Study on Surface Residual Stress of Nano-Zirconia Toughened Alumina Ceramics under Two-Dimentional Ultrasonic Vibration Assisted Grinding

Based on good processing property of two-dimentional ultrasonic vibration assisted grinding (TUVAG), the precision finishing of nano-zirconia toughened alumina ceramics (nano-ZTA) is carried out. According to theoretical analysis, TUVAG may obtain higher machining efficiency and better surface quality. Especially, experimental results show it may obtain the compressive stress in the finished surface of nano-ZTA that may restrain the expansion of surface microcrack, and surface residual stress of nano-ZTA under TUVAG differs from that under diamond grinding, and TUVAG may obtain the better surface quality of nano-ZTA than diamond grinding, as is characterized by scanning electronic microscope (SEM). As a result, it is good for TUVAG as a kind of processing method for nano-ZTA.

Controlled Fracture of Nonmetallic Thin Wafers Using a Laser Thermal Shock Method

We developed a theoretical model of a novel thermal laser shock method for separation of glass and glass-ceramic wafers into chips. The suggested model allowed us to determine the operating parameters of the device for wafer splitting. The investigated method involves two stages: 1) formation of a surface (blind) microcrack (or a grid of surface microcracks) using a double thermal shock method, and 2) splitting the cracked wafer into chips along the microcrack contour by applying small bending stresses. The emphasis was given to splitting of thin wafers with the thickness less than 1 mm. The latter process is more involved because of the undesirable spontaneous transition of a surface microcrack into a through crack.

Formation of Surface Microcrack for Separation of Nonmetallic Wafers Into Chips

In recent years a technology for a high quality separation of nonmetallic materials into chips using a surface (“blind”) microcrack attracted considerable attention in the electronic industry. In this method a wafer is positioned on the translated X-Y table and is heated by a laser beam up to a temperature of the order of 300–400°C. The wafer is then cooled by an air-water spray, and a surface microcrack is formed due to relaxation of the thermal stresses. The initial microcrack with a depth of the order of several hundred microns then propagates in a subsurface region of a wafer and follows the path of the laser beam. Theoretical modeling based on the solution of the equations of thermal elasticity was performed to determine the distributions of temperature and thermal stresses that cause formation of an “edge” microcrack (at the edge of a wafer) followed by its transformation into a surface microcrack. The results of thermal stresses analysis are in an agreement with experimental observations. [S1043-7398(00)00804-5]