Abstract: The interface reaction between the Cu substrate and two lead-free solders of SnAgCu and SnAgCu-TiO₂ was investigated, and the growth of intermetallic compounds (IMCs) and mechanical properties of solder joints during aging at 140℃ were analyzed systematically. The results indicate that Cu₆Sn₅ was detected at the as-soldered interface,and aging at 140℃ resulted in the growth of IMCs. Moreover,it was found that the thickness of IMCs was proportional to the square root of aging time. When the aging time was 300 h,Cu₃Sn appeared at the interface, and the results show that the addition of TiO₂-nanoparticles could inhibit the growth of IMCs. In addition,after analyzing the mechanical properties of solder joints,it was found that with the development of aging time,the average tensile force decreased obviously,and the mechanical properties of the joint soldered with SnAgCu-TiO₂ were higher than that with SnAgCu.