Soldering and brazing processes are utilized widely in numerous fields of industrial applications, such as electronics or in heat exchangers [1]. A good quality of the joint is of vital interest by controlling the joining process. For instance, typical failures, such as filler metal overflow or incomplete filled gaps result in less adhesion force or initial points for corrosion [2]. To avoid such failures, an ideal contact between the surface and the filler material is necessary, as well as having regions with higher contact angles to stop the flow of the liquid metal.
Direct Laser Interference Patterning (DLIP) is utilized to manufacture periodic surface pattern on stainless steel to tailor the contact angle of a liquid nickel-based brazing alloy. An interference setup of two laser beams generates periodic line-like structures with a spatial period of 6.0 µm. By controlling the processing parameters, a maximum structure depth of 2.0 µm is achieved. In addition, the formation of laser induces periodic surface structures (LIPSS) with a period of ~800 nm is examined on top of the DLIP structures. Importantly, the contact angle of the molten metal is increased from 13° up to 96°, depending on the resulting structure depth. This enables adjusting the contact angle for various soldering and brazing applications as well as a filler metal stop.
In consequence, the surface chemistry could be also playing an important role in the measured CA. As known from previous studies, laser processes with ps pulses can also affect the surface chemistry if stainless steels, mainly by forming oxides [3]. Thus, additional research is necessary for more precise statements [4].