Toward Reliable Hybrid Electronics: Understanding the Role of Surface Roughness in Aerosol Jet Printing

Recent advancements in hybrid additive manufacturing (AM) have enabled compact, high-quality, three-dimensional electronic systems. Among the various techniques for printed electronics, aerosol jet printing (AJP) stands out for its versatility and compatibility with hybrid AM systems. Its contactless deposition with up to five axes of motion allows printing of conductive traces and interconnects on complex or nonplanar surfaces, and its compatibility with both conductive and non-conductive materials enables integration of functional and insulating layers. Despite these advantages, AJP typically produces line widths on the order of a few microns, while many AM-produced substrates exhibit surface roughness of similar or larger magnitude. Such variations can disrupt trace continuity and compromise electrical connectivity, making the understanding of roughness effects on AJP deposition critical for effective process planning. This study investigates the effects of substrate roughness on particle deposition and printed line morphology on FDM-printed substrates. Surface roughness was found to significantly affect line uniformity and continuity. Layer heights at or below 0.2 mm consistently yielded fully continuous traces across all tested conditions, while layer heights at or above 0.4 mm consistently resulted in discontinuity regardless of parameter adjustments. Under higher deposition rate conditions, roughness-induced capillary flow promoted material accumulation within surface grooves, increasing line width variability by up to 37.05 μm. These findings highlight the necessity of integrating surface roughness characterization into process planning for AJP-based hybrid AM, opening new pathways for improving the reliability and precision of hybrid-printed electronics.