Experimentally validated analysis and parametric optimization of monotonic 4-point bend testing of advanced BGA packages

With continuing miniaturization and more prevalent use of Ball Grid Array (BGA) packages in the microelectronics industry, the mechanical strength of Printed Circuit Board Assemblies (PCBAs) with BGA packages is becoming very critical. In a variety of applications ranging from smart phones to high end switches and routers, the mechanical robustness of PCBAs is becoming the key differentiator in product reliability. To enable a standard way to benchmark mechanical reliability, the IPC/JEDEC-9702 test method was developed several years ago. The test method has helped compare different PCBAs to optimize overall mechanical reliability. However, a key challenge with mechanical testing is that by the time the testing is performed, it is too time consuming and expensive to make changes to the package if it´s mechanical reliability needs improvement. In this study, bending tests for various BGA packages have been conducted based on the IPC/JEDEC-9702 standard, under different applied deflections to obtain the required data for studying the failure modes. Three-dimensional Finite Element Models (FEM) were developed to understand the relationship between PCB strain and solder joint strain. The strain values at different locations in the PCBA were estimated from the model, and compared with experimental data. Good agreement between model predictions and experimental data has been obtained. Then, a series of FEM analyses were performed with different design parameters. High performance cluster computing was used to reduce computation time without compromising accuracy. Finally, based on the results presented in this study, optimization analysis was performed to improve BGA mechanical reliability for any given geometry.