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Homogeneous (Cu, Ni) 6 Sn 5 intermetallic compound (IMC) joints were rapidly formed in asymmetrical Ni/Sn/Cu system by an ultrasound-induced transient liquid phase (TLP) soldering process. In the traditional TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system consisted of major (Cu, Ni) 6 Sn 5 and minor Cu 3 Sn IMCs, and the grain morphology of (Cu, Ni) 6 Sn 5 IMCs subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the joints. However, in the ultrasound-induced TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system only consisted of the (Cu, Ni) 6 Sn 5 IMCs which exhibited an uniform grain morphology of rounded shape with a remarkably narrowed Ni concentration gradient. The ultrasound-induced homogeneous intermetallic joints exhibited higher shear strength (61.6 MPa) than the traditional heterogeneous intermetallic joints (49.8 MPa). [ABSTRACT FROM AUTHOR]

The grain morphology and mechanical strength of the high-melting-temperature intermetallic joints formed in the asymmetrical Ni/Sn/Cu system using a transient liquid phase (TLP) soldering process were investigated. The grain morphology of the (Cu, Ni) 6 Sn 5 compounds subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the intermetallic joints. The thermodynamic analysis indicates that the critical Ni concentration which determined the grain morphology between the needlelike shape and the coarse rounded shape is approximately 11 at% at the soldering temperature of 260 °C. The growth of the Cu 3 Sn compounds was suppressed and exhibited the grain morphology of fine rounded shape. The melting temperature and the shear strength of the intermetallic joints are 418.4 ± 0.1 °C and 49.8 ± 0.3 MPa, respectively. The shear fracture was inclined to occur in the area of (Cu, Ni) 6 Sn 5 grains with the coarse rounded shape. [ABSTRACT FROM AUTHOR]

The grain morphology evolution and mechanical strength change of the intermetallic joints formed in a Ni/Sn/Cu system by the transient liquid phase (TLP) soldering at 260 °C, 300 °C and 340 °C were investigated. The grain morphology evolution of the (Cu, Ni) 6 Sn 5 intermetallic compounds (IMCs) was highly correlated with the Ni concentration gradient across the joints and strongly affected by the soldering temperatures, which was analyzed in detail from the aspect of thermodynamics. The shear strengths of the three types of intermetallic joints were 49.8 MPa, 50.3 MPa and 42.7 MPa, respectively. The correlation between the grain morphology evolution and the mechanical strength change of the intermetallic joints was revealed. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of complete intermetallic joints rapidly formed by the ultrasonic-assisted transient liquid phase (TLP) soldering process were investigated. Compared to the intermetallic joints formed by the traditional TLP soldering process, the resulted intermetallic joints consisted of remarkably refined Cu 6 Sn 5 grains, with an average size of 3.5 μm. They also demonstrated more uniform mechanical properties with elastic modulus and hardness values of approximately 123 GPa and 6.0 GPa, respectively, as well as higher reliability, in terms of higher shear strength of 60.1 MPa. These results provided a new insight into the effects of ultrasonic on the microstructures and properties of intermetallic joints. [ABSTRACT FROM AUTHOR]

The non-interfacial growth of Cu 3 Sn intermetallic compounds (IMCs) in a Cu/Sn/Cu interconnection structure during the ultrasonic-assisted transient liquid phase (TLP) soldering process was investigated. In the traditional TLP soldering process, the Cu 3 Sn phase always nucleated at Cu 6 Sn 5 /Cu interfaces and grew at the expense of the Cu 6 Sn 5 phase and towards the joint centre, eventually forming a full intermetallic joint consisting of a single Cu 3 Sn phase with columnar grains. While in the ultrasonic-assisted TLP soldering process, the Cu 3 Sn phase nucleated and grew randomly within the whole joint, the resulting intermetallic joint consisted of a single Cu 3 Sn phase with equiaxed grains. This anomalous behaviour can be wholly ascribed to the effects ultrasonic on the nucleation and growth mechanisms of Cu 3 Sn. [ABSTRACT FROM AUTHOR]