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Abstract: The effects of aging time, strain rate and solder thickness on fracture behaviors of Sn–3Cu/Cu single crystal joints were investigated. Experimental results showed that short aging time (less than 10days) did not obviously affect the tensile strength and fracture behaviors of the solder joints. However, strain rate and solder thickness played significant roles in the strength and fracture behaviors of the solder joints. It was observed that these joints broke in a ductile manner at low strain rates with a rapid increase in the tensile strength, but displayed a brittle manner at high strain rates with a slow increase in the tensile strength. A model was proposed to explain such ductile-to-brittle transition between solder and intermetallic compounds. In addition, the solder joints broke in a ductile manner and presented a low tensile strength for the joints with thicker solder, but displayed a brittle manner and a higher tensile strength for the joints with thinner solder. [Copyright &y& Elsevier]

The segregation of Bi at the Cu/Cu3Sn interfaces of the SnBi/Cu couple dramatically decreases this couple’s mechanical properties. Here, we deliberately add Ag, Al, Sn and Zn elements into the Cu substrate to eliminate the interfacial segregation and embrittlement of the SnBi/Cu couple. Experimental results confirmed that there is always a perfect Cu3Sn/Cu alloy interface without Bi segregation, and excellent mechanical properties are thus maintained. The most important finding is that the interfacial embrittlement of SnBi/Cu alloy joints was successfully eliminated even after prolonged aging. [Copyright &y& Elsevier]