Dissolution Behavior of Cu-2.0 wt.% Be (Alloy 25) and Cu-0.1 wt.% Fe (C19210) Substrates in Molten Sn-9 wt.%Zn Solder

This study investigates the dissolution behavior of the Cu-2.0 wt.% Be (Alloy 25) and Cu-0.1 wt.% Fe C19210 substrates in Sn-9 wt.%Zn solder (SZ) at temperatures of 240°C, 270°C, and 300°C for 5–100 min. The consumption of Alloy 25 and C19210 dissolved into the molten SZ solder exhibited a linear decrease, with C19210 demonstrating a higher dissolution rate compared to Alloy 25. The layer-type Cu₅Zn₈ and scallop-type CuZn₅ phases were observed in both systems. The Cu₅Zn₈ phase becomes dominant and is sufficiently thick in the SZ/C19210 system. The total thickness of the intermetallic compounds (IMCs) becomes thinner in the SZ/Alloy 25 system. The Alloy 25 substrate significantly inhibited the IMC growth at the SZ/substrate interface. The value of the activation energy in the SZ/Alloy 25 system, measured at 128.8 kJ/mol, was notably higher than that of the SZ/C19210 system, in which the activation energy value was 18.2 kJ/mol. Consequently, the Alloy 25 can effectively resist the IMC growth at the interface and enhance the solder-joint reliability.