A reproducible extrusion printing process with highly viscous nanoparticle inks

Printing of functional materials such as nanoparticle inks is a class of additive fabrication techniques complementary to standard subtractive electronics fabrication techniques such as pcb technology on pcb level or silicon based microelectronics on integrated circuit level. To date the majority of digital printing processes for (micro)electronics is inkjet based. Moreover aerosol jet based printing also establishes itself for printing on non-planar substrates and for materials with higher viscosities. A material deposition technique available since decades and mainly used for dispensing of adhesives and sealing materials is fluid-filament printing. It allows to cover a wide range of materials and viscosities and thus, also holds potential for additive manufacturing of electronics. In this paper we systematically study the influences on fluid filament printing both theoretically taking into account ink and equipment tolerances and experimentally using mainly standard dispensing equipment and two commercial screen printing inks. At the end of the paper we derive recommendations for reproducible printing of conductive lines and pads and give an outlook to printing 2.5D structures.