Effect of Atmospheric-Pressure Plasma Treatment on the Adhesion Characteristics of Screen-Printed Ag Nanoparticles on Polyimide

We investigated the adhesion characteristics of screen-printed silver (Ag) tracks on polyimide (PI) treated by atmospheric-pressure plasma (APP). Oxygen plasma was applied to the PI surface, and the APP-treated surface was exposed to air for various periods of time in order to evaluate the sustainability of the APP treatment. The adhesion of the Ag/PI interface was measured using a roll-type 90 peel test. The peel strength was dramatically increased by the APP treatment, but the strength decreased by around 62.7% when the APP-treated PI surface was exposed to air for 2 h. The peeled PI surface showed ductile fracture immediately after the APP treatment; however, after 2 h of exposure to air, the fracture behavior returned what was observed before the APP treatment. To analyze the deterioration of adhesion, the interface between the printed Ag track and the APP-treated PI was investigated physically and chemically. The surface morphology became rougher after the APP treatment, but the roughness slightly decreased after being exposed to air for 2 h. X-ray photoelectron spectroscopy (XPS) was used to investigate the chemical bonding of the printed Ag and the PI interface. XPS analyses show that the concentration of oxygen-containing groups decreased as the exposure time to air increased.