Fundamental Study of Acid Copper Through-Hole Electroplating Process

Through-hole plating experiments were carried out with a gap cell and with Plexiglas boards. The gap cell provided good simulation of the plated through-hole system and allowed accurate and nondestructive profile analysis of copper deposits. As the current density and the aspect ratio were increased, the copper distribution inside the hole (gap) became more nonuniform. Plugging of holes was observed at high current levels due to current crowding into the hole entrance where the mass transport rate was high. The experimental findings were confirmed by mathematical models which were developed on the basis of electrochemical engineering principles and were applied to the geometric domain that included both the surface of the board and the through-hole wall. The limits of present through-hole plating technology are pointed out and possible means for process improvement are discussed. © 1989, The Electrochemical Society, Inc. All rights reserved.