Evenness Of Mold Electroforming Layer And Fabrication Of Microstructures With Diverse Cross-section

Micro electroforming technology is a kind of important micro-machining method in the field of MEMS. Micro electroforming has many advantages in fabricating metal mold with micro-structure or micro-device, which is widely applied in electronic information, biological detection, optical engineering, national defense industry and other fields. However fabrication process of metal micro mold which is based on micro electroforming, still faces some problems. In this paper, two of the problems are studied.(1) The unevenness of metal mold surface caused by bending deformation of electroforming layer and electroforming tumor, can affect the replication precision of microstructure.(2) Lacking of fabrication process of metal mold with diverse cross-section microstructures.In this paper, the improvement of bending deformation of metal mold and the elimination method of electroforming tumor are discussed. And the fabrication processes of nickel molds with triangular, rectangular and arch cross-section microstructures are studied. The main work content in this paper is as follows:1. The micro electroforming platform is designed and set up, which provides the experimental conditions for the study. Micro electroforming solution composition and process parameters are analyzed and optimized to obtain good quality of electroforming layer, which can satisfy the basic requirement of nickel mould.2. On the basis of analyzing the reason for bending deformation of metal mold, the influence of current parameters on bending deformation is discussed. Pulse electroforming and direct current electroforming are combined with diverse current density. The bending deformation degree of electroforming layer is evaluated, according to the height difference and radius of curvature of bending curve. Therefore the best current parameters combination is obtained.3. Analyzing the reason for electroforming tumor. And the method that setting the cathode shielding structure is presented to eliminate electroforming tumor. The distribution of current density at cathode surface is simulated by ANSYS software, to find out the optimization of shielding structure height. And the simulation results are verified through electroforming experiments.4. Combining optimized micro electroforming process with body silicon technology, the nickel molds with triangular, rectangular and arch cross-section microstructures are fabricated respectively. The fabrication process routes of nickel molds with diverse cross-section microstructures are enriched. The experimental results show that pulse electroforming with small current density is proposed, which can effectively improve the bending deformation of electroforming. When the measure length is2cm, the height difference of mold surface is10μm. The method of setting the cathode shielding structure is proposed to eliminate the electroforming tumor, when the shielding structure height is2.4cm. The fabricated nickel molds with diverse cross-section microstructures have high surface quality and low deformation, which can be applied to the replication of polymer microstructures, such as hot embossing and injection molding.