ASME Winter Annual Conference: 9th Symposium on Mechanics of Surface Mount Assemblies , Novermber 1997.

Thermomechanical Durability Analysis of Flip Chip Solder Interconnects without Underfill

K. Darbha, J.H. Okura, A. Dasgupta
CALCE Electronic Packaging Research Center
University of Maryland,
College Park, MD 20742
Jo F. J. M Caers
Philips CFT Technology,
5600 MD Eindhoven, The Netherlands


A generalized multi-domain Rayleigh-Ritz (MDRR) approach developed by Ling et al. [1995], is extended in this paper, to obtain the stress field in flip chip solder interconnects, under cyclic thermal loading. Elastic, plastic and time-dependent viscoplastic analysis is demonstrated on flip chip solder interconnects. The method has been applied to other surface-mount interconnects in the past such as J-lead [Ling et al., 1996] and ball-grid joints [Ling et al., 1997]. The analysis results for the J-lead and ball grid joints have confirmed that the MDRR technique is capable of providing stress, strain hysteresis with adequate accuracy, at a fraction of the time required by finite element model generation and analyses. Nonlinear viscoplastic stress analysis results for flip-chip interconnects without underfill are presented in this paper. The effect of the underfill will be presented in a future paper. The goal is to predict the stress, strain and strain energy density distributions in the solder with good accuracy, but at a fraction of the computational effort typically required in a full-scale finite element analysis. The fatigue endurance of the solder joints is assessed by combining results from this stress analysis model with an energy-partitioning damage model [Dasgupta el al., 1992]. The life predicted by the analytical damage model is compared with experimental results.

Complete article is available to CALCE Consortium Members.

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