Edge chipping in rotary ultrasonic machining of silicon

With the increase in demand of energy, more and more silicon-based solar panels are used to convert solar energy to electricity. In solar panel manufacturing, to increase the efficiency of solar cells, electrical contacts of the front side need to be connected to the back side of the panel. Therefore, holes of different sizes need to be drilled in silicon solar panels of certain designs. Because silicon has high brittleness and hardness, drilling of silicon solar panels using traditional drilling methods might lead to solar panel cracking and low tool life. Rotary Ultrasonic Machining (RUM) is one of the nontraditional drilling processes. It has been used to drill holes in many brittle materials. However, there is no report in the literature on RUM of silicon. This paper presents a study on edge chipping in RUM of silicon. Twolevel three-factor full factorial design was employed to experimentally determine effects of input variables on edge chipping and cutting force. The experimentally determined relation between edge chipping and cutting force was compared with that obtained by Finite Element Analysis (FEA). Higher tool rotation speed, higher ultrasonic power and lower feedrate led to smaller edge chipping and lower cutting force. An important influencing parameter on edge chipping is cutting force. Large edge chipping is almost always accompanied by higher cutting force.