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Nonlinear Deformation And Crack Interactions In Semiconductor Packages


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A O Ayhan & H F Nied


Nonlinear deformation and crack interactions in semiconductor packages A. 0.Ayhan1 and H. F. Nied2 1Global Research Center, General Electric Company, Niskayuna, U.S.A. 2Mechanical Engineering and Mechanics, Lehigh University, Bethlehem, U.S.A. Abstract In this study, three-dimensional enriched crack tip elements were employed to analyze interfacial cracking problems encountered in electronic packaging. These elements are located at the crack tip region and contain the correct 3-D crack tip displacement and singular strain fields with unknown stress intensity factors. Using enriched elements, the elastic-plastic behavior of solder balls and interaction effects with nearby cracks in a flip-chip semiconductor package were investigated. Applying periodicity boundary conditions, a slice near the central region of the device was considered. Results from two differently shaped interfacial cracks near the fillet region are presented. Including plasticity effects on the solder balls, the interaction between plastic deformation and fracture parameters was investigated (elastic crack tip behavior). The two interfacial crack configurations are; a vertical crack between the fillet and the Si-chip, and an "L," shaped crack between the underfill material and the chip. The results from these calculations showed that plastic deformation, especially on the outermost solder ball, is affected by the presence of a crack in its vicinity and vice versa. It was observed that the plastic strains increase as the crack tip approaches the outermost solder ball. Depending on the type of crack under consideration, the fracture parameters can also vary significantly along the crack front even for the straight through cracks presented in this paper. In studying the "L" shaped crack, it was concluded that inclusion of crack surface contact is critical for accurate determination of plastic strains and fracture parameters.