Laser writing for selective plating of electro-conductive lines for electronics has several significant advantages, compared to conventional printed circuit board technology. Firstly, this method is faster and cheaper at the prototyping stage. Secondly, material consumption is reduced, because it works selectively. However, the biggest merit of this method is potentiality to produce moulded interconnect device, enabling to create electronics on complex 3D surfaces, thus saving space, materials and cost of production. There are two basic techniques of laser writing for selective plating on plastics: the laser-induced selective activation (LISA) and laser direct structuring (LDS). In the LISA method, pure plastics without any dopant (filler) can be used. In the LDS method, special fillers are mixed in the polymer matrix. These fillers are activated during laser writing process, and, in the next processing step, the laser modified area can be selectively plated with metals.
In this work, both methods of the laser writing for the selective plating of polymers were investigated and compared. For LDS approach, new material: polypropylene with carbon-based additives was tested using picosecond and nanosecond laser pulses. Different laser processing parameters (laser pulse energy, scanning speed, the number of scans, pulse durations, wavelength and overlapping of scanned lines) were applied in order to find out the optimal regime of activation. Areal selectivity tests showed a high plating resolution. The narrowest width of a copper-plated line was less than 23 μm. Finally, our material was applied to the prototype of the electronic circuit board on a 2D surface.
Metal films on transparent substrates are widely applied for mask production in lithography, and lasers are frequently
used for their patterning. Quality of the patterning is limited by fundamental phenomena taking place close to edges of the laser ablated area. We experimentally and numerically investigated transformations in metal films during their
irradiation with the nanosecond laser beam with fluence above the ablation threshold. Ridges of the resolidified metal with non-uniform thickness were always formed on edges of the cleaned area. Instabilities during the ablation process forced the molten metal in the ridges to break up into droplets with the periodicity predicted by the Plateau–Rayleigh instability. The droplets on ridges were starting points for formation of self-organized lines of metal film by irradiation with partially overlapping laser pulses. The initial droplets and later the self-organized parallel lines of chromium metal were heat sinks that cooled down the metal in their close proximity. Temperature modulation along the laser irradiation spot was high enough to initiate the Marangoni effect which resulted in movement of the molten metal from hot to colder areas.