Fabrication of high-aspect-ratio microscale Ta mold inserts with micro electrical discharge machining

We report fabrication of microscale Ta mold inserts by micro-electrical-discharge-machining (mu EDM). Morphology, chemistry, and structure of the near-surface region of as-mu EDMed Ta blanks have been characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. A TaC surface layer forms on as-mu EDMed Ta surfaces. This altered surface layer was removed by electro-chemical-polishing. Further modification of Ta insert surfaces was accomplished by deposition of a conformal Ti-containing hydrogenated carbon coating. We demonstrate successful replication of high-aspect-ratio microscale structures in Al and Cu by compression molding with such surface-engineered Ta mold inserts.