Fatigue crack growth and life descriptions of Sn3.8Ag0.7Cu solder joints: A computational and experimental study

D. Bhate, D. Chan, G. Subbarayan, L. Nguyen

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Scopus citations

Abstract

The need for predicting fatigue life in solder joints is well appreciated at the present time. Currently, however, there are very few experimentally validated material parameters for popular SnAgCu alloys. Furthermore, the validity of Coffin-Manson life models, being empirical, also needs to be explored for these alloys which creep in a manner significantly different from SnPb solder alloys. In this paper, we present a modeling approach inspired by cohesive zone theory of modern fracture mechanics and Weibull distributions of material failure. The approach relies on the accurate estimation of inelastic strains at the crack tip estimated through finite element analysis, which are then used to make decisions on crack propagation. Like most popular cohesive zone models, the modeling approach presented here requires the estimation of two parameters. Unlike most cohesive zone models however, no special elements are needed in the finite element model and estimation of the parameters is more straightforward. We demonstrate the applicability of the modeling approach via the simulation of fatigue crack growth in Sn3.8Ag0.7Cu solder joints subjected to anisotropic thermal cycling. Anisotropic thermal cycling conditions were created experimentally using a simulated power cycling testing device and fatigue crack fronts were tracked at different life cycles using traditional dye-and-pry methods. The experiments were repeated for varying temperature profiles. Experimental results were coupled with numerical analysis to obtain fracture parameters for Sn3.8Ag0.7Cu. The model and the parameters were then validated by verifying their predictive ability against a variety of temperature profiles. In a separate study, the authors have developed a time hardening creep model for describing the behavior of Sn3.8Ag0.7Cu. The time hardening model accounts for primary and secondary creep and does not restrict itself to the assumption of steady state creep. The need for accurate estimation of inelastic strains in the finite element model is thus met using a valid constitutive model to describe solder creep behavior. The ability of the model to predict three dimensional crack fronts for a variety of fatigue loading environments, with sufficient accuracy, is a key result of this work.

Original languageEnglish (US)
Title of host publicationProceedings - 57th Electronic Components and Technology Conference 2007, ECTC '07
Pages558-565
Number of pages8
DOIs
StatePublished - Oct 22 2007
Externally publishedYes
Event57th Electronic Components and Technology Conference 2007, ECTC '07 - Sparks, NV, United States
Duration: May 29 2007Jun 1 2007

Publication series

NameProceedings - Electronic Components and Technology Conference
ISSN (Print)0569-5503

Other

Other57th Electronic Components and Technology Conference 2007, ECTC '07
CountryUnited States
CitySparks, NV
Period5/29/076/1/07

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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    Bhate, D., Chan, D., Subbarayan, G., & Nguyen, L. (2007). Fatigue crack growth and life descriptions of Sn3.8Ag0.7Cu solder joints: A computational and experimental study. In Proceedings - 57th Electronic Components and Technology Conference 2007, ECTC '07 (pp. 558-565). [4249937] (Proceedings - Electronic Components and Technology Conference). https://doi.org/10.1109/ECTC.2007.373851