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

Abstract

Phase transformations in SnAg-Ni(80)P(20) films were studied ex situ in parallel with in situ measurements of the corresponding transformation-induced stresses. Layered formation of Ni(3)Sn(4) and Ni(3)P phases at an early stage of a reaction between SnAg and Ni(80)P(20) films resulted in a tensile stress similar to the stress evolution in Sn-Ni(80)P(20) films, despite the additional formation of Ag(3)Sn phase. Ag(3)Sn phase did not significantly affect the degree of stress evolution because of its islandlike and sporadic formation on the top surface of the Ni(3)Sn(4) layer. Isothermal annealing showed that compressive stress, which was induced by the dominant formation of Ni(3)Sn(4), developed after an initial evolution of tensile stress.