Recently, Pb-free solder has been widely used in the electronics industry due to the world wide increase in environmental awareness. However, Pb-free solder has the higher melting point, lower wetting and the formation of brittle Metal compounds by Cu diffusion has reported. In addition, UBM which have good reliability for the Pb-free solder become very important. In particular, the electroless Ni-P/Au UBM is widely used due to the better wetting and diffusion prevention of Cu. In this research, Sn-4Ag, Sn-4Ag-0.5Cu, and Sn-4Ag-1.0Cu solder alloy and the electroless Ni-P/Au UBM Cu-Plate were used. To compare the Pb-free solder alloys with Pb containing solder alloys, Sn-37Pb was also used. Micro Shear-Punch Creep test executed temperature of 30℃, 50℃and 80℃. Test Load was 4∼23MPa. Evaluate methods include the power law relationships, the Monkman-Grant relationship were used to extrapolate and the creep data in this research. To compare Ni-P/Au UBM Creep data and Non-UBM Creep data in the research. The main objective of this research is to evaluate the Pb-free solder joints with Ni-P/Au UBM which have steady reliability, the creep property.
The follows of this research shows the results.

1. The Ni-P/Au UBM solder joints creep test in the Pb-free solder is superior creep properties than Sn-37Pb appeared. Non-UBM creep test of preceding research shows the results of lead-free solder excellent creep resistance proved.

2. Sn-Ag-Cu Pb-free solder joints in the high-stress creep Characteristic than the Sn-Ag Solder joint is excellent. Especially, Sn-4Ag-1.0Cu solder joints were most excellent creep properties in the 30℃, 50℃. On the other hand, three Pb-free solder joints have similar creep behavior showed in the 80°C.

3. The Cu addition of a small amount of change with Ni-P/Au UBM deposition of Pb-free solder joints creep characteristics affects Can be seen in the high stress.

4. The Pb-free solder joints Showing the stress exponent (n, m) is higher than Sn-37Pb, activation energy (Q) decreases as the load increases. The same stress conditions showed that the Sn-Ag-Cu solder joint higher than the activation energy of the Sn-4Ag solder joint.

5. Ni-P/Au UBM compared Non-UBM ,excellent creep resistance was found in high-stress. In particular, Sn-4Ag-0.5Cu showed excellent creep resistance in the all stress area.

6. Sn37Pb as well as Pb-free solder with Ni-P/Au UBM showed that the long rupture time in the high stress. Ni-P/Au UBM Showed improved creep resistance in the high-stress areas. Ni-P/Au UBM and Non-UBM between, seems Intermetallic compounds behavior to be the difference.

7. At the same stress condition, Ni-P/au UBM are higher than the Non-UBM with the value of the activation energy was found.