Filling Behavior of Polymer Material into Sub-μm Structure in Injection Molding Process

The moldability of sub-μm pillar injection molding was investigated by using polycarbonate with four kinds of die material; SKD11, WC/Co, Ni and DLC coated on SKD11. It was also investigated by using Cyclic olefin polymer (COP) with SKD11 and DLC coated on SKD11. The cross-sectional profiles of molded object were precisely measured by a critical dimension FE-SEM. In the case of injecting polycarbonate with a SKD11 or Ni die, a tip of molded object had a paraboloid shape which may be caused by extrusion with large friction between the die materials and polycarbonate. In the case of injecting polycarbonate with a WC/Co or DLC die, a frustum shape with plateau due to low friction was exhibited in spite of large wettability between WC/Co and the melted polycarbonate. It may be considered that a multitude of small void on the WC/Co surface caused the moldability with low friction. On the other hand, The moldability was insensitive with molding conditions in COP with SKD11 or DLC coated on SKD11 die.