High peel strength and excellent solder heat‐resistance epoxy adhesive for flexible copper clad laminate

Abstract Flexible copper clad laminate (FCCL), commonly composed of copper foil, epoxy adhesive, and polyimide (PI) film, is widely used as the substrate material of flexible printed circuit boards. Carboxyl‐terminated acrylonitrile butadiene (CTBN) and four curing agents were used to prepare the modified epoxy adhesive. FCCL's peel strength was improved by treating PI with plasma. The results showed that when the epoxy adhesive was toughened by adding 30 phr CTBN and PI film was treated with nitrogen plasma, the comprehensive performance of the modified epoxy adhesive and FCCL was the best. The impact strength of the modified epoxy adhesive was 39.32 kJ m −2 (149.7% higher than that of the unmodified), and the gelation time was 330 s at 160°C. The peel strength of FCCL was 1.29 kgf cm −1 , which was higher than required. It can pass the lead‐free solder heat‐resistance test at 320°C 10 s −1 as well. A new way is provided to expand the application of FCCL in areas requiring higher peel strength.