Microstructure and mechanical properties of Cu joints soldered with a Sn-based composite solder, reinforced by metal foam

• Published in: Journal of alloys and compounds 2020-12, Vol.845, p.156240, Article 156240
• Main Authors: He, Huang, Huang, Shangyu, Ye, Yongchao, Xiao, Yong, Zhang, Zhihao, Li, Mingyu, Goodall, Russell
• Format: Article
• Language: English
• Subjects: Copper; Copper base alloys; Cu interconnects; Dissolution; Foamed metals; Joints (anatomy); Mechanical properties; Metal foams; Microstructure; Nickel; Shear strength; Sn-based solder; Soldering; Solders; Substrates; Tensile strength; Tin
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.156240

In this study, Ni foam, Cu coated Ni foam and Cu-Ni alloy foams were used as strengthening phases for pure Sn solder. Cu-Cu joints were fabricated by soldering with these Sn-based composite solders at 260 °C for different times. The tensile strength of pure Sn solder was improved significantly by the addition of metal foams, and the Cu-Ni alloy/Sn composite solder exhibited the highest tensile strength of 50.32 MPa. The skeleton networks of the foams were gradually dissolved into the soldering seam with increasing soldering time, accompanied by the massive formation of (Cu,Ni)6Sn5 phase in the joint. The dissolution rates of Ni foam, Cu coated Ni foam and Cu-Ni alloy foams into the Sn matrix increased successively during soldering. An increased dissolution rate of the metal foam leads to an increase in the Ni content in the soldering seam, which was found to be beneficial in refining the (Cu,Ni)6Sn5 phase and inhibiting the formation of the Cu3Sn IMC layer on the Cu substrate surface. The average shear strength of the Cu joints was improved with increasing soldering time, and a shear strength of 61.2 MPa was obtained for Cu joints soldered with Cu-Ni alloy/Sn composite solder for 60 min. •Ni foam, Cu coated Ni foam and Cu-Ni alloy foam were used to reinforce pure Sn solder.•(Cu,Ni)6Sn5 phase was largely formed accompanied by the dissolution of metal foams.•The dissolution rates of Ni, Cu coated Ni and Cu-Ni alloy foams increased successively.•An increased Ni content could refine (Cu,Ni)6Sn5 phase and inhibit Cu3Sn IMC layer.•Cu joints soldered with Cu-Ni alloy/Sn composite solder had the highest shear strength.