Development of a micro-accretion process for three dimensional structures

• Main Author: Choo, Jian Huei.
• Other Authors: Yeo, Swee Hock
• Format: Theses and Dissertations
• Published: 2008
• Subjects: DRNTU::Engineering::Manufacturing::Product engineering
• Online Access: http://hdl.handle.net/10356/5634
• Institution: Nanyang Technological University

The development of Microelectromechanical Systems has initiated the birth of various types of micro fabrication processes. These processes in turn serve as a platform for the invention of newer improved processes with increasingly higher fabrication resolution. This work reports on an investigative study on the growth characteristics of nickel micro-columns grown by Localized Electrochemical Deposition (LECD) - a new truly 3-D micro-rapid prototyping and direct-fabrication process capable of producing extremely high aspect ratio microstructures. This process uses the principles of electrodeposition but as its name indicates, localization of the electric field that induces the deposition, holds the key to its capability for fabrication with high feature resolution. Nickel columns were electrochemically deposited on copper cathodes from a nickel sulphamate plating solution using a non-soluble microelectrode as the anode. Initial experiments showed that zero, partial or complete growths of the columns were revealed, depending on the vertical traverse speed of the microelectrode away from the horizontal copper surface - the preferred traverse speed profile being a decreasing quadratic function that starts from a low traverse speed value followed by a constant function at a higher speed value with respect to time. Further work conducted based on this finding achieved constant growth with analog close-loop feedback control of the process, which produced columns with more even dimensions at a higher deposition rate. The dimensional control of the deposited structures was further found to be improved with the use of electrode rotation.