2001 Volume 42 Issue 5 Pages 814-819
This paper introduces the partial melting soldering process as a new soldering technology and investigates the mechanism, mechanical properties, and interface reactions between Cu and off eutectic binary alloys: Sn–7 mass%Ag, Sn–3 mass%Cu, and Sn–2 mass%Ni. In order to show the possibility of the partial melting soldering, reflow was conducted under various temperature conditions between the eutectic and the liquidus temperatures. As a result, intermetallic compound layers were formed at the joint in their partial melting zone. In cases of the Sn–7Ag and Sn–3Cu solders, Cu6Sn5 intermetallic layers were formed, while the intermetallic layer formed between Sn–2Ni and Cu plate was a ternary compound of Sn–Ni–Cu. Hardness test showed that partial melted joint was harder than the full melted joint, indicating that the solid phase in the mushy zone had an effect of reinforcement. According to the aging experiments, the growth rate of intermetallics of partial melted joint was lower than that of full melted one. This indicates that the solid phase in mushy zone also prevented excessive growth of the intermetallics. Finally, shear test had been made to evaluate joint strength, showing that the strength of the partial melted joint was almost 80% that of a full melted joint.
