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Mass Transport and Current Distribution
Published in Madhav Datta, Electrodissolution Processes, 2020
The RDE is a commonly used hydrodynamic analytical tool for electrochemical studies. The uniqueness of the RDE system is that the diffusion layer thickness does not depend on the radius thus the mass transport rate is uniform all over the surface. The RDE consists of a disk made of the working electrode material which is set into an insulating surround generally PTFE or a ceramic material. The RDE is rotated about its vertical axis typically between 100 and 10,000 rpm. The principle of operation of an RDE is shown in Figure 4.6. The electrolyte is drawn towards the disk by its rotation while the tangential forces project the electrolyte outward toward the edge of the disk.
Control Systems Engineering
Published in L. Ashok Kumar, M. Senthilkumar, Automation in Textile Machinery, 2018
L. Ashok Kumar, M. Senthilkumar
The rotating disk electrode (RDE) consists of a disk on the end of an insulated shaft that is rotated at a controlled angular velocity. Providing the flow is laminar over all of the disk, the mathematical description of the flow is surprisingly simple, with the solution velocity toward the disk being a function of the distance from the surface, but it is independent of the radial position. Consequently, the mass transport conditions are uniform over the surface of the disk, and the limiting current is given by () iL=1.554zFAD2/3V−1/6C∞ω1/2The rotating cylinder electrode provides more uniform behavior over the electrode surface than the RDE when turbulent flow conditions are used (the central region of the RDE is always laminar).Flow channels have the advantage that the electrode remains stationary, and is therefore easily examined during the experiment. The design of a flow channel to achieve well-defined flow conditions requires considerable care. In particular, the electrodes must be accurately aligned with the wall of the channel, with no gaps or steps that could induce turbulence, and the flow pattern must be well-established before reaching the electrodes, which requires a long entry region to allow the flow to stabilize.
Study of microvia filling process based on multi-physical coupling
Published in Transactions of the IMF, 2018
Linxian Ji, Hexian Nie, Shidong Su, Yuanming Chen, Wei He, Kehua Ai
According to Figure 4, the thickness of the concentration boundary layer gradually became small with increasing fluid velocity. In the electrochemical test, a rotating disc electrode (RDE) is normally used to analyse the properties of the plating solution. For copper electrodeposition on the RDE, the decreasing of concentration boundary layer thickness was at first abrupt when velocity changed from 0 rev min−1 to 1000 rev min−1 and then slowed gradually when rotating speed increased from 1000 rev min−1 to 4000 rev min−1. The same change of speed was also observed for the cathode of the Haring cell. With the increase of fluid velocity, mass transfer of cupric ions to the cathode surface was improved and the reaction rate of cupric ions was enhanced. Therefore, the diffusion boundary layer built a bridge between the theoretical and experimental study of copper electrodeposition. By concentration boundary layer, the effect of electrolyte flow pattern on plating thickness and current distribution was associated with that of the rotating speed of the RDE in the electrochemical test. The challenge of microvia filling is to overcome the pinch-off effect due to the accumulation of electric field at the opening of the microvia. Many efforts have been made to realise the superfilling of microvia by using complex chemical additives. The effects of additives on copper electrodeposited potential have been investigated by RDE technology.