sapphire wafer, Slicing is the first step and plays a determinant role in the cost and quality of final product. Today,shifting Multi-wire sawing is the most commonly used technology for the slicing of sapphire ingot. However, the effects of the rocking and reciprocating of the saws are to be understood yet.In this paper, a theoretical model was built to study the contact length between wire saws and sapphire ingots subject combined rocking and reciprocating motions. Subsequently, the surface morphology and geometric parameters such as thickness, total thickness variation, warp, bow, roughness,of sapphire wafers sliced by a multi-wire saw with rocking and reciprocating motions was characterized at variable positions on the wire web. In doing so,a relationship between the surface and geometric parameters of sliced sapphire wafers and the motions of multi-wire saws was established. Finally,the influence of the surface quality of sliced sapphire wafers on subsequent grinding and annealing process was investigated and discussed in this paper.In summary, the results obtained during this research can be summarized as follows:1. Theoretical analysis shows that a proper combination of rocking, feeding and reciprocating of the multi-wire saw can reduce the wire consumption and stabilize contact length between wire saw and the workpiece during slicing process.2. During slicing process, the wear of the saw wire results in a significantly difference in the wafer qualities obtained at different locations on the wire web. From the supplying side to the collecting side of wire web, the thickness and warp increases with decreasing surface roughness. The total thicknessvariation and the bow remain relatively stable in the middle of the wire web;3. the shape of sliced wafers changes from the waviness at supplying side to torsion at collecting side along the wire web. A new criterion considering both the wafer surface waviness(Wave) and the degree of torsion(Twist) has been proposed to evaluate surface quality of sliced wafers. Compared to the conventional indicators of warp and bow, this newly proposed criterion can more represent the shape features of sliced sapphire wafers.4. The process parameters during slicing have a remarkable influence on the final surface and geometric quality of wafer. An appropriate increase in the feed speed of wire saw, the swing angle, or yaw angle, and a decrease in the cutting speed ratio have been found to effectively reduce the warpage and curvature of wafer, resulting in a better surface quality of final product.5. After slicing process, subsequent grinding and annealing treatments can improve the surface quality of the wafer; however the improvement is dependent on the surface topography previously obtained during slicing process. A small variation of the surface quality resulting from slicing process leads to notable deviations of consequent grinding and annealing processes.