Location of the Critical Solder Joint of a PBGA under Temperature Cycling Load for SAC and SnPb Solder. Results of Experiments vs. FE-Simulations on System and Board Level.

摘要

PBGAs with SnPb and SnAgCu (SAC) solder joints were stressed with temperature cycles on board- andsystem-level. A significant influence of the different solder materials on the location of the most damaged PBGAsolder balls was observed in the experiment. The reason for this experimental finding was investigated andexplained by FE–simulation. The simulations of the PBGAs were done on package-, board- and system-level(PCB within a metal housing). For the system level simulation a 2-step sub-model technique described in [1]was used. Through such an approach the transient PCB deformation and the transient temperature field withinthe ECU-housing can be incorporated into a creep simulation of the PBGA solder joints. The creep results forboth SnPb and SnAgCu solder joints from the board- and system-level simulation were compared. Thecalculated damage factor due to the ECU-housing influence is different for PBGA with SnPb and SAC solderjoints. The simulation results were validated step by step with measurements and experiments: warpage of thenon-soldered PBGA, mechanical strain and temperature on the mounted PCB, crack length evaluation of allPBGA solder joints.