Microstructural and shear strength properties of RHA-reinforced Sn–0.7Cu composite solder joints on bare Cu and ENIAg surface finish

Abstract

In this study, the joint effect of rice husk ash (RHA) reinforcement as an alternative silica source and electroless nickel immersion silver (ENIAg) surface finish on the intermetallic compound (IMC) formation and shear strength of the Sn-0.7Cu solder system was investigated. A series of plain and composite lead-free solder systems (Sn-0.7Cu−xRHA; x = 0, 0.01, 0.05 and 0.1 wt%) was successfully developed and subjected to reflow soldering on bare Cu and ENIAg surface finish. After conducting a comprehensive microstructural study using the scanning electron microscopy and energy dispersive spectroscopy techniques, the Cu6Sn5 and Cu3Sn intermetallic compound (IMC) phases were observed at the interface of the Sn-0.7Cu−xRHA/Cu composite solder joints. On the other hand, the (Cu,Ni)6Sn5 and Ni3Sn4 IMC phases dominated the interface of the Sn-0.7Cu−xRHA/ENIAg counterparts. Given the promising potential of the ENIAg surface finish, the Sn-0.7Cu−xRHA/ENIAg exhibited IMC thickness values within a range of 3.81-4.74 µm as compared to the 6.13-9.3 µm range exhibited by the Sn-0.7Cu−xRHA/Cu counterpart. More so, the ENIAg surface finish was effective in improving the shear strength of the plain solder joint, with the Sn-0.7Cu/ENIAg exhibiting 13.44 MPa relative to the 11.5 MPa exhibited by the Sn-0.7Cu/Cu counterpart. Overall, the strengthening effect of the RHA reinforcement was well marked in the Sn-0.7Cu−xRHA/Cu composite solder joints with the composite having 0.1 wt% RHA exhibiting the highest shear strength (14.6 MPa) across the board.

Shear analysis of rice husk ash (RHA) reinforced tin‐0.7‐copper composite solders on electroless nickel/immersion silver (ENIAg) surfaces

“…It can be deduced from the decrease in the shear strength of composite solders that the nanoparticles (rice husk ash) added to the solders were unable to strengthen the solder due to non-uniform particle dispersion and thus, dropped the solder deformation resistance by allowing the movement of dislocation and pin grain boundaries in the solder matrix, Figure 5. This can be further rationalized by a study where the introduction of rice husk ash to the solder joint promoted the formation and localization of intermetallic compound clusters close to the solder/ substrate interface [30]. Solder joint fracture through the interface when the applied stress is less than the solder strength and the interfacial strength is higher than the interfacial bonding strength.…”

“…Solder joint fracture through the interface when the applied stress is less than the solder strength and the interfacial strength is higher than the interfacial bonding strength. Hence, the deterioration of the composite solder joints increased with rising rice husk ash addition [30]. More so, the added rice husk ash has the possibility of not entirely dispersing in the solder after soldering.…”

Effectiveness of Dimple Microtextured Copper Substrate on Performance of Sn-0.7Cu Solder Alloy

“…Teoh et al [20] reported that the mechanical strength of Sn-0.7Cu improved by adding Bi into the solder alloy. Hanim et al [21] reported that the electroless nickel immersion silver (ENIAg) surface finish significantly enhanced the shear strength of the solder joint, as it provided a more stable metallurgical bond of the solder joint. Despite the abovementioned studies and others involving the improvement of the performance of Sn-0.7Cu, studies on the modification of the substrate used in the soldering process remain limited.…”