Surface modification of an ambient UV-cured dielectric to realise electrically conducting traces

There has been much interest in the printing of silver inks onto flexible substrates, for which intermediate dielectric layers are often required to achieve suitable wettability. This work seeks to realise continuous silver traces overprinted onto UV-curable dielectrics through surface modification techniques (thermal and UV-ozone post-treatments), when the UV light source used for the curing is non-optimal. Two UV curable dielectric materials were deposited and the effects of curing time and curing atmosphere on the inkjet printability of a commercially available silver ink were investigated. Good wettability of the silver ink was obtained following ozone treatment of the dielectric layers, where the treatment required was found to be a function of the dielectric formulation and the curing atmosphere. Water droplet contact angle measurements were used to analyse the resulting changes in the surface conditions of the dielectric layers. The results provided an indication, but were not sufficient for predicting whether silver traces with measurable resistance could be subsequently obtained. Instead, measurable silver trace resistances were found to be influenced by the occurrence of cracks in the trace and possibly the degree of cross-linking present in the dielectric. Following these results, the authors demonstrate that electrically conductive traces can be achieved on ambient cured samples, which yields a more flexible solution compared to inert cured samples.