Current distributions on patterned electrodes in laminar flow

The paper deals with the prediction of current distributions at patterned e lectrodes in the presence of forced laminar flow. The pattern considered co nsisted of a series of parallel tracks oriented perpendicularly to the flow and submitted to copper deposition from a sulphuric bath. The active featu res - 35 mu m high and 80 mu m wide - are relevant to the production proces ses for micromechanical and electronic applications. Due to the fair conduc tivity of the bath and the small dimensions of the features, the overvoltag e was shown to be uniform within less than one millivolt over the patterned region of the cathode. Therefore ed distributions on the vias could be cal culated regardless of the potential distribution. Flow patterns, concentrat ion profiles and ed distributions are discussed depending on the average ve locity of the fluid, the current applied, and the distance between two neig hbouring tracks. Whereas the flow patterns are perfectly symmetrical due th e low Reynolds in the cavity, concentration gradients and current densities are quite higher on the downstream part of the cavity, due to the presence of the inactive zone between the tracks. (C) 1999 Elsevier Science Ltd. Al l rights reserved.