A study of transient liquid-phase bonding of Ag-Cu using differential scanning calorimetry

A novel approach using differential scanning calorimetry (DSC) to quantify interface kinetics in a solid/liquid diffusion couple is applied to characterize the isothermal solidification stage during transient liquid-phase (TLP) bonding of Ag and Cu using a Ag-Cu interlayer. When the DSC results are properly interpreted, the measured interface kinetics are more accurate than those obtained using traditional metallographic techniques. Experimental results are compared to predictions for isothermal solidification given by a selection of analytical models. The comparison yields close agreement with a solution that assumes a moving boundary; but accuracy of the predictions is very sensitive to selection of solute diffusivity. Metallographic inspection of the DSC samples and traditional TLP bonds validates the kinetics measured using this technique, and supports the prediction given by the analytical model. This study shows that the method of using DSC to quantify interface kinetics is valuable in the refinement of process parameters for TLP bonding. Furthermore, simple analytical solutions can be applied to predict the process kinetics of isothermal solidification in simple binary systems with considerable accuracy when the effects of grain boundaries can be neglected, thus reducing the need for complex numerical models when developing process parameters.