Differential scanning calorimetry was used to characterize the energetics and kinetics of interdiffusion in solder/metal diffusion couples. The heat of formation of Cu3Sn from Cu6Sn5and Cu thin films was found to be &Dgr;Hr=−4.3±0.3 kJ/mol, similar to the results of previous measurements on bulk samples. We have seen that the nucleation of Cu3Sn begins at temperatures near 360 K, but that the nucleation and initial growth of Cu3Sn is not a well‐defined Arrhenius process in these diffusion couples. Later portions of our differential scanning calorimetry scans were identified with diffusion‐limited growth of Cu3Sn. From these calorimetry data we have estimated the averaged interdiffusion coefficient,D˜(cm2/s)=D0 exp (−E/kbT), wherekbis Boltzmann’s constant andD0=3.2×10−2cm2/s andE=0.87 eV/atom. ©1995 American Institute of Physics.