New precision electroforming process for the simultaneous improvement of thickness uniformity and microstructure homogeneity of wafer-scale nanotwinned copper arrays

Zhan, Xiaofei; Shen, Chunjian; Zhu, Zengwei; Zhu, Di

doi:10.1016/j.ijmachtools.2023.104006

Cited by 8 publications

(2 citation statements)

References 72 publications

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“…A pure Ni (99.5%) mould as shown above in Fig. 2 was manufactured using dry etching, electroforming, and moulding based on silicon lithography [ 41 ] and electroforming [ 42 ]. Two design features were patterned on 4-inch silicon wafers using ultraviolet lithography, deep reactive ion etching (DRIE), followed by a conductive layer of titanium (50 nm) and nickel vanadium (200 nm), which was electroformed and then etched in a solution of potassium hydroxide (KOH).…”

Section: Methodsmentioning

confidence: 99%

Optimization of forward pulsed currents for combining the precision shaping and polishing of nickel micro mould tools to reduce demoulding defects

Zaki,

Zhang,

Gilchrist

2024

Int J Adv Manuf Technol

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Precise tooling is vital for defect-free production of micro injection moulded (μ-IM) or hot-embossed products. The demoulding stage of such moulding and forming processes poses a serious challenge to the integrity of thin miniature features because of friction, adhesion, and thermal stresses. Typically, micro moulds involve geometrically textured patterns or features such as linear ridges, pillars, channels, and holes, the characteristic dimensions of which range from 10 to 300 μm. Realistically complex mould designs, containing precision micro features (enhanced fillet radius and positive draft angle) and high surface quality, are presented in this work. Electropolishing based on forward pulse currents (PC) has been used to shape and polish Ni micro moulds that contain sets of micron-scaled linear ridges and star patterns in order to ease the separation of moulded polymeric parts from the metallic mould during ejection and demoulding. The use of forward pulsed currents improved the mould design by increasing the fillet radii and draft angle while keeping the surface roughness low and maintaining a good surface shine. An optimization study of forward PC using a green solution of nickel sulfamate varied EP times (0–70 min) and duty cycles (40, 50, 60, and 70%) at a process conditions of 2.8 V, 50 °C, and 250 rpm. The best topographical and morphological changes were observed for a typical microfluidic channel (w × h, 100 × 110 μm) with an EP time of 70 min and 50% duty cycle: fillet radius increased by 3.8 μm, draft angle by 3.3°, and the channel width reduced by 11.4% while surface roughness changed by 8.6% and surface shine improved by 48.9%. Experimental validation was performed using hot embossing wherein the electropolished Ni mould replicated the micro channels and star patterns in PMMA chips with notably fewer burrs, material pile up, and no feature distortion. Moreover, there was a reduction in the side wall roughness of micro channels in PDMS casting with electropolished Ni mould by 16%. Hence, this work presents a significant scientific contribution to improving the efficiency of micro mould tools and reduces the defects caused by friction and adhesion in replicated polymeric parts.

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Section: Methodsmentioning

confidence: 99%

Optimization of forward pulsed currents for combining the precision shaping and polishing of nickel micro mould tools to reduce demoulding defects

Zaki,

Zhang,

Gilchrist

2024

Int J Adv Manuf Technol

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“…This ensured that the microstructures were distributed equally across all layers on the wafer, while also minimizing the detrimental impact of current redistribution on individual thickness uniformity. 45 Li et al investigated the effects of two different processing methods, PC and PRC, on the microstructure and nanomechanical characteristics of nickel micro-pillars. According to their results, the PC technique produced an uneven microstructure with bigger columnar grains and numerous nanocrystals, as seen in Fig.…”

Section: Advancement In Micro-electroformingmentioning

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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In situ epitaxial thickening of wafer-scale, highly oriented nanotwinned Ag on tailored polycrystalline Cu substrates

Zhan,

Zhu

2024

Acta Materialia

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New precision electroforming process for the simultaneous improvement of thickness uniformity and microstructure homogeneity of wafer-scale nanotwinned copper arrays

Cited by 8 publications

References 72 publications

Optimization of forward pulsed currents for combining the precision shaping and polishing of nickel micro mould tools to reduce demoulding defects

Optimization of forward pulsed currents for combining the precision shaping and polishing of nickel micro mould tools to reduce demoulding defects

Review—Electroforming Process for Microsystems Fabrication

In situ epitaxial thickening of wafer-scale, highly oriented nanotwinned Ag on tailored polycrystalline Cu substrates

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