A multi-scale model for ultra-short pulsed parallel laser structuring: part II. the macro-scale model

Abstract

The increasing pixel density in displays demand a high quality in the production of Fine Metal Masks (FMMs). The production process of FMMs boils down to structuring tiny holes in thin metal sheets or foils. The manufacturing requirements of FMMs are high precision in terms of the hole geometry in order to let enough light escape from each diode and high productivity to produce the required amount. To achieve both objectives, high power Ultra Short Pulse (USP) lasers can be utilized. Since USP lasers fall short of the productivity requirements, they are combined with multi-beam scanners. During production, the multi-beam scanners deposit a lot of heat in the metal foil which can ultimately yield temperature-induced distortions. In order to understand and finally avoid such distortions, a process simulation is sought. In a preceding study, the structuring of a single hole (the micro-scale) has been investigated, but due to the large differences in the time and spatial scales involved, it is not feasible to simulate the production of a whole part (the macro-scale). Within this treatise, a multiscale approach is described, taken into account the necessary information from the micro-scale to describe temperature-induced distortions on the macro-scale. First, a Representative Volume Element (RVE) is generated from the results of the micro-scale model. Then, this RVE is utilized in the thermo-elastic structural mechanics simulation on the macro-scale. The multiscale model is validated numerically against a hole-resolved computation which shows good agreement. Naturally, the simulation is highly dependent on the micro-scale model which in turn depends on the material properties. In order to handle material changes well, an experimental calibration has to be performed. This calibration is not part of this treatise, but will be described in a future publication. Besides the calibration process, the validation against experiments is still to be conducted in future research. Additionally, the authors envision the automation of the whole process resulting in a first-time-right approach for the development of FMMs. Last but not least, the procedure might be extended to the requirements of other filtration purposes.