Surface Silanization of Polyimide for Autocatalytic Metallization

Due to its superior chemical stability, mechanical strength, light weight, and flexibility, polyimide (PI) has been widely used as a polymeric substrate of flexible printed circuit boards such as flexible copper clad laminates (FCCLs). The development of an adhesiveless dual-layer structure is imperative for the application of FCCLs in globalized 5G consumer electronics. In this work, autocatalytic metallization on a silane-grafted PI film was developed to fabricate a high-quality Cu/PI substrate. PI was functionalized by amine-terminated organosilanes to load polyvinylpyrrolidone-capped Pd nanoclusters (PVP-nPd) as a catalyst. The effects of organosilanes with different numbers of amine functional groups on the adsorption of the PVP-nPd catalyst and the subsequent metallization of Cu were systematically investigated. Comprehensive surface characterizations were carried out on the PI films before and after silanization. The organosilane bearing three amine groups was found to outperform its counterpart with one amine group, exhibiting a fourfold increase in catalyst adsorption, which also improved the metallization efficiency.