Molecular simulation of cu-sam adhesion force

The interface of Copper-EMC (Epoxy Molding Compound) is known to be the weakest joint in the electronic package design, which causes delamination during reliability test. A prime reason is the poor adhesion between Cu and epoxy compound. To solve the problem, We have used self-assembly monolayer (SAM) to improve adhesion of copper-epoxy system. This paper focuses on simulation of adhesion in Cu-SAM system. In this study, molecular models of bi-material system, which consists of SAM and Cu, were built to evaluate adhesion force of the Cu-SAM system. In order to dramatically reduce the computational time, only the copper tip and SAM substrate were modeled with a limited number of atoms. After energy minimization of the whole structure, tensile stresses were applied to the whole structure to simulate the debonding process, and the ultimate stress was obtained when the two materials delaminates completely. The adhesion force between the copper tip and the SAM can be evaluated from the ultimate tensile stress. The molecular model results were compared with AFM results in which adhesion force between Cu tip and SAM coated copper substrate were measured. Two different types of SAM material were used in this study. The paper intended to relate closely adhesion by using MD simulation, and the underlying physics for the explanation to the adhesion phenomenon for further understanding of failure mechanism of interfacial delamination.