Surface modification of fused filament fabrication (FFF) 3D printed substrates by inkjet printing polyimide for printed electronics

Abstract

Recent advances in additive manufacturing (AM), also known as 3D printing, have enabled exponential growth in its application to the field of electronics and radio frequency (RF) technology. One of the most common 3D printing technologies, fused filament fabrication (FFF), can be used to fabricate a wide range of parts and is compatible with robust, production-ready materials. While FFF 3D printed parts have several attractive attributes, they tend to suffer from poor surface morphology – a critical parameter for printing high-quality conductive traces for electronics devices. In this paper, we present a novel methodology for modifying the surface of polyetherimide (PEI) FFF printed substrates using inkjet printed layers to form a smooth surface for accurate conductive trace formation. PEI substrates are commonly used in applications that must withstand harsh environments and require good dielectric performance. Therefore, the surface modification approach must also meet these high-performance requirements. As part of this work, an inkjet-compatible, thermally robust dielectric polyimide (PI) ink was utilized for the surface modification of the PEI substrates. However. the aggressive solvent present in the PI ink was not compatible with the PEI substrate. To solve this material compatibility issue, an intermediate layer of poly(ethylene glycol) diacrylate (PEGDA) was introduced between the PI and PEI substrate. It was demonstrated that the inkjet surface modification process dramatically reduces the surface roughness, making it suitable for printing conductive ink traces with improved RF performance. This surface modification methodology therefore presents an entirely AM-based fabrication solution for high quality AM components for next generation electronics and RF devices.