Theoretical model for diffusion bonding

Abstract

Despite successful applications of diffusion bonding, there is uncertainty as to the dominant mechanisms which operate when the two surfaces to be joined are brought together under an applied pressure at an elevated temperature. This paper describes a theoretical model for solid-state diffusion bonding, the aim of which is to understand how the various competing mechanisms operating at the bond interface are affected both by process variables (time, temperature, pressure) and by the properties of the materials being joined. Thus in the model the rate-controlling mechanisms governing the elimination of the interface between the two surfaces are identified, their relative kinetics predicted, and their individual importance in the various stages of diffusion bonding assessed. The approach adopted bears some similarity with that used when modelling the pressure sintering of powders, although the geometry at the interface of a diffusion bond results in differences.