The comparison studies on growth kinetic of IMC of Cu/Sn3.0Ag0.5Cu (Sn0.4Co0.7Cu)/Cu joints during isothermal aging and their tensile strengths

Abstract

PurposeThe purpose of this paper is to compare the growth kinetics of interfacial intermetallic compound (IMC) layer and its effect on the tensile strength of two solder (Sn3.0Ag0.5Cu and Sn0.4Co0.7Cu) joints.Design/methodology/approachThe samples annealed, respectively, at 85, 120 and 150°C up to 1,000 h were tensile tested and their cross‐sections were observed by scanning electron micrography.FindingsThe results showed that, for both solder joints, an approximately linear reduction in tensile joint strength with an increase in the IMC layers' thickness occurred. The tensile strength of Cu/Sn3.0Ag0.5Cu solder joints is slightly better than that of Cu/Sn‐0.7Co‐0.4Cu solder joints under analogous aging conditions. In addition, the growth kinetics of the overall interfacial IMC layer in Sn0.4Co0.7Cu solder joints can be simply described by the classical growth kinetic theory for solid‐state diffusion with an activation energy of 2,996.85 J/mol and interdiffusion constant of 4.15×0−17 m2/s which are relatively lower, compared with Sn3.0Ag0.5Cu solder on copper with 14,167.8 J/mol and 65.33×10−17 m2/s, respectively.Originality/valueThe paper is of value in evaluating the growth kinetics of Sn3.0Ag0.5Cu and Sn0.4Co0.7Cu solder joints, and in discussing and contrasting the influence of IMC growth on their tensile strength.