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A multi-scale method for the prediction of delamination in electronic packages

Authors Fan, Haibo
Issue Date 2005
Summary Interfacial delamination, due to the presence of dissimilar material systems, is one of the primary concerns in electronic package design. The present study is focused on delamination at the interface of the epoxy molding compound (EMC) and copper interface. Based on traditional method, the obtained energy with different button shear testing configurations provides no clear indication that the proposed energy parameter could be used as a limiting factor in a strength-based failure criterion. In order to incorporate the interfacial bonding into the finite element model, an interfacial layer is built at the interface, which has material properties significant different from the bulk EMC and copper substrate. The results presented could be incorporated into a strength-based failure criterion for the prediction of interfacial delamination. And the concept of virtual internal bond (VIB) approach was introduced to complements the interfacial layer model by providing a methodology to evaluate the interfacial material properties. Atomic force microscopy (AFM) tests were conducted to measure the adhesion force between the EMC and copper substrate, which directly provided the deflection-distance curve. The deflection-distance curve was used to evaluate the energy parameters of the Lennard-Jones potential, which was used to describe the interaction of EMC and copper atoms at the interface. The investigation of the adhesion between the EMC and copper substrate was addressed using MD simulation. The simulation results reveal the interaction behavior between the EMC and copper substrate and provide a qualitative trend which is consistent to the energy curve derived from AFM results. Based on the Lennard-Jones potential, the force-distance curve for each EMC material was derived. The corresponding relation of stress and strain could be extracted from the force-distance curve. A multi-scale model was built by introducing the concept of VIB in which atomic interactions of the interface can be packed in a hyperelastic solid. The interfacial material properties were input to the layer element at the interface, representing the behavior of the EMC/Cu interface. The interfacial energy was calculated when the shear forces from the button shear tests were applied to the model. All the energies remained almost constant with a small variation when the shear height and angles changed, which could be incorporated into a strength-based failure criterion for interfacial delamination. The proposed criterion was benchmarked by its application in real package models, in which two kinds of packages, SOT#1 and SOT#2, were studied to investigate delamination in the soldering reflow process. Based on the proposed method, the delamination in the two packages could be predicted, which is consistent with the C-SAM result.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005
Language English
Format Thesis
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