Stress-strain simulation of solder joints in a BGA package

A nonlinear finite element analysis was carried out to investigate the viscoplastic deformation of solder joints in a ball grid array (BGA) package under temperature cycling. The effects of constraint on print circuit board (PCB) and stiffness of substrate on the deformation behaviour of the solder joints were also studied The results indicated that high inelastic strain was developed in the joints close to the package center. On the other hand, high constraint was associated with the joint closest to the edge of the silicon chip. Increasing external constraint on the PCB caused a slight increase in stress triaxiality in the joint closest to the edge of silicon chip. There was an increase of inelastic strain in the solder joints with increasing the Young´s modulus of the substrate.