Ultraprecise Printing of $D$-Band Transmission Lines

This letter discusses the fabrication of coplanar waveguide (CPW) transmission lines by ultraprecise deposition (UPD) and their characterization in the D -band (110–170 GHz). UPD is a direct printing process for the deposition of functional nanoinks. It has recently been introduced by XTPL as an alternative to aerosol jet and ink jet printing techniques. In UPD, a micrometer-scale nozzle is in direct contact with the substrate that is printed on. This approach allows the application of highly viscous nanoinks. A silver-filled ink with a viscosity exceeding 10$^5$ mPa ⋅ s is used in combination with a nozzle opening size of 5 μ m to print CPWs with an air gap of 10 μ m on Corning 1737 display glass and fused silica substrates. The lateral precision of the printing process is approximately 1–2 μ m. To de-embed the transmission line performance, thru–reflect–line (TRL) calibration standards were manufactured on substrate. For a single, 400-nm-thick layer of the cured nanoink, the CPWs show approximately 1.0 dB/mm of loss at 140 GHz on fused silica and broadband transmission in the entire D -band.