Surface activation of polyimide with dielectric barrier discharge for electroless metal deposition

Electroless plating of non-conducting materials needs, prior to the metal deposition itself, to make the sample surface catalytically active. The route involving the chemical reduction of a thin solid metal–organic coating has, for this purpose, a significant potential in reducing the number of steps which are required today in conventional wet chemical metallization processes. In this work, a novel activation process using a dielectric barrier discharge (DBD) is described for the first time. This process is based on the plasma-induced chemical reduction at atmospheric pressure in air of palladium acetate (PdAc) layers resulting in the formation of palladium (Pd) on non-active surfaces. Fast surface activation of polymers like polyimide (PI) was found to occur in only a few seconds using a simple DBD device instead of expensive excimer UV lamps or complicated laser systems. The DBD-induced Pd layers on PI exhibit high activity with regard to initiation of the electroless copper plating. Indeed, copper deposition starts immediately after dipping the activated PI samples in the electroless solution without any inhibition time. Homogeneous copper coatings on PI were achieved under optimal plasma treatment conditions. The results are compared to those achieved with excimer UV lamps and excimer UV lasers.