Design Method of Solder Joint in Surge Protective Device by Simulation

Surge protective devices (SPDs) with metal oxide varistors have the function of stabilizing circuit voltage and protecting electrical equipment from damage caused by lightning strikes. SPD solder joint needs to withstand the lightning current and timely trip in case of overheating. The design of SPD solder joint directly determines its tripping capability, and further determines its reliability. This paper proposes a combination of one-dimensional and three-dimensional simulation modeling method for the design of SPD solder joint under thermal stability condition. Through a three-dimensional simulation method, using the resistance characteristic curve of the varistor and the material characteristics of each component, the temperature distribution of the internal components and the shell of the SPD, including the solder joint, is obtained; through an one-dimensional simulation method, using the temperature-stress curve of the solder, the contact surface of the solder joint is first integrated, then the stress of the joints is obtained at different moments, in order to judge the tripping state of the SPD under thermal stability condition. After comparison with test data, the tripping time interval giving by the solder joint design method proposed in this paper (6960s-7080s) can contain the experimental tripping time (7000s), and the design method can be more accurately used for the design of SPD solder joint.