Fabrication Of Metal Micro Devices And The Study On Bond Strength Of Micro Electroforming Layers

With the rapid development of MEMS technology, micro structures which have requirements of form accuracy and surface quality, are increasingly demanded in the fields of micro-electronics, national defense and bio-engineering. Micro electroforming based on UV-LIGA technology has been widely applied in the micro structure fabrication. However, in the micro electroforming process, the bond strength of the interface between substrate and electroformed layer affects the success rate of micro structures manufacture and their lives. The primary work of this study mainly concentrates on two aspects:fabrication processes of micro device and micro mold, and the bond strength of the interface between substrate and electroformed layer. The research result provides process reference and theoretical analysis to improve the success rate of micro structures manufacture and prolong their lives.Micro injection mold was fabricated. Over-plating method combined with the following grinding and polishing processes, which fulfills±3μm error requirement of the electroforming insert in height, was employed to eliminate the nonuniformity of the insert.The fabrication processes of moveable micro-device with double layers were ameliorated. Based on the UV-LIGA technology, the improved processes consist of SU-8thick photoresist lithography, micro electroforming, no back plate growing process and sacrificial layer process. The new method contracts the process cycle, cuts the cost and keeps the material consistency of the device. The process provides a new option for the fabrication of the devices.It was studied that current density influences the interfacial bond strength of electroformed layers. Based on micro electroforming experiment, the quantitative measurement of the interfacial bond strength by the scratch test, the effect of current density on interfacial bond strength and its mechanism were investigated. The experimental result indicates that, within the range of chosen current densities, the bond strength keeps a decreasing trend along with the increase of current density. This phenomenon was discussed with the partial discharge theory and the relationship between current density and overpotential.The influence of pre-electroforming with different parameters on bond strength was studied in the paper. In the experiment different current densities and corresponding time of pre-electroforming were separately applied, obtaining samples sharing different pre-electroformed layers, and the bond strength of the samples was measured with scratch test to obtain optimal pre-electroforming parameters. Applying the parameters can improve the interfacial bond strength of electroformed layers, which will increase the fabrication success rate of micro structures and prolong their life.