Surface integrity analysis of ultra-thin glass molding process

Abstract Curved ultra-thin glass is widely used in mobile electronic devices such as smartphones, and its market demand is gradually increasing. The ultra-thin glass molding process (UTGMP) is a new type of glass molding process with a short processing period and high precision. However, the UTGMP is restricted to the development of curved ultra-thin glass because of its low pass rate and high cost. In particular, surface defects, including cracks, microbubbles and water ripples result in poor surface integrity of curved ultra-thin glass. Therefore, the surface integrity of the curved ultra-thin glass was comprehensively studied and analyzed in this study. First, the principles and apparatus of the UTGMP are introduced. Second, a thermo-mechanical coupling model of ultra-thin glass is established to simulate the temperature and stress distribution of curved glass using the finite element method. The results demonstrate that close to the curved area and slot, the variation in the temperature gradient is significant, and the internal stress is clearly large and concentrated. A series of experiments are conducted to further study the respective effects of various UTGMP parameters on the breakage rate and the densities of microbubbles and water ripples. A comparison of the simulation and experiment results reveals that the molding temperature has a significant effect on the breakage rate and the densities of microbubbles and water ripples, while the molding pressure has a significant effect on the breakage rate. Based on a comprehensive analysis, an optimal molding temperature of 806 °C and a molding pressure of 0.45 MPa are selected. Under this condition, the breakage rate decreases from 67% to 0%, the density of microbubbles decreases from 1.03/mm2 to 0.89/mm2, and the water ripple phenomenon weakens. This study contributes to a better understanding and improvement of the surface integrity of high-precision glass molding processes for curved ultra-thin glass.