“…Besides Dk and Df, the electrical performances of designed circuits are related to some other parameters of CCL, such as the moisture absorption, thermal coefficient, copper peel, and so on, and even the CCL manufacturing process, especially for the frequency of millimeter‐wave or terahertz bands. In recent years, the researchers mainly focus on some areas for circuit performance improvements, such as the performance investigation for accurate design of various circuits, 1,2 flexion modification for flexible or conformal applications, 3–5 improvement of manufacturing process, 6,7 usage of advanced material, 8 and gap waveguide technique 9,10 . It is known that the adhesive layer is normally necessary in traditional lamination process, which is composed of epoxy and acrylic resin.…”