“…With the rapid progression of 5G communication technology, information processing has progressively advanced into the domain of high-frequency communication electronics and high-speed data transmission. − As the foundation of high-frequency communication, dielectric filters have garnered increasing attention toward cost-effective and range-massive communication electronics in the past few years. , Among the various types of dielectric filter substrates, polyamide-imide (PAI) substrates have been widely utilized in fields including radar reconnaissance, field communication, and communication base station, with advantages of smaller volume, lighter weight, better temperature adaptability, etc. − Up to now, various techniques such as burning infiltration silver, sputtering, and coating have been extensively investigated for the fabrication of conductive layers on PAI substrates. − Nevertheless, the high-temperature aging process of silver paste is time-consuming and energy-intensive. Meanwhile, the conventional sputtering process necessitates high-vacuum and voltage, which results in significant energy consumption. − Furthermore, the metallized PAI substrate prepared through coating typically results in a thick layer of copper, which cannot meet the requirements for ultrathin layers. − To achieve the metallization of substrates with superior adhesion, prospective metal thickness, and optimal cost-effectiveness, extensive research has been conducted on the process of electroless copper plating (ECP) onto the modified substrate surface. − As a well-established autocatalytic technique, electroless deposition is extensively utilized for the production of high-adhesion and low-resistivity metal layers on various types of materials, including polymer plastics, − papers, , ceramics, − and glasses. − Nevertheless, achieving strong adhesion between autocatalytic sites and smooth surfaces of PAI substrates without combinative functional groups or mechanical bonding points is full of challenges. −…”