Numerical Simulations of the Screen-Printing Process for Solar Cell Metallization

The metallization of silicon wafers is an essential part of the production process for Si-solar cells. Due to its robust and costeffective production capability, flatbed screen printing is by far the most used metallization technology nowadays. In order to achieve maximum efficiency and optimum material usage, the parameters of the printing process must be adjusted to the print layout. The huge interdependent parameter space of flatbed screen printing makes it difficult to predict the optimal settings. To this day, these parameters are still chosen based on experience and by iterative manner until a satisfying print result is achieved. Another approach to handle the complexity of choosing the correct parameters is the use of Computational Fluid Dynamics (CFD) simulations. The successful setup of a CFD simulation could prevent cost-intensive iteration procedures and propose the right choice of parameters via numerical simulations. With the help of CFD simulations, the influence of structural changes in the screen on the flow of the shear-thinning paste is studied. Therefore, a model is built from scratch representing the different process steps of screen printing. Finally the results of different screen structures and paste models are compared and verified with experimental print results.