Creep in microelectronic solder joints: finite element simulations versus semi-analytical methods

The presence and change of thermal stresses in solders, which are used for mounting microelectronic packages on PC-boards, will eventually lead to material fatigue. The number of cycles to failure can be predicted from empirical relations of the Coffin–Manson type provided the increments of creep strains and/or energy densities are known, for example, from (rather extensive) FE-simulations. A special problem arises for newly developed solders for which the Coffin–Manson equations are not known yet and need to be established first from a combination of FE and costly reliability experiments. In any case the goal of the industry and research institutions is to replace experiments as much as possible by reliable predictive simulations. However, FE calculations, which are widely used to perform this task, can—as indicated—be rather time-consuming, due to the huge effort involved for component meshing, and due to the various non-linear constitutive equations required for the description of creep in solders and other package materials. In a previous paper (Müller and Hauck in Mech Adv Mater Struct, 15(6):485–489, (2008)) a simple analytical 1D-model was presented that allows computing characteristic damage quantities, such as creep strain and creep energy density, for different solder materials and different temperature profiles in a very efficient manner, provided a creep law is known. In this paper the proposed procedure is validated by comparison with results from detailed FE-simulations.