Cold spray surface patterning of aluminum on aluminum, silicon, glass, and printed circuit board substrates

The aim of the present study is to investigate the feasibility and the criteria of using the cold spray technique for surface patterning to create two-dimensional surface features on various substrates. Metal meshes (16, 45, 170, 200, 400, and 5/16″) were used as screens for surface patterning in this investigation; fabricated features were characterized with optical microscope, scanning electron microscope, and optical profilometer. Processing parameters like mesh size, standoff distance, gun traverse speed, and number of spray passes were examined to study their influence to the morphology of the fabricated features. Two-dimensional aluminum features were successfully fabricated on aluminum, soda-lime glass, silicon wafer, and the copper foil-layer of printed circuit board. The smallest feature created with −45 to +5 μm aluminum feedstock powders, has an average size of 67.4 μm. It was determined that the pore size of a mesh needs to be at least 3.3 times bigger than the average size of feedstock powders in order to create features successfully. To estimate the probability of feedstock powders passing through a mesh and simulate the topography of the fabricated features, a Monte Carlo simulation incorporating the particle size distribution and the geometries of meshes was developed. With the capability of creating features on diverse substrates, the cold spray surface patterning technique shows promising potential to create heterogeneous two-dimensional functional features or devices at micron-sized with high efficiency.