Development of Plastic Injection Molding Using the LIGA Process

Plastic injection molding was conducted with a mold cavity mounting a precision Ni stamper, which was fabricated by the LIGA process. The used thermoplastic materials were PC (polycarbonate), TPX (polymethylpentene), and POM (polyacetal) in consideration of applications in the optical, medical, and mechatronics felds. To evaluate the high aspect ratio microstructures fabricated by plastic injection molding, the microstructures were measured as to thermoplastic material filling, mold release, flatness, and transferability. In a test pattern having lines and spaces, each material filled the bottom of a stamper having a height of 100μm and a line width of 20μm. In a test pattern including posts and gear teeth, materials filled the bottom of a stamper having 300μm in height. Measured surface roughness of both the stamper and the molded product was several tens of nm, which of a sufficient transferability for practical application using plastic injection molding.