Optimization of laser printing of nanoparticle suspensions for microelectronic applications

Digital printing of interconnects for electronic devices requires processes capable of delivering controlled amounts of conductive inks in a fast and accurate way. Laser-induced forward transfer (LIFT) is an emerging technology that enables controlled printing of voxels of a wide range of inks with micrometer resolution. Its use with high solids content nanoparticle suspensions results in the deposition of voxels shaped as the impinging laser beam. This allows higher processing speeds, increasing the throughput of the technique. However, the optimum conditions for printing spot-like voxels have not been determined, yet. In this work, we perform a systematic study of the main experimental parameters, including laser pulse energy, laser beam dimensions, and gap distance, in order to understand the role that these parameters play in laser printing. Based on these results, we find that there is a narrow fluence range at distances close to the receiving substrate where spot-like voxels are deposited. We also provide a detailed discussion of the possible mechanisms that may lead to the observed features.