Non-Masking Local Electroplating by Electrolyte Jet

Abstract

This paper presents a novel selective electroplating method that utilizes an electrolyte jet, instead of insulation masking on a substrate. The deposits have a convex shaped cross-section in the jet electroplating, so that the electrolyte jet is appropriately applied to selective electroplating. Even without masking process, a definite boundary between plated and non-plated area needs to be achieved in selective electroplating. The flat electroplated area, in which the current density distribution is nearly uniform, is deposited by using the nozzle with a center bar. However, the boundary becomes indistinct with this nozzle. The current density distribution on a cathode surface can be simulated by applying a finite element method based on the Laplace equation in steady state. The calculations suggest that the flat deposit area with a definite boundary will be created, if the electrolyte jet is limited to strike only on the projected nozzle area of a substrate. A modified nozzle with high velocity air holes adjacent to an electrolyte jet is designed, which successfully creates the flat deposit similar to the simulated cross-section profile.