Self-propagating exothermic reactions are known to occur in multilayer films with alternating layers of a transition metal and a light element. The high velocity of these reactions, associated with high heat release rate, convert these systems in a unique heat source. The possibility of tailoring such a heat source to meet the needs of a particular process is very attractive to applications such as brazing or solid-state diffusion bonding. The solid state reactions occurring in Ni and Al multilayer thin films, produced by d.c. magnetron sputtering with bilayer thickness (period) of 5, 14 and 30 nm, were studied by differential scanning calorimetry (DSC). DSC results demonstrated that reaction temperature and heat released increase with the period of Ni/Al multilayer thin films.