Direct-write printed broadband inductors

The capability to additively manufacture fully-functioning electronic circuits is a frontier in 3D-printed electronics that will afford unprecedented scalability, miniaturization, and conformability of electronic circuits. The printed passives, such as resistors, capacitors, and inductors, however, are rarely capable of performances comparable to that of the commercially available versions. In this paper, we report a novel procedure that employs three-dimensional (3D) additive manufacturing techniques to fabricate high-frequency, tapered-solenoid type inductors for RF applications capable of wide bandwidth performance. The design includes a polymer support structure to reduce the parasitic capacitance between the inductor and the substrate, a tapered solid core, and conducting windings. Each design component is printed using aerosol-jet (AJ) printing methods on a grounded coplanar waveguide such that the small end of the conical-shaped inductor is connected to the transmission line and the base of the inductor is connected to ground. Two types of solid-core inductors were fabricated: one with a printed polymer core and another with a non-printed iron core. Scattering parameter measurements establish that the polymer and iron-core inductors, combined with a 45 degrees-polymer support structure, can achieve usable bandwidths up to 18 GHz and 40 GHz, respectively, with low insertion loss. 3D model and circuit model simulations were also carried out to study inductor performance in terms of self-resonance and insertion loss.