Design of an evaporation system using multi-stage optimization based on heat analysis

Abstract

In this study, a multi-stage meta model based design optimization is proposed to improve thin film uniformity by minimizing temperature deviation in an OLED evaporation system. Temperature distribution in the evaporation system is one of important factors to improve thin film uniformity. If temperature distribution is not uniform, it leads to unequal amount of evaporation resulting in an uneven thin film. The shape of the evaporation system is modeled using Pro-engineer. A simplified quarter finite element model is generated for thermal analysis using Abaqus to shorten analysis time. A design problem is formulated to find the pitches and lengths of the upper and lower heaters, the hole areas of the upper and lower frames that minimize temperature deviation in the evaporation system. To solve the formulated design problem, the meta model based design optimization is adopted in which sampling, meta modeling, and optimization is sequentially performed. In this study, five-stage optimization is performed to obtain the optimum solution. At each stage, design variables are changed based on the optimization results of the previous stage. A commercial process integration and design optimization (PIDO) software, PIAnO, is used for this multi-stage meta model based design optimization. Temperature deviation is reduced to 2.74℃ of the optimum design from 32.7℃ of the initial design, which achieves about 1200% reduction. This demonstrates the effectiveness of the proposed multi-stage meta model based design optimization.