Dependence of Cu/Sn and Cu/60Sn40Pb Solder Joint Strength on Diffusion Controlled Growth of Cu3Sn and Cu6Sn5

Abstract
The growth of intermetallic compounds and the strength of Cu/ Sn and Cu/ 60Sn40Pb butt joints were studied as a function of isothermal aging. The effects of single-crystal (100), (110), and (111) oriented copper on the growth rates of Cu3Sn and Cu6Sn5 intermetallic compounds are characterized and the influence of elevated temperature aging on the tensile strength of butt joints analyzed. Substrate orientation appears to influence the growth rate. Metallographic measurements showed that the intermetallic compounds grew at a rate proportional to the square root of time. Tensile tests of aged butt joints revealed a more complex time dependence.