A Novel Additive Technique to Fabricate 24-GHz Array Patch Antenna Using LCP Film

In this study, a promising environmentally friendly additive technology that can be used for fabricating a patch array antenna for a 24-GHz high-frequency application is proposed. This methodology combines printing Al paste and a galvanic replacement reaction. The copper sulfate waste effluent is used to convert the aluminum electrode into a copper electrode with high conductivity by using a galvanic replacement reaction. For a millimeter-wave (mm-wave) band antenna application, a high conductivity (
$4.782\times 10^{-8}\,\,\Omega \cdot \text{m}$
) and low roughness (
$1.12~\mu \text{m}$
) Cu conductor on a flexible liquid crystal polymer (LCP) was obtained, when the printed Al electrode was immersed in the CuSO4 solution with level agent at 85 °C for 20 min. The developed Cu conductor on a flexible LCP substrate used in a co-planar waveguide (CPW) and array antenna for mm-wave band frequency shows very promising performance including the maximum gain of 8.3 dBi, beamwidth of 3 dB, and 22° at 24 GHz in the radiation pattern. The peak gain angle of the antenna is also observed to be consistent with that of copper foil, indicating that the directivity is quite efficient.