An average contact resistance of a COG joint bonded with 48Sn-52In solder was characterized using daisy chain structure. The average contact resistances of the 48Sn-52In solder joint of 29 mm diameter and 14 mm height were 132 m/bump, 28.5 m/bump, and 8.6 m/bump on Ti(0.1 mm)/Cu(1.5 mm), Ti(0.1 mm)/Cu(1.5 mm)/Au(0.1 mm), and Ti(0.1 mm)/Cu(3 mm)/Au(0.1 mm) UBMs, respectively. Such difference in the average contact resistance of the 48Sn-52In solder joint on each UBM could be attributed to partial oxidation of the Cu UBM layer during solder evaporation and a difference of the thickness of the Cu UBM layer remaining underneath the intermetallic compounds after soldering.

No abstract