Dynamic Stress of Solder Joints under Board-Level Drop/Impact

A 3-D finite element model of board level BGA package was built and the Input-G method was used to analyze dynamic solder joint stress in the package during drop/impact. Boundary condition, bolt effects of the test board and peeling stress mechanism were emphasized in current investigation. Dynamic responses of solder joint in frequency domain and time domain were analyzed to find main mechanism of stress generation. The results show that bolt constraints have a significant influence on the dynamic stress in solder joints. The bolt constraints must be treated as zero horizontal displacement in the area the bolt acted in the numerical model. The stress in the solder joint reaches its peak at 0.4ms and the maximum peeling stress is located at the most outer corner of the package. The peeling stress is dominated by the deflection of the PCB board. Due to effect of the 5th vibrating mode, the stress-time curve of the solder joints is not smooth.