Automated Laser Soldering Techniques for Ultrasonically Embedded Wires in a Hybrid Additive Manufacturing Environment for Electric Multifunctionality

The layer-by-layer manufacturing approach utilized in additive manufacturing (AM) allows access to layers offering opportunities to embed technologies at each layer leading to 3D electronics, for example. Achieving this goal requires the coupling of multiple technologies including material extrusion 3D printing, machining, and robotic component placement & soldering. When exploited synergistically in this hybrid manufacturing (HM) approach, additional functionalities can be integrated in parts to produce multifunctional parts, or parts containing any additional functionality beyond rendering of basic shape. By combining additively manufactured dielectrics and non-conductive materials with conductors (wiring and electronics) via mechatronic equipment/tooling, the 3D printing process can be interrupted to embed and enclose sophisticated electronics within materials to produce electrically functional, end-use devices for custom and embedded sensing capability. To embed and connect electrical circuits, we developed methods for ultrasonic wire embedding and laser soldering. Laser soldering was studied to create joints on wire-wire and wire-component junctions. Of particular importance was the placement, spacing, and fixturing of 1608 components (1.6 x 0.8 mm) relative to adjacent wires in a butt joint configuration. Additionally, resistor-capacitor circuits were fabricated (i.e., embedded within printed polycarbonate material) in series and parallel. Both circuit variants were characterized via visual observations and impedance spectroscopy. The electrical test results demonstrated feasibility of the manufacturing approach, however, elevated failure rates of encapsulated circuitry warrant further investigation into process improvement.