An effective analytical method for the interface reliability design of System-in-Package in thermal environments

The design for manufacturability and the design for reliability of System-in-Package (SiP) are of great importance for packaging technology. The interfacial delamination is the most critical failure mode during solder reflow process and reliability test. The delamination is driven by the mismatch between material properties of packaging materials, for instance, the coefficient of thermal expansion (CTE) and Young’s modulus. In this paper, an analytical model based on interface fracture mechanics is systematically established to promptly evaluate the reliability of the laminated-based SIP modules. The governing equation of SIP interface system is derived, and the continuity condition of longitudinal and vertical deformation for crack-tip element is described by interface compliances. The normal and shear stress distribution between heterogeneous interfaces (e.g., the epoxy molding compound (EMC) and solder mask, EMC and substrate, etc.) subjected to temperature change are calculated. The strain energy release rate (SERR) for the interface facture toughness is also considered in present analytical model. The capability and accuracy of the proposed method are verified against solutions from finite element software ABAQUS, showing remarkable agreements. The mixed mode ratio is also evaluated for SiP structures with thermal stress. The influence of temperature changes on the interfacial fracture toughness is investigated to shed light on the interface reliability of package. The accuracy and computational efficiency of proposed analytical solution are discussed in the estimation of the interfacial delamination risk for SIP module design.