The manufacture of micromould and microparts by vacuum casting

Micromoulds are generally produced by lithography methods that often use glass and silicon wafer as substrates, with the exception of the Lithographie Galvanoformung Abformung (LIGA) method, which uses metal substrate. These fabricated moulds are then integrated into the injection moulding machine for mass production. This paper presents the use of vacuum casting methods to produce micromoulds instead of lithography. Silicone rubber is used as the mould material, which is capable of achieving nanometre surface finish. The master pattern of 1-mm diameter microgear of 60-μm teeth width and 38-μm thickness was created by standard ultraviolet (UV) lithography using SU8 photoresist. Using the vacuum casting method, ten polyurethane microgear specimens of 1-mm diameter and 38-μm thickness using the silicone rubber micromoulds have been successfully cast under vacuum conditions as a demonstration. Measurement from white-light interferometry (WLI) showed that all of the microgear cavities in the micromoulds were dimensionally accurate and consistent to the master microgear, proving that its repeatability is possible.