Low temperature interconnect fabrication on PDMS polymeric substrates using Ag nanoparticles and submicron particles

Abstract

Taking the advantage of low sintering temperature and high processing flexibility, metallic nanoparticles (NPs) have been widely used to fabricate interconnections. To obtain excellent electrical conductivity, the surfactants protecting the nanoparticles have to be removed thermally and thus the particles can be well linked. Considering the interconnect fabrication on flexible substrates (usually polymers and papers) utilizing roll-to-roll technique, low processing temperature, short heating time or localized heating is required. By doing so, heat damages of the substrates and components can be prevented. Considering the application as interconnections for wearable electronics, this study develops a low-temperature chemical reduction process for the fabrication of conductive circuits on PDMS (Polydimethylsiloxane) substrate using carboxylate-capped Ag nanoparticles. Ag nanoparticle sintering can be achieved by soaking the nanoparticle deposits in a gentle reductive solution even at room temperature. Surface roughening treatment is performed to enhance the adhesion between conductive films and the substrate. The results of reliability tests demonstrate that the higher the bending deformation (curvature), a greater the electrical resistance for the conductive films. As for bending fatigue (shear strain: 0.25), the electrical performance of the flexible interconnections deteriorates in the first 300 bending cycles mainly due to the formation of crevices. It is interesting that after that the electrical resistance remains almost constant up to 1000 bending cycles. In addition, a novel interconnect fabrication method using Ag submicron particles will also be introduced in this report.