Analytical model to study interfacial delamination propagation in a multi-layered electronic packaging structure under thermal loading

Single Level Integrated Module (SLIM) is a next-generation electronic packaging module that has the potential for high performance, low cost and small size. The proposed SLIM structure is a multi-layered structure with embedded passive layers in addition to signal, ground and power planes. At fabrication, assembly and different field conditions, significant interfacial stresses could develop due to the mismatch of the Coefficient of Thermal Expansion (CTE) among its different material systems. One of the most common failure modes in such a multi-layered structure is interfacial delamination. The objective of this research is to examine the possibilities of interfacial delamination in this multi-layered structure under thermal loading. A sophisticated analytical model has been developed in this work to determine energy release rate and stress intensity factor for delamination propagation. The model takes into consideration the temperature-dependent material properties as well as orthotropic material properties. Although delamination between two adjacent layers is studied, the model takes into consideration the effect of all dielectric, metallization, and substrate layers. Assuming that an initial delamination exists between the base layer and the metallization Copper layer, this work studies the propagation of delamination. In the analytical model, the base layer is modeled as an orthotropic thermoelastic material. Copper and the polymer dielectric material are modeled as isotropic elastic material. For the Copper/base layer interface, the variation of bimaterial constant (/spl epsi/) with temperature is obtained through the analytical model. The effect of some key parameters, such as the base layer material, the interlayer dielectric material, the metallization layer material, the base layer thickness, and the temperature range, etc. on energy release rate and fracture mode ratio is presented. Design recommendations for improved thermomechanical reliability are proposed.