Pad printing of polymeric silver ink conductors on thermoplastic foils

Purpose: The aim of this study was to evaluate the feasibility of pad printing for producing electrical conductors and to define the factors affecting the print quality of polymeric silver ink conductors. Design/methodology/approach: Polyethylene terephthalate (PET) film and polyphenylene oxide (PPO) compound film were used as substrate materials. Three different polymeric silver inks, marked A, B and C, were used and tested. Findings: The results indicated that the important factors in the pad printing of silver ink conductors are the printing parameters and characteristics of the ink, pad, cliché and substrate. The interactions of these factors should be considered on a case-by-case basis. The sheet resistances of triple-pressed ink conductors varied between 20 and 110 mO/sq for 5.7- to 8.5-µm-thick conductors. Ink (B) had a higher sheet resistance than Ink (A) because of its lower silver particle content but also because of the shorter curing time and lower curing temperature. Ink (A) showed excellent adhesion on PET, and Ink (B) had moderate adhesion on PET without corona or plasma pre-treatments, but both inks adhered weakly on PPO compound. Both corona and plasma treatments raised adhesion of these two inks on all test substrates to the highest classification value, 5B. Originality/value: This paper contains a survey and preliminary testing of the pad printing of polymeric silver ink conductors on flexible thermoplastic foils. Finally, the paper introduces the advantages and drawbacks of the technique.