A FINITE-VOLUME-BASED TIME-SPLITTING SCHEME FOR COMPUTATION OF ELECTRODEPOSITION

Abstract

The LIGA process is emerging as a viable contender in the microfabrication of metallic high-aspect-ratio microstructures. The final step in the LIGA process is the electroplating of the metal part. In this step, metallic ions are transported to the cathode by the fluid and are deposited on it through chemical reactions. There are two kinds of chemical reactions: homogeneous dissociation reactions in the electrolyte bath, and finite-rate surface reactions on the electrode. In this article we develop a finite-volume method for computing electrodeposition in the LIGA process. We employ a time-splitting algorithm for coupling the bulk and surface reactions. First there is an instantaneous equilibration step in which the species existing in a cell are equilibrated to yield an intermediate concentration distribution. This serves as the initial condition to the transport step in which slow reactions and convective and diffusive transport are computed. As an alternative, the species concentration field is solved over the whole domain using a direct method. The two methods are compared to establish the validity and efficiency of the time-splitting algorithm.