Material Modeling of PMMA Film for Hot Embossing Process.

Dongwon Yun,Jong-Bong Kim

doi:10.3390/polym13193398

Abstract

This study provides an analysis of the hot embossing process with poly methyl methacrylate (PMMA) film. The hot embossing process engraves a fine pattern on a flexible film using a stamp, applied heat and pressure. As the quality of the embossing pattern varies according to various process variables, the mechanism of making the embossed shape is complicated and difficult to analyze. Therefore, analysis takes much time and cost because it usually has to perform a lot of experiments to find an appropriate process condition. In this paper, the hot embossing process was analyzed using a computational analysis method to quickly find the optimal process. To do this, we analyzed the embossing phenomenon using the finite element method (FEM) and arbitrary Lagrangian–Eulerian (ALE) re-mesh technique. For this purpose, we developed a constitutive model considering the strain, strain rate, temperature-dependent stress and softening of the flexible film. Work hardening, strain softening, and temperature-softening behavior of PMMA materials were well described by the proposed method. The developed constitutive model were applied in the embossing analysis via user-subroutine. This proposed method allowed a precise analysis of the phenomenon of film change during the hot embossing process.

Highlights

The hot embossing process is a technique used to engrave micro or nano-sized patterns onto a flexible substrate
Based on the developed model and finite element analysis method, a simulation of the hot embossing process for the poly methyl methacrylate (PMMA) film, which is the purpose of this study, was performed, and the deformation shape, stress, and temperature change of the material according to the amount of pressing of the stamp could be calculated
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Summary

Introduction

The hot embossing process is a technique used to engrave micro or nano-sized patterns onto a flexible substrate. Since the behavior of the film changes from an elastic region to a plastic region, it is difficult to theoretically predict or calculate in advance the amount of deformation produced by the process For this reason, many studies have had to focus on finding process conditions suitable for each film and pattern, using multiple experiments. The filling process of a micro prism array by isothermal hot embossing in solid-like state (IHESS) with different mold temperature, pressure, and holding time were simulated by DEFORM to cut the cycle time [9]. Based on the developed model and finite element analysis method, a simulation of the hot embossing process for the PMMA film, which is the purpose of this study, was performed, and the deformation shape, stress, and temperature change of the material according to the amount of pressing of the stamp could be calculated

Proposed Modeling Method

Modeling of Initial Yield Stress

Modeling of Work Hardening

Modeling of Softening

Results and Discussion