C.H. Cho and Y.J. Choi
Keywords: printed electronics, surface treatment, polyimide, copper, flash light sintering
Summary:In this presentation, we report improving adhesion property between a screen printed copper electrode and polyimide substrate through chemically modifying the surface of polyimide (PI) substrate. The PI surface was modified with KOH and HCl solutions. And, the copper electrode was printed by screen printing method with binder-free copper ink and sintered by the flash light sintering process. The interface between copper electrode and PI substrate was monitored by FE-SEM and the resistance of Cu electrode was measured by 2 point probe method. The surface state of the PI was analyzed chemically and physically by FT-IR, AFM and nano indentation. And the depth of chemically modified layer was estimated by collecting 41K+ ion signal from ToF-SIMS. The adhesion between the copper and modified film shows 5B, which is the highest adhesion level under ASTM-D3359 cross cut test, while the electrode on non-treated film shows the worst adhesion level, 0B class. We attribute the mechanism of the enhanced adhesion to the change of the surface state of PI substrate from PI to potassium polyamate (PAA) by chemical treatment and the recovery from PAA to PI by flash light sintering process.