In this thesis, the response of solder balls under high-speed impact was investigated. Five solder compositions, such as Sn/4.0Ag/0.5Cu,Sn/3.5Ag/0.75Cu,Sn/1.0Ag/1.0Cu, Sn/3.0Ag/0.5Cu and Sn/2.6Ag/0.6Cu with two pad surface finishes and ball impact test system were used to implement four kinds of experiments including different impact speeds, different hammers, different reflow times and different aging time in room temperature after reflow. From experiments, the variations of solder strength and mechanical properties were received and discussed. At the same time, failure modes and variations of solder structure after reflow were observed by using SEM and X-ray EDS. The experimental results show that maximum impact force on solder joints increases with the increasing of impact speed when it reaches a critical value. The impact force of Sn/2.6Ag/0.6Cu with Ni/Au pad finish is the maximum among all the solder compositions at varied impact speeds. Maximum impact force on solder joints will decrease with the increasing of mass of hammer. The strength of solder ball were reduced significantly after reflow, however, it makes no difference for solder strength to reflow twice. It was found that maximum impact force and impact energy of solder joints didn¡¦t change a lot, but the ductility and stiffness of them varied unstably under the condition of room temperature for seven days after reflow.