Solid-state reactions and stress evolutions between SnAg and Ni(P) thin films

Abstract

Phase transformations in SnAg–Ni80P20 films were studied ex situ in parallel with in situ measurements of the corresponding transformation-induced stresses. Layered formation of Ni3Sn4 and Ni3P phases at an early stage of a reaction between SnAg and Ni80P20 films resulted in a tensile stress similar to the stress evolution in Sn–Ni80P20 films, despite the additional formation of Ag3Sn phase. Ag3Sn phase did not significantly affect the degree of stress evolution because of its islandlike and sporadic formation on the top surface of the Ni3Sn4 layer. Isothermal annealing showed that compressive stress, which was induced by the dominant formation of Ni3Sn4, developed after an initial evolution of tensile stress.