Computer simulation of particle interference in abrasive jet micromachining

Abrasive jet micro-machining (AJM) uses a high-speed stream of particles to create small-scale features in substrates through controlled erosion, often through a mask which defines the feature edges. The shape of the profile machined in the substrate depends on the particle energy distribution available to the surface. In machining of masked samples, the sample is exposed to a uniform particle mass flux and velocity distribution due to the small ratio of the mask width to the blast area. However, the particle mass flux in the vicinity of the mask edge is disturbed due to particle collisions, resulting in a non-uniform flux. Moreover, particles rebounding from the edge of mask or the target surface can ricochet and hit the surface or mask wall a second time. These so called “second strike effects” have been reported in Slikkerveer and in’t Veld and Yamahata et al. [P.J. Slikkerveer, F.H. in’t Veld, Model for patterned erosion, Wear 233–235 (1999) 377–386 and C. Yamahata, F. Lacharme, Y. Burri, M.A.M. Gijs, A ball valve micropump in glass fabricated by powder blasting, Sensors Actuat. B 110 (2005) 1–7].A computer simulation model of particle second strike has been used to improve an analytical surface evolution model in AJM. Results of the computer simulation are used in the analytical model of ten Thije Boonkkamp et al. [J.H.M. ten Thije Boonkkamp, J.K.M. Jansen, An analytical solution for mechanical etching of glass by powder blasting, J. Eng. Math. 43 (2002) 385–399] to predict the channel profile. The shape and depth of channels predicted using this approach was compared with experimental profiles obtained with aluminum oxide particles blasted at glass substrates.