Effects of crosshead speeds on solder strength of Cu/Sn–9Zn/Cu lap joints

In this study, the effects of crosshead speeds on solder strength of Cu/Sn–9Zn/Cu lap joints were determined. The solder strength of lap joints increased with increasing crosshead speeds. The highest solder strength value obtained was 130.41 MPa ± 4.85 at crosshead speed 3.0 mm/min while the lowest was 106.11 MPa ±5.20 at 0.5 mm/min. The corresponding strain value was inversely proportional with increasing crosshead speeds. In every lap joint formed, a constant joint interfacial strength was determined. This particular value is important in determining the failure mode of lap joints under different crosshead speeds. Failure occurred at the solder bulk region when the solder strength obtained was below the joint interfacial strength. Meanwhile, the failure mode transited from the bulk region to the joint interface as soon as the solder strength was higher than the joint interfacial strength. Fracture analyses were performed at the cross-sections of lap joints to support the statement.