The Interfacial Intermetallic and Shear Strength of Ni Nanoparticle‐Decorated Reduced Graphene Oxide Reinforced Sn2.5Ag0.5Cu Lead‐Free Composite Soldering Joints

Abstract

The Ni nanoparticle‐decorated reduced graphene oxide (Ni‐rGO) reinforced Sn2.5Ag0.5Cu lead‐free composite solder, as well as the interfacial intermetallic (IMC) and the shear strength of soldering joints, are investigated with scanning electron microscopy (SEM), X‐ray diffraction (XRD), and transmission electron microscope (TEM). The results show that Ni‐rGO can be synthesized by the thermal decomposition method, and the adsorption type between Ni atoms and rGO is chemisorption. When the amount of Ni‐rGO addition reaches 0.05 wt%, the high strength and toughening Ni‐rGO reinforced lead‐free composite solder is obtained, with a tensile strength and elongation of 58.0 MPa and 32.3%, respectively. The growth of the interfacial IMC layers is restrained by the addition of Ni‐rGO, and the highly reliable soldering joints are obtained accordingly. When the amount of Ni‐rGO addition reaches 0.05 wt%, the shear strength of the Ni‐rGO reinforced lead‐free composite solder is 28.1 MPa, which is 26.6% higher than that of the plain Sn2.5Ag0.5Cu soldering joints. With the increase in the amount of Ni‐rGO, the fracture pattern is transforme from a ductile‐brittle mixed fracture to a ductile fracture. Additionally, the fracture pathway shifts from a transition zone, consisting of soldering seam and interfacial IMC, to the direction of the soldering seam.

Environmentally Friendly and Controllable Pyrolysis Method to Synthesize Ni-Modified Graphene Nanosheets as Reinforcement of Lead-Free Solder

“…As a result, the (111), (200), (311), and other preferred growth planes of Ni appear (inset in Figure 7c). This is well consistent with our previous research [42]. An FCC twin crystal appeared in Region D, suggesting that the lattice distortion of Ni or the defect of GNSs existed here.…”

Microstructures and Properties of Sn2.5Ag0.7Cu0.1RE Composite Solders Reinforced with Cu-Coated Graphene Nanosheets Synthesized by Pyrolysis

“…However, both of the adsorption heights are greater than the 1.92 Å of the covalent radius sum of Cu and C atoms, which indicates that the Cu/IG interface is a physisorption interface with weak bonding. In addition, during the high-energy ball milling, shear forces would delete certain carbon atoms in graphene to form VG [20]. The equilibrium adsorption energy and adsorption height of the top/bridge position Cu atoms on the VG are shown in Figure 3c,d, respectively.…”

“…which are compatible with the matrix [18]. Our previous studies proved that trace addition of Ni had positive effects on microstructure refinement and the discussed properties of solder and Ni-GNSs doped composite soldering joints [19,20]. Although the bonding strength between Cu and GNSs is less than the counterpart of Ni-GNSs, lattice defects of GNSs by high-energy milling give Cu nanoparticles the potential to form strong bonding with defected GNSs [21,22].…”

Dynamic Observation of Interfacial IMC Evolution and Fracture Mechanism of Sn2.5Ag0.7Cu0.1RE/Cu Lead-Free Solder Joints during Isothermal Aging

“…The distance between the interface and the marked point ("P") was measured by the Image-Pro Plus 6.0 software (Media Cybernetics, Rockville, MD, USA). The average thickness of the interfacial IMC (d) was calculated by the Equation (1) [31]:…”