Meaning
Electrochemical coating of a conductive substrate with a layer of metal from a solution under the influence of an electric current represents a standard industrial fabrication method. This electrodeposition is governed by Faraday’s laws of electrolysis, which define the relationship between the electrical charge passed through the cell and the mass of the deposited metal. It is bounded by the solubility limit of the metal ions in the electrolyte and the presence of unwanted secondary reactions.
Plating Mechanism
Positively charged metal ions migrate toward the cathode where they accept electrons and reduce to their metallic state. This cathodic reduction allows a uniform metallic layer to grow on the exposed surface of the workpiece. The rate of the electrodeposition depends directly on the current density applied to the system.
Bath Equilibrium
Continuous chemical replenishment of the plating bath is required to maintain a stable metal ion concentration during long manufacturing cycles. Soluble anodes slowly dissolve to replace the metal ions consumed at the cathode, balancing the bath chemistry. If this balance fails, the quality of the deposit deteriorates quickly.
Industrial Application
Printed circuit board manufacturing relies on this electrochemical process to form the conductive pathways and line the walls of microvias with copper. Fine-line circuits demand precise control of the organic additives in the electrolyte to ensure that the electrodeposition is concentrated within the deep vias rather than on the outer surface of the board. This localized acceleration of plating prevents the formation of voids and guarantees the mechanical reliability of high-density interconnects.
