Laser micro-printing dynamics and scalability of solution-precursor silver films

• Laser-induced silver reduction micro-printing processing scalability. • Silver micro-printing dynamics are studied for various laser operation regimes. • Photochemical and thermal laser printing regimes of silver are quantified. • Single spot and line deposition dynamics are presented from scalability standpoint. • Enables fast arbitrary pattern deposition of silver microstructures. Laser micro-printing by reduction of metal salts is an emerging direct laser writing technique, capable of producing precise conductive metallic structures with feature sizes smaller than a micrometer. Previous research focused on effects of chemical composition and additives, miniaturization of features and applications. This work explores variations in laser operating regimes towards micro-printing scalability. Single spot and line scanning deposition dynamics were analyzed by high-speed visible and infrared thermal imaging, comparing the effects of pulse energy, pulse repetition rate, incident pulse count and scanning speed on the dynamics and thermal effects of the silver deposit. The large variation of laser parameters was achieved by using a custom frequency doubled pulsed fiber-based laser, emitting 500 fs pulses in green 515 nm wavelength at up to 30 MHz repetition rate in pulse-on-demand operation regime. Pulse energy for silver deposition was in the range from 0.5 nJ to 6 nJ. Side-effects present during micro-printing, such as bubble formation and deposit ablation, were studied to omit imperfections, such as void formations in the deposit. Scanning speed provided an additional control parameter for line deposition, changing the dynamics and topography dramatically from low scanning speeds and high pulse energies to high speeds and a multi-pass scanning strategy. An optimal average linear density range of 10⁻ 3 –10⁻4 J/mm was determined. Understanding the effects of laser parameters and multi pass, high scanning speed strategy, turned out to be an enabler for homogeneous silver lines printed orders of magnitude faster than previously reported.