(445b) Direct-Write Fabrication of Nanoparticle Suspensions for High-Density Interconnects

This paper presents a detailed study on the suitability of direct write (DW) technology for the fabrication of high-resolution wear sensing devices. The study is focused on understanding key device circuit requirements followed by materials selection and process development to meet such requirements. The study will also highlight the fabrication of high density parallel interconnect traces and provide recommendations for further improvement in materials formulations and process control. In this experiment, we fabricated high-density DW printed interconnect lines using silver particle concentrated pastes. In order to create the finest smooth print line possible, we simulated the volumetric flow rate through the assembly and looked at printing parameter’s influence on line geometry. The printed interconnects were sintered and subsequently characterized. The consistency of direct writing interconnects is further quantified in terms of the variation in dimensions and electrical conductivity of the printed and sintered lines.

This study presented ink formulation analysis for high resolution printing, utilized a novel approach to optimize the print line resolution and opened a new angle for additive manufacturing process control: line-to-line spacing. Parallel silver lines with 50 μm center-to-center spacing and 15 μm line width were achieved using nScrypt DW system. A couple of 150 μm spacing devices, close to aerosol jet printing resolution, were made to challenge the limit of extrusion-based (or micro-dispensing) DW. The printed and sintered silver lines are sufficiently conductive for displacement sensing applications.