A multi scale finite element methodology to evaluate wire bond pad architectures

Abstract

This work focuses on a multi scale finite element method (FEM) in order to model the wire bonding process. The methodology and results aiming at understanding and predicting the bond pad failures are detailed. Due to the very detrimental aspect ratios involve in the wire bonding process modeling, the use of a multilevel technique is mandatory. However, results highlight that precautions are needed at the macro scale when choosing the representative unit cell (RUC) during the homogenization step. More precisely, a simple law of mixture leads to a wrong evaluation of the displacements at the global scale and impacts strongly the local stress field. The FE method is applied in a linear three dimensional analysis. Both thermal and force loadings are tested and their contributions are discussed on several wire bond pad layouts.