Influence of porous Cu interlayer on the intermetallic compound layer and shear strength of MWCNT-reinforced SAC 305 composite solder joints

Abstract

In this study, the synergetic effect of multi-walled carbon nanotubes (MWCNTs) and porous Cu interlayer (PCI) on the intermetallic compound (IMC) formation and shear strength of Sn–3.0Ag–0.5Cu (SAC 305) solder system was investigated. The solder joints were prepared by subjecting two different series of MWCNTs-reinforced SAC 305 solder systems (i.e., SAC–0.01CNT and SAC–0.04CNT) sandwiched with porous Cu interlayer having pores per inch (PPI) of 15, 25 and 50 to reflow soldering on Cu substrate. Electron microscopy and spectroscopy techniques were used to view and detect the intermetallic compound phases, respectively. The scallop-shaped Cu6Sn5 IMC phase was observed at the solder/PCI interface, while on the other hand, an additional layer-type Cu3Sn IMC phase formed alongside the Cu6Sn5 IMC at the solder/Cu interface. Given the promising properties of PCI material, empirical findings showed that the presence of PCI in the solder joint inhibited the formation of interfacial IMC layer at the solder/Cu substrate with the SAC–0.01CNT–25PCI exhibiting the least IMC thickness. More so, the PCI material effectively enhanced the shear strength of the MWCNTs-reinforced composite solder joints. Generally, the strengthening capacity of the PCI material was greatly underscored in the SAC–0.01CNT–xPCI series with the sample prepared with PCI of 15 PPI demonstrating the superior shear strength of 21.1 MPa.