Three-Dimensional Printed mm-Wave Monolithic Waveguide Twists: End-to-End Manufacturing and Surface-Treatment Solutions

This article presents an end-to-end manufacturing and post-processing solution for 3-D-printed millimeter-wave (mm-Wave) monolithic waveguide (WG) components. A high-precision micro laser sintering (MLS) process, two internal surface polishing methods—abrasive flow machining (AFM) and Hirtisation—and an electroless gold plating process are combined to address the surface quality challenges commonly associated with current 3-D-printed mm-Wave components. This is the first demonstration of the two polishing techniques on mm-Wave devices. An experimental study was conducted on two mm-Wave WG twists for WR-15 and WR-5 bands, respectively. The impact of the surface treatment processes on both mechanical and electrical properties was investigated. The surface roughness of both WG twists was reduced to below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\mu $</tex-math> </inline-formula>m. For the WR-15 WG twist, the dissipative attenuation factor ranged from 5.4 to 2.7 dB/m, with a worst case return loss of 30 dB. For the WR-05 WG twist, the dissipative attenuation factor ranged from 17 to 10 dB/m, with a worst case return loss of 14 dB. The significant improvement in insertion losses (ILs) demonstrates the effectiveness of the two surface treatment methods, enabling complex monolithic mm-Wave WG components with enhanced surface quality.