Conductive silver ink printing through the laser-induced forward transfer technique

- We have devised a strategy which allows eliminating the bulging problem during the LIFT of conductive lines.
- The strategy consists of the alternate deposition of two sets of non-overlapping droplets with an intermediate drying step.
- The process allows mitigating capillary flows along the printed line which are responsible for bulging and line breakup.
- Conductivity measurements of laser cured lines prove the feasibility of the technique for the fabrication of interconnects.

Laser induced forward transfer (LIFT) is a technique which allows printing a wide variety of materials. It presents several advantages over inkjet printing, such as a potentially higher resolution, being free from clogging issues, and the possibility to work with a much broader range of viscosities. LIFT appears, therefore, as an interesting alternative in all those fields where miniaturization is a major requirement, as in the microelectronics industry. The fabrication of electronic devices requires the printing of small, narrow and thin conductive lines, and in this work we investigate the printing of continuous lines of conductive silver ink on glass substrates through LIFT. Lines are initially formed through sequentially printing adjacent droplets with different overlaps. We show that above a certain overlap continuous lines can be obtained, but unfortunately they show bulging, a problem which compromises the functionality of the lines. In order to solve the problem, other printing strategies are tested; they consist in printing adjacent droplets in alternate sequences. It is found that the alternate printing of two overlapping sets of droplets with an intermediate drying step allows obtaining functional continuous lines without bulging.