Comparative Study of Plastic Strain Accumulations at Thermal Cycles for Solder Alloys

Abstract

This paper presents an investigation of plastic strain accumulation at thermal cycles for 4 different solder alloys used in electronics. The investigation was performed on an assembly which is part of an electronic packaging. The behavior of the solder was numerically analyzed by means of the finite element method, using Ansys program. This work was carried out for a thermal variation of 165°C, in the range of -40…+125°C. The first material (60Sn40Pb) was described using Elastic-Plastic, Chaboche and Anand models, which combine the plasticity with creep. Following the investigation of the first solder alloy, a correlation between the Anand model and the Elastic-Plastic one was proposed, this being obtained by using a numerical constant. It was observed that the proposed correlation factor is closely related to hardening constant (a parameter of the Anand model). Following the first investigation, another 3 types of solder alloys were also analyzed. Each new material was described with both the Anand model and the Elastic-Plastic model. The possibility of correlation between the two models, as well as the verification of the relationship between the used correlation factor and hardening constant, were investigated. Following these investigations, it was concluded that, for the studied thermal field, the material models can be correlated. Also, for 50% of investigated cases, the correlation factor is closely related with a parameter of the Anand model.