Development of Mold Manufacturing Method of Transcribing Master on Aluminum alloy for Fine Plastic Product

—Application to Mold for Microneedle—

Abstract

Micro injection molding methods for realizing fine plastic products attracts great attention. A low-invasive plastic microneedle imitating mosquito is an example that fabricated by micro injection molding. Since processing of a sharp needle-shaped part having a diameter of 100 µm or less in the mold requires microfabrication using a micro tool, the cost of mold becomes high. To address this, transcription method was employed, in which a hard master shape is pressed against a soft material to form the mold. However, it turned out that the conventional method using ceramics as a master mold material is difficult to apply, since the micro-sized shape is difficult to fabricate on the ceramic, and it is easily broken when pressed against the mold material, both of which are due to brittleness of ceramics. In this research, instead of ceramics, a hard metal, e.g., SUS440C, trade name ELMAX, is used as master material, which is tough and easily machined compared to ceramics. As for mold material, a soft metal, e.g., A7075 of aluminum alloy, is used. Using aluminum is effective for two reasons; one is that the hurt and degraded master can be easily and frequently exchanged at low cost; another is that the material appropriately deforms to seal the gap of parting line between upper and lower molds, preventing the occurrence of burr.