ارزیابی تجربی از یک مدل شبیه سازی اچینگ برای ماشینکاری فتوشیمیایی

Photochemical machining can satisfy the large demand coming from the microproducts market. The metal etching technologies lack however a precise control over the micro-geometry of surfaces. Metal etching results from diffusive and kinetic phenomena whose relative importance depends on process parameters. The effects of the chemical kinetics on the etching regime and, consequently, on the surface generated by wet-chemical etching need a thorough investigation. This paper reports an experimental assessment of a 2D simulation model of etching, where also the role of reaction products dynamics is considered. Furthermore an experimental analysis of the process parameters on micro-geometry is reported.

Among the production processes available to manufacture innovative products, etching technologies are very attractive for the high volume production they can provide. Dry and wet etching technologies are widely used in many emerging applications which require metal removal to produce micro-components and micro-systems [1], [2] and [3]. The development of environmentally safe processes contributes furthermore to the industrial diffusion of chemical etching [4]. Photochemical machining (PCM), in particular, seems a good etching technology to satisfy the large request coming from the microproducts market [5]; furthermore this technology could play an important role for the development of functional surfaces [6]. PCM lacks however a precise control over the surface micro-geometry. Metal etching is basically a result of diffusive and kinetic phenomena: their relative importance depends on the process's parameters, such as temperature and dilution of the etchant solution. Analytic models and simulation techniques provide valuable tools for the theoretical study of the etching process. The effects of the chemical kinetics on the etching regime and, consequently, on the surface generated by wet-chemical etching have been theoretically investigated by many authors [7]. Recent studies have considered both the diffusive resistance and the chemical kinetics, proposing models of diffusion and reaction controlled etching, including convection phenomena [8] and [9]. At micro-scale the experimental study of chemical etching poses several problems; the in-process evaluation of fundamental parameters, such as the local concentration and velocity of the etchant and reaction products, is currently impossible. These limits suggest the use of simulation techniques. An experimental assessment of a new 2D simulation model that considers the effects of the chemical kinetics on the etching regime and the role of reaction products dynamics is discussed.

A 2D Monte Carlo simulation model for PCM has been discussed; the model proves to be successful in describing temperature and geometric effects of an anisotropic surface disaggregation. The experimental tests and the relevant data fitting suggest that the etching process at lower temperatures shifts towards a reaction-limited regime. Besides, the etchant motion seems to have a great influence on the macroscopic anisotropy of the global process.