A study of factors affecting solder joint fatigue life of thermally enhanced ball grid array assemblies

In this study, a finite element study of design factors, including material constants and geometry parameters, affecting fatigue life of solder joints of atypical cavity-down Thermally Enhanced Ball Grid Array (TEBGA) assembl y subjected to an accelerated temperature cycling load is performed. In ord er to precisely characterize the fatigue life of solder joints, the geometr y profile of solder joints within the package is substantially predicted us ing an energy-based method-the Surface Evolver (see, e.g., Brakke, 1994; Ch iang et al., 2000). In addition, a finite-volume-weighted averaging techniq ue is proposed to describe the strain/stress response of solder joints at m aterial/geometry discontinuities. The analysis employs a plane strain FE mo del with the purpose of reducing the computational cost. To validate the FE modeling so as to corroborate the nonlinear and complex mechanical behavio rs of materials in the assembly, a typical interferometric displacement mea surement method-- Moire interferometry (see, Han and Guo, 1995) and 3-D sol id modeling are used. Through the parametric design of the fatigue life of solder joints, the reliability characteristics of the TEBGA assembly are th en effectively identified.