The interactions among additives employed in acidic copper plating solution for microvia filling are characterized by galvanostatic measurement (GM) and electron paramagnetic resonance (EPR), respectively. These additives include polyethylene glycol (PEG), chloride ion, 3-mercapto-1-propanesulfonate (MPS), and bis-(3-sulfopropyl) disulfide (SPS). EPR patterns show that MPS can reduce Cu2+ to Cu+ before electrochemical reduction. However, the GMs show that MPS is an inhibiting reagent for copper electrodeposition. An inhibition mechanism of the MPS is proposed according to the EPR patterns. GMs also revealed that the combination of MPS and Cl− could result in a strongly catalytic effect on the Cu2+ reduction rate. This synergistic effect between MPS and Cl− on enhancing copper electrodeposition is attributed to an inner sphere electron transfer net constructed by a competitive coordination of MPS and Cl− on Cu2+ complexes. SPS also exhibits similar electrochemical behavior to MPS. However, the response speed of SPS in enhancing the Cu2+ reduction rate is slower than that of MPS. GM results obtained by adopting two different rotating speeds of the working electrode demonstrate that PEG competes with MPS to grab Cl− through Cu+, and that the competitive adsorption between PEG- Cl− and MPS­Cl− on the cathodic surface is strongly convection-dependent. © 2005 The Electrochemical Society. All rights reserved.

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

Printed circut boards (PCBs) have diminished in size and, simultaneously, their circuit densities have increased. Conventional multi‐layered PCBs have a limitation to higher packaging densities. This paper introduces a new copper electroplating formula that is able to fill vias and through holes simultaneously and is used in a DC plating method, in which the copper thickness deposited on the board surface is relatively very thin after the electroplating is completed.

The development of high density interconnects (HDI) of IC packaging substrate and printed circuit board (PCB) will be a key technology for fabrication of consumer electronic products in next generation. To meet the demands and requirements of state-of-the-art microelectronic products, not only the microvias but also the through holes (THs) of IC substrate and PCB, which both are responsible for the interconnection, are needed to be metallized in a mode of full fill with copper. However, current copper electroplating technology using a direct current (DC) cannot carry out the through hole filling, but only the microvia filling. In this work, a novel copper electroplating formula is developed in order to achieve the through hole filling by employing a DC plating. In addition, this new plating formula can also simultaneously achieve the filling of microvia and through hole in one step, which effectively reduces the process steps of fabrication.