3D packaging using through silicon via (TSV) technology is becoming important in IC packaging industry. However, increased number of interconnects and extreme miniaturization suggest that thermo-mechanical reliability and fatigue will aggravate. In traditional package, thermo-mechanical fatigue failure mostly occurs as a result of damage in the solder joint. In TSV technology, however, the driving failure may be the TSV via or TSV interconnects. In this study, the durability of TSV technology is investigated using finite element method. Thermal fatigue phenomenon due to the plastic strain caused by repetitive temperature cycling is analyzed, and possible failure locations are discussed. In particular, the effects of via size, underfill material, and via filling material on the thermal fatigue reliability are investigated. The expected fatigue life indicates that the presence of underfill material is essential in improving the durability of the TSV structure. The plastic strain increases with the via size increases, therefore the thermal fatigue life increases as the via size decreases. For different via filling materials such as copper, nickel and tungsten, amount of plastic strain is very similar, suggesting that nickel could be used for via filling material. However, the locations of the maximum strain are different for each filling material.