Tuning formation process of void defects in microcolumn arrays via pulse reverse electrodeposition

Dong, Yanzhuo; Jiang, Bingyan; Qiang, Jun; Ma, Zhigao; Drummer, Dietmar; Zhang, Lu

doi:10.1016/j.jmrt.2023.03.201

Cited by 6 publications

(4 citation statements)

References 34 publications

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“…7d. According to previous pulse reverse electroforming simulation, 35 it was found that the pulse reverse current realized the defect-free electroforming of the microcolumn by accelerating the dissolution of the electroforming layer at the top of the microcavity.…”

Section: The Electroforming Experiments Of Void-free Microcolumnsmentioning

confidence: 90%

Effect of Ion Mass Transfer and Electric Field Distribution on the Formation of Void Defect in Electroformed Nickel Microcolumns

et al. 2023

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The void defect inside the electroformed nickel microcolumns is a common problem affecting the performance of the microsystem. In this study, a simulation model for the dynamic deposition of microcolumns is set up to clarify the changing characteristics of ion mass transfer and electric field distribution inside the microcavities under the electroforming process, with the aim of revealing the formation mechanism of the void effect. The simulation results show that the dynamic aspect ratio (DAR) of the microcavity increases from the initial 2 : 1 to infinity during the electroforming process. As a result, the ion mass transfer within the microcavity decreases, resulting in a gradual deterioration in the uniformity of the nickel ion concentration distribution along the microcavity sidewall. The increased difference in the electrolyte potential along the microcavity sidewall leads to a reduction in the uniformity of the overpotential distribution. These two factors lead to a faster deposition rate at the open side of the microcavities, and consequently to the formation of a void defect inside the microcolumn. Compared to the overpotential distribution, the nickel ion concentration distribution plays a dominant role in the size of the void defect. Aiming to eliminate the void defect, several approaches have been carried out to improve the uniformity of the nickel ion concentration distribution inside the microcavity. The experimental results show that compared to a high current density (1 A/dm 2 ), the low current density (0.25 A/dm 2 ) helps to reduce the ion consumption rate, thus contributing to a uniform distribution of nickel ion concentration, as well as a reduced void defect size. The pulse reverse current proves effective in eliminating the effects of the nonuniform distribution of the ion concentration and the overpotential on the microcavity deposition and realized the defect-free electroforming of the microcolumn with a width of 30 µm and a height of 60 µm.

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Section: The Electroforming Experiments Of Void-free Microcolumnsmentioning

confidence: 90%

Effect of Ion Mass Transfer and Electric Field Distribution on the Formation of Void Defect in Electroformed Nickel Microcolumns

et al. 2023

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“…Therefore, it is necessary to use other methods to enhance the supplementation efficiency. In our previous study, it was found that when the forward pulse current density, reverse pulse current density, frequency, and forward pulse duty cycle were 1 A dm −2 , 2 A dm −2 , 1 Hz, and 0.9, respectively, the pulse reverse current could supply ions by dissolving the deposited layer and improve the filling ratio [24], as shown in figure 14(f). This indicates that the ion supplementation indeed plays an important role in the mass transfer within the microcavities with different aspect ratios.…”

Section: Experimental Verification Of Mass Transfer Controlling Factorsmentioning

confidence: 96%

“…At the same time, according to our previous studies on the mechanism of pulse reverse current, it is known that in addition to accelerating ion supplementation, increasing the reverse pulse current density can directly accelerate the dissolution of the electroformed layer at the top of the microcavity to achieve complete deposition of the microcolumn and eliminate void defects [24]. Thus, the void defects inside the microcolumns with a large width (30 µm) or a high aspect ratio (3:1) were eliminated by increasing the reverse pulse current density from 2 A dm −2 to 6 A dm −2 , as shown in figures 15(a) and (b).…”

Section: Experimental Verification Of Mass Transfer Controlling Factorsmentioning

confidence: 99%

Mass transfer characteristics at cathode/electrolyte interface during electrodeposition of nickel microcolumns with various aspect ratios

Dong,

Jiang,

Drummer

et al. 2023

J. Micromech. Microeng.

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The filling behaviour of electrodeposited microcolumns is strongly influenced by the mass transfer characteristics at the cathode/electrolyte interface. This study aims to elucidate the influence of the mass transfer characteristics (ion supplementation via diffusion and ion consumption via deposition) on the electrodeposition of microcolumns, thus providing feasible solutions for improving void defects with different feature sizes. The results indicate that ion consumption plays an important role in the mass transfer within large-width microcavities (100 μm). For large-width microcolumns, longer electroforming times lead to higher ion consumption, resulting in nonuniform ion concentration distribution, and consequently uneven deposition rates along the microcavity wall. In microcavities with high aspect ratio (5:1), ion supplementation plays a major role. The low ion supplementation rate does not support a uniform deposition, resulting in a large void defect and a low filling ratio in the deposited microcolumns. Therefore, reducing the ion consumption rate by decreasing the current density from 1 A/dm2 to 0.25 A/dm2 can effectively increase the filling ratio in large-width microcolumns with no significant effect on high aspect ratio microcolumns. On the contrary, the pulse reverse current (forward pulse current density 1 A/dm2, reverse pulse current density 2 A/dm2, frequency 1 Hz, forward pulse duty cycle 0.9) can increase the filling ratio in the high aspect ratio microcolumns by accelerating ion supplementation through dissolution of the deposited layer. By further increasing the reverse pulse current density from 2 A/dm2 to 6 A/dm2, void defects can be completely eliminated and even void-free deposition of high aspect ratio microcolumns (5:1) can be achieved.

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“…Finally, tertiary current distribution, which integrates all three elements, accounts for differences in electrolyte composition caused by mass transfer effects. 121,122 The first numerical studies of electroforming, which comprises the properties of current efficiency and periodic reversal on the mandrel is examined by McGeough and Rasmussen in 1976. They tried to solve the problem of uniformity on the mandrel having sinusoidal irregularities that are influenced by the time intervals of the polarity-cycle and the current efficiencies.…”

Section: Significance and Challenges Of Electroforming Modellingmentioning

confidence: 99%

Review—Electroforming Process for Microsystems Fabrication

Rai,

Gupta

2023

J. Electrochem. Soc.

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Being an unconventional technique of additive micro-manufacturing, electroforming has garnered significant interest by various industrial sectors because of its capability to offer advanced micro-manufacturing competences with high precision in achieving dimensional uniformity and replication accuracy at small scale. This paper reports a comprehensive review of the electroforming process as a microsystem fabrication technique. This process is superior compared to 3D printing, stereolithography, selective laser sintering, and fused deposition modeling etc., in many aspects due to its unique properties. It can deposit a wide variety of metals and alloys, including precious metals, making it appropriate for variegated applications in microfabrication domain. We cover the fundamental aspects of electroforming and its history followed by the current state of the art advancement, modelling associated with it, and its importance from industrial context. Additionally, we discuss the advantages and limitations of this technique and their respective microsystems applications. Finally, we conclude with a discussion on the future prospects and potential advancements in the field of electroforming contributing to micro-systems development.

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Tuning formation process of void defects in microcolumn arrays via pulse reverse electrodeposition

Cited by 6 publications

References 34 publications

Effect of Ion Mass Transfer and Electric Field Distribution on the Formation of Void Defect in Electroformed Nickel Microcolumns

Effect of Ion Mass Transfer and Electric Field Distribution on the Formation of Void Defect in Electroformed Nickel Microcolumns

Mass transfer characteristics at cathode/electrolyte interface during electrodeposition of nickel microcolumns with various aspect ratios

Review—Electroforming Process for Microsystems Fabrication

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