For the flip chip joints processed using Cu pillar bumps and Sn pads, thermal cycling and high temperature storage reliabilities were examined as a function of the Sn pad height. With increasing the height of the Sn pad, which composed of the flip chip joint, from 5 ${mu}m$ to 30 ${mu}m$, the contact resistance of the flip chip joint decreased from 31.7 $m{Omega}$ to 13.8 $m{Omega}$. Even after thermal cycles of 1000 times ranging from $-45^{circ}C$ to $125^{circ}C$, the Cu pillar flip chip joints exhibited the contact resistance increment below 12% and the shear failure forces similar to those before the thermal cycling test. The contact resistance increment of the Cu pillar flip chip joints was maintained below 20% after 1000 hours storage at $125^{circ}C$.