A multi-scale interfacial delamination model of Cu-SAM-epoxy systems

Interfacial delamination, due to the presence of dissimilar material systems, is one of the primary concerns in electronic package design. The mismatch in coefficient of thermal expansion between the different layers in the packages can generate high interfacial stresses due to thermal loading during fabrication and assembly. More and more functional materials at the nano scale are, such as self-assembly monolayer (SAM) and CNT, used in electronic packaging for the improvement of the interfacial performance, traditional continuum model without considering these nano materials are obviously not suitable to study performance of electronic packages. In this study, a multi-scale model was built to investigate interfacial failure between EMC and SAM coated copper substrate. The interfacial material behavior was derived from the molecular dynamics simulation. The constitutive relation for the EMC-SAM-Cu interface under tensile load was derived from MD simulation. Tapered double cantilever beam tests (TDCB) were conducted on the laminated specimens to quantify the load during delamination propagation along the EMC-Cu interface with SAM and without SAM. Finite element models of the DCB test were built using ANSYS with interfacial element at the Cu-EMC interface. The constitutive relations from MD simulations in the form of a traction-displacement plot were introduced into the cohesive zone model to study the constitutive response of the EMC-Cu interface under the tensile loading, which is traversed across the length scale from nanoscale to macroscale. and assigned to the continuum model. The critical loading forces for the EMC/Cu interface with SAM and without SAM were obtained from the multi-scale model. It was found that interfacial strength between EMC and Cu substrate could be improved by SAM. Based on the proposed method, the predicted results were found to be comparable with those from experimental measurement.