Study On The Influence Of Arc Zone On The Sawing Mechanism Of Sapphire Wafer

Sapphire has been widely used because of its excellent characteristic of machinery, optics and chemistry. Sapphire wafer needs to be cut into specifications before put into used, such as separating the LED wafer into grain, cutting the wafer into specifications used on windows, etc. The last step of changing the sapphire material into a finished product is wafer cutting process, its quality directly affects the yield of the product. Diamond cutting wheel which is considered as a kind of traditional machining tool has the advantages of low cost and high efficiency. However, because sapphire belongs to difficult-to-machine materials which has high hardness and brittleness, the processing is difficult and easy to from edge-breaking. Therefore, further study on the mechanism of wafer machining process should be taken. The change of arc zone in the process of sawing has a great influence on the sawing mechanism of sapphire wafer. The difference of arc zone will affect single grits chip morphology, and chip morphology determines the way of material removal which directly affects the edge-breaking.In this paper, ultra-thin sawing wheel is used to carry out experiment on sawing sapphire wafer. In the experiment, the chip morphology of single grit is controled by changing the arc zone, rotating rate of grinding wheel and workpiece feed rate. In order to judge the material removal mode of different arc zone, microscope is used to observe grooving morphology and chipping edge. After analysis of sawing force, force ratio and specific energy under different arc zone, the material removal mechanism is discussed. Mathematical model of sawing force is established to have further explore the formation mechanism of sawing force and its variation characteristics of different arc zone. The main results of this paper are summarized as follows:1.Material removal characteristics in different arc zone: when the arc zone is low, chips are difficult to discharge, so a lot of broken chips embedded in the cutting groove; while the arc zone is high, single abrasive cutting depth is larger and brittle broken quantity increase. The size of chipping edge is relevant to the material removal mode, lower or higher the arc zone is, larger the chipping edge is.2. The influence law of arc zone changing on the sawing force: under the same set of parameters, with the arc zone increases, the unit width of normal force increases and the unit width of tangential force increases first then decreases. On the sawing force ratio: with the arc zone increases, sawing force increase. On specific energy: with the arc zone increases, specific energy increase first then decrease.3. Mathematical model of sawing force is established, then combined with the experimental data sawing force formula of different arc zone is deduced and then verified. The changing law of normal force coefficient k and tangential force coefficient k’ in the mechanics model is explored: with the increase of arc zone, k linear increases linerly and k’ increases with lower and lower increased speed.