Contact Resistance of the Chip-on-Glass Bonded 48Sn–52In Solder Joint

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 μm diameter and 14 μm height were 132 mΩ/bump, 28.5 mΩ/bump, and 8.6 mΩ/bump on Ti(0.1 μm)/Cu(1.5 μm), Ti(0.1 μm)/Cu(1.5 μm)/Au(0.1 μm), and Ti(0.1 μm)/Cu(3 μm)/Au(0.1 μm) 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.

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