Electrical properties of ultrasmall low temperature solder joints for LCD driver IC packaging applications

We studied the electrical characteristics of ultrasmall eutectic Bi-Sn and eutectic In-Ag solder joints for LCD driver IC packaging applications. Using the eutectic Bi-Sn and eutectic In-Ag solder bumps of 80-50 /spl mu/m pitch sizes, a ultrafine solder joint between an IC and the glass substrate was successfully made at 160/spl deg/C. The contact resistances of the solder joint were 42 m/spl Omega/ at 50 /spl square/ pitch and 8-12 m/spl Omega/ at 80 /spl square/ pitch, which was much lower than that of the joint made using the conventional ACF bonding technique. The Bi-Sn solder joints with underfill showed excellent reliability in a hot humid environment.