Manufacturing Millimeter-Wave Horn Antennas Using 3D Printing and Direct Electrodeposition
Authors: Van Laar Timo , Collet Thomas , Peumans Dries , Rolain Yves 
Published: September 2023

Additive manufacturing has undergone huge development in recent years. It has become commonplace both for the hobbyist community and industry, with important applications in several domains (e.g. biomedical, aerospace and automotive). Its main strength lies in the fact that custom parts can be quickly prototyped and manufactured, regardless of their complexity. However, many of the 3D printing techniques still have limitations in terms of strength, materials, production speed and overall usability. One of the main limitations is that most techniques utilize polymers, which are intrinsically non-conductive. This limits their use in electronics and telecommunication applications.
Meanwhile, a lot of equipment used in telecommunications, such as antennas, tuners, waveguides, etc. remain very expensive due to complex and time-intensive manufacturing techniques. This leads to high prices, long lead times and limitations in the complexity of the geometries. The main goal of this research is to develop a fast and cost-effective method to produce conductive structures using additive manufacturing, more specifically fused deposition modeling (FDM) 3D printing. A special focus is put on horn antennas for microwave applications, as this application is very demanding on both the accuracy of the geometry and the conductivity of the structure.
The approach in this work mainly consists of two steps: optimizing the plating conditions on flat test samples and extending this knowledge to the three-dimensional horn antenna. The chosen material is a PLA-based polymer with carbon black as an additive, which provides the polymer with some electrical conductivity (factor ~107 lower than copper). This conductivity is too low for any meaningful application but allows for the use of electrodeposition of copper directly onto the polymer to increase the conductivity. By focusing on reducing the distance from the electrical contact to the surface to be plated and by tuning the deposition parameters, high-quality uniform copper deposition is obtained on test samples. The achieved results outperform the current state-of-the-art in this field.
The knowledge acquired from the test samples is then applied to the horn antenna. To this end a conductive antenna holder is developed. The antenna holder serves to keep the potential as constant as possible over the entire antenna surface in order to promote homogeneous deposition. It also aligns the electrodes, keeping the distance between electrodes as constant as possible and preventing short circuits. This method results in good partial coverage and again produces better results than can be found in the literature. However, direct deposition of a nicely uniform layer over the entire surface remains very challenging. An indirect electrodeposition method using conductive silver paint is used to produce the final version of the printed horn antenna.
Measurements in an anechoic chamber demonstrate that the copper-coated version of the printed antenna has similar radiation performance as a commercial counterpart. An exponential horn antenna is made with decent performance, demonstrating the ease of production of more complexly shaped antennas. Our antennas can be produced within a couple of hours at a fraction of the price of commercial counterparts ($3 instead of $500-1500). This opens up new possibilities to quickly validate simulation results of new antenna designs. Further research focuses on the use of electroless plating to obtain more homogeneous copper deposition on three-dimensional structures, as well as extending our methodologies to more complex geometries.