Improved Uniformity of Conformal Through-Hole Copper Electrodeposition by Revision of Plating Cell Configuration

Abstract

Bath geometry and uniform electrolyte flow are the foundations of a uniform copper electrodeposition for printed circuit boards (PCBs) and electronic packaging applications. In order to achieve requirements for uniform electrodeposit thickness, a revised bath configuration was introduced to achieve copper electrodeposition of through holes (THs). Compared with Haring cell, uniformity of plated through hole (PTH) had been improved, especially for high aspect ratio TH. Furthermore, an electrochemical model for TH filling was constructed by multi-physical coupling technique. The model was utilized to investigate performances of copper electrodeposition, such as electrolyte flow field, resistance, current density distribution and electrodeposit thickness. The results indicated that for high aspect ratio TH filling, electrolyte flow played an increasingly important role in uniform electroplating process, which was in good agreement with the experiments. Furthermore, the effects of forced convection on mass transport during copper electrodeposition were analyzed by electrochemical measurements. The re-optimized bath configuration is effective for uniform TH filling.