Effect of Mask Wall Angle on Shape Evolution during Through‐Mask Electrochemical Micromachining

Shenoy, RV; Datta, Madhav

doi:10.1149/1.1836477

Cited by 43 publications

(31 citation statements)

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“…[38][39][40][41][42] The boundary was first discretized into line segments where the concentration was approximated along each segment using discontinuous, linear functions. 43 Such boundary elements are easy to implement and allow for discontinuities at corner points and at the edge between the metal and the insulator.…”

Section: Simulationmentioning

confidence: 99%

Through-Mask Electrochemical Micromachining of Aluminum in Phosphoric Acid

Baldhoff

Nock

Marshall

2017

J. Electrochem. Soc.

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Aluminum micro-channels have been machined in phosphoric acid via mass-transfer limited electrochemical dissolution through photoresist masks. The results of shape evolution experiments using a rotating disk electrode are presented in terms of the dimensions, shape profile and uniformity of the machined micro-channels. The influences of applied potential, cumulative passed charge and hydrodynamic conditions on the shape evolution process are discussed. Experimental results are compared with a shape evolution model assuming the rate of aluminum removal is solely controlled by diffusive mass transfer. The degree of agreement between experimental and simulated results depends mainly on the hydrodynamic conditions in the electrochemical cell and indicates a shift from purely diffusive to mixed convective-diffusive mass transfer. Through-Mask Electrochemical Micromachining (TMEMM) is an unconventional machining process, in which a metal substrate is made the anode in an electrochemical cell and thereby dissolved.1,2 Localized material removal is achieved by covering the substrate with an insulating mask. The use of common photolithography processes for the creation of the mask enables the fabrication of micrometer-sized structures. Thereby, TMEMM can be used in two ways to fabricate microfluidic devices: firstly, cavities and channels can be machined into the substrate surface and secondly, through-holes and slits can be machined into metal foils or shims.1 Compared to classical wet chemical and dry etching processes, TMEMM offers higher rates of material removal, better control of surface finish, more selective machining of substrates and enhanced process safety. [3][4][5] In addition, combining photolithography with electrochemical dissolution processes is expected to enable the fabrication of a large number of microfluidic devices in parallel and at low cost. 6Aluminum is widely used as a construction material for the manufacture of microfluidic devices such as micro-heat exchangers, 7 microreactors 8 and micro-fuel cells. 9 Other areas of interest are the fabrication of intricate parts in optical, electronic, automotive and aerospace systems. 10,11 Its chief advantages compared to other materials used in these fields are its high thermal conductivity, low electrical resistivity, easy machinability and low density. In addition, it is possible to modify the surface structure of aluminum substrates via the formation of highly ordered, porous oxide films along the surface. 12,13 It has been demonstrated, that these films can be subsequently used to incorporate noble metal catalysts along the surface of micro-channels within a micro-reactor. [14][15][16] Electrochemical dissolution of aluminum in phosphoric acid is known to produce reflective aluminum surfaces with sub-micrometer surface roughness at sufficiently high electrolyte concentration and temperature.17 This property makes it attractive for TMEMM of micrometer-sized structures made from aluminum. The observed leveling and brightening effect is caused by the m...

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Section: Simulationmentioning

confidence: 99%

Through-Mask Electrochemical Micromachining of Aluminum in Phosphoric Acid

Baldhoff

Nock

Marshall

2017

J. Electrochem. Soc.

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“…[2]. Selecting a proper current density as a function of the substrate shape and cell geometry can significantly reduce the metal removal rate in the lateral direction.…”

Section: Through-mask Emmmentioning

confidence: 99%

Types of EMM

Bhattacharyya

2015

Electrochemical Micromachining for Nanofabrication, MEMS and Nanotechnology

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“…3b), the equations describing its mathematical models were based on the assumptions shown in West et al, Datta, Shenoy and Datta, Shenoy et al, and Li et al [21][22][23][24][25], and the function of influence factor, ηω, was adopted from Li et al [26], presented as follow…”

Section: Model Development and Solvingmentioning

confidence: 99%

Fabrication of through-hole with biconically shaped cross sections by using electroforming and inert metal mask electrochemical machining

Ming

Bao

Qiaoling

et al. 2014

Int J Adv Manuf Technol

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Based on the inert metal perforation plate acted as both mandrel and mask, a hybrid electrochemical fabrication process combining electroforming and mask electrochemical machining was proposed to manufacture metal through-hole arrays with double tapered openings. The feasibility of this novel hybrid process was first investigated theoretically according to developed numerical models, and then, the effect of structure parameters of the inert metal plate on profile characteristics of the through-hole being processed was numerically analyzed where optimal structure parameters were further determined. Subsequent experimental results, on the whole, agreed with those from numerical analysis. Research results showed that the profile characteristics of the shaped throughhole were significantly dependent on the structure parameters of the inert metal plate used. Smaller through-holes with a better symmetry between the opening profiles can be achieved if the inert metal plates with bigger thickness and larger hole wall angle were used. With the reduction of hole spacing in the inert metal plate, the achievable aspect ratio of the machined through-hole gradually increased, and the profile symmetry between entry and exit became better. With the increase of hole size of the patterned inert metal plate, the thickness limitation of the through-hole plates that can be achieved rose, but the minimum diameter tended to be smaller and the symmetry worsened. In addition, nonconventional inward horn-shaped profile can be shaped in the mask electrochemical machining step only when the inert metal plates having small hole spacing and hole wall angle are utilized. With a diameter deviation between the entry and the exit, 9.7 % and an expanding rate 110.1 %, favorable through-holes featuring good opening profile symmetry (88.8 %) and smooth surfaces can be machined using this hybrid process.

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Effect of Mask Wall Angle on Shape Evolution during Through‐Mask Electrochemical Micromachining

Cited by 43 publications

References 1 publication

Through-Mask Electrochemical Micromachining of Aluminum in Phosphoric Acid

Through-Mask Electrochemical Micromachining of Aluminum in Phosphoric Acid

Types of EMM

Fabrication of through-hole with biconically shaped cross sections by using electroforming and inert metal mask electrochemical machining

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