Ultraprecise Printing of D-Band Interconnects Using Dielectric Ramps

In this paper, the fabrication of coplanar waveguide (CPW) based interconnects by Ultraprecise Deposition (UPD) and their characterization in the D-band (110–170 GHz) is discussed. UPD was recently introduced by XTPL as an alternative to aerosol jet and ink jet printing technologies. Its most distin-guishing feature is that the printing nozzle is in contact with the substrate during printing, allowing for the application of highly viscous inks with a lateral precision of 1–2 µm. The high viscosity of the silver-filled ink is used to print interconnects between a Corning 1737 display glass substrate and a 100 µm thin AF-45 glass die. The interconnects are realized using low-cost dispensed dielectric ramps made of a suspension of alumina particles in an epoxy resin. This approach requires neither highly precise milling of the substrate, nor precise alignment of chip and substrate, nor a complex fabrication process for the dielectric ramps. The interconnects with an air gap of 9 µm show as little as approximately 0.65 dB of insertion loss at 160 GHz, and broadband transmission in the entire D-band.