Characterization of conductive surface printing via electric field induced ion transport
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A novel methodology to imprint micron size features on copper surface has been adopted in this study. The process of printing is based on focused electric field induced ion transport across a cation selective NafionRTM membrane. The imprinting technology itself is environmentally benign because electrolyte consists of Sulfuric Acid (H2SO4) and Cupric Sulfate (CuSO4) are encapsulated by NafionRTM membrane in a copper made cathode chamber and it is sealed and recycled. In addition, the imprinted surface does not come in contact with corrosive chemicals which minimize the post cleaning process.;Three different methods of printing were embraced here in this study. They are direct contact mask-modulated electric field printing, non-contact mask-modulated electric field printing and non-contact uniform electric field mask printing. Process parameters for each type of methods have been studied in order to understand the effect on material removal rates, dimensions of the printed patterns compare to original mask and limitations on the printing process. The identified process parameters are the applied voltage, separation distance between two electrodes, variation on suctioned pressure, electrolyte concentration and conductivity, and variation of total pulse duration for the chopped direct current. Different mask types were used as an electrode to induce ions transportation. This include a 50PPI copper wire mesh, perforated stainless steel with O=570mum hole, polymer sheet with single drilled 2mm hole, copper TEM mesh with 35mum and 80mum window opening. Experimental results have shown that direct contact printing promises the best printing accuracy and geometric conformity among three methods, followed by mask printing with uniform electric field, especially for features in the range of tens of microns. Results from mask printing with chopped DC voltage needs further improvement for features in the micron range to overcome lateral diffusion at many interfaces of the process as well as the divergence of the electric field within the electrolyte, the D.I. water and the ion transporting membrane.