Investigation of the interfacial reactions and mechanical strength in the Sn-Ag-Cu (SAC)/Cu-Be alloy (Alloy 25) couple

The liquid/solid reaction couple technique was used to investigate interfacial reactions between Sn-3.0Ag-0.5Cu (SAC, in wt%) solder and Alloy 25. The results indicated that the dominant IMC formed in the SAC/Alloy 25 couples was the Cu
₆
Sn
₅
phase at 240 °C. When the reaction time was increased to 2 h, the Cu
₃
Sn phase close to the Alloy 25 side was formed. Both the Cu6Sn
₅
and Cu
₃
Sn phases were formed at the interface, when reaction temperatures were raised to 255 and 270 °C. When the reaction temperatures and times were increased, the thick IMC layer was observed and the grain ripening occurred. Simultaneously, the grain became an abnormal condition resulting in Cu
₆
Sn
₅
not accumulating at the interface, the massive spalling phenomenon were found in the Cu6Sn5 layer.