Using Conformal Printed Electronics for 3D Printed Antenna Systems Building Blocks

Abstract

Printed Electronics is one of the fastest growing science and technology applications worldwide. This growth is driven by many factors including cost reduction, reduced lead times, and quicker design and test cycle times. This paper focuses on adding to the building blocks that enable Printed Electronics to Additively Manufacture (AM) a complete Radio Frequency (RF) system on conformal and low permittivity, porous surfaces by Aerosol Jet Printing (AJP). The first element of this paper compares the electrical characteristics of AM and subtractive manufactured RF filters. AJP and a LPKF Proto U4© laser are used to create functional 7.5-8.0GHz, edge-coupled filters. The AM filter scattering parameters are compared to a traditionally manufactured subtractive filter results as well as computer simulation to validate AJP as a viable manufacturing technique for RF structures. The second element examines the application of high conductivity silver ink by AJP onto a porous, low permittivity, syntactic foam surface. This substrate has a relative permittivity similar to air. A method is presented to apply and cure silver ink, where conductivity is only degraded by 2-3x as compared to bulk silver. In addition, oven curing is compared to laser curing of silver inks because laser curing can provide faster cure times and localized heating. In this element, laser sintered ink lines show 25% higher resistance than oven cured lines. The third element examines the opportunity to create AM resistors by AJP since resistors are important elements of RF power attenuation circuits. This evaluation includes the application of carbon and ruthenium oxide resistors on various surfaces. Laser curing of the AJP resistors makes it possible to create functional thick film style resistors on low-temperature circuit card substrates for the first time. An important finding is that the 537$\Omega$ AM resistor created by AJP is capable of handling up to 15W of continuous power without failure, which is rewired in specific MIL-Standards.