On the mass transport of direct and pulse microplating andthe thermoelectric property of the micrometer alloying deposit

• Main Authors: Ting-kang Chang, 張庭綱
• Other Authors: Jing-chie Lin
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/29265056472924966847

博士 === 國立中央大學 === 機械工程研究所 === 97 === Micrometer copper and nickel columns were fabricated by direct and pulse current micro anode guided electroplating (MAGE) in this study. A micro reference electrode coupled with potentiostat was used to probe the local potential during electrodeposition and record the deposition current. The local concentration of metallic ions can be estimated from the local potential probed to calculate the supplying rate of the ions. The consumption rate was calculated from the deposition current. The surface morphology and the internal structure of the deposits were majorly determined by the electric bias and duty cycle due to their influence on the rate of electrical discharge and the rate of mass transport of the metallic ions. The metal column could be grown with a smooth surface and compact internal as the supplying rate of metallic ions (mass transport) is sufficient to compensate the consuming rate of the ions (caused by electrical discharge). On the other hand, the metal column would be grown with rough surface and porous internal. The alloy Ni/Cu columns also could be fabricated by MAGE process. The composition of Ni-Cu alloys was determined by the applied voltage and the concentration of cupric ions in the bath. With higher voltage applied, the Ni-content in the alloy is higher; increasing the concentration of cupric ions, the Ni-content in the alloy is becoming less. A micro column alloy with similar composition to the commercial Ni-Cu thermocouple was fabricated in the citrate bath containing 0.012M Cu2+ at 3.8V. Continuous MAGE was developed by means of visual control, image process and current feedback to maintain a steady strength of electric field. This method is better than intermittent MAGE to fabricate microcolumns with good quality.