Wettability, roughness and surface treatment methods are essential for the majority of practical applications, where liquid–solid surface interactions take place. The present study experimentally investigated the influence of different mechanical surface treatment methods on the static wettability of uncoated and amphiphobic-coated aluminium alloy (AlMg3) samples, specially focusing on the interaction between surface finishing and coating. Five different surfaces were prepared: as-received substrate, polished, sandpapered, fleece-abraded and sandblasted. After characterisation, the samples were spray-coated using an amphiphobic coating. The characterisation of the uncoated and coated samples involved measurements of the roughness parameters and the apparent contact angles of demineralized water and rapeseed oil. The coating was initially characterised regarding its adhesion to the sample and elevated temperature stability. The applied surface treatments resulted in the scattered sample roughness in the range of Sa = 0.3–15.8 µm, water contact angles of θ a p , w = 78°–106° and extremely low oil contact angles. Coating the samples more than doubled the surface roughness to Sa = 13.3–29 µm, whereas the initial surface treatment properties (structure, anisotropy, etc.) were entirely repressed by the coating properties. Coating led the water contact angles to increase to θ a p , w _ c o a t e d = 162°–173° and even more pronounced oil contact angles to increase to θ a p , o _ c o a t e d = 139°–150°, classifying the surfaces as superhydrophobic and oleophobic.

Power electronics is concerned with the use of electronic devices to control and transfer electric power from one form to another. Power electronics can be found in laptop chargers, electric grids, and solar inverters. Die-attach interconnections form a critical part of power electronics devices. Silver sintering is traditionally used for die-attach interconnections because of its high melting point and ability to form very thin thicknesses. However, the processing time compared with soldering is very long. Sintered layers might contain large voids that affect the mechanical stability of the structure. Stresses caused by mechanical and environmental conditions might cause degradation and possibly early failures. This work focuses on studying the combined effect of process factors on the shear strength of small-area die-attach interconnections in silver sintering. Design of Experiments (DoE) tools were used to build an experimental matrix with a 95% confidence level. The results have shown that holding time has a considerable effect on the mechanical stability of the die-attach interconnections. Intermetallic compounds formed in the sintered joints at higher holding times resulted in lesser voids. Furthermore, the treatment level of the holding time highly affects the shear strength under the other factors of temperature and pressure.

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