Hot embossing of micro-lens array on bulk metallic glass

This study presents a new process to fabricate micro-lens array. The process of Micro-Electro-Mechanical Systems (MEMS) includes photoresist reflow technique, and nickel-cobalt (Ni-Co) electroplating to fabricate a first mold. Then, this first mold is applied to hot emboss on Mg-Cu-Y amorphous alloy to form a secondary mold. The secondary mold is a bulk metallic glass (BMG) material, whose thermal properties such as the glass transition temperature (T_g ), the onset temperature for viscous flow (T_onset ), the steady-state viscous flow temperature (T_vs) , and the finish temperature for the viscous flow (T_finish)  are investigated using differential scanning calorimetry (DSC) and thermomechanical analyzer (TMA). The glass transition temperature of BMG is around 140 °C (413 K). Therefore, the temperature of the hot embossing experiment is set at 423 K. This hot embossing process on BMG material makes molding process faster and more diverse applications. Next, the secondary mold is used to emboss on polymethylmethacrylate (PMMA) sheets. BMG is not only a good material for hot embossing process to fabricate micro-structure directly, but also fast-molding material for hot embossing process. Molding process using BMG material as a secondary mold can be more cost-effective and time-saving than the traditional MEMS process does.