Laser-induced forward transfer of conductive screen-printing inks

Laser-induced forward transfer (LIFT), unlike inkjet printing, presents few constrains concerning ink viscosity or loading particle size. This is clearly favorable for printed electronics applications, since high solid content inks, such those of screen printing, can be thus transferred in a digital fashion. In this work we propose a study of the transfer mechanisms during the LIFT of a commercially-available silver screen printing ink. The printing of single voxels on glass through the variation of pulse energy and donor-receiver gap reveals a linear dependence of voxel volume respect pulse energy for low energies and small gaps. The analysis of the transfer dynamics demonstrates that for the entire range of analyzed conditions the deposit takes place through bubble contact with the receiver. The printing of lines through variation of the overlap between successive voxels reveals that under none of the analyzed conditions we obtain uniform continuous lines through single scan: the lines always show scalloping, bulging, or discontinuities. These defects are a consequence of the modification of the donor film morphology induced by previous pulses in the line, which makes the transfer dynamics unstable. A final multiple scan approach proves the feasibility of the technique for printing uniform stable lines.