The use of epoxy resin in the thinning of Copper Clad Laminate (CCL) requires high technical expertise to meet performance demands. Thinning CCL technology addresses challenges in enhancing PCB board rigidity, process operability, mechanical strength, and reducing warpage. Achieving thinning in CCL involves improving prepreg processing, resin composition, and reinforcement technology. Three main technical approaches for CCL thinning include enhancing glass fiber cloth hardness, adding high rigidity fillers, and modifying the epoxy resin to enhance cured CCL rigidity. Epoxy resin plays a crucial role in improving substrate rigidity and insulation reliability, as seen in the development of extremely thin CCL with enhanced flexural modulus and reduced warpage. Epoxy resin and curing agents are required to exhibit high dielectric properties and moisture resistance. Addressing compatibility and storage stability of the resin composition is critical in enhancing CCL performance, which has led to increased patent results in Japan. Epoxy resin manufacturers have focused on improving compatibility between epoxy resin and curing agents and storage stability of resin compositions.