Interface design and the strengthening-ductility behavior of tetra-needle-like ZnO whisker reinforced Sn1.0Ag0.5Cu composite solders prepared with ultrasonic agitation

Abstract

To develop a lead-free solder with high strength and ductility, a novel interface was designed between the tetra-needle-like ZnO whisker (T-ZnOw) and Sn1.0Ag0.5Cu solder matrix. First, surface modification of T-ZnOw was conducted using a pyrolysis method based on self-assembly to deposit NiO nanoparticles densely and evenly on the whisker surface. The interfacial relationship between T-ZnOw (100) and NiO (101) planes was semi-coherent with a misfit of 0.145. In-situ transmission electron microscopy was used to explore the surface modification mechanism. Next, a composite solder of 0.3mass% NiO/T-ZnOw reinforced Sn1.0Ag0.5Cu was prepared with ultrasonic agitation, and the introduced reinforcement was uniformly distributed in the solder matrix. A thin NiO transition layer existed between the reinforcement and matrix, indicating the formation of the Sn1.0Ag0.5Cu/NiO/T-ZnOw sandwich structure interface. No gaps, pores, or new phases were formed at the interface, and atomic interdiffusion occurred at the interface to form effective bonding. The composite solder shows improved wettability compared with plain solder. The ultimate tensile strength (UTS) and elongation of the composite solder were 32.5 MPa and 28.1%, respectively, being 19.0% and 35.1% higher than those of the plain Sn1.0Ag0.5Cu solder. The strengthening-ductility mechanisms primarily included load transfer, grain refinement, and misfit dislocation effects.

Keywords

• Sn1.0Ag0.5Cu composite solder
• Tetra-needle-like ZnO whisker
• Interface
• Surface modification
• In-situ TEM
• Strengthening-ductility mechanism