Theoretical and Experimental Investigations on Microelectrodeposition Process
Electrodeposition is one of the main techniques for fabricating conductive parts with one or two dimensions in the micron size range. This technique is utilized to coat surfaces with protective films of several micrometers thickness or fabricate standalone microstructures. In this process, an electrochemical reaction occurs on the electrode surface by applying an electric voltage, called overpotential. Different electrochemical practices were presented in the literature to obtain kinetic parameters of an electrochemical reaction but most of these practices are hard to implement for the reactions occur on a microelectrode. Toward addressing this issue, the first part of the dissertation work presents a combined experimental and analytical method which can more appropriately provides for the kinetic measurement on a microelectrode.
Another issue which occurs for electrodeposition on microscale recessed areas is the deviation of the profile of the deposition front from the substrate shape. Non-uniform deposition front usually obtains for a deposit evolved from a flat substrate with microscale size. Consequently, a subsequent precision grinding process is required to level the surface of the electrodeposited microparts. In order to remove the need for this subsequent process, in the second and third parts of the dissertation work, multiphysics modeling was used to study the effects of the fabrication parameters on the uniformity of the deposit surface and suggest a design strategy.
Surface texture of the deposit is another parameter which depends on the fabrication parameters. Several important characteristics of the electrodeposited coating including its wettability depend on the surface texture. The next part of the dissertation work presents an experimental investigation and a theoretical explanation for the effects of the overpotential and bath concentration on the surface texture of the copper deposit. As a result of this investigation, a novel two-step electrodeposition technique is developed to fabricate a superhydrophobic copper coating.
In the last part of the dissertation work, similar investigation to the previous sections was presented for the effects of the fabrication parameters on the crystalline structure of the deposit. This investigation shows that nanocrystalline and superplastic materials can be fabricated by electrodeposition if appropriate fabrication parameters are applied.