Method for polymer hot embossing process development

Molding technologies associated with fabricating macro scale polymer components such as injection molding and hot embossing have been adapted with considerable success for fabrication of polymer microparts. While the basic principles of the process remain the same, the precision with which the processing parameters need to be controlled especially in the case of molding high aspect ratio (HAR) polymer microparts into polymer sheets is much greater than in the case of macro scale parts. It is seen that the bulk effects of the mold insert fixture and molding machine have a dominant influence on the molding parameters and that differences in material parameters such as the glass transition temperature (T (g)) of polymer sheets are critical for the success and typically differ from sheet to sheet. This makes it very challenging to establish standard processing parameters for hot embossing of sheet polymers. In the course of this paper, a methodology for developing a hot embossing process for HAR microstructures based on known material properties and considering the cumulative behavior of mold, material, and machine will be presented. Using this method force-temperature-deflection curves were measured with the intent of fine tuning the hot embossing process. Tests were carried out for different materials using a dummy mold insert yielding information that could be directly transferred to the actual mold insert with minimum development time and no risk of damage to the actual microstructures.