Numerical Multiphysics Model for Cu-Al Wire Bond Corrosion Subjected to Highly-Accelerated Stress Test

A novel multiphysics model for the corrosion of Cu-Al wirebonds operating under highly accelerated stress test conditions has been developed. Corrosion kinetics of the Cu-Al WB system has been modeled using a combination of Butler-Volmer Equation and the Nernst-Planck Equation to capture the diffusion mechanisms and the corrosion kinetics. The Tafel Parameters have been from polarization curves measured under a number of temperature and molar concentrations in three-electrode electrochemical cell. Diffusion coefficients of the molding compounds have been measured in a diffusion cell under a number of temperatures and electric field conditions. In addition, a framework has been developed using regression to compute the Tafel parameters under a range of conditions in between the conditions measured in the three-electrode electrochemical cell test. The initiation of corrosion crack and propagation has been modeled using corrosion current tracking through combination of four sequential steps of initiating the model through definition of current state geometry, locating the current state corrosion boundary, computation of next state corrosion boundary, and computation of next state simulation geometry, implemented in MATLAB (TM). Model predictions have been validated using parts tested in HAST.