Purpose -The purpose of this paper is to optimize experimental parameters and gain further insights into the plating process in the fabrication of high-density interconnections of printed circuit boards (PCBs) by the rotating disc electrode (RDE) model. Via metallization by copper electrodeposition for interconnection of PCBs has become increasingly important. In this metallization technique, copper is directly filled into the vias using special additives. To investigate electrochemical reaction mechanisms of electrodeposition in aqueous solutions, using experiments on an RDE is common practice. Design/methodology/approach -An electrochemical model is presented to describe the kinetics of copper electrodeposition on an RDE, which builds a bridge between the theoretical and experimental study for non-uniform copper electrodeposition in PCB manufacturing. Comsol Multiphysics, a multiphysics simulation platform, is invited to modeling flow field and potential distribution based on a two-dimensional (2D) axisymmetric physical modeling. The flow pattern in the electrolyte is determined by the 2D Navier-Stokes equations. Primary, secondary and tertiary current distributions are performed by the finite element method of multiphysics coupling. Findings -The ion concentration gradient near the cathode and the thickness of the diffusion layer under different rotating velocities are achieved by the finite element method of multiphysics coupling. The calculated concentration and boundary layer thicknesses agree well with those from the theoretical Levich equation. The effect of fluid flow on the current distribution over the electrode surface is also investigated in this model. The results reveal the impact of flow parameters on the current density distribution and thickness of plating layer, which are most concerned in the production of PCBs. Originality/value -By RDE electrochemical model, we build a bridge between the theoretical and experimental study for control of uniformity of plating layer by concentration boundary layer in PCB manufacturing. By means of a multiphysics coupling platform, we can accurately analyze and forecast the characteristic of the entire electrochemical system. These results reveal theoretical connections of current density distribution and plating thickness, with controlled parameters in the plating process to further help us comprehensively understand the mechanism of copper electrodeposition.
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.
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