Thermocompression bonding of conductive polymers for electrical connections in organic electronics

The thermocompression bonding of conductive polymer films was investigated to achieve a flexible wiring and packaging technique for organic and flexible electronics. Conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films were successfully bonded together by thermocompression even at rather low temperatures of 50-100 degrees C, especially through surface activation treatment using ultraviolet light irradiation. After thermocompression, the PEDOT:PSS films maintained their ohmic electrical conductivity even though the adhered interface had a contact resistivity of less than 1.3 omega cm(2). To examine the applications to electrical bonding, PEDOT:PSS patterns were fabricated on polyethylene naphthalate (PEN) substrates, and the bonding force after thermocompression was investigated. The adhesiveness of bonding was highly improved, and the films were strongly adhered at a bonding temperature of 100 degrees C, which was lower than the glass transition temperature (T-g: 160 degrees C) of the PEN substrates. X-ray photoelectron spectroscopy (XPS) analysis of both the PEDOT:PSS and PEN surfaces and the attenuated total reflectance FT-IR (ATR-FT-IR) for the PEN surfaces indicated that the oxidized species of alcohol and carboxylate were generated after the surface activation process. These chemical species can form hydrogen bonds or covalent bonds that provide robust bonding interfaces.