3D ICs is a promising new technology that has many advantages over traditional planar packages. To take advantage of this technology, new bonding techniques have to be developed to satisfy the need for high density micro interconnects. Solid liquid inter-diffusion bonding in which the bond is established by placing a low melting temperature material between high temperature melting substrate and applying heat and pressure, is a new technology that may resolve issues with other type of bonding. This manuscript presents a 1D analytical phase lag model to estimate the complete bonding time (complete transformation to IMCs) for bonds with different thicknesses. The time for complete transformation of the bond to IMC is estimated using this technique for bonds with range of thicknesses of 10 microns to 200 microns. An experiment is conducted to produce bonds with variety of thicknesses. Bonding was carried out at 260°C and process parameters were varied to produce bonds with thicknesses varying between 15 microns and 250 microns. The SEM and EDS imaging is used to determine the extent of copper diffusion in the bonds and different IMC compounds. This analysis show that 45 minutes is long enough to transform all bonds with variety of thicknesses to η phase of IMC. Traces of ε phase of IMC were also found in all the cases and were more significant in the case of 15 micron thickness.