Thermomechanical Durability of High I/O BGA Packages

Efficient modeling strategies are developed to study thermomechanical durability of high I/O Ball Grid Array (BGA) packages, in order to facilitate virtual qualification and accelerated testing of component designs. A viscoplastic stress analysis technique is developed where the critical solder joint(s) (joint(s) at which failure first occurs) are modeled in detail with a multi-domain Rayleigh-Ritz (MDRR) methodology (Ling and Dasgupta, 1996; Ling and Dasgupta 1997; Ling 1997; and Rassian and Lee, 1998) while the load-sharing offered by non-critical joints is modeled with a simplified compact model. This hybrid technique is used to study the behavior of solder interconnects in selected Ball Grid Array (BGA) package under thermal cycling environments. Parametric studies are conducted to determine the optimal scheme for allocating a critical number of solder joints to the MDRR model, and the remaining non-critical joints to the compact models. Damage calculations are made with the Energy Partitioning Solder Durability model (Dasgupta et al., 1992) and cycles-to-failure predictions are compared with both finite element model predictions as well as experimental failure data provided by CALCE EPSC sponsors. Parametric studies on change in solder joint durability with interconnect volume are also discussed in this paper.