Sn-Ag共晶はんだとCuの接合界面の微細組織と強度

抄録

Sn-Ag eutectic solder has been examined as one of the candidates of the lead-free solder comparing with Sn-Pb eutectic solder and pure Sn. All interfaces have Cu₃Sn and Cu₆Sn₅ reaction layers. Cu₆Sn₅ grows into solders like “peninsula”. Kirkendall voids are formed at the Sn/Cu and Sn-Pb/Cu interfaces but not at the Sn-Ag/Cu interface. The tensile strength of the Sn-Ag/Cu joint is higher than those of the Sn/Cu and Sn-Pb/Cu joints. Fracture takes place along the Cu₆Sn₅ layer and the linkage of preceding microcracks at the bottom of Cu₆Sn₅ peninsulas is responsible for the fracture. Sn-Ag solder has fine dispersion structure of Ag₃Sn particles forming subgrains. Ag₃Sn particles have a specific orientation relationship with the Sn matrix as shown below.
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