Investigation and improvement of the dispenser printing of electrical interconnections for smart fabric applications

摘要

Electrical interconnections are essential for the integration of electronic functions in a fabric. These interconnects can be dispenser printed on a fabric; however printing directly on a breathable woven fabric surface is challenging due to the high surface variation and porosity defined by the weave. This paper, for the first time, experimentally shows that fabric surface variation leads to inconsistent printed structures which adversely affects the electrical properties of printed conductive tracks. It investigates a solution of overcoming the fabric surface variation in the form of dispenser printing an interface layer between the conductive ink and the fabric surface. Four dielectric inks DuPont 5018, Electra EFV4/4965, Fabinks-UV-IF-1004 and Fabinks-UV-TC0233 are quantitatively evaluated, as interface materials, in terms of surface consistency, thickness consistency, repeatability, flexibility, thermal stability and the electrical characteristics of conductive tracks printed on them. All four of the evaluated interface materials significantly reduced the fabric surface variation by more than 95% and provided a suitable low variation surface for printing subsequent electronic layers. Conductive tracks, dispenser printed on the four interface materials, produced similar to 90% lower electrical resistivity compared to tracks printed directly on the fabric and similar resistivity to dispenser printed tracks on Kapton, a traditional printed electronic substrate. An increased focus on low powered electronics especially for wearables requires the electrical interconnections to dissipate minimum power. The innovative interface layer approach allows fabrication of low resistance electrical interconnections on fabric substrates reducing interconnect power dissipation, making this approach highly suitable for smart fabric applications. Reported details of dispenser printing of interface materials can be used for replicating these results on a range of fabric substrates. The paper also reports a novel thermal imaging based method of analysing resistance distribution within a printed conductive track to assess the geometrical consistency of printed electrical interconnections.