A multi-step electrochemical etching process for a three-dimensional micro probe array

Abstract

We present a simple, fast, and cost-effective process for three-dimensional (3D) micro probe array fabrication using multi-step electrochemical metal foil etching. Compared to the previous electroplating (add-on) process, the present electrochemical (subtractive) process results in well-controlled material properties of the metallic microstructures. In the experimental study, we describe the single-step and multi-step electrochemical aluminum foil etching processes. In the single-step process, the depth etch rate and the bias etch rate of an aluminum foil have been measured as 1.50 ± 0.10 and 0.77 ± 0.03 μm min −1 , respectively. On the basis of the single-step process results, we have designed and performed the two-step electrochemical etching process for the 3D micro probe array fabrication. The fabricated 3D micro probe array shows the vertical and lateral fabrication errors of 15.5 ± 5.8% and 3.3 ± 0.9%, respectively, with the surface roughness of 37.4 ± 9.6 nm. The contact force and the contact resistance of the 3D micro probe array have been measured to be 24.30 ± 0.98 mN and 2.27 ± 0.11 , respectively, for an overdrive of 49.12 ± 1.25 μm.

Through-Mask Electrochemical Micromachining of Aluminum in Phosphoric Acid

“…In the absence of convection the etch rate ranged between 0.6 and 2.4 μm/min, which is typical for TMEMM of aluminum in electrolytes consisting of viscous mineral acids. 27,28 At 900 rpm etch rates ranging between 1.9 and 5.3 μm/min were calculated. In all cases the etch rate decreased sharply with the cumulative passed charge.…”

“…30 The majority of this work [27][28][29] was conducted in mixtures of perchloric acid, acetic acid and ethanol, which are linked z E-mail: tobias.baldhoff@pg.canterbury.ac.nz to specific safety concerns due to their reactivity, flammability and limited long-term stability. In addition, previous studies focused mainly on device fabrication and the influence of current density, electrolyte composition, machining time or initial surface structure.…”

Review—Through-Mask Electrochemical Micromachining

“…In addition, initially present oxide films must be stripped first and their regrowth prevented, either via chemical 183 or electrochemical means. 185,186 Alcohol-based electrolytes have also proven useful when machining aluminum, 192 cobalt 91 and iron alloys, 119,126 as well as steels. 4,119,126,170 Nonetheless, their application is likely limited to metals and alloys, which are otherwise only machinable with difficulty.…”

“…Through-foil etching allowed a bewildering variety of parts to be formed for use in mechanical, electronic, optical, analysis and separation systems. Articles thus machined encompass stainless-steel edge filters, 4,170 tantalum specimen holders, 177 molybdenum apertures, 5 elgiloy springs, 211 copper and stainless-steel ink-jet printer nozzle plates, 58,59 invar shadow masks, 33,147 molybdenum evaporation masks, 111 copper/palladium gas separation membranes, 55 aluminum cantilevers, 192 and stainless-steel bumping masks. 171 Critically, these foils could be subjected to twosided TMEMM, as there was no need for an insulating support, leading to rapid through-etching and the formation of straight side walls in shorter time intervals.…”

Investigation on particle assisted through-mask electrochemical etching of micro pits array

“…Deep metal microstructures are widely used in various research fields such as aerospace, optical instrumentation, automotive and biomedical technology. Deep metal microstructures have been increasing interest [17][18][19]. However, the poor localization and uniformity of the deep metal microstructures array limit the application of TMEE.…”