Tailoring L-PBF process parameters to investigate surface roughness effects on AlSi10Mg waveguides

The Laser Powder Bed Fusion (L-PBF) process enables the fabrication of highly complex geometries, making it a promising technique for producing advanced waveguides. However, compared to conventional manufacturing methods, L-PBF typically results in higher surface roughness, which can potentially increase electrical losses—particularly in high-frequency applications. In this study, AlSi10Mg rectangular waveguides operating in the 26.5–40 GHz frequency range (Ka-band/WR28) were fabricated using different L-PBF process parameters and scanning strategies. By tuning these parameters, we controlled the surface roughness of the inner walls, either globally or selectively, to evaluate the impact of roughness distribution on waveguide performance. The resulting samples exhibited a range of roughness levels and surface textures. Despite the higher intrinsic roughness of L-PBF parts, our measurements show that electromagnetic losses remained relatively low across all tested configurations. These findings suggest that the performance of L-PBF waveguides can be acceptable—even without extensive post-processing—in certain high-frequency bands. Additionally, thermal treatments were applied to modify the microstructure of the AlSi10Mg alloy and enhance its electrical conductivity. Improvements in microstructural homogeneity led to slight but measurable enhancements in waveguide performance, highlighting the complementary role of thermal post-treatments in optimizing both structural and functional properties. Overall, this work demonstrates that by tailoring process parameters and applying targeted heat treatments, it is possible to mitigate the limitations of L-PBF-induced roughness and produce functional high-frequency waveguides with minimal additional processing.