A new flip-chip bonding technique using micromachined conductive polymer bumps

Using niicrornachining techniques with thick photoresists, a new conductive polymer flip-chip bonding technique that achieves both a low processing temperature and a high bumping alignment resolution has been developed in this work. By the use of UV-based photolithography with thick photoresists, molds for the flip-chip bumps have been patterned, filled with conductive polymers, and then removed, leaving molded conductive polymer bumps. After flip-chip bonding with the bumps, the contact resistances measured for 25 /urn-high bumps with 300 fim x 300 /urn area and 400 /um x 400 /urn area were 35 m£7 and 12 m£7 respectively. The conductive polymer flip-chip bonding technique developed in this work shows a very low contact resistance, simple processing steps, a high bumping alignment resolution (<±5 /urn), and a lower bonding temperature (~170 °C). This new bonding technique has high potential to replace conventional flip-chip bonding technique for sensor and actuator systems, bio/chemical /u-TAS, optical MEMS, OE-MCM's, and electronic system applications.