Interaction of thermal cycling and electric current on reliability of solder joints in different solder balls

This paper deals with the effects of electric current on the thermomechanical lifetime of solder joint as the most vulnerable part in electronic packages. The main focus of this paper is located on the Sn3.8Ag-0.5Cu based solder. Different current densities from 1 A mm−2 to 10 A mm−2 are under considered in two well-known solder ball joints, namely barrel- and hourglass-type, in the temperature cycling conditions. Electrical properties of the interested solder joints are experimentally extracted and applied to the finite element analysis in order to reveal the thermomechanical coupling effects of thermal cycling and electric current. Two most important phenomena including joule heating effects and induced triaxility play major roles in determination of solder joint types in the electronic packages. The results reveal that at the lower current density in which the joule heating effects are insignificant, the sharp triaxiality in the barrel-type solder joint is evident due to sharp tilting angle of solder joint. However, in the higher current densities in which the joule heating effects come into play, the number of cycle to failure of hourglass-type solder joint is lower in comparison with barrel-type solder joint. This event may be due to the lower diameter of hourglass-type solder joint in its neck so that more losses in the neck of hourglass-type solder joint, the more effective joule heating is occurred.