The use of fibre-based materials as substrates in printed electronics has been increasing, mainly due to its attractive
characteristics, such as low-cost or wide availability. Additionally, paper enables recycling and it shows attractive
features, such as high thermal stability, when compared to traditional polymer-based substrates
(Tobjörk and Österbacka, 2011 [1]). Nevertheless, one of the drawbacks of using paper substrates is that the surface
usually is very rough, typically, showing roughness values above 10 μm2
. In most cases, printing structures
that need to be highly uniform, without disruptions, require additional coating. Inkjet printing provides sharp
detail reproduction and strict lines on printed structures. Sintering is required for drying the ink. Thermal
sintering is the traditionally used method, but requires long periods of time and promotes the ageing of the
paper due to a long exposure at high temperature. When printing conductive structures on paper alternative
photonic sintering methods such as IR-sintering show some attractive characteristics. IR-sintering is compatible
with roll-to-roll fabrication, providing low-cost, fast and localized sintering, which makes it suitable for fibrebased
substrates (Tobjörk et al., 2012 [3]). This work has been carried out to study and compare the efficiency
of thermal and IR sintering of conductive structures on different paper and polymer substrates. All substrates
were printed using silver based ink, which was applied on the substrate surface by inkjet. Resistivity values of
the printed structures were used to compare the performance on the substrates. IR-sintering showed the best results
in terms of achieved conductivity of the printed lines when using short sintering time of no more than
10 min. The conductivity values of the inkjet-printed silver lines on Lumi silk substrate reached about 40% of
the bulk silver value after IR-sintering, whereas with thermal-sintering this value only reached about 20% of
the bulk silver value. IR-sintering improves the sintering process, increasing the conductivity of the printed structures
and at the same time reducing significantly the sintering time. In the case of Lumi silk substrate, high conductivity
was observed after only two minutes of sintering time when IR-oven was used.
Both techniques can be used in a roll-to-roll mass manufacturing process, enabling the fabrication in large scale of
flexible electronic devices, on paper substrates, without the need for extra steps, such as coatings