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 2nd 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 dice within the MCM package on the package warpage was studied. Secondly, the effect of package dimensions (the heat spreader thickness, structural adhesive thickness and substrate thickness) on the maximum residual stress and 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 the solder joints is estimated by Darveaux's approach. A series of parametric studies is performed by changing the package dimensions. The results obtained from the modeling are useful for the design of multichip packages.