The FEM analysis of stress and strain in stacked solder bump under power load

The PBGA (Plastic Ball Grid Array) stacked solder bump finite element analysis model was set up, the temperature field analysis and thermal-structural coupling analysis were carried out under power load based on the model. The effects of solder pad size and solder volume on thermal stress distributed in the solder ball were analyzed. The results illustrated that the distribution of temperature in the PBGA package structure is non-uniform. The chip has the highest temperature. At the far end of PCB diagonal, the temperature reaches the minimum. The maximum stress and the maximum equivalent plastic strain occur in the most distal corner solder ball. The contact area between upper solder ball and chip has the maximum stress and strain. With the variation solder pad size, the thermal stress in the solder ball changes corresponding. With variation of the solder volume, the equivalent stress in the ball changes corresponding. The equivalent stress decreases with solder volume increased.