The process and reliability tests of glass-to-glass laser bonding for top-emission OLED device

Recently the active-matrix organic light-emitting diode (AMOLED) has emerged as a very promising flat-panel display technology because of its potential widely application for the development of high resolution and flexible full color flat panel displays. However, the encapsulation of AMOLED is studied and developed due to the top-emission structure used in AMOLED. Different from the bottom-emission structure, the top-emission structure requests the light escaping from the device through the transparent moisture barrier layer. In this paper, we investigate the hermetic joining process for glass-to-glass laser bonding with glass frit as an intermediate layer, using a simplified encapsulation structure. The whole process includes steps such as screen printing, presintering and laser bonding. Through experiments study, parameters as laser power, scan speed, laser beam radius and preheating temperature show a significant effect on the bonding process. The influences of process parameters on laser bonding quality are also studied. Furthermore, the strengths of bonded specimens are measured using a shear strength tester and results show that the laser bonding specimens satisfy the military standard MIL-STD-883G. Micrographs of the bonded glass-to-glass interface are observed and analyzed. The optimal parameters are acquired by orthogonal test and then proved in five experiments.