Fabrication of 3D conductive circuits: print quality evaluation of a direct ink writing process.

The use of conductive inks and direct writing techniques for the fabrication of electronic circuits on complex substrates is attracting ever increasing interest. However, the existing knowledge is only focused on the electrical performances of the produced smart objects with no direct correlation with the conductive paths morphology and printing conditions. In order to evaluate the printing quality of a direct writing process using an eccentric screw dispenser, a printing device for the deposition of silver paste on 3D objects was developed. Lines of different widths were printed on flat PC + ABS substrates by means of the developed printing device and a conventional screen printing process. The developed process permitted printing lines as thin as possible with screen printing but with a better regularity of their edges. However unlike screen printed lines, the thickness of the lines was dependent on their width. Finally, the possibility to print on 3D objects was demonstrated.