Additive manufacturing of high-density (2.5 micrometer L/S) Ag-Cu stacked interconnects on organic substrates

Low conductivity of sintered nanoparticle inks/pastes is one of the major drawbacks to the adoption of inkjet-printed electronics in advanced packaging for high performance computing applications. In this work, we address this concern by exploiting selective electroless copper plating on organic substrate to further improve the conductivity of electrohydrodynamic (EHD) printed and photonically sintered silver nanoparticle interconnects. The conductivity was increased more than five times, from 2.21 x 10 MS/m to 13.66 x 10 MS/m, after 800 nm copper was plated on a printed and sintered silver test vehicle. The resulting resistivity to be about four times that of bulk copper. The printing and electroless plating parameters were optimized to fabricate local high-density interconnections to bridge two chips directly on an organic substrate coated with a dielectric. In successfully utilizing the potential of technologies like EHD jet printing, intense pulsed light (IPL) curing and electroless plating, this work aims to further the cause of establishing additive manufacturing (AM) as a competitive and sustainable solution in high-density RDL fabrication for 2.1D and 2.3D packages.