Purpose – This paper aims to find an optimal surface treatment of commonly used polymeric substrates for achieve the high adhesion of printed structures. For this reason, the investigation of substrates surfaces from different perspectives is presented in this paper. Design/methodology/approach – The contact angle measurements as well as the roughness measurements were realised for the analysis of surface properties of investigated substrates. The impact of applied chemical agents for surface treatment onto the wettability is analysed for polyimide, polyethylene terephthalate and polyethylene naphthalene substrates. Findings – The results prove the correlation among wettability, surface energy and work of adhesion with respect to the theoretical background. The surface treatment of polymeric substrates by chemical agents, such as acetone, toluene, ethanol, isopropyl and fluor silane polymer, has a significant impact onto the wettability of substrates which affects the final deposition process of nanoinks. Originality/value – The main benefit of the surfaces’ investigation presented in this paper lays in surface modification by readily available chemical agents for optimising the deposition process nanoinks used in inkjet printing technology.

Abstract-The sintering of elements performed with the inkjet printing technique is one of the stages of flexible printed circuit manufacturing process. It is a crucial factor to determining the printed paths conductivity playing often an important role in the printed circuit. In this paper the study of the influence of thermal sintering conditions (temperature, time) on the resistance of paths made with inkjet printing on flexible substrates by using two electrically conductive inks was presented. The results of the investigations show that the sintering temperature is the main factor determining the paths resistance. Therefore, in some applications the sintering temperature higher than the one specified by the ink manufacturer can be used to decrease the paths resistance and to improve some circuit parameters. However, it should be noticed that the effective resistance decrease occurs only up to a certain temperature due to the appearance cracks in the printed paths.

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Purpose This paper aims to study drop formation in piezoelectric industrial printheads during the inkjet printing processes. It presents how the piezoelectric printhead forms drops of nanoparticle ink and how the problems with different values of drop parameters may influence the printed pattern’ defects and quality. Design/methodology/approach A piezoelectric printhead with 128 nozzles was activated to operate in a controlled manner, and the droplets ejected from the nozzles were observed during falling and analysed in the printview system. The effect of varying the values of drop parameters on print quality and pattern defects has been analysed and discussed. Findings The obtained results allow the identification of the sources of the technological problems in obtaining repeatable performance drops with the desired properties, and indicate the importance of choosing the appropriate individually chosen strategy of controlling the printing for each individual application to get good-quality and free-from-defects patterns. Research limitations/implications Because of the chosen research method (arbitrary selected printhead type and ink manufacturer), this study could have limited universality. Authors encourage the study of other kinds of piezoelectric heads or other conductive inks. Practical implications This study includes practically useful applications for users to improve the inkjet print quality. Originality/value This study presents results of original empirical research works on problems of the drops forming in the inkjet printing process, and finally, it identifies problems that must be resolved to disseminate this technology.

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Purpose This paper aims to study the packing density of printed paths on different substrate materials. It presents problems which appear when the necessity of printing one or more narrow paths occurs. Design/methodology/approach A piezoelectric printhead containing nozzles with a diameter of 35 µm was used for printing nanoparticle silver ink on different polymer substrates which were treated by plasma or not treated at all. The shape, defects, resistance and printing parameters for the printed paths were analysed. Findings The obtained results allow the identification of the sources of the technological problems in obtaining a high packing density of the paths in a small area of substrate and the repeatable prints. Research limitations/implications The study could have limited universality because of the chosen research method; printhead, ink, substrate materials and process parameters were arbitrarily selected. The authors encourage the study of other kinds of conductive inks, treatment methods and printing process parameters. Practical implications The study includes practically useful information about widths, shapes, defects and the resistance of the paths printed using different technological parameters. Originality/value The study presents the results of original empirical research on problems of the packing density of inkjet printed paths on a small area of substrate and identifies problems that must be resolved to obtain effective interconnections in the inkjet technology.

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