Conductive silver coatings with ultra-low silver consumption on polyimide film via a mild surface ion exchange self-metallization method

Abstract

In this work, we developed a new potassium permanganate oxidation modification-ion exchange-reduction (OIR) process which is a mild surface ion exchange self-metallization method to fabricate conductive silver coatings with ultra-low silver consumption on polyimide film. Firstly, a hydrophilic manganese oxide modified layer loaded with K⁺ as a novel silver ion carrier was prepared on polyimide film by potassium permanganate oxidation modification. Secondly, Ag⁺ was loaded onto the manganese oxide modified layer by the ion exchange effect. Thirdly, a conductive silver layer was fabricated successfully with the reduction of Ag⁺ and the redox dissolution of the manganese oxide modified layer by a reduction process. Finally, the silver coating prepared by the OIR method has good adhesion, an 80 nm thickness value (0.56 wt% silver consumption), and a sheet resistance value of 261 Ω sq⁻¹. At the same time, characterization of the film during the preparation process and the influence of the O, I and R process times on the performance of the silver coating were studied systematically. Compared with the traditional fabrication methods of conductive silver coatings, this new technology does not require a sintering process, causes almost no damage to the chemical structure of the polyimide molecules and leaves no residual modifier. Importantly, the silver layer prepared by this method has an ultra-low silver consumption value and better conductivity at the same time. Moreover, the silver layer fabricated by this method can be used as the bottom layer of the electroplating layer in a more economical way in flexible printed circuit boards (FPCBs) and may have many potential applications in various areas.