Formation of Micromoulds via UV Lithography of SU8 Photoresist and Nickel Electrodeposition

Abstract

Current lithography methods for creating micromoulds, other than LIGA, often use glass or silicon wafer as substrates. Since they are nonconductive, a metallic seed layer is required to be deposited over the substrate for electrodeposition to take place. This paper demonstrates a new method of creating a micromould directly onto a metal substrate, which can then be immediately utilized for microinjection moulding after nickel electrodeposition. The selected metal brass substrate is machined by a single-point diamond turning process to achieve a nanosurface of 12 nm. Standard UV lithography using SU8 photoresist was then employed to create a microgear onto the brass. At approximately 20 μm depth, nickel microcavity gear of 1 mm diameter was successfully created directly onto the brass substrate, after electrodeposited in nickel solution. A pulse current deposition method at a current density of 400 A/m2 was used for the deposition process.