Abstract: Swelling of SU-8 photoresist leads to deformation of photoresist and width reduction of electroformed parts when nickel mould is fabricated with this photoresist as master die of micro electroforming, which is the main influence factor of electroformed parts dimensional precision. The micro electroforming of nickel mould with multiple serpentine channels is fabricated by using SU-8 photoresist with 200 μm thickness as master die. A closed and equally distance isolation belt is designed around the graphic zone in the mask to improve the dimensional precision of electroformed parts. The isolation belt is used to reduce the SU-8 photoresist volume around the graphic zone, prevent thermal swelling of the photoresist outside the isolation belt from affecting the graphic zone and decrease dimensional change of electroformed parts. Experimental results show that the maximum dimensional error of master die added with isolation belt reduces from 61 μm to 31.4 μm, and the maximum dimensional relative error of electroformed parts reduces from 31.3% to 16.7%. This method obviously improves the dimensional precision of electroformed parts.

Key words: Dimensional precision, Isolated wall, Micro electroforming, SU-8 photoresist, Thermal swelling, Adjustable phase, Kinematic simulation, Linear hypocycloid, Structure design, Tail-swing propulsion