A multiscale method to predict delamination in Cu-epoxy systems in electronic packages

The interface of epoxy molding compound (EMC) and Cu is known to be one of the weakest points in the electronic package design. Self-assembly monolayer (SAM) has been suggested as adhesion promoter of EMC-Cu system. Due to the length scale issues, traditional finite element or Molecular dynamic simulation can not individually simulate the behavior of the EMC-SAM-Cu interface in electronic packages. Therefore, an atomic based continuum model using combination of MD simulation and finite element analysis is proposed to investigate delamination at the EMC-SAM-Cu interface. The present study is focused on incorporating material behavior at the interface, derived from MD simulations, into the continuum model. The MD simulations were conducted to construct the constitutive relation of SAM at the EMC/Cu interface under the tensile loading. Tapered double cantilever beam tests (TDCB) were conducted on laminated specimens to quantify the fracture load for delamination along the EMC-Cu interface with and without SAM. Finite element models of the TDCB 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. The critical failure forces for the EMC/Cu interface with SAM and without SAM were obtained from the multi-scale model and verified by experimental results.