A study of highly crosslinked Epoxy Molding Compound and its interface with copper substrate by molecular dynamic simulations

Abstract

A novel Epoxy Molding Compound (EMC) with a crosslinked network structure was formed by curing tri-/tetrafunctionalized EPN1180 with Bisphenol-A. A full atomistic model reflecting the network nature of the material was constructed by applying an iterative crosslinking algorithm to an amorphous cell with 3D periodic boundary condition containing the stoichiometric mixture of constitutive monomers. The geometry of the model was then optimized using the COMPASS force-field in Materials Studio [1]. The variation of system density and volume against temperature was simulated using a cooling down profile, which was employed to derive the glass transition temperature and coefficient of thermal expansion of the system. Furthermore, the Young's modulus and Poisson's ratio were calculated by uni-axial tensile molecular statics simulations. The material properties computed by molecular dynamics/mechanics simulations were in good agreement with experiment measurements. An epoxy resin/copper interface model was constructed and the interfacial adhesion energy was calculated as the energy difference between the total energy of the entire system and the sum of the energies of individual materials. The traction-displacement law of the interface was derived when the system was subjected to a molecular statics uniaxial tension. The work of separation and the peak traction, considered as the two key parameters required by cohesive zone finite element simulation, were extracted from the traction-displacement law.

Modeling of separation behavior of epoxy/Cu interface using molecular dynamics simulation

“…(c) curing reaction mechanism [26] To accurately predict the epoxy molding compound's adhesion and separation with copper substrate, the atomistic model used in MD simulation must be able to represent its crosslinked network structure. Yang et al [27] proposed a crosslinking scheme based on polymerization molecular dynamics simulation, i.e., iteratively creating covalent bonds between reactive sites (epoxy carbons on epoxy molecules and hydroxyl oxygens on BPAs) and relaxing the structure, and applied it to a MD study of bulk epoxy molding compound's properties. The methodology was slightly modified to build the atomistic model for epoxy slab in the epoxy/copper interface system in this work.…”

Establishment of the Mesoscale Parameters for Separation: A Nonequilibrium Molecular Dynamics Model

“…In order to construct a crosslinked structure of the epoxy layer, crosslinking of the epoxy and hardener monomers was simulated according to the procedure reported previously [24,26]. A three-dimensional polymeric structure was built.…”

Establishment of the coarse grained parameters for epoxy-copper interfacial separation

“…24,26 A three-dimensional polymeric structure was built. The models were assigned with a non-periodic boundary conditions, in order to avoid the over constraint induced at the boundary.…”

“…Iwamoto 21 investigated the separation of an epoxy-copper oxide system with the molecular dynamics (MD) approach, the maximum change in potential energy upon separation was taken as the interaction energy and the average separation distance was used to estimate the equilibrium distance. Yang et al 24 considered the stressdisplacement relations for the separation of an intimate contacted epoxy-copper system with a molecular model. They applied molecular statics (MS) to calculate the reaction force of the copper atoms at different separation distances to the epoxy and to obtain the interaction energy.…”