Monitoring and exploration for the process of Ni-microelectroplating with a one-dimensional step-moving anode in Watts bath

• Main Authors: Rei-wei You, 游睿為
• Other Authors: J. C. Lin
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/72239669719128890834

碩士 === 國立中央大學 === 機械工程研究所 === 89 === Abstracts Key words: Microelectroplating, Pulse plating, Reference electrode, Electrochemical impedance spectroscopy A piece of platinum wire (diameter 125μm) was used as a reference electrode to monitor the potential variation of the cathode in the nickel micro electroplating, Ni-microelectroplating was carried out in a Watts bath using the platinum wire (diameter 125μm) as the anode and pure copper (10mm×10mm) as the cathode. The pt-anode was mounted in an epoxy resin which was driven by a micro step-motor to move perpendicularly to the cathode surface inμm. DC (direct current) and PC (pulse current) microelectroplating had been monitored by the platinum reference electrode. It was found that pt electrode is more proper than SCE (saturated calomel electrode) to be a reference for measurement the local potential of the cathode. The analysis of the variation of local potential of the cathode is helpful for choose optimal conditions to obtain a column deposit of nickel with fine grain and uniform diameter. Monitoring of the pulse-current microelectroplating of nickel by pt-reference electrode indicates the results: (1) The local and bulk potentials for the cathode are influenced by its surface treatment, and the outset potential for Ni-micro electroplating is also affected by the surface treatment. (2) Micro electroplating of nickel on copper starts initially at a bias ＞5V (＞－1760±7 mVpt); it grows into fine grains in a constant diameter at bias between the 5.6 ~ 6.0V (in the range－1919±11∼－1989±11 mVpt), and the growth rate of the Ni-microdeposition is practically accepted. (3) A cylindrical Ni-platform is obtained by conducting the PC-microelectroplating at optimal conditions control. Monitoring of the DC-potentiostatic Ni-microelectroplating by pt-reference electrode demonstrates the following results: (1) The cathodic polarization curve results from the potentiostatic experiments is better than that from potentiodynamic cathodic polarization. (2) The magnitude of the cathodic current affects he grain size of the microdeposit, and the electric field between the cathode and the micro-anode affects the shape of the Ni-micro deposit. The exploration of electrochemical impedance spectroscopy for Ni-micro electroplating by using pt as a reference electrode exhibits: (1) The polarization resistance (Rp) decreases but the capacitance of the double layer (Cdl) increases with increasing the bias applied for both the traditional Ni-plating and Ni-microplating. (2) The electric field is much greater for the micro plating (about 1000 V/m) than for the traditional plating (about 30 V/m), thus mass-transport limiting is more remarkable. (3) The magnitude of Rp is relatively negligible as compared this microelectroplating (about 0.01Ω‧cm2) with traditional electrodeposition (about 103∼10－1Ω‧cm2).