Modeling of interfacial void closure and prediction of bonding time in solid-state diffusion bonding

An analytical model of the void closure during diffusion bonding was established by coupling finite element analysis (FEA) based on the deformation mechanism and numerical analysis based on the diffusion mechanism. The maximum stress was concentrated at the tip of the microconvex in contact with the bonding interface. With increasing bonding temperature and pressure, the stress concentration region moved from the tip of the microconvex region to the void neck region. The stress distribution was concentrated on the tip of the microconvex region (void neck region) to the opposite direction of the applied bonding pressure. Using the model, the characteristic time parameter (time constant) t_c was defined based on the evolution of the void closure. At this moment, the predicted bonded ratio was the sum of (1 −1/e) times the normal limit bonded ratio and 1/e times the normal initial bonded ratio. Furthermore, a model for predicting the bonding time was established by coupling the required bonded ratio and the limitation of the deformation rate, the model can be used to predict the bonding time within the operation window. Contour maps of time constant (t_c/min) and the nominal limit bonded ratio (f_ult/%) were constructed for visual representation.