Abstract: The SAC105 solder paste was modified by doping TiO₂ nanoparticles with different contents. The rheological properties of the modified solder pastes were studied by using rotating rheometer, viscometer and other equipment. The mechanical properties and microstructure of the joints welded with the modified solder pastes were studied by tensile machine and scanning electron microscope. The results show that the shear strength of TiO₂ nano doping SAC105 paste welded joints reaches up to 71.4 MPa, which is 65% higher than that of undoped SAC105 joint. This is attributed to the second phase strengthening of TiO₂ nanoparticles in the solder joint. The creep elastic deformation area of SAC105 solder paste with 1%TiO₂is about 50% smaller than that of undoped SAC105 solder paste. Adding 1%-2% TiO₂ nanoparticles can significantly adjust the paste viscosity value from 96.2 Pa·s to 120.2 Pa·s with the thixotropic coefficient of 0.73-0.74 basically unchanged. It provides a new method for coupling regulation of thixotropic coefficient and viscosity of printing paste.