Physical principles and miniaturization of spark assisted chemical engraving (SACE)

Abstract

Spark assisted chemical engraving (SACE) is an unconventional micromachining technology based on electrochemical discharge phenomena for glass and various ceramics. The limits of SACE with respect to small dimensions in the particular case of glass are explored. It is found, using a specially developed set-up based on an AFM, that even using extremely sharp tool-electrodes does not allow us to produce a smaller pattern than typically 25 µm. It is concluded that the gas film thickness, in which the electrochemical discharges take place, is the main limiting factor. Further experimental investigations on its formation are investigated. By adding surfactants to the electrolyte, in order to increase the wettability of the tool-electrode and therefore to reduce the gas film thickness, it is observed experimentally that the critical voltage reduces significantly. This observation may lead to a novel method of characterizing the gas film thickness in SACE.

Spark assisted chemical engraving (SACE) in microfactory

“…From these pictures it becomes clear that during the time of machining of a single microhole (about half a minute), it is not possible to get an error of 20 µm because of tool wear. Indeed, as already mentioned, the main limiting factor is the stability of the gas film [7]. Newest results, which will be published elsewhere, show that it is possible by influencing the wettability of the tool-electrode (by adding surfactants to the electrolyte for example) to reduce this variance to below 5 µm [13].…”

“…WEDG can then be used to shape the tool for SACE. Other methods to produce the tool on the same machine were also proposed [6,7], where the tool is sharpened by inverting the polarity of the process electrodes.…”

“…The table-top SACE machining installation and some machining results will now be presented while the phenomenological description of the process and its theoretical interpretation are discussed in more detail in another contribution [7].…”

A mechanistic model of the gas film dynamics during the electrochemical discharge phenomenon

“…However, according to [30,31] only an extension of about 10% of U crit is observed. Further, the mean current once the gas film is formed, is predicted significantly too large with this model compared to experimental observations (a few percents of j crit [30,31]). To address these issues, one has to look more closely to Eq.…”

Primary to ternary current distribution at a vertical electrode during two-phase electrolysis

“…Nevertheless, nowadays, with the increasing interest in hydrogen production and clean, sustainable fluorine production for the nuclear industry, these processes have to be revisited with modern experimental and numerical tools for further optimization. Many authors [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have worked on this topic and some interesting experimental observations and numerical modelling are now available for engineering optimization and process intensification.…”