With the advancement of 5G/6G telecommunication technologies, the information loss through the substrate material during the signal transportation has become a severe challenge in designing high-performance antenna devices. Consequently, the utilization of low-dielectric materials for Copper Clad Laminates (CCLs), a fundamental component of Printed Circuit Boards (PCBs), is essential. Specifically, developing polymer materials with low dielectric properties at sub-THz for substrate and adhesive is an important challenge. In this study, we propose a copolyimide designed by incorporating aliphatic/alicyclic functional groups into the polymer backbone. Our polyimide exhibited low dielectric properties with Dk = 2.426, Df = 0.0031 @100GHz, as well as robust interfacial adhesion strength with 3.229 N/mm at the low roughness copper surface. We will also demonstrate the composition dependence of the physical properties to determine the optimal copolyimide composition.