Simulation and analysis for backward compatibility of solder joints under thermal cycle

In this paper, the backward compatibility solder joints were chosen in simulation of perimeter PBGA272 assembly. A double-symmetric plane FE model of a PBGA272 was established using the software ANSYS. Based on the maximum von Mises stress and von Mises strain, the position of the most danger solder joints were obtained under thermal cycle with the temperature condition from -40degC to 125degC (JESD22-A104-B Condition G) , Viz. the inner (1#) solder joint and the outside (6#) solder joint are the two key solder joints which are the easiest to failure. On the basis of above analysis, the geometry parameters of the chosen assembly are optimized by design of experiment (DOE). The factors included PCB size, PCB thickness, chip size, chip thickness, substrate size, substrate thickness, solder height and solder radius. The simulating results have shown that substrate thickness (factor F), solder radius (factor H) and solder height (factor G) performed the main factors. The optimal scheme is F3H2G1C2D1E2B3A2 (substrate thickness 0.7 mm, solder radius 0.38 mm, solder height 0.4 mm, chip size 2.54 mm, chip thickness 0.4 mm, substrate size 13.5 mm, PCB thickness 1.8 mm and PCB size 15 mm) by comprehensively considered with every factorpsilas effect.