Acid Copper Electroplating

Bath Mechanism

Aqueous solutions containing copper sulfate, sulfuric acid, and chloride ions form the base of the electrolyte. In acid copper electroplating, the acid increases the conductivity of the bath and prevents the precipitation of copper salts, while copper sulfate supplies the metal ions. The chloride ions promote uniform anode dissolution and help organic additives function.

Organic suppressors and accelerators regulate the deposition rate across the board surface, ensuring that vias fill without trapping voids. Air agitation or mechanical movement of the board maintains a fresh supply of ions at the cathode surface during operation.

Plating Defect

Non-uniform current distribution causes thin metal on hole walls and excess deposition at the corners. During acid copper electroplating, high current densities can starve the center of high-aspect-ratio holes of copper ions. This deficiency results in thin plating or voids that break electrical continuity under thermal stress.