Development of BGA solder joint vibration fatigue life prediction model

The objective of the present study is to develop a vibration fatigue life prediction model for ball grid array (BGA) solder joint. In this study, 3-D global/local finite element models were first constructed with MSC/PATRAN code. For the global model including EGA package soldered onto the printed wiring board (PWB), linear finite element dynamic analyses with an excitation normal to the PWB was conducted using MSC/NASTRAN code to determine the dynamic responses at the two ends of EGA solder joint. In these analyses, a single-degree-of-freedom system was assumed. A steady-state harmonic (or frequency sweep) response provides phase angle values while a random response furnishes the power spectral densities as well as their root mean square (RMS) values. For the local model having a refined mesh to simulate the local region in detail, a linear finite element static analysis was conducted by applying the derived RMS values with their corresponding phase angles to this model (at the two ends of the critical corner solder joint) in order to determine the solder effective stress/strain RMS value. A vibration fatigue life model, evolved from an empirically derived formula of universal slopes based on high-cycle fatigue test data, was established. This model combined with a three-band technique and the derived solder effective strain was then us ed to predict the EGA solder joint survivability/durability. This prediction will be compared to test results, which will be provided by in-house on-going R&D, to validate the proposed EGA solder joint vibration fatigue life prediction model. An example of a 600-pin plastic EGA soldered onto the various locations of the PWB was illustrated in the present study.