Void dynamics in lead‐free Sn‐Ag‐Cu solder joints

As a result of thermal and mechanical loading of Sn‐Ag‐Cu solder joints pores, flaws and voids may nucleate and grow. Such void nucleation is studied here by means of a phase‐field approach which accounts for the decomposition of the solder into phases described by its concentration c . In this investigation, the void growth results from boundary inward flux only, effects due to grain size and interstitials are not involved, cf. [1]. The free energy functional is approximated by a second order Taylor expansion and thus composed of a bulk free energy density and a Ginzburg‐type gradient term. The bulk free energy density ϕ follows a classical Ginzburg‐Landau double‐well potential. The gradient‐energy coefficient κ depends on ϕ and is calculated similar to [2]. Experimental data have been adapted for the modeling of the temporal evolution of the concentration of voids located on a square domain in 2D. The simulation is based on a B‐spline finite element analysis. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)