Over the last few decades, a significant interest towards the manufacturing of complex three-dimensional (3D) structures for conceptual models have led to an incredible amount of research and development. 3D structures have been an integral part of physical models or functional end-products and are widely adapted as a miniaturizing technique in manufacturing industries, and in particular, the electronics industry. Advancement in electronics technology has lead to the need for fabricating consumable electronics within a smaller lattice space. To meet the challenge of high functional density integration, Additive Manufacturing (AM) techniques by 3D printing is a promising solution for satisfying the ever-increasing demand for a higher quality product with the ability to customize based on an individual customer needs. AM techniques allows the possibility of developing low cost, multifunctional, compact, lightweight, and miniaturized electronics that can be easily integrated with conventional systems or platforms. In this dissertation, approaches towards utilizing existing AM techniques for fabricating structures that are compatible to carry electrical functionality for RF applications is proposed. The end goal is to develop processes using AM technique as an alternate manufacturing approach to achieve a fully functional electronics system. Specifically, AM holds significant potential in realizing low-loss, high-performance, and light-weight RF components such as transmission lines, waveguides, resonators, filters, and antennas. In order to realize a complete RF system by AM, multiple processes are developed. First, to establish connection for allowing electrical functionality, conductive traces must be patterned on the substrate. Two different metal patterning techniques for selectively patterning conductive traces on the 3D printed substrate is developed. Next, to realize a compact system, a smaller form factor is a necessity and this can be achieved by utilizing the flexibility in the third dimension (z-axis) in designing non-planar RF structures. A number of non-planar RF structures are demonstrated showcasing the advantages of AM in fabricating compact designs. Moreover, for fabricating efficient RF circuits, the losses associated with the printed plastics should be minimized. The currently available printing polymers have high dielectric loss and hence an alternative process that utilizes air as a substrate is developed by using a LEGO-like self-alignment procedure in which the structure is printed in multiple parts and snapped together face to face to integrate the complete structure. Furthermore, a number of active and passive components must be integrated into the printed plastic to achieve a RF system. For this purpose, three different solder-free embedding processes are developed to embedded active devices such as diodes into the 3D printed plastics. Finally, a combination of the above-mentioned processes is utilized to achieve a fully 3D printed electronics system and a potential application of such multi-functional system is demonstrated. Overall, this work demonstrates that 3D printing can be adopted in the fabrication of microwave and millimeter wave high functional density circuits and systems.
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