Influence of drying temperature on inkjet printed droplets and lines morphology by using silver nanoparticles based ink: relation with electrical performances

摘要

For several years, printed electronics have been a creative sector with the printing of numerous electrical devices such as transistors, capacitors, diodes, transistors, lightings, solar panels, memories, etc. In order to ensure the electrical connection of these different electronic components, the printing of conductive tracks with low resistances and homogeneous properties is essential. Thanks to its main advantages, inkjet printing process was identified as a relevant technology to print these conductive tracks. Indeed, inkjet printing is a direct writing process which offers the possibility to produce fine elements on a large variety of substrate. However, with inkjet process, the printing pattern morphology, i.e. the transversal profile of the printed tracks still remains an important issue to consider. Indeed, it is well-known that the different flows that may arise during the drying phase (Coffee-ring effect, Marangoni... etc.) can lead to inhomogeneous profile and affect strongly the electrical conductance of the printing patterns. In this work, the piezoelectric inkjet printing of individual droplets and fine lines was performed by using a commercially silver nanoparticles ink. To complete an accurate printing, the ink compatibility with the inkjet printing requirements was checked thanks to a dimensionless analysis. A set of measures based on four geometrical indexes was defined to precisely characterize the particles distribution within dried printed droplets and lines. The droplet profile variations were monitored over different substrate temperatures. Correlations between droplet profile, line profile and resulting electrical conductance are proposed in the discussion part of this paper. Up to our knowledge, it is the first time that such analysis was conducted with a silver conductive inkjet ink at a picoliter scale.