Guidelines for Accurate in-House Electroplating and 3-D-Printing Processes Applied to mm-Wave Devices

This letter details the metallization process of 3-D-printed WR-28 and WR-10 waveguides using electroplating. The 3-D printing technique is stereolithography, so the printed parts are plastic-based. A two-step metallization process is followed: a premetallization with nickel spray to make the part conductive and a subsequent electroplating process, emphasizing the chemical compounds and quantities needed to improve the result obtained, as well as the metallization times and currents applied on the parts. In addition, manufacturing deviations are measured and compensated. The results obtained are compared with simulations and commercial waveguide sections. Measurements show
$S_{11}$
below −33 and −21 dB for WR-28 and WR-10, respectively. Measured average losses are around 1 dB/m for WR-28 and 4 dB/m for WR-10, which is equivalent to copper with an effective surface roughness lower than
$0.4~\mu \text{m}$
.