Flip-chip packaging with micromachined conductive polymer bumps

A new conductive polymer flip-chip bonding technique has been developed and characterized using micromachined conductive polymer bumps. By using UV-based photolithography with thick photoresists, molds for the flip-chip bumps have been patterned, filled with conductive polymers, selectively cured, and then stripped, leaving molded conductive polymer bumps on contact metal pads. After flip-chip bonding with the micromachined conductive polymer bumps, the contact resistances measured for 25 μm-high bumps with 300 μm×300 μm area and 400 μm×400 μm area were 35 mΩ and 12 mΩ, respectively. The conductive polymer flip-chip bonding technique developed in this work showed a very low contact resistance, simple processing steps, a high bumping alignment resolution (<±5 μm), and a lower bonding temperature (~170°C)