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

Heinigk, Christian; Barthels, Thilo; Schulz, Wolfgang; Nießen, Markus

doi:10.1117/12.2608151

Cited by 4 publications

(18 citation statements)

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“…In addition, the authors acknowledge the publication of a prior version of this treatise in the Proceedings of the SPIE Photonics WEST 2022 conference. 21 The authors have no relevant financial interests in this manuscript and no other potential conflicts of interest to disclose.…”

Section: Acknowledgmentsmentioning

confidence: 97%

Multiscale model for ultrashort pulsed parallel laser structuring—part II. The macroscale model

et al. 2022

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The increasing pixel density in displays demands 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 to let enough light escape from each diode and high productivity to produce the required amount. To achieve both objectives, high power ultrashort pulse (USP) lasers can be utilized. Because USP lasers fall short of the productivity requirements, they are combined with multibeam scanners. During production, the multibeam scanners deposit a lot of heat in the metal foil, which can ultimately yield temperature-induced distortions. To understand and finally avoid such distortions, a process simulation is sought. In a preceding study, the structuring of a single hole (the microscale) was investigated, but due to the large differences in the time and spatial scales involved, it was not feasible to simulate the production of the whole part (the macroscale). Within this treatise, a multiscale approach that takes into account the necessary information from the microscale to describe temperature-induced distortions on the macroscale is described. This approach targets laser ablation processes with pulse durations ranging from picoseconds up to nanoseconds provided the ablation is not melt-driven. First, a representative volume element (RVE) is generated from the results of the microscale model. Then, this RVE is utilized in the thermo-elastic structural mechanics simulation on the macroscale. The multiscale model is validated numerically against a hole-resolved computation, which shows good agreement. Naturally, the simulation is highly dependent on the microscale model, which in turn depends on the material properties. To handle material changes well, an experimental calibration has to be performed. This calibration is not part of this treatise, but it will be described in a future publication. In addition to the calibration process, the validation with experiments will 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. Finally, the procedure might be extended to the requirements of other filtration purposes.

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Section: Acknowledgmentsmentioning

confidence: 97%

Multiscale model for ultrashort pulsed parallel laser structuring—part II. The macroscale model

et al. 2022

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“…Heinigk et al [ 11 ] showed that the threshold fluence dependence on the temperature can be expressed as follows:

where

is the temperature at which

is (experimentally) determined,

is the internal energy, and

is the stored heat. Equation (9) can be rewritten as follows:

where

is a material-dependent constant.…”

Section: Temperature Influence In Parallel Line Scanningmentioning

confidence: 99%

“…It is possible to couple the TTM with FEM simulations to calculate the temperature of the material before every pulse in order to define

and

for every point [ 11 ]. This can first be achieved by exporting the material geometry to an FEM solver to calculate the heat distribution and then the material parameters can be updated into the TTM, but this approach would significantly increase the modelling time.…”

Section: Temperature Influence In Parallel Line Scanningmentioning

confidence: 99%

Three-Dimensional Pulse-Based Modelling of Femtosecond Laser Ablation of Metals: Validation with Grooves

et al. 2023

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The femtosecond (fs) laser ablation of metals is a precise method used to create microfeatures on the surface of the material with a minimized heat-affected zone (HAZ). Despite its many advantages, fs laser ablation often requires extensive trial-and-error experimentation before finding the optimal laser strategy for a desired geometry with minimal HAZ. The pulse-based two-temperature model (TTM) can significantly shorten this process by predicting the ablated geometry based on a set of material and laser parameters. However, this model has only been validated for percussion drilling and single lines. In this study, the pulse-based TTM is tested against parallel line experiments and subsequently modified to include geometry-dependent material parameters. More specifically, the threshold fluence and reflectivity of the material are modified to incorporate the temperature increase inside the standing features between parallel lines. The introduced geometry-dependent factors are fitted with experimental data and their inclusion in the model is shown to have a positive impact on the simulation results. The results show a clear amelioration in the shape and depth of the simulated profiles, with the error on the average depth and width of the modified TTM being lower than the average standard deviation on the experiments.

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“…For a more efficient design of the USP machining process, the essential material properties of stainless steel are determined within the scope of this work to subsequently calibrate an already existing simulation model of USP laser process. 1 The existing simulation model is a multiscale model for ultrashort pulsed parallel laser structuring and is presented as part I. the microscale model in the JLMN journal in 2021. Based on the existing microscale simulation model a multiscale model for ultrashort pulsed parallel laser structuring will be developed and soon presented with manuscript title: a multiscale model for ultrashort pulsed parallel laser structuring-Part II.…”

Section: Introductionmentioning

confidence: 99%

“…The machining with USP laser radiation depends on the characteristic material properties of the workpiece to be machined and the machining process varies with different machining systems and metallic workpieces. For a more efficient design of the USP machining process, the essential material properties of stainless steel are determined within the scope of this work to subsequently calibrate an already existing simulation model of USP laser process 1 . The existing simulation model is a multiscale model for ultrashort pulsed parallel laser structuring and is presented as part I. the microscale model in the JLMN journal in 2021.…”

Section: Introductionmentioning

confidence: 99%

Multiscale model for ultrashort pulsed parallel laser structuring—Part III. Characterization of material properties

2022

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In the field of microstructuring and nanostructuring ultrashort pulsed (USP) laser processing attracts increasing attention due to its ability to generate high-precision structures. A simulation of the USP process can lead to a reduced process development time and help to achieve a better geometrical quality of the manufactured microstructures. To predict the ablation shape, temperature distribution, and distortion in a USP ablation process, a detailed simulation of the physical processes during and after the laser ablation is required. Different simulation tools such as multiscale simulations are already established but still need different and accurate input parameters regarding the material properties of the workpiece to be machined. A material characterization procedure that can be used in a standardized way for different materials and processing stations needs to be developed. The procedure determines the absorption coefficient, penetration depth, and ablation threshold precisely matched to a USP machine and the material used. Based on the material characterization procedure a calibration of the used simulation has to be carried out as precisely as possible. The simulation can then be applied for a digital process development and subsequently validated with specific experiments.

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

Cited by 4 publications

References 4 publications

Multiscale model for ultrashort pulsed parallel laser structuring—part II. The macroscale model

Multiscale model for ultrashort pulsed parallel laser structuring—part II. The macroscale model

Three-Dimensional Pulse-Based Modelling of Femtosecond Laser Ablation of Metals: Validation with Grooves

Multiscale model for ultrashort pulsed parallel laser structuring—Part III. Characterization of material properties

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