Pitch Interconnection and Packaging Studies for Hybrid Electronics with Aerosol Jet Printed Particle-Free Ag Ink

Additive manufacturing of conductive interconnects has become essential in the electronic industry due to the requirements of having smaller electronic components with high performance and producing functional electronics that meet the applications demand. Thus, fabricating conductive lines and patches is key to reduce the challenges of mechanical and thermal reliability associated with advanced electronic technologies. In this work, high-resolution conductive interconnects were fabricated by aerosol jet printing (AJP) across different substrates using a novel particle-free silver ink. The conductivity of the metallic ink was assessed after post-processing at various curing conditions and methods. The printing process parameters of the particle-free ink were optimized to yield high-quality printed features and to investigate the printed film’s continuity on a non-flat surface, including printing from the top of a silicon die to a flexible substrate. The current carrying capacity of the printed particle-free silver ink on NEA 123 material was evaluated and compared against a commonly used nanoflake-based silver ink by performing a current sweep increasing the current by 5mA every 10 seconds until failure. In this research, conductive interconnects with sub-micron thickness have been obtained. Photonic curing using PulseForge system was found to improve the conductivity at energy density of 3.22 J/cm2 to four times the conductivity of a conventional convection oven curing. The enhancement in conductivity appears to be due to the changes in the film’s microstructure, forming metallic connections between the needle-shaped crystallized grains as revealed by X-ray microtomography. The particle-free ink can be used for irregular surfaces with smooth transitions between the electronic components. Furthermore, the current carrying capacity tests show the printed interconnect’s resistivity increased and then reduced during the test before failure; the failure of the particle-free ink occurred at 2.022 x 105 ± 0.2 A/cm2 compared to 0.99 x 105 ± 0.18 A/cm2 for the nanoflake-based silver ink which makes the particle-free ink an attractive material for high-power electronics applications. Our findings assist the application of flexible hybrid electronics and electronic packaging by providing significant guidelines for electronics manufacturers.