Selective Electrodeposition of Graphitic Materials for Additve Manufacturing of Printed Circuit Boards (PCBs)

The rise of flexible electronics, particularly for wearable applications, has increased the demand for additive manufacturing approaches for printed circuit boards (PCBs). These techniques leverage innovation at both material and fabrication process levels to reduce cost and streamline production. Among various techniques, printed electronics enabled by laser processing are advantageous due to their accessibility, precision, scalability, and cost-effectiveness. Recently, laser-induced graphene (LIG) has emerged as a versatile functional material used in several devices and applications including sensors, actuators, batteries and energy harvesters. In this work, we introduce a novel laser-enabled technique for manufacturing of single- and double-sided printed circuit boards using LIG as a seed layer for selective copper plating. This new utilization of LIG offers an additive, low-cost, maskless approach that not only minimizes material waste but also reduces the need for subtractive processes typically used in the electronics industry. We developed a comprehensive process flow that includes direct writing of PCB layouts, VIA formation, assembly of surface mount components, and protective coating, resulting in the production of flexible PCBs on polyimide substrates. These PCBs can be readily transferred to transparent and stretchable substrates, owing to the unique 3D porous structure of LIG. Our approach effectively resolves PCB traces as small as 50 µm with various lengths and patterns. A key feature presented in our work is the streamlined two-step process for VIA formation. Optimizing the laser parameters enabled the formation of graphitized 250 µm holes across the polyimide substrate that serves as conductive VIAs upon copper electrodeposition. This approach reduces traditional multi-step VIA fabrication methods and results in efficient production of double-sided PCBs, allowing for the integration of electronic circuits on one side with functional graphene devices on the other, enhancing both functionality and device integration. Characterization using scanning electron microscope (SEM) and Raman spectroscopy was performed to confirm the presence of a graphitic 3D porous structure in the generated LIG. Extensive optimization of laser parameters and copper plating conditions was performed, significantly reducing LIG trace resistance from 900 Ω to 0.2 Ω, making them highly conductive and suitable for conventional circuit applications. The practical utility of the developed technique was demonstrated by fabricating PCBs integrated with functional LIG devices, including a strain sensor, temperature sensor, thin film heater, and soft electrothermal actuators, all powered and controlled via PCBs fabricated using our method. This addresses the existing challenge of establishing homogeneous electrical contacts to LIG devices while providing seamless integration of circuit boards and functional devices on a single substrate. In future, we plan to develop a tabletop machine that integrates LIG processing with a streamlined plating process, providing an all-in-one digital fabrication solution. Additionally, this approach can be extended for the fabrication of PCBs on 3D geometries and curved surfaces, demonstrating the potential of multifunctional materials and hybrid manufacturing techniques in contributing to the electronics industry.