| In the MEMS field, Micro-injection molding technology is receiving increasing attention. It not only has the molding plastic parts, high efficiency, size and quality of consistency, but also meets all kinds of small devices or components of complex plastic parts needs, while the accuracy and quality of micro-injection mold cavity have a direct impact on small plastic parts7 quality. Based on SU-8 photoresist UV-LIGA technology has the complex structure of micro-molding, high aspect ratio and near-vertical sidewalls such prominent advantages. The use of sacrificial layer UV-LIGA technology or overlay process can fabricate step structure. Therefore, fabrication of micro-injection mold cavity based on UV-LIGA technology meets the requirements of its size and precision and has great significance.A fabrication method of micro-injection mold cavity of cell culture device is studied in this paper. For the structural characteristics of micro injection mold cavity, using appropriate alloy steel as the substrate and based on overlay UV-LIGA technology, microstructure was fabricated through optical lithography of SU-8 photoresist technology and micro-electroforming technology respectively twice, and then micro-exhaust passage was etched on electroforming deposit applying mask etching technology. With these processes, micro-injection mold cavity with micro-array structure, micro-injection gate, micro-exhaust passage was fabricated on the metal substrate directly.Research on UV-LIGA technology was carried out in the micro-cavity production process. Experiments combined with theoretical analysis, the problems encountered in the production of the SU-8 plating mold on the metal substrate and micro-electroforming process were discussed and solved by appropriate and effective improvement measures. The micro-injection mold cavity of good quality, high bonding strength between the substrate and nickel electroforming deposit is gained successfully.This article focuses on the swelling mechanism analysis of SU-8 thick photoresist. For the swelling phenomenon of SU-8 thick photoresist, the method of designing and fabricating 20μm and 30μm wide closed isolation strips around the mask graphics was presented to reduce the volume of SU-8 thick photoresist around the graphics and to improve the swelling deformation of plating mold, so that the dimension error of electroforming deposit was from 35μm down to 10μm and 300μm high micro-square-cylinder side wall was steep. The introduction of closed isolation strip improved the dimensional and shape precision of nickel electroforming deposit effectively.
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