3D Inductive Frequency Selective Structures Using Additive Manufacturing and Low-Cost Metallization

Abstract

The use of additive manufacturing and different metallization techniques for prototyping radio frequency components such as antennas and waveguides are rising owing to their high precision and low costs. Over time, additive manufacturing has improved so that its utilization is accepted in satellite payloads and military applications. However, there is no record of the frequency response in the millimeter-wave band for inductive 3D frequency selective structures implemented by different metallization techniques. For this reason, three different prototypes of dielectric 3D frequency selective structures working in the millimeter-wave band are designed, simulated, and manufactured using VAT photopolymerization. These prototypes are subsequently metallized using metallic paint atomization and electroplating. The manufactured prototypes have been carefully selected, considering their design complexity, starting with the simplest, the square aperture, the medium complexity, the woodpile structure, and the most complex, the torus structure. Then, each structure is measured before and after the metallization process using a measurement bench. The metallization used for the measurement is nickel spray flowed by the copper electroplating. For the electroplating, a detailed table showing the total area to be metallized and the current applied is also provided. Finally, the effectiveness of both metallization techniques is compared with the simulations performed using CST Microwave Studio. Results indicate that a shifted and reduced band-pass is obtained in some structures. On the other hand, for very complex structures, as in the torus case, band-pass with lower loss is obtained using copper electroplating, thus allowing the manufacturing of inductive 3D frequency selective structures in the millimeter-wave band at a low cost.

3-D Metamaterials: Trends on Applied Designs, Computational Methods and Fabrication Techniques

“…This manufacturing option is the most common in the literature for the fabrication of 3-D metamaterials. Several examples of this type of 3-D manufacturing can be seen in the prototypes of the following [125,126,[134][135][136]161,164,[175][176][177][178][179][180]. Different technologies related to plastic 3-D printing are also available and some of them were used in previous work.…”

“…However, the difference between both of them is that the SLA makes the cure in a tank full of resin while MJ cures the material after the material has been sprayed. Unit cell designs that have employed SLA in their prototyping are presented in [126,161,164,176,179,180]. The last technology applied for the manufacture of 3-D metamaterials using 3-D printing on plastic is called selective laser sintering (SLS) used in [125,177].…”

“…Since the 3-D printing technologies described above print the unit cells on plastic and they have conceived to be metallic, a metallization process is needed to coat the surface of the printed unit cells with a highly conductive metal. Different techniques to metallize the surface of the unit cells have been seen in previous work: brush paint [136,177], spray [164], electroplating [178,180], electroless plating [175], sputtering [134,176], dip coating [125], and vacuum chamber metallization [179]. Metallization is a crucial part of this manufacturing process as each of the above techniques offers a level of roughness, conductivity, and layer thickness that must be taken into account depending on the operating frequency range and geometry of the unit cell.…”