Additive Manufacturing of Millimeter Wave Passive Circuits on Thin Alumina Substrates

Aerosol Jet Printing was used to fabricate microwave and millimeter wave passive devices (transmission lines, inductors, and a patch antenna) on thin alumina substrates. The devices were subjected to sintering temperatures 135 - 350°C and scattering parameters were recorded at each temperature step. Tape tests showed good adhesion of silver ink to the alumina substrate. All structures remained functional after 350°C sintering. The performance of the passive elements improved (due to reduction in conductor loss) with increase in sintering temperature. For example, both the microstrip transmission line and the coplanar waveguide (CPW) showed decreased loss after high-temperature sintering, with microstrip transmission line design improving from 0.1372dB/mm loss to 0.0653dB/mm after sintering at 350°C. Both the simulation and measured results for all the passive elements are presented in the paper.