Brittle Properties of Copper Base Lead Frame at Soldered Joint

Copper base alloys, containing 2.4mass%Fe and 0.1mass%Zn, etc, were soldered using Pb-63%mass%Sn and then heated at 100°C, 125°C and 150°C for 1000-2000h to grow intermetallic compounds at the solder/alloy interfase. Elemental analysis at the interfase was performed by using EPMA. The fractured interfase, where the solder was peeld off after the 30° bending test, was observed by optical microscopy, and the concentrated elements were analyzed by EPMA. The copper alloy containing Fe, Zn showed a higher intermetallic compound growth rate, thus larger decreasing in the peel strength at the soldered joint. Intermetallic compounds formed at the solder-copper alloy interface were found to be typically, at the solder side, η-cu6sn5, and, at the copper alloy side, ε-cu3sn in which Iron element was found to have been segregated.