Wall Profile Developments in Through‐Mask Electrochemical Micromachining of Invar Alloy Films

Kwon, Giyun; Sun, Hongwei; Sohn, Hun‐Joon

doi:10.1149/1.2048678

Cited by 20 publications

(20 citation statements)

References 9 publications

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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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“…In through-mask EMM, metal dissolution takes place at the workpiece surface that lies at the bottom of the cavity created by the photoresist mask [1]. The photoresist patterned metal workpiece is made an anode in an electrochemical cell so that the exposed metal surface is removed by high rate anodic metal dissolution.…”

Section: Through-mask Emmmentioning

confidence: 99%

“…However, in the case of 2 1 2 D and 3D microfeatures, feature depth is comparatively higher, which necessitates close monitoring of the inter-electrode gap (IEG) and precisely controlled microtool movement during EMM. Two-dimensional (2D) and three-dimensional (3D) microfeatures of different shapes, sizes, and finishes need to be machined on microproducts or macroproducts for their practical applications, which can be machined by electrochemical micromachining (EMM).…”

Section: Introductionmentioning

confidence: 99%

Types of EMM

Bhattacharyya

2015

Electrochemical Micromachining for Nanofabrication, MEMS and Nanotechnology

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“…Under these parametric conditions, the overcut of the machined hole produced by the EMM is comparatively low. Throughmask EMM of Invar alloy films was investigated and mathematical modeling was reported to predict the wall profile development during EMM [59].…”

Section: Production Of High Accuracy Holesmentioning

confidence: 99%