CC BY
12LP-PS-15
Laser printing of silver screen printing inks
P. Sopeña1, J.M. Fernández-Pradas1, P. Serra1
1Universitat de Barcelona, Applied Physics Department, Barcelona, Spain
Laser-induced forward transfer (LIFT) is a widely extended direct-write printing technique, being able to deposit from biological solutions to inorganic inks. In LIFT a very thin layer of material is spread on a donor substrate which is placed facing a receiver substrate. Then, through the action of a laser pulse focused on the donor film a bubble is created inside the ink, which expansion and further collapse leads to the formation of a jet that propels forward till it reaches the receiver, leading to liquid deposition. Finally, the jet breaks up and a voxel is thus printed. By the successive repetition of this process along the donor film multiple droplets and complex patterns can be reproduced.
The use of LIFT is especially interesting for printed electronic applications. Since there is no nozzle, unlike its major competitor, inkjet printing, there are almost no constrains on the rheological properties of the ink. Thus, extending the range of printable inks from low to high viscosity and from small to large particle size. For instance, this is relevant in the case of conductive inks because screen printing inks can be deposited. The high solid content of these inks allows obtaining very low sheet resistances usable for conductive pads. Since these inks are non-printable using inkjet printing due to nozzle-clogging, we propose LIFT for such task.
In this work we investigate the LIFT of silver screen printing inks for producing highly conductive pads. We determine the optimum working conditions for obtaining conductive continuous lines with the lowest sheet resistance by varying the laser pulse energy, repetition rate and donor-receiver gap. Finally, as a proof-of-concept of the technique, we print a high-frequency passive component that performs accordingly to the designed layout.
