Aerosol Jet Printed Interconnects for Millimeter-Wave Components

ABSTRACT As millimeter wave RF device applications expand above traditional microwave frequency bands in the global communications, automotive and Mil-Aero markets, the need to limit interconnect signal losses related to parasitic elements has never been more important. As the frequency increases, device designers are facing numerous challenges, complications, and costs when fabricating interconnects with techniques such as copper pillar bumps, wire, ribbon or wedge bonding in 3DIC packaging. Printing conformal interconnects with Aerosol Jet® direct-write technology can offer package designers and RF engineers a new approach for optimizing interconnect transitions to active die, tailoring the loss characteristics to specific application requirements and eliminating the need to compensate for high signal transmission losses. Printed interconnects can be digitally designed into the package with a variety of metallic and dielectric materials. As these interconnects are conformally printed on the 3D surface of the package, the trace length can be minimized with zero loop height, reducing parasitic inductance to active die circuitry specifically for die on board, die in trench, or die on die with pads-up packaging configurations. In this work, Aerosol Jet® printed interconnects with silver nanoparticle inks are compared with the gold microstrip transmission lines as well as traditional gold bond wires, for performance up to 110 GHz. We will share examples showcasing that the printed interconnects can have similar RF transmission performance to microstrip, with significantly lower loss than bondwires especially at high frequencies. We will also discuss design effects for Aerosol Jet® printed RF interconnects up to 110 GHz based on a set of results for different line heights with a given line width printed with a silver ink.