Preparation and properties of adhesive-free double-sided flexible copper clad laminate with outstanding adhesion strength

In this paper, the synthesized thermoplastic polyimide (TPI) precursor is coated on both surfaces of the surface-treated polyimide (PI) base film, and the TPI/PI/TPI multilayer films is obtained by thermal imidization. The mechanical properties, heat resistance, water absorption of the multilayer film and the interface between the TPI and the PI base film were investigated in detail. Then, multilayer film-2 (MF-2) with excellent comprehensive performance and the two copper foils were pressed together to prepare a double-sided flexible copper clad laminate (FCCL) by thermal lamination method, and the properties of FCCL were studied in detail. The results show that the FCCL has a high peel strength of 1.22 N/mm, passed a solder bath test of 288°C, and the surface condition was good under hot-pressing temperature of 360°C, hot-pressing pressure of 15 MPa and hot-pressing time of 60 s. In addition, the SEM and EDS spectra of the stripped copper foil confirmed that the TPI layer was immersed into the interstitial space of the Cu nodules, forming a strong physical bite with the copper foil. The current work provides a promising solution for the design and fabrication of multilayer printed circuit boards with excellent performance.