Research On Pulse Micro-Nano Electroforming Relevant Questions

Micro-electroforming is extensively applied to manufacture micro-nano metal structure in micro mechanical electrical system (MEMS), and become a key fabricating technology of non-silicon microstructures and devices. Micro-electroforming as a complicated process, there are many factors impact on the properties of its deposit microstructures, for example, current density, temperature and components of electroforming solution, deposit rate, and use of additives, et al.. Nano-electroforming is based on the development of micro-electroforming, According to fine grain strengthening theory, micro-electroforming process is adjusted to part or all grain sizes of deposit smaller than 100 nm. Microstructures with small grains and high density can be obtained to improve physical and mechanical properties.In this dissertation, electrocrystallization of pulse micro-electroforming is studied on. The relation between overpotential and time is established by mult-current step method under different pulse current parameters. It is shown that overpotential is the primary kinetics factor that induces electrodeposition on the cathode. The concept of metal adatom in intermediate is used to analyse the crystal seed formation and nucleation. A related model of crystal nuclei formation is set up in order to explain electrocrystallization in pulse micro-electroforming. Based on equivalent circuit of micro-electroforming, the electrode process kinetics of micro-electroforming nickel structure is studied with alternating current impedance method. Taken the crossing electroforming layer on micro-mold of micro-fluid chip as the example, the mathematical model is established. The current density and fluid field are describe with partial derential equation. Then three dimension numerical simulation of micro-electroforming is performed with the finite element method. The distribution of current density and fluid feild are helpful to plan and design micro-electroforming process, and reduce the developing time of micro-electroforming process.Periodic pulse reverse micro-electroforming with zero positive on-tmie is proposed, and the reason that the kind of micro-electroforming decreases grain sizes of electroforming layer is analysed. Under pulse reverse micro-electroforming condition, the duplex diffusion lyer between electroforming layer and bulk solution is build. Then the limiting current density of pulse reverse micro-electroforming is studied on. Pulse reverse micro-electroforming and pulse micro-electroforming are done respectively with the same compositions of electroforming solution. Microstructure, grain sizes and height uniformity of deposit change with pulse current are analysed. The mechanical properties, microhardness and wear resistance of electroforming layer is also studied.The limiting current density of pulse reverse micro-electroforming is larger than that of pulse micro-electroforming. The larger average current density effects on refine nanocrystalline structure. The negative average current density is 10% of the positive average current density in pulse reverse micro-electroforming, positive on-time and pulse off-time is correspond to those of pulse micro-electroforming. While positive average current density is larger than 10A/dm2, the average grain size of pulse reverse deposit is smaller; the microhardness of the pulse reverse deposit is higher; the wear resistance is better. This kind of pulse reverse micro-electroforming may improve the quality of electroforming microstructure.