Modeling thermo-mechanical reliability of bumpless flip chip package

Abstract

Finite element modeling of thermo-mechanical reliability of a Bumpless Flip Chip Package (BFCP) was investigated. Both package-level and board-level assemblies are modeled using 2-D plane strain models. The package-level temperature cycliing profile used was -65C to +150C, with 2 cycleshour, upper and lower soak time of 10 minutes. The package survived 2000 cycles without any failures. The board level assembly test is planned and modeling is conducted for a temperature cycling profile of -4OC to +125C, with 1 cyclelhour, upper and lower soak time of 15 minutes.For the package level analysis, the copper interconnection material properties were modeled using different properties from bulk Cu and electroplated Cu data. The mechanical properties of both the bulk and electroplated copper were used in the FEA simulation and the results compared. Fatigue life prediction study, using the appropriate thin-film propzrties of copper and the fatigue properties of thin-film copper gave reasonable predicted life.For the second level solder joint analysis, the deformation behavior of the compliant terminals with the solder joints were investigated. Visco-elastic properties was used for the epoxy resin, viscoplastic properties was used for the eutectic Sn-Pb solder joints. The in elastic energy density method was used for solder joint fatigue life prediction.

Thermal cycling fatigue analysis of copper pillar-to-solder joint reliability

“…The elastic-plastic and stress-strain data for plated copper material and the low cycle fatigue data were reported earlier by Che et al [6].…”

“…Parametric design was employed in this study and the solder j oint reliability was investigated. The lead-free solder material properties for Sn-Ag-Cu were taken from references reported earlier [2][3][4][5] and the plated copper pillar elastic plastic stress-strain and fatigue properties were adopted from Che et al [6]. The finite element analysis modeling study of the new interconnect design can be done in two parts.…”

“…The copper-pillar fatigue life prediction model [6] is given in equation (3). To assess the thermal cycling fatigue life of this composite flip chip interconnect structure, FEA and fatigue analysis of the solder material and copper-pillar material fatigue damage parameters have to be calculated separately and the appropriate solder and copper low cycle fatigue models used respectively.…”

Design, simulation and fabrication of a flexible bond pad with a hollow annular protuberance to improve the thermal fatigue lifetime for through-silicon vias

“…where N f is the fatigue lifetime, Δε p is the amplitude of cyclic plastic strain, and the parameters C and m are known as the fatigue ductility exponent and fatigue exponent, respectively. In the case of bond pads, constants for electroplated Cu, which are obtained from literature [30], are 0.0121 and −2.433 for C and m, respectively. These constants are both different from other Cu products, such as bulk Cu and rolled Cu.…”

Development of failure assessment methodology for lead-free electronic assembly

“…In this study, these two solder constitutive models will be used in FEA simulation for comparison.Finite element modeling and simulation is powerful tool and takes an important role in fatigue life prediction for solder joints. In order to reduce the element size in the FEA simulation for solder joint reliability, some reduced models were used by researchers, including slice or strip model[13], one-eighth or octant model[29,88], 2D model containing 2D plane strain[103], 2D plane stress[14] and axisymmetric models[100]. Some trade-off in accuracy is expected in these simple models.…”