Solder joints in electronic packages and devices serve as mechanical and electrical connections as well as thermal paths for heat dissipation. Due to the miniaturization of electronic packaging, nowadays solder joints contain large volume fraction of IMCs. It has been observed that solder joint strength is controlled largely by intermetallic strength at higher strain rate. Macroscopic properties such as tensile and shear strength, creep, ductility depend on Intermetallic layer's properties of solder joints. This study is carried out to determine elastic-plastic properties of Cu6Sn5 intermetallic in Sn-3.5Ag/Cu system with reflow soldering by nanoindentation. Elastic properties such as elastic modulus and hardness were determined from the load-depth curve. A widely used reverse analysis model described by Dao et al.  was considered to extract plastic properties such as yield strength and strain hardening exponent using nanoindentation results. Anisotropy of Cu 6Sn5 was taken into consideration to see if that has any effect on the mechanical properties. Our study considered crystallographic grain orientation along normal to the growth axis of Cu6Sn5 IMC which was extracted using Electron backscatter diffraction (EBSD) mapping. Statistically indistinguishable properties were observed for Cu 6Sn5 IMC. Average elastic-plastic properties of Cu 6Sn5 were than compared with already published results in literatures.