Durability/reliability of BGA solder joints under vibration environment

The objective of the present study is to develop an experimentally validated vibration fatigue damage model for a plastic ball grid array (PBGA) solder joint assembly. A 3-D modeling technique is used to simulate the vibration responses of the BGA packages soldered onto a printed wiring assembly (PWA). In the study, a method to determine the stresses/strains of BGA solder joints resulting from exposure of the PWA to random vibration environments is first described. Linear static and dynamic finite element analyses using MSC/NASTRAN/sup TM/ computer code, combined with a volume-weighted average technique, are then conducted to calculate the effective strains of the solder joints. In the calculation process, several in-house developed Fortran programs, in conjunction with the outputs obtained from MSC/NASTRAN/sup TM/ static and frequency response analyses, are used to perform the required computations. A vibration fatigue life model, evolved from an empirically derived formula of universal slopes based on high-cycle fatigue test data, is established. This model combined with a three-band technique and the derived solder effective strain is then used to predict the PBGA solder joint survivability/durability. This prediction is compared to in-house test results to qualitatively calibrate (in the sense of conservation) the proposed PBGA solder joint vibration fatigue damage model. This validated model is then recommended to serve as an effective tool to determine the integrity of the PBGA solder joints during vibration. Selecting more study cases with various package sizes, solder ball configurations, vibration profiles to further calibrate this vibration fatigue damage model is also recommended. An example of a 313-pin PBGA is illustrated in the present study.