Investigation of PZT/Si Wafer Micro Milling Using Diamond Coated Tool

The cutting performance of the PZT/Si wafer micro milling was investigated by using the diamond coated micro end mill. At the same time, the cutting force and AE signals collected during cutting were also investigated to identify their capability of monitoring the surface condition and ductile/brittle cutting mode. To analyze the cutting performance of PZT thin film and corresponding signals, an experiment was conducted on a micro-machining equipment with resolution of 1 um. The PZT thin film with thickness of around 1 um was deposited on the Si wafer by a Sol-Gel method. During cutting, the AE signal was collected by an AE sensor clamped on the top of wafer, and the cutting force was collected by a Kistler 9256C dynamometer installed under a vacuum chuck. After the cutting, the finished surface was investigated by a white light interferometer system, and the chip was also investigated by a scanning electronic microscopic (SEM). The results show that the while light interferometer can be used to identify the cracked spot on the bottom of the machined surface. For the cutting mode analysis, the ductile mode cutting cannot be reached for the PZT thin film machining in this study. However, it can be obtained for Si wafer at the same cutting condition. Moreover, the RMS cutting force for PZT machining is higher than the Si wafer machining and its surface finish is not as good as in cutting the pure Si wafer. In analyzing the collected AE and cutting force signals, the AE signal, the time domain cutting force signals, and the RMS cutting force signals demonstrate their high correlation with the ductile/brittle cutting mode and surface condition.