The Three-Dimension FE Fracture Analysis Of Ball Grid Array Packaging Under Cycle Temperature Load

A three-dimensional FE model is used according to the investigation of solder creep and fracture between interfaces on the Plastic Ball Grid Array package (PBGA). The numerical simulation of PBGA-FM is carried out, and high-level stress is observed at joints, which locate on central and beneath the edge of die. For simplification of calculation, an effective model of package is made for study. As to the result of simplified model, high inelastic strain and strain energy can be found on sites which are on the central joint and ones closed to the edge of die. Compared to the two-dimension model, the three-dimensional FE model can simulate the characteristics of stress on package than that of two-dimensional model. The effects of stiffness of substrate and external constraint conditions on printed (PCB) are also investigated.This paper also investigates the interface failure of PBGA (Ball Grid Array) package under the cyclic temperature by numerical analysis. The potential dangerous site in adhesive bond assembled between silicon chip and substrate was confirmed, the critical failure site in solder joints was also considered. Both the 2D and 3D finite element simulation models of PBGA package were established for different investigation purposes, the comparison between different models was discussed. The viscous behavior of adhesive material was considered, while for solder linear elastic and viscous material model were assumed for different tasks. The deformation trend can be observed among the molding, adhesive bonds and substrate, which is due to the mismatch of the coefficients of thermal expansion (CTE) of different materials under cyclic temperature. The stress distribution on adhesive bond and solder joints under thermal cycle was obtained and the region of high stresses was indicated. The numerical results also proved that the viscous behavior of solder joint has a slight influence on stress distribution of adhesive layer, thus when only to investigate the interface failure between silicon chip and substrate, the solder can seen as full linear. The influence of shape of joints on distribution of stress of adhesive bond is also studied.