Journal of SMT Article


Authors: Pradeep Lall, Milan Shah, Luke Drake, Timothy Moor
Company: Auburn University Department of Mechanical Enginee
Date Published: 7/30/2008   Volume: 21-3

Abstract: In this work, thermo-mechanical models for reliability prediction of BGA package interconnects mounted on integral copper-core (Cu-CORE) and no integral copper core (NO-CORE) printed circuit assemblies in harsh environments have been developed. The models have been developed based on thermo-mechanical reliability data acquired on Cu-CORE and NO-CORE assemblies in four different thermal cycling conditions. Solder alloys examined include SnPb and SAC alloys. Multivariate linear regression (MLR), and non-linear finite element models have been developed for prediction of geometry and material effects. The models presented in this paper provide decision guidance for smart selection of component packaging technologies and perturbing product designs for minimal risk insertion of new packaging technologies. In addition, qualitative parameter interaction effects, which are often ignored in closed-form modeling, have been incorporated in this work. The statistics models are based on accelerated test data acquired as part of this paper, in harsh environments, while finite-element models are based on damage mechanics and material constitutive behavior. Convergence of statistical, failure mechanics, and FEAbased model sensitivities with experimental data has been demonstrated. Validation of model predictions with accelerated test data is presented for various parameters including Die to Package Ratio, Ball Count, Ball Diameter, Package Pad Diameter, Surface Finish, Temperature Cycle Condition. The modeling methodology shows good correlation with experimental data.

Keywords: Ball grid array (BGA), design guidelines, solder joint fatigue, statistical model, thermal reliability prediction, Finite element models.

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