Through-Hole Filling by Copper Electroplating

Abstract

Through holes (THs) with different shapes were formed by laser drilling on a printed circuit board to evaluate the filling capability of two copper plating formulas. The shapes of these THs were cylindrical, V- and X-shaped. Two copper plating formulas, accelerator-free formula (AFF) and accelerator-containing formula (ACF), were employed in this work. The AFF contained only one organic additive and the ACF was composed of multiorganic additives. The electrochemical characteristics of the AFF were investigated by cyclic voltammetry, which could be utilized to explain the results of filling plating. The plating results showed that the cylindrical TH could be fully filled using AFF. However, the V- and X-shaped THs could be fully filled using ACF. TH and microvias could be simultaneously filled in one plating bath using the AFF. A filling mechanism based on an adsorption/consumption/diffusion mode was proposed to explain these plating results. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2988134] All rights reserved

Modeling Macro-Sized, High Aspect Ratio Through-Hole Filling by Multi-Component Additive-Assisted Copper Electrodeposition

“…45,48 Obviously this will depend on the specific additives used and the geometry of the scaffold. This paper has shown that simplified rules which only consider channel aspect ratio are not useful over all size scales.…”

Polyquaternium-2: A New Levelling Agent for Copper Electroplating from Acidic Sulphate Bath

“…5,7,8 Organic additives are widely used in copper electrodeposition as an effective way to control the current distribution in TH during electroplating or other certain properties of the copper deposit. [9][10][11] The additive system, used for PCB electroplating, generally includes accelerator (i.e., bis(3-sulfopropyl) disulfide), inhibitor (i.e., poly (ethyleneglycol)) and leveler (i.e., Janus Green B). [12][13][14][15] The synergy of these additives gives rise to a uniform plating or superfilling in the TH.…”

“…[12][13][14][15] The synergy of these additives gives rise to a uniform plating or superfilling in the TH. 9,12 Some literatures indicated that leveler plays an important or decisive role in the accelerator-inhibitor-leveler system. 9 The addition of leveler, for example Janus Green B (JGB), can significantly enhance the performance of a plating formula because the forced convection acting on the board surface is always stronger than that at the middle of the TH during electroplating.…”

“…9,12 Some literatures indicated that leveler plays an important or decisive role in the accelerator-inhibitor-leveler system. 9 The addition of leveler, for example Janus Green B (JGB), can significantly enhance the performance of a plating formula because the forced convection acting on the board surface is always stronger than that at the middle of the TH during electroplating. 16,17 It is a very time-consuming work to search or design additives for TH electroplating.…”

“…Until now, only few additives used for TH electroplating have been reported. 18,19 Most of the levelers used for copper electrodeposition bear quaternary ammoniums and halide in their molecular structure and can ionize a cation with one or two quaternary ammoniums and halide ions in aqueous solution. Hence, the cation could reach the cathode surface easily and inhibit the copper electrodeposition under the electric field, particularly the protrusion with high current density during electroplating.…”