Study of Thermo-Mechanical Stress Distribution for CBGA Package

In this paper, the two-dimensional model of the CBGA device is established to study its mechanics behavior under thermal cycling conditions by ANSYS. The results show that the position of the maximum stress located on the outmost solder balls of the device, where it would cause cracks easily and damage the device. The three-dimensional model (containing a single solder ball) of the CBGA device is also established to simulate the stress distribution of the device affected by the shape of solder ball. According to the simulation results, when the radius of solder ball is about 0.45 mm and height is about 0.65 mm, the Von Mises stress and total strain are smaller comparatively, in the condition of the spot pitch 1.27 mm, thus the reliability of solder ball and devices can be improved.