Thermo-mechanical analysis for a multi chip build up substrate based package

This paper presents a thermo-mechanical analysis of a multichip module (MCM) package design, with emphasis on the package warpage, thermally induced stress and the 2(nd) level solder joint reliability. The MCM package contains four flip chips which are mounted on a build up substrate. Firstly, the effect of the positioning of four silicon dies within the MCM package on the warpage of the package was studied. Secondly, the effect of package dimensions (the heat spreader thickness, the structural adhesive thickness and the substrate thickness) on the maximum residual stress as well as the warpage of the package were performed. Finally, this paper presents a 3D sliced model for solder joint reliability of the MCM assembly. A creep constitutive relation is adopted for the 63Sn/37Pb solder to account for its time and temperature dependence in thermal cycling. The fatigue life of solder joint is estimated by the Darveaux's approach. A series of parametric study is performed by changing the package dimensions. The results obtained from the modeling are useful in suggesting design of multi chip package.